Influence of modeling choices on seismic response of a steel reticulated dome
Akshay Arun Somkuwar, Ryota Matsui, Taichiro Okazaki
Journal of Constructional Steel Research, 226, 109260, 109260, Elsevier BV, Mar. 2025, [Peer-reviewed]
English, Scientific journal

Cyclic behavior of steel self-centering prestressed beam-column connection with weakened FCP
Zi-Qin Jiang, Zi-Yao Niu, Xiao-Feng Yang, Zhong-Shuai Yang, Taichiro Okazaki
Journal of Constructional Steel Research, 224, 109153, 109153, Elsevier BV, Jan. 2025, [Peer-reviewed]
English, Scientific journal

Cyclic pushover analysis for seismic response evaluation of a full-scale 10-story steel building tested on the E-Defense shake-table
Jialiang Jin, Takuya Nagae, Tatsuya Asai, Taichiro Okazaki, Jionghui Li, Dimitrios G. Lignos, Yu-Lin Chung, Jun Fujiwara, Akiko Kishida, Koichi Kajiwara
Journal of Building Engineering, 96, 110552, 110552, Elsevier BV, Nov. 2024, [Peer-reviewed]
English, Scientific journal

A Survey on Perceptions of Current Design Code Provisions of Steel Structural Buildings and Their Internationalization
Hayato Asada, Satoshi Yamada, Taichiro Okazaki, Tsuyoshi Koyama, Tetsu Usami
AIJ Journal of Technology and Design, 30, 76, 1299, 1304, Oct. 2024, [Peer-reviewed]
Scientific journal

An experimental study on the shear, tensile and peel strength of adhesively bonded steel-to-steel joints
Haruna Takano, Yosuke Watanabe, Taichiro Okazaki
Steel Construction Engineering, Japan Society of Steel Construction, 31, 123, 37, 47, Oct. 2024, [Peer-reviewed], [Corresponding author]
Japanese, Scientific journal, 31428767

Bidirectional Cyclic Loading Performance of a Prefabricated Self-Centering Metallic-Damped Steel Column Base
Junxian Zhao, Hao Qin, Taichiro Okazaki, Yan-Wen Li, Chaohai Guo
Journal of Structural Engineering, 150, 10, American Society of Civil Engineers (ASCE), Oct. 2024, [Peer-reviewed]
English, Scientific journal

Effect of composite slab and connection detail on cyclic behavior of steel beam-to-HSS column moment connections
Jialiang Jin, Tianhao Yan, Takuya Nagae, Taichiro Okazaki, Tomohiro Matsumiya, Noriyuki Takahashi
Journal of Building Engineering, 95, 110254, 110254, Elsevier BV, Oct. 2024, [Peer-reviewed]
English, Scientific journal, 11746794

A comprehensive review of shear connectors in demountable composite beams
Xin Li, Jing He, Yuxin Zhou, Fei Xu, Taichiro Okazaki, Han Fang
Journal of Constructional Steel Research, 218, 108723, 108723, Elsevier BV, Jul. 2024, [Peer-reviewed]
English, Scientific journal

Seismic resilient steel moment connections with top shear tabs and bottom replaceable metallic fuse: Analytical and experimental study
Junxian Zhao, Hao Qin, Taichiro Okazaki, Fangxin Hu, Zexin Cai
Engineering Structures, 306, 117789, 117789, Elsevier BV, May 2024, [Peer-reviewed]
English, Scientific journal

Seismic performance of self-centring connections with two energy dissipation stages for reusable modular steel buildings
Jing He, Xuhong Zhou, Fei Xu, Yu Shi, Taichiro Okazaki
Thin-Walled Structures, 196, 111442, 111442, Elsevier BV, Mar. 2024, [Peer-reviewed]
English, Scientific journal

Modeling uncertainty of specimens employing spines and force‐limiting connections tested at E‐defense shake table
Bryam Astudillo, David Rivera, Jessica Duke, Barbara Simpson, Larry A. Fahnestock, Richard Sause, James Ricles, Masahiro Kurata, Taichiro Okazaki, Yohsuke Kawamata, Zhuoqi Tao, Yi Qie
Earthquake Engineering & Structural Dynamics, 52, 4638, 4659, Wiley, 26 Jul. 2023, [Peer-reviewed]
English, Scientific journal, 31428741

Numerical simulation of the cyclic‐loading behavior of steel chevron‐braced moment‐resisting frames
Ilanildo Dias, Akiri Seki, Taichiro Okazaki
JAPAN ARCHITECTURAL REVIEW, 6, 1, Wiley, Jan. 2023, [Peer-reviewed], [Corresponding author]
English, Scientific journal

Japanese Efforts to Promote Steel Reuse in Building Construction
Masanori Fujita, Tetsuya Fujita, Mamoru Iwata, Yoshihiro Iwata, Tomomi Kanemitsu, Urara Kimura, Kazuhiko Koiwa, Mitsumasa Midorikawa, Taichiro Okazaki, Satoshi Takahashi, Teruhisa Tanaka, Masatoshi Wada
Journal of Structural Engineering, 149, 1, 04022225-1, 04022225-13, American Society of Civil Engineers (ASCE), Jan. 2023, [Peer-reviewed], [Corresponding author]
English, Scientific journal

IN-SITU TESTS TO EVALUATE THE STRUCTURAL PERFORMANCE OF A LARGE, IMPORTED STEEL-FRAMED GREENHOUSE
Yuta FUKE, Taichiro OKAZAKI, Ryota MATSUI
AIJ Journal of Technology and Design, 28, 70, 1236, 1241, Architectural Institute of Japan, 20 Oct. 2022, [Peer-reviewed]
Japanese, Scientific journal

Mechanism and Experimental Validation of Frictional Steel Truss Coupling Beams
Yao Cui, Qi Tang, Tianjiao Wu, Taichiro Okazaki, Tao Wang
Journal of Structural Engineering, 148, 9, American Society of Civil Engineers (ASCE), Sep. 2022, [Peer-reviewed]
English, Scientific journal

SEISMIC PERFORMANCE OF A LARGE STEEL UNIT HOUSE FURBISHED WITH EXTERNAL WALL PANELS
Ryosuke MATSUDA, Taichiro OKAZAKI, Takuya NAGAE, Tomohiro MATSUMIYA, Noriyuki TAKAHASHI, Yoshikazu KANZAKI, Takahiro FUKUI, Toshihiko IIJIMA, Yoshiro KIRIYAMA, Koichi KAJIWARA
AIJ Journal of Technology and Design, 28, 69, 679, 684, Architectural Institute of Japan, 20 Jun. 2022, [Peer-reviewed]
Japanese, Scientific journal

Cyclic-Loading Performance of Steel Beam-to-Column Moment Connections to an I-Section Column
Martin Somarriba, Taichiro Okazaki, Junxian Zhao, Kensuke Komatsu
Journal of Structural Engineering, 148, 4, American Society of Civil Engineers (ASCE), Apr. 2022, [Peer-reviewed]
English, Scientific journal, 11746795

SHAKE TABLE TESTS TO EXAMINE THE SEISMIC PERFORMANCE OF STEEL UNIT HOUSES
Ryosuke MATSUDA, Taichiro OKAZAKI, Takuya NAGAE, Tomohiro MATSUMIYA, Yoshikazu KANZAKI, Takahiro FUKUI, Toshihiko IIJIMA, Yoshiro KIRIYAMA, Koichi KAJIWARA
AIJ Journal of Technology and Design, 28, 68, 209, 214, Architectural Institute of Japan, 20 Feb. 2022, [Peer-reviewed]
Japanese, Scientific journal

Seismic performance of steel chevron braced frames designed according to Japanese practice
Akiri Seki, Keisuke Inoue, Taichiro Okazaki, Shogo Hashioka, Hayato Asada
Journal of Constructional Steel Research, 189, 107066, 107066, Elsevier BV, Feb. 2022, [Peer-reviewed]
English, Scientific journal, 11746794

Pixel‐level multicategory detection of visible seismic damage of reinforced concrete components
Zenghui Miao, Xiaodong Ji, Taichiro Okazaki, Noriyuki Takahashi
Computer-Aided Civil and Infrastructure Engineering, 1, 18, Wiley, 15 Feb. 2021, [Peer-reviewed]
English, Scientific journal, 31693108

INFLUENCE OF VISCOUS DAMPING MODEL ON TIME-HISTORY RESPONSE ANALYSIS OF ELASTIC-PLASTIC SYSTEMS (PART 1): COMPARISON OF DAMPING MODELS
Sho FUKUTOMI, Taichiro OKAZAKI, Ryota MATSUI, Tetsuhiro ASARI
Journal of Structural and Construction Engineering (Transactions of AIJ), 85, 778, 1555, 1563, Architectural Institute of Japan, Dec. 2020, [Peer-reviewed], [Corresponding author]
Japanese, Scientific journal, 11746794

Full-Scale Testing and Design of Special Truss Moment Frames for High-Seismic Areas
Shih-Ho Chao, Chatchai Jiansinlapadamrong, Sanputt Simasathien, Taichiro Okazaki
Journal of Structural Engineering, 146, 3, 04019229, 04019229, American Society of Civil Engineers (ASCE), Mar. 2020, [Peer-reviewed]
English, Scientific journal

Numerical Analysis Focusing on Stiffness Deterioration Behavior of Composite Beam Subjected to Cyclic Deformations.
Yusuke Nonoyama, Takuya Nagae, Taichiro Okazaki, Tomohiro Matsumiya, Noriyuki Takahashi, Koichi Kajiwara, Hiroshi Nakazawa, Tadashi Mikoshiba
AIJ Journal of Technology and Design, 26, 62, 153, 158, Feb. 2020, [Peer-reviewed]
Japanese, Scientific journal, 11746794

Response of hybrid isolation system during a shake table experiment of a full scale isolated building
Camila B. Coria, Keri L. Ryan, Eiji Sato, Tomohiro Sasaki, Taichiro Okazaki
Earthquake Engineering and Structural Dynamics, 47, 12, 2214, 2232, Sep. 2018, [Peer-reviewed]
English, Scientific journal, A full-scale 5-story steel moment frame building was subjected to a series of earthquake excitations using the E-Defense shake table in August, 2011. For one of the test configurations, the building was seismically isolated by a hybrid system of lead-rubber bearings and low friction roller bearings known as cross-linear bearings, and was designed for a very rare 100 000-year return period earthquake at a Central and Eastern US soil site. The building was subject to 15 trials including sinusoidal input, recorded motions and simulated earthquakes, 2D and 3D input, and a range of intensities including some beyond the design basis level. The experimental program was one of the first system-level full-scale validations of seismic isolation and the first known full-scale experiment of a hybrid isolation system incorporating lead-rubber and low friction bearings. Stable response of the hybrid isolation system was demonstrated at displacement demands up to 550 mm and shear strain in excess of 200%. Torsional amplifications were within the new factor stipulated by the code provisions. Axial force was observed to transfer from the lead-rubber bearings to the cross-linear bearings at large displacements, and the force transfer at large displacements exceeded that predicted by basic calculations. The force transfer occurred primarily because of the flexural rigidity of the base diaphragm and the larger vertical stiffness of the cross-linear bearings relative to the lead-rubber bearings.

Effect of out-of-plane stiffness and strength on buckling strength of hss brace with single-shear bolted joints
Hayato Asada, Taichiro Okazaki, Tsuyoshi Tanaka, Saya Nakai, Shogo Hashioka
Journal of Structural and Construction Engineering, 83, 744, 309, 319, Feb. 2018, [Peer-reviewed]
Japanese, Scientific journal, © 2018 Architectural Institute of Japan. All rights reserved. A typical bracing connection for hollow-structural-section (HSS) braces comprises a flat plate welded to the brace, a gusset plate, and a single-shear bolted joint between the flat plate and gusset plate. Where such bracing connection is adopted, the rotational stiffness and strength of the bracing connection must be taken into account to evaluate the brace strength in compression. This paper proposes analysis models for this problem, derives buckling strength formulae, and verifies the formulae with monotonie loading tests. Validated finite element models are used to conduct an extensive parametric study to verify the formulae over a wide range of geometrical properties. The proposed formulae predicted the buckling modes for 110 of 118 cases and estimated the brace strength within a coefficient of variation of 3.7% and error margin of 10% for the range of properties examined.

Panelized Residential Roof System. I: Structural Design
Susan C. Mantell, Giovanni L. Di Muoio, Jane H. Davidson, Carol K. Shield, Brian J. Siljenberg, Taichiro Okazaki
Journal of Architectural Engineering, 23, 4, 04017020-1, 04017020-16, American Society of Civil Engineers (ASCE), 01 Dec. 2017, [Peer-reviewed]
English, Scientific journal, Two roof panel designs for residential applications were developed to span from ridge to soffit without intermediate supports. The two designs, the truss core and the stiffened plate, incorporate both structural and insulation features such that a conditioned attic space can be achieved. The structural component of the truss-core and stiffened-plate panels is fabricated from steel webs laser welded to steel face sheets. The truss core includes an exterior (roof side) and interior (attic side) face sheet, whereas the stiffened plate includes only an interior face sheet. A separate polyurethane foam insulating layer is located on either the panel interior or exterior face. Structural performance requirements are developed from residential building codes for web failure, flexural capacity, and deflection. The structural analysis includes dead, live, and wind loads for all three U.S. climate zones. A model for panel performance was developed and validated through prototype panel tests. Truss-core and stiffened-plate panel designs were identified that satisfy the loading requirements for horizontal spans ranging from 3 to 8 m. Stiffened-plate panels are generally lighter weight than truss-core panels by 10-25%. However, only the truss-core panel satisfies the most extreme loading case for 8-m roof spans.

Seismic behavior and fragility curves of replaceable steel coupling beams with slabs
Xiaodong Ji, Yandong Wang, Junshan Zhang, Taichiro Okazaki
ENGINEERING STRUCTURES, 150, 622, 635, ELSEVIER SCI LTD, Nov. 2017, [Peer-reviewed]
English, Scientific journal, Replaceable steel coupling beams (RSCB) have been proposed as an alternative to conventional reinforced concrete (RC) coupling beams for enhanced seismic resiliency of coupled wall systems. This paper presents a series of quasi-static tests conducted to examine the seismic behavior of RSCBs with RC slabs and to identify reasonable slab configurations that can minimize the damage to RC slabs. A total of five large-scale specimens were designed and tested. The first four specimens adopted the same end plate link-to-beam connection but adopted different types of RC slabs, including a composite slab, bearing slab, isolated slab or slotted slab. The fifth specimen adopted splice plate link-to-beam connection and a bearing slab. The test results indicate that all specimens developed a large inelastic rotation capacity of more than 0.05 rad with stable hysteretic response. The presence of RC slabs is found to have limited effect on the shear strength and inelastic rotation capacity of RSCBs. Some types of RC slabs increased the initial elastic stiffness of RSCBs, but in the plastic stage, none of the slabs affected the loading or unloading stiffness. Among those four types, of slabs, the composite slab suffered the most significant damage, as a result of pulling out of shear studs and subsequent pouching failure of the slab. Compared with the bearing slab or slotted slab, the isolated slab developed much fewer and smaller cracks, which should allow for easier repair. Based on the observations of this test and previous tests, four damage states for RSCBs were identified, corresponding to different repair methods. Fragility curves of RSCBs at various damage states were developed, which can provide the criteria for seismic performance assessment of RSCBs. (C) 2017 Elsevier Ltd. All rights reserved.

Bolted Built-Up Columns Constructed of High-Strength Steel under Combined Flexure and Compression
Xuchuan Lin, Taichiro Okazaki, Kazuhiro Hayashi, Masayoshi Nakashima
JOURNAL OF STRUCTURAL ENGINEERING, 143, 2, 04016159, ASCE-AMER SOC CIVIL ENGINEERS, Feb. 2017, [Peer-reviewed]
English, Scientific journal, New high-strength structural steel, named H-SA700, is utilized to achieve a structural system that enables continuous use after very large earthquakes. Columns are built up of H-SA700 plates using bolts only, and bolted connections are adopted extensively for easier replacement or reuse of structural components. An analytical study is performed to predict three distinctive local buckling modes of the column and estimate its elastic flexural stiffness, yield strength, and maximum strength subjected to combined flexure and compression. Cyclic loading behavior of the column is examined through five half-scale specimens, which vary with axial force, bolt pitch, and loading direction (about major or minor axis). The columns achieve a very large elastic rotation, approximately 0.02 rad at the axial force ratio of 0.2, and a maximum bending strength surpassing the plastic moment of the reduced section accounting for bolt holes without fracture. The proposed equations predict the local buckling modes well and present a reasonably conservative estimation on the column strength subjected to combined flexure and compression. (C) 2016 American Society of Civil Engineers.

Cyclic Behavior of Replaceable Steel Coupling Beams
Xiaodong Ji, Yandong Wang, Qifeng Ma, Taichiro Okazaki
JOURNAL OF STRUCTURAL ENGINEERING, 143, 2, 04016169, ASCE-AMER SOC CIVIL ENGINEERS, Feb. 2017, [Peer-reviewed]
English, Scientific journal, For improving the seismic resiliency of coupled shear wall systems, a type of replaceable steel coupling beam was developed, which consists of a central fuse shear link connecting to steel beam segments at its two ends. Inelastic deformation is concentrated in the shear link during a severe earthquake, and the damaged links can be replaced easily as specialized link-to-beam connections are adopted. This paper presents a series of quasi-static tests conducted to examine the seismic behavior and replaceability of the replaceable coupling beams. A total of four large-scale specimens were designed and tested, where different types of beam-to-link connections were adopted, including end plate, splice plate, bolted web, and adhesive web. All specimens fully developed the shear strength of the fuse links and showed large inelastic rotation capacity of no less than 0.06rad, except for the specimen with the adhesive web connection, which failed at an early stage. The specimen with the end plate connection had inelastic deformation concentrated in the shear link, showing very stable hysteresis behavior. Slippage of high-strength bolts was observed at the splice plate and bolted web connections, which led to increased deformation and pinching in hysteresis loops of coupling beams. Interestingly, at a coupling beam rotation exceeding 0.01rad, a large axial force developed in the steel coupling beams, the maximum value of which reached approximately a quarter to half of the axial yield strength of the shear link. In addition, on-site replacement of shear links was demonstrated after the coupling beam specimens experienced 0.02-rad rotation. The end plate connection was replaced within the shortest time, whereas the bolted web connection was able to accommodate the largest residual deformation. (C) 2016 American Society of Civil Engineers.

Seismic Simulation of an Integrated Ceiling-Partition Wall-Piping System at E-Defense. I: Three-Dimensional Structural Response and Base Isolation
Keri L. Ryan, Siavash Soroushian, E. Manos Maragakis, Eiji Sato, Tomohiro Sasaki, Taichiro Okazaki
JOURNAL OF STRUCTURAL ENGINEERING, 142, 2, ASCE-AMER SOC CIVIL ENGINEERS, Feb. 2016, [Peer-reviewed]
English, Scientific journal, The seismic response of a full-scale, 5-story steel moment frame building in base-isolated and fixed-base configurations with an integrated suspended ceiling-partition wall-sprinkler piping system that was shaken at E-Defense is critically assessed. Horizontal floor accelerations were constrained by the isolation systems to relatively low levels, which allowed observation of damage to the integrated system that was directly related to the vertical component of input acceleration. The floor slabs exhibited single mode vibration at their natural periods with widely varying effective damping. Peak vertical accelerations were amplified by an average factor ranging from 3 to 6 from the table to the middle of the floor slabs, at which amplification factors increased as slab vibration periods lengthened. Damage to the ceiling-partion-piping components initiated at slab accelerations of approximately 2 g and became extensive for slab accelerations exceeding 5 g. These metrics establish target vertical accelerations for achieving desired performance objectives. (C) 2015 American Society of Civil Engineers.

Cyclic Behavior of Very Short Steel Shear Links
Xiaodong Ji, Yandong Wang, Qifeng Ma, Taichiro Okazaki
JOURNAL OF STRUCTURAL ENGINEERING, 142, 2, 04015114, ASCE-AMER SOC CIVIL ENGINEERS, Feb. 2016, [Peer-reviewed]
English, Scientific journal, A replaceable coupling beam is proposed comprising of steel hybrid shear links that are shorter than typical shear links in eccentrically braced frames (EBFs). Cyclic loading tests were conducted to examine the behavior of these very short shear links. The test variables included the steel type, length ratio, web stiffener configuration, and loading protocol. The link specimens showed two types of failure modes: link web fracture and fracture at the weld connecting link flange to end plate. The link specimens had an inelastic rotation capacity of approximately 0.14 rad, which is significantly larger than the capacity assumed for EBF links. Links using LY225 steel instead of Q235 steel achieved a 25% increase in inelastic rotation and 44% increase in cumulative plastic rotation. The overstrength factors of the very short shear links reached 1.9, significantly exceeding 1.5, which is the value assumed for EBF links by design provisions. Analysis suggests that large overstrength can develop in very short shear links due to the contribution of flanges and cyclic hardening of web steel under large plastic strains. In addition, axial deformation was measured as the links underwent inelastic shear deformation. (C) 2015 American Society of Civil Engineers.

Seismic Simulation of an Integrated Ceiling-Partition Wall-Piping System at E-Defense. II: Evaluation of Nonstructural Damage and Fragilities
Siavash Soroushian, E. Manos Maragakis, Keri L. Ryan, Eiji Sato, Tomohiro Sasaki, Taichiro Okazaki, Gilberto Mosqueda
JOURNAL OF STRUCTURAL ENGINEERING, 142, 2, 04015131, ASCE-AMER SOC CIVIL ENGINEERS, Feb. 2016, [Peer-reviewed]
English, Scientific journal, A full-scale, 5-story steel moment frame building in base-isolated and fixed-base configurations was subjected to a number of ground motions using the E-Defense shake table. In these experiments, more than 84 m(2) (900 ft(2)) of suspended ceiling with lay-in tiles, 90 m (300 linear ft) of partition walls with individual lengths varying from 1.5 to 9.8 m (5 to 32 ft), and three sprinkler branch lines were installed below the fifth and sixth (roof) floors of the building. Because the horizontal floor accelerations were generally constrained to relatively low values by the base isolation system, several damage states related to vertical floor system acceleration were observed. One key observation is that use of lateral bracing with compression posts did not improve the seismic response of suspended ceilings when subjected to strong vertical excitation. Acceleration amplification factors of the ceiling-partition-partition components relative to structural floor accelerations were computed. The code-prescribed amplification factors for the design of nonstructural components was consistent with the observed amplification in the horizontal direction, but unconservative in the vertical direction, because the code neglects the additional amplification produced by slab vibration. (C) 2015 American Society of Civil Engineers.

Seismic simulation of integrated nonstructural systems at E-Defense, Part 1: Influence of 3D structural response and base isolation
Keri L. Ryan, Siavash Soroushian, E. Manos, Maragakis, Eiji Sato, Tomohiro Sasaki, Taichiro Okazaki
Journal of Structural Engineering, American Society of Civil Engineers, 142, 2, 04015131, Feb. 2016, [Peer-reviewed]
English, Scientific journal

Improved Link-to-Column Connections for Steel Eccentrically Braced Frames
Taichiro Okazaki, Michael D. Engelhardt, Jong-Kook Hong, Chia-Ming Uang, Apostolos Drolias
JOURNAL OF STRUCTURAL ENGINEERING, 141, 8, 04014201, ASCE-AMER SOC CIVIL ENGINEERS, Aug. 2015, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Link-to-column connections in steel eccentrically braced frames must be capable of sustaining large cyclic forces and inelastic rotations. United States code provisions require that satisfactory performance of link-to-column connections be verified by testing under a prescribed loading protocol. However, there are few link-to-column connection details that have satisfied these testing criteria. This paper describes a pilot investigation of two promising link-to-column connection details, as follows: (1) the fillet welded connection, which uses fillet welds or a combination of fillet and groove welds between the link and the column flange; and (2) the supplemental web doubler connection, which reinforces the connection region using a pair of doubler plates in the first link web panel next to the column, parallel to but offset from the link web. These two details showed excellent performance in a series of eight tests. This paper describes these link-to-column connection details, summarizes the results of cyclic loading tests, and discusses design issues and approaches for these connections. (C) 2014 American Society of Civil Engineers.

Link-to-Column Connection with Supplemental Web Doublers in Eccentrically Braced Frames
Jong-Kook Hong, Chia-Ming Uang, Taichiro Okazaki, Michael D. Engelhardt
JOURNAL OF STRUCTURAL ENGINEERING, 141, 8, 04014200, ASCE-AMER SOC CIVIL ENGINEERS, Aug. 2015, [Peer-reviewed]
English, Scientific journal, When an eccentrically braced frame configuration requires that the links be connected to the columns, standard seismic guidelines offer little guidance on the link-to-column connection design. Recent testing showed that several welded moment connection details that have been developed after the 1994 Northridge earthquake for special moment frames still cannot prevent brittle fracture in the link flange groove welds. In support of an experimental study on the development of reliable link-to-column connection details, the supplemental web doubler connection is proposed. The connection uses a pair of partial-height doubler plates that are parallel to and offset from the web in the link panel next to the column. Finite-element analyses were conducted to guide the development of design requirements, including the minimum reinforced length, minimum supplemental doubler thickness, and weld design requirement. A closed-form solution, with some minor adjustment based on the finite-element analysis results, for the calculation of the required shear force in the supplemental doublers is also proposed. A step-by-step design procedure is presented. (C) 2014 American Society of Civil Engineers.

Bolted beam-to-column connections for built-up columns constructed of H-SA700 steel
Xuchuan Lin, Taichiro Okazaki, Masayoshi Nakashima
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, 101, 469, 481, ELSEVIER SCI LTD, Oct. 2014, [Peer-reviewed]
English, Scientific journal, A research program is underway to develop a new structural system using a high-strength structural steel called H-SA700. In this system, columns are built up of H-SA700 plates using bolts only, and bolted connections are used extensively to allow structural components to be replaced or reused. Bolted beam-to-column connections using an end plate are developed for the system. Bolted stiffeners are devised to control yielding and local distortion of the column against local tension delivered by the beams. Four specimens, two with stiffeners proposed in this study and two without stiffeners, are tested under quasi-static cyclic loading. Finite element simulation is carried out to allow more detailed investigation on the yielding distribution in the connection. The specimens with the proposed stiffeners avoid the yielding and notable local distortion that occurred with the absence of the stiffeners. It is found that with the aid of the proposed stiffeners, the built-up column of H-SA700 steel would remain elastic and thus reusable even after major earthquakes. Design equations are presented to estimate the stiffness of the connection, the strength of the column against local tension, and the shear yielding of the panel zone. (C) 2014 Elsevier Ltd. All rights reserved.

Beam-to-Column COnnections for Bolted Built-Up Columns made of H-SA700 Steel
Kasuhiro Hayashi, Taichiro Okazaki, Xuchuan Lin, Masayoshi Nakashima
Steel Construction Engineering, Japanese Society of Steel Construction, 21, 82, 39, 50, Jun. 2014, [Peer-reviewed]
Japanese, Scientific journal

Stability of beams in steel eccentrically braced frames
Gul Yigitsoy, Cem Topkaya, Taichiro Okazaki
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, 96, 14, 25, ELSEVIER SCI LTD, May 2014, [Peer-reviewed]
English, Scientific journal, When an eccentrically braced frame (EBF) is subjected to a severe seismic event, large axial force and bending moments are produced in the beam outside of the link Designers face significant difficulties in meeting the capacity design requirement to keep these beams elastic. On the other hand, previous research suggests that controlled yielding in the beams is not detrimental to EBF performance as long as stability of the beam is maintained. A computational study was undertaken to investigate the stability of cyclically loaded EBFs. A total of 51 EBF sub-assemblage models, none of which satisfies the capacity design requirement, were selected and investigated through three-dimensional, nonlinear finite element analysis. The results indicate that the link overstrength factor should be a function of the link length for performing capacity design of the beam outside of the link This is because flexure yielding links, which are more problematic to beam stability, tend to develop smaller overstrength compared to shear yielding links. Furthermore, designs with demand-to-capacity ratios greater than unity were found to be viable provided that the stability of the beam is maintained by making use of a slenderness limit developed herein. (C) 2014 Elsevier Ltd. All rights reserved.

Effect of vertical stiffness and foundation uplift on the seismic response of building structures
Tetsuhiro Asari, Daisuke Ujiie, Mitsumasa Midorikawa, Taichiro Okazaki
Journal of Structural and Construction Engineering, 79, 705, 1569, 1578, Architectural Institute of Japan, 2014, [Peer-reviewed]
Japanese, Scientific journal, Five-degrees-of-freedom models that account for uplift, rocking, and sway of the foundation, in addition to horizontal and vertical deformation of the superstructure, were used to study the beneficial effect of foundation uplift to reduce the seismic damage to building structures. The elastic models accounted for geometric nonlinearity and expressed soil-foundation interaction as a function of contact area. The nonlinear models were subjected to a suite of ground motions. The results indicated that the vertical component of ground motions does not significantly affect the horizontal response of the superstructure and that the vertical response of the superstructure is produced primarily by foundation uplift.

Out-of-Plane Stability of Buckling-Restrained Braces Placed in Chevron Arrangement
Tsuyoshi Hikino, Taichiro Okazaki, Koichi Kajiwara, Masayoshi Nakashima
JOURNAL OF STRUCTURAL ENGINEERING, 139, 11, 1812, 1822, ASCE-AMER SOC CIVIL ENGINEERS, Nov. 2013, [Peer-reviewed], [Corresponding author]
English, Scientific journal, Large-scale shake table tests were performed at E-Defense to examine the out-of-plane stability of buckling-restrained braces (BRBs). Two specimens were subjected repeatedly to a near-fault ground motion with increasing amplification. The test specimens comprised a single-bay, single-story steel frame and a pair of BRBs placed in a chevron arrangement. The specimens were not braced at the brace-to-beam intersection in order to produce a condition where the BRBs were susceptible to out-of-plane instability. Standard BRBs were used in the first specimen, while BRBs with a flexible segment at each end of the steel core were used in the second specimen. A simple stability model predicted the BRBs in the second specimen to fail because of out-of-plane buckling. The first specimen exhibited excellent ductility during the shake table tests, while the second specimen developed severe out-of-plane deformation that compromised the ductility of the BRBs. Based on the experimental observations and the stability model, a methodology is proposed to evaluate bracing requirements at the brace-to-beam intersection.

Experimental Performance of Steel Braced Frames Subjected to Bidirectional Loading
Keith D. Palmer, Charles W. Roeder, Dawn E. Lehman, Taichiro Okazaki, Carol Shield
JOURNAL OF STRUCTURAL ENGINEERING, 139, 8, 1274, 1284, ASCE-AMER SOC CIVIL ENGINEERS, Aug. 2013, [Peer-reviewed]
English, Scientific journal, Concentrically braced frames (CBFs) are stiff, strong systems frequently used to resist seismic loading. Special CBF (SCBF) behavior is dominated by brace buckling, while buckling restrained braced frames (BRBFs) develop tensile and compressive yielding and avoid brace buckling. Both systems are widely used in seismic design, and both have a number of specific design issues. This paper describes a first of its kind, 2-story, 1-bay by 1-bay frame tested at the University of Minnesota Network for Earthquake Engineering Simulation facility to examine the large-displacement, bidirectional behavior of SCBFs and BRBFs with realistic boundary conditions and to verify the design approach. The SCBF had rectangular hollow steel section (HSS) braces in a single-story X configuration, and the BRBF used a single-diagonal configuration. The design of the gusset plates for the HSS braces followed a previously proposed balanced design procedure with an elliptical clearance to permit out-of-plane rotation caused by brace buckling. The single-story X-brace SCBF concentrated damaged into one-half the brace length, and the first HSS brace fractured at 2% story drift. The BRBF gusset-plate design followed current design standards, and two of the BRB cores fractured at 3.6 and 4.2% story drift prior to any instability in the BRB or system. The SCBF sustained limited damage to the beams and columns; however, the BRBF had much more significant damage to these members because of larger deformations and BRBF behavior. The results indicate that these systems have a stable response to large cyclic deformations and the impact of bidirectional loading on the measured response was minimal.

Dynamic response of a chevron concentrically braced frame
Taichiro Okazaki, Dimitrios G. Lignos, Tsuyoshi Hikino, Koichi Kajiwara
Journal of Structural Engineering (United States), 139, 4, 515, 525, 01 Apr. 2013, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Large-scale shake table tests were conducted at E-Defense, Japan, to examine the dynamic response of a steel concentrically braced frame. The specimen was a single-bay, single-story frame with a pair of square hollow structural section braces placed in a chevron arrangement. The gusset plates connecting the brace to the framing elements were provided with an elliptic fold line to accommodate out-of-plane rotation of the brace in compression. The specimen was subjected repeatedly to a unidirectional ground motion with increasing magnitude until the braces buckled and eventually fractured. The bracing connections performed as intended
the gusset plates folded out of plane, and no crack was observed in the gusset plate or in the critical welds. Consequently, the test results demonstrated excellent performance of the bracing connections. Elastic deformation of the beam prevented the braces from developing their full tensile strength. Yielding in the middle of the beam, which was predicted by monotonic loading analysis, did not occur. The specimen response was reproduced by a numerical model using fiber elements. This model was able to predict the occurrence of brace buckling and fracture and thereby accurately trace the dynamic behavior of the frame. © 2013 American Society of Civil Engineers.

E-defense tests on the seismic performance of beam-to-column moment frame connections in high-rise steel buildings
Taichiro Okazaki, Tomohiro Matsumiya, Takuya Nagae, Kunio Fukuyama, Takahito Inoue, Masayoshi Nakashima
Journal of Structural and Construction Engineering, 78, 685, 569, 578, Mar. 2013, [Peer-reviewed], [Lead author, Corresponding author]
Japanese, Scientific journal, Two full-scale steel moment-resisting frames were constructed and tested at E-Defense to examine the performance of high-rise buildings subjected to long-period ground motions. Frame 1 adopted typical design and detailing from the 1970's employing both field- welded and shop-welded details for the moment frame connections. Frame 2 was identical to Frame 1 except that all connections were field-welded and upgraded using three strengthening methods. A number of connections in Frame 1 fractured during a simulated long- period motion. No damage was observed in Frame 2 until the same motion was repeated multiple times. The performance of field- welded connections in existing high-rise buildings and the effectiveness of upgrade methods are discussed.

Damage to Steel Buildings Observed after the 2011 Tohoku-Oki Earthquake
Taichiro Okazaki, Dimitrios G. Lignos, Mitsumasa Midorikawa, James M. Ricles, Jay Love
EARTHQUAKE SPECTRA, 29, S1, S219, S243, EARTHQUAKE ENGINEERING RESEARCH INST, Mar. 2013, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, A joint U.S.-Japan reconnaissance team examined the damage to steel building structures caused by the 2011 Tohoku-oki earthquake. In the city of Sendai, where the peak horizontal ground acceleration exceeded 1 g, the majority of steel buildings performed well. Buildings that used older cladding systems for external finish sustained damage to their claddings even if their structural performance was excellent. Damage to a few braced frames offer insight into the seismic design of bracing connections. In areas attacked by the violent tsunami, many steel buildings stood upright after the tsunami subsided, although these buildings lost much of their external and internal finishes along with their contents. These steel buildings did not provide safe shelter for tsunami evacuation when the building submerged under the tsunami wave. A number of buildings suffered foundation failure, which was likely caused by scouring or liquefaction or a combination of multiple effects.

Flexural performance of bolted built-up columns constructed of H-SA700 steel
Xuchuan Lin, Taichiro Okazaki, Yu-Lin Chung, Masayoshi Nakashima
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, 82, 48, 58, ELSEVIER SCI LTD, Mar. 2013, [Peer-reviewed]
English, Scientific journal, The H-SA700 is a new high-strength structural steel that is more environmentally friendly and more suitable for mass production than conventional high-strength steel. A research program is underway to develop a new structural steel system that extends the benefits of H-SA700 steel to achieve sustainable and seismically resilient buildings. The envisioned system uses built-up columns that are fabricated from H-SA700 plates by high-strength bolts and uses these built-up columns in weld-free construction. This paper summarizes the first phase of the program, whose objective was to establish the flexural properties of the built-up columns. Three column specimens were fabricated and subjected to cyclic lateral loading. The tests demonstrated the very large elastic deformation capacity and stable inelastic behavior of H-SA700 columns. The flexural strength was not governed by fracture of the reduced section with bolt holes, but by inelastic buckling of the flanges. The strength was limited by the plastic strength of the reduced section. The test results were used to identify the key limit states and to develop a design methodology that addresses the unique behavior of the built-up columns. Finite element simulation suggested that bolt holes help distribute yielding over a wide area of the flanges, to supply some ductility and help avoid net section fracture of the flanges. (C) 2012 Elsevier Ltd. All rights reserved.

H-SA700 鋼を用いたボルトによる組立柱部材の曲げ性能
林和宏, 岡崎太一郎, 林旭川, 中島正愛
鋼構造論文集, 76, 685, 569, 578, Dec. 2012, [Peer-reviewed]
Japanese, Scientific journal

Concentric X-braced frames with HSS bracing
Keith D. Palmer, Charles W. Roeder, Dawn E. Lehman, Taichiro Okazaki, Carol K. Shield, Jacob Powell
INTERNATIONAL JOURNAL OF STEEL STRUCTURES, 12, 3, 443, 459, KOREAN SOC STEEL CONSTRUCTION-KSSC, Sep. 2012, [Peer-reviewed]
English, Scientific journal, Concentrically braced frames are stiff, strong systems frequently used to resist wind and seismic loading; in regions of high seismicity in the US special concentrically braced frames (SCBFs) are used. CBF configurations vary, but in low rise or other structures with modest levels of demands single-story, X-configured braced frames (X-braced) are commonly used. The brace sections used also vary but hollow structural sections (HSS) are the most common in the U.S. Although important, in part because low-rise structures sustain large demands, few research programs have focused on the single-story X-brace configuration. A large research program was undertaken to understand and improve the response of SCBFs with selected testing on single-story X braced SCBFs. The test matrix consisted of two, full-scale planar X-braced frame experiments and one nearly-full-scale three-dimensional X-braced frame. The tests were designed using a new design and detailing philosophy, called the Balanced Design Method. In this paper, application of this design method to the frame is investigated, with a focus on the center-splice connection. The results show that the ultimate inelastic deformation capacity of the system is less dependent on the specific design detail at this splice. Additionally, the bi-directional load testing indicated that the out-of-plane demands did not impact the system performance.

Impact of Residual Stresses and Initial Imperfections on the Seismic Response of Steel Moment Frames
Kapil Mathur, Larry A. Fahnestock, Taichiro Okazaki, Matthew J. Parkolap
JOURNAL OF STRUCTURAL ENGINEERING-ASCE, 138, 7, 942, 951, ASCE-AMER SOC CIVIL ENGINEERS, Jul. 2012, [Peer-reviewed]
English, Scientific journal, The 2010 AISC specification establishes the direct analysis method (DM) as the standard stability analysis and design procedure. Although the DM has important benefits over conventional stability design methods, the interface between the DM, the AISC seismic provisions, and the seismic design requirements in ASCE-7 is not fully established. Because the DM, which was developed for design scenarios that do not contain seismic loading, includes the effects of initial geometric imperfections and inelastic behavior owing to residual stresses, it is critical to explore the impact of these parameters on the seismic behavior of typical steel buildings. To examine these issues, a series of steel special moment-resisting frame models were subjected to monotonic pushover, cyclic pushover, and response history analyses. The observed behavior was used to draw comparisons between systems with and without residual stresses and initial imperfections. Cyclic strength degradation at beam-to-column connections was also considered to examine the potential interaction it may have with the other parameters. Whereas the well-known impact of strength degradation on cyclic stability was noted, residual stresses and initial imperfections did not have any appreciable effect on stability behavior for the systems considered. The analyses conducted in this study indicate no clear benefit to using the DM when designing regular ductile steel systems in high seismic regions and simpler design methods may be equally effective. DOI: 10.1061/(ASCE)ST.1943-541X.0000512. (C) 2012 American Society of Civil Engineers.

Local shear buckling and bearing strength in web core sandwich panels: Model and experimental validation
Casey R. Briscoe, Susan C. Mantell, Taichiro Okazaki, Jane H. Davidson
ENGINEERING STRUCTURES, 35, 114, 119, ELSEVIER SCI LTD, Feb. 2012, [Peer-reviewed]
English, Scientific journal, A model and experimental validation of shear buckling and local bearing failure of web core sandwich panels are presented. Of particular interest are steel-faced panels with stiffening metal webs and a polymer core. The metal webs provide the required panel stiffness and the foam core serves the dual purposes of preventing local buckling and providing thermal insulation. In applications, such as the building sector, in which thermal performance is crucial, the webs are thin and widely spaced to reduce conduction between the face sheets. The models of shear buckling and bearing failure account for the influence of the core material on web strength and provide closed-form solutions. The models are validated by symmetric four-point bending tests to evaluate shear buckling and asymmetric three-point bending for bearing failure. The shear buckling model predicted buckling strength to within 4% of the test results. The bearing failure model overpredicted the observed strength by 11% on average, similar to test results reported in the literature for the bearing strength of webs with no foam support. (C) 2011 Elsevier Ltd. All rights reserved.

Strength evaluation of composite structural connection with steel studs embedded in SFRCC slab
K. Hoki, Y. Luo, M. Nakashima
Journal of Structural and Construction Engineering, 77, 676, 975, 984, 2012, [Peer-reviewed]
English, The performance of high-rise steel moment frame buildings constructed in the 1970’s is examined by using the E-Defense shake-table facility. Typical design and detailing in the 1970’s are incorporated in a four-story, steel moment frame specimen. The specimen is subjected to a series of response deformations representing a high-rise building. Long-period ground motions impose a substantial number of inelastic deformations, which eventually cause fracture in the beam-to-column connections.

Design Procedure for Web Core Sandwich Panels for Residential Roofs
Casey R. Briscoe, Susan C. Mantell, Jane H. Davidson, Taichiro Okazaki
JOURNAL OF SANDWICH STRUCTURES & MATERIALS, 13, 1, 23, 58, SAGE PUBLICATIONS LTD, Jan. 2011, [Peer-reviewed]
English, Scientific journal, Panelized construction of residential buildings is gaining popularity due to the architectural and energy efficiency benefits that can be achieved. An important challenge to the design of panel structures for buildings is the balance between long-term structural performance and the thermal insulating requirement. In this study, foam core and web core panels are designed for residential roofs. Both panels are comprised of two face sheets and an insulating foam core. In the web core panel, thin metal webs that connect the face sheets are added to improve panel shear stiffness and enable longer spans. A design procedure is developed that considers R-value, panel deflection, core shear failure, bearing failure, and buckling of the face sheets and webs. The buckling model includes the ability of the foam core stiffness to restrain the buckling deformation. Panel designs are presented that provide R-5.3 m(2) K/W for roof loads of 1500, 2000, and 3000 N/m(2), corresponding to climate zones in the US. It is demonstrated that the web core panel can be designed for these structural and thermal requirements with unsupported span lengths as long as 7 m, while span lengths for foam core panels are limited to 4 m. Web shear buckling and R-value are the two performance criteria that limit panel span length and depth.

Nonlinear Finite-Element Analysis of Critical Gusset Plates in the I-35W Bridge in Minnesota
Minmao Liao, Taichiro Okazaki, Roberto Ballarini, Arturo E. Schultz, Theodore V. Galambos
JOURNAL OF STRUCTURAL ENGINEERING-ASCE, 137, 1, 59, 68, ASCE-AMER SOC CIVIL ENGINEERS, Jan. 2011, [Peer-reviewed]
English, Scientific journal, Reported evidence suggests that failure of gusset plates initiated the collapse of the I-35W Bridge in Minneapolis, Minnesota. The particular gusset plates were at a panel point designated as U10. Therefore, an analytical investigation was conducted on the condition of the U10 gusset plates at the time of bridge collapse. The forces delivered to panel point U10 were reproduced using available information of the bridge. These forces were introduced to detailed nonlinear three-dimensional finite-element models to calculate stress and strain states of the gusset plates. The results indicate that substantial portions of the U10 gusset plates were yielded at the time of collapse, confirming earlier findings from federal and state investigations. Weight increase due to past deck reconstruction and construction material and equipment staged on the day of collapse, along with insufficient thickness of the gusset plate, were identified as the main contributing factors to the substantial yielding. The results also suggest that the interaction of compression and shear played an important role in the gusset plate failure.

Reduced Link Sections for Improving the Ductility of Eccentrically Braced Frame Link-to-Column Connections
Jeffrey W. Berman, Taichiro Okazaki, Heidrun O. Hauksdottir
JOURNAL OF STRUCTURAL ENGINEERING, 136, 5, 543, 553, ASCE-AMER SOC CIVIL ENGINEERS, May 2010, [Peer-reviewed]
English, Scientific journal, Eccentrically braced frames (EBFs) are desirable seismic load resisting systems as they combine the high elastic stiffness of concentrically braced frames with the ductility and stable energy dissipation of moment resisting frames. EBFs with links attached to the columns are particularly appealing for architectural flexibility as they provide multiple locations for placement of doors and hallways. However, previous research has shown that link-to-column connections are prone to failure at low drift levels, due to their susceptibility to fracture at the link flange-to-column welds. This paper investigates the application of the reduced beam section concept for links in eccentrically braced frames to enhance the ductility of link-to-column connections. A design procedure for link section reduction is proposed and preliminary finite-element analyses are conducted on a shear link with various reduced section geometries. A parametric study performed on an array of links having various cross sections and lengths suggests that the reduced link section may substantially reduce the plastic flange strains at the link ends, which can improve the fracture life. The reduction in plastic flange strains is found to be significant for all links, with larger reductions for intermediate and flexural links. Furthermore, the detrimental kinking deformation of the flanges, caused by the large rotation demands in shear links, is moved away from the column face when reduced sections were used. While the analysis results show promise, experimental verification is recommended before the proposed design procedure can be implemented in practice.

Web crippling strength of a steel sandwich panel with V-shaped webs
Taichiro Okazaki, Brian J. Siljenberg, Carol K. Shield, Susan C. Mantell
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, 65, 8-9, 1721, 1730, ELSEVIER SCI LTD, Aug. 2009, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Steel sandwich panels with V-shaped web flutes (V-core panels) serve the structural functions of a proposed energy-efficient roof system for residential construction. Due to its intended use as a flexural member spanning between a ridge beam and a structural wall, and required slender webs for weight considerations, web crippling under end one-flange loading is a critical strength limit state for the V-core panels. Although the 2001 North American Specification for the Design of Cold-Formed Steel Structural Members provides a design procedure to address web crippling, those design rules were developed for members whose cross sections are different from that of V-core panels. Consequently, nine specimens were tested to collect data on V-core panels subjected to end one-flange loading. Test observations suggested that V-core panels behave very similarly to multi-web decks that are strapped and unfastened to the supports. Experimental data reported in the literature was used to modify the web crippling strength equation in the Specification to reflect these particular conditions. The modified equation was found to adequately predict the measured web crippling strength of V-core panels. (C) 2009 Elsevier Ltd. All rights reserved.

Experimental investigation of link-to-column connections in eccentrically braced frames
Taichiro Okazaki, Michael D. Engelhardt, Apostolos Drolias, Eric Schell, Jong-Kook Hong, Chia-Ming Uang
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, 65, 7, 1401, 1412, ELSEVIER SCI LTD, Jul. 2009, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, The design of link-to-column connections in seismic-resistant eccentrically braced frames remains a largely unresolved problem. In order to address this problem, twenty-four large-scale specimens were tested under cyclic loading. The test parameters included the connection detail, link length, link section, and cyclic loading protocol. The test results suggest that link-to-column connections are susceptible to fracture at the link flange welds, regardless of the link length. A large number of specimens failed prematurely, before meeting the plastic link rotation requirement in US code provisions. However, two promising link-to-column connection details were developed as an outcome of this research. The new connection details include a detail using all-around fillet welds between the link and the column flange, and a reinforced connection detail that welds a pair of stiffeners in the first link web panel next to the column, parallel to the link web. Test specimens using either of these two details were able to exceed the plastic link rotation requirement. (c) 2009 Elsevier Ltd. All rights reserved.

Cyclic loading behavior of EBF links constructed of ASTM A992 steel
Taichiro Okazaki, Michael D. Engelhardt
JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH, 63, 6, 751, 765, ELSEVIER SCI LTD, Jun. 2007, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Cyclic loading tests were conducted to study the behavior of link beams in steel eccentrically braced frames. A total of thirty-seven link specimens were constructed from five different wide-flange sections, all of ASTM A992 steel, with link length varying from short shear yielding links to long flexure yielding links. The occurrence of web fracture in shear yielding link specimens led to further study on the cause of these fractures. Since the link web fracture appeared to be a phenomenon unique to modern rolled shapes, the potential role of material properties on these fractures is discussed. Based on the test data, a change in the flange slenderness limit is proposed. The link overstrength factor of 1.5, as assumed in the current U.S. code provisions, appears to be reasonable. The cyclic loading history used for testing was found to significantly affect link performance. Test observations also suggest new techniques for link stiffener design and detailing for link-to-column connections. (c) 2006 Elsevier Ltd. All rights reserved.

Interaction between cladding and structural frame observed in a full-scale steel building test
Taichiro Okazaki, Masayoshi Nakashima, Keiichiro Suita, Tomohiro Matusmiya
EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS, 36, 1, 35, 53, JOHN WILEY & SONS LTD, Jan. 2007, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, Interaction between the external wall cladding and the seismic load resisting frame was examined in a full-scale cyclic loading test of a three-storey steel building structure. The building specimen had Autoclaved Lightweight Concrete (ALC, also designated as Autoclaved Aerated Concrete) panels installed and anchored to the structural frame as external wall cladding, using a standard Japanese method developed following the 1995 Kobe earthquake. ALC panelling is among the most widely used material for claddings in Japan. In the test, the ALC panel cladding contributed little to the stiffness and strength of the overall structure, even under a very large storey drift of 0.04 rad. No visible damage was noted in the ALC panels other than minor cracks and spalling of the bottom of the panels In the first storey. Consequently, in a Japanese steel building with properly installed ALC panel cladding, the structural frame is likely to be little affected by its cladding, and the ALC panels are capable of accommodating the maximum storey drift generally considered in structural design without sustaining discernible damage. Copyright (C) 2006 John Wiley & Sons, Ltd.

Impact of recent research findings on eccentrically braced frame design
Paul Richards, Taichiro Okazaki, Michael Engelhardt, Chia-Ming Uang
ENGINEERING JOURNAL-AMERICAN INSTITUTE OF STEEL CONSTRUCTION INC, 44, 1, 41, 53, AMER INST STEEL CONSTRUCTION, 2007, [Peer-reviewed]
English, Scientific journal

Stability requirements for beams in seismic steel moment frames
Taichiro Okazaki, Dawei Liu, Masayoshi Nakashima, Michael D. Engelhardt
JOURNAL OF STRUCTURAL ENGINEERING-ASCE, 132, 9, 1334, 1342, ASCE-AMER SOC CIVIL ENGINEERS, Sep. 2006, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, An analytical study was conducted on the cyclic loading behavior of beams in steel moment frames. Lateral-torsional buckling and local buckling were explicitly considered in the analysis. Beam cross-sectional dimensions were varied to represent a wide range of rolled wide flange shapes. The unbraced length of the beams corresponded to slenderness ratios about the weak axis ranging between 60 and 100. Based on the analyses, flange and web width-thickness limits were established that would permit the beam to achieve various target rotation capacities. These limits are presented in terms of limit curves which plot the flange width-thickness ratio against the web width-thickness ratio. The limit curves clearly show strong flange-web interaction. Different limit curves were developed for a range of target rotation angles, weak axis slenderness ratios, and residual strength levels. Postbuckling behavior and strength degradation mechanism were studied. The results of the analyses are compared against current building code requirements for beam stability in seismic steel moment frames, and the adequacy of the current code requirements are evaluated.

Experimental performance of link-to-column connections in eccentrically braced frames
Taichiro Okazaki, Michael D. Engelhardt, Masayoshi Nakashima, Keiichiro Suita
JOURNAL OF STRUCTURAL ENGINEERING, 132, 8, 1201, 1211, ASCE-AMER SOC CIVIL ENGINEERS, Aug. 2006, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, A total of 12 large-scale link-column specimens were tested to study the cyclic loading performance of link-to-column connections in eccentrically braced frames. Four different link-to-column connection types with varying configuration and welding details were tested. Each of the four connection types was tested with three different link lengths to consider a wide range of force and deformation environments at the link-to-column connection. The specimens representing the pre-Northridge practice failed after developing only half of the inelastic link rotation required in U.S. building codes. Additional connection types were tested that implemented improved welding practices, as well as specimens that implement design and detailing modifications. This included connections that used the free flange concept and connections that eliminated the weld access holes. The experimental program and key test results are presented in this paper.

Experimental study of local buckling, overstrength, and fracture of links in eccentrically braced frames
T Okazaki, G Arce, HC Ryu, MD Engelhardt
JOURNAL OF STRUCTURAL ENGINEERING-ASCE, 131, 10, 1526, 1535, ASCE-AMER SOC CIVIL ENGINEERS, Oct. 2005, [Peer-reviewed], [Lead author, Corresponding author]
English, Scientific journal, A total of 23 tests were conducted to study the cyclic loading performance of links in steel eccentrically braced frames. The objectives of these tests were to reevaluate flange slenderness limits and overstrength factors for links. The effect of loading history on link performance was also investigated. Link specimens were constructed from five different wide-flange sections, all of ASTM A992 steel, with various lengths ranging from short shear yielding links to very long flexural yielding links. In addition to providing data on the effects of flange buckling and overstrength, these tests also showed some unexpected failure modes. The paper provides an overview of this experimental investigation, describing the overall research program, as well as details of the test specimens and test results. The paper concludes with a number of design recommendations for links in eccentrically braced frames.

米国信頼性耐震設計の概要と梁の塑性変形能力の確率的評価の日米比較
日下彰宏, 加登美喜子, 岡崎太一郎
鋼構造論文集、日本鋼構造協会, 12, 45, 9, 24, Mar. 2005, [Peer-reviewed]
Japanese, Scientific journal

柱梁接合部の設計規範と構造性能に関する日米比較
松本由香, 浅井英克, 岡崎太一郎
鋼構造論文集、日本鋼構造協会, 12, 45, 87, 100, Mar. 2005, [Peer-reviewed]
Japanese, Scientific journal

Collaboration between practice and research for development of steel construction in Japan.　　　　　　　　　　　　　　　
Masayoshi Nakashima, Mikiko Kato, Taichiro Okazaki
International Journal of Steel Structures, Korean Society of Steel Construction, 4, 4, 249, 262, Dec. 2004, [Peer-reviewed]
English, Scientific journal

Longitudinal elastic waves in columns due to earthquake motion
T Nonaka, RJ Clifton, T Okazaki
INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, 18, 7-8, 889, 898, PERGAMON-ELSEVIER SCIENCE LTD, Oct. 1996, [Peer-reviewed]
English, Scientific journal, An analysis is presented of longitudinal waves in a thin elastic column. Velocity is specified at one end, and the boundary condition at the other end is expressed in terms of a range of effective impedances of an attached structure. Propagation, reflection and interference of the waves are followed by the method of characteristics. Integration of differential equations along characteristics yields the wave-induced stress, which is then applied to problems of earthquake excitation. Numerical examples are given for recorded updown ground motion of the Kobe Earthquake. Copyright (C) 1996 Elsevier Science Ltd.

3-D detailed finite element analysis of full-scale shaking table rest on a 10-story steel building　　　　　　　　　　　　　　　
Jun Fujiwara, Takuya Nagae, Tianhao Yan, Jialiang Jin, Jionghui Li, Taichiro Okazaki, Akiko Kishida, Ryota Nishi, Koichi Kajiwara, 18th World Conference on Earthquake Engineering (18WCEE), Jul. 2024, [Peer-reviewed]
English, Summary international conference

Panel zone and column response in a shake-table test on a 10-story steel moment-resisting frame
Jionghui Li, Taichiro Okazaki, Jun Fujiwara, Koichi Kajiwara, Akiko Kishida, Ryota Nishi, Takuya Nagae, Jialiang Jin, Tatsuya Asai, 18th World Conference on Earthquake Engineering (18WCEE), Jul. 2024, [Peer-reviewed], [Corresponding author]
English, Summary international conference, 31428741

Effective width of slab for composite beam at joint region　　　　　　　　　　　　　　　
Masaki Arita, Yuichi Nishida, J.Y. Richard Liew, Taichiro Okazaki, 11th International Conference on Behavior of Steel Structures in Seismic Areas (STESSA 2024), Jul. 2024, [Peer-reviewed]
English, Summary international conference

Shake-table collapse tests of a reduced-scale, 4-story steel moment resisting frame
Martin Somarriba, Jionghui Li, Taichiro Okazaki, Takuya Nagae, Tomohiro Matsumiya, 11th International Conference on Behavior of Steel Structures in Seismic Areas (STESSA 2024), Jul. 2024, [Peer-reviewed]
English, Summary international conference, 31428741

Numerical simulation of a reduced-scale, 4-story steel moment-resisting frame tested to collapse
Jionghui Li, Martin Somarriba, Taichiro Okazaki, Takuya Nagae, Ryota Matsui, 11th International Conference on Behavior of Steel Structures in Seismic Areas (STESSA 2024), Jul. 2024, [Peer-reviewed]
English, Summary international conference, 31428741

Experimental investigation of cyclic loading performance of stubby steel braces　　　　　　　　　　　　　　　
Ryota Matsui, Yoshihiro Abe, Ibrahim Abiodun Raheem, Naoki Sadanaga, Ilanildo Dias, Taichiro Okazaki, 11th International Conference on Behavior of Steel Structures in Seismic Areas (STESSA 2024), Jul. 2024, [Peer-reviewed]
English, Summary international conference

Force limiting connections to mitigate accelerations in moment resisting frames with pinned-base spines
Jessica Duncan (Duke, Bryam Astudillo, Richard Sause, James Ricles, Larry Fahnestock, Barbara Simpson, Masahiro Kurata, Yohsuke Kawamata, Taichiro Okazaki, Zhuoqi Tao, Yi Qie, 11th International Conference on Behavior of Steel Structures in Seismic Areas (STESSA 2024), Jul. 2024, [Peer-reviewed]
English, Summary international conference, 31428741

Scientific and educational impact of experimental research　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Structure、JSCA, 171, 36, 37, Jul. 2024, [Invited], [Lead author]
Japanese, Introduction other

Residual performance and geometric imperfection of structural steels after plastic deformation and strain aging　　　　　　　　　　　　　　　
Haruna Nakagawa, Fumika Arai, Shaoqi Yang, Taichiro Okazaki, Proceedings of Constructional Steel, Japan Society of Steel Construction, 30, 497, 506, Dec. 2022, [Peer-reviewed]
Japanese, Summary national conference

主題解説 (3) 米国の鋼構造規準の現状　　　　　　　　　　　　　　　
『JIS A 3305から見た国内構造基準の課題と荷重規定』構造部門（荷重）パネルディスカッション資料、2022年度日本建築学会大会（北海道）, 13, 18, Sep. 2022
Japanese, Lecture materials

Shake Table Tests to Examine the Seismic Performance of Prefabricated Steel Unit Houses
Ryosuke Matsuda, Taichiro Okazaki, Takuya Nagae, Tomohiro Matsumiya, Yoshikazu Kanzaki, Takahiro Fukui, Toshihiko Iijima, Yoshiro Kiriyama, Koichi Kajiwara, Lecture Notes in Civil Engineering, STESSA 2022: Proceedings of the 10th International Conference on Behaviour of Steel Structures in Seismic Areas, 1116, 1123, May 2022, [Peer-reviewed]
Springer International Publishing, English, Meeting report

Frame-Spine System with Force-Limiting Connections for Low-Damage Seismic-Resilient Buildings
Larry Fahnestock, Richard Sause, James Ricles, Barbara Simpson, Masahiro Kurata, Taichiro Okazaki, Yohsuke Kawamata, Zhuoqi Tao, Jessica Duke, David Rivera, Bryam Astudillo, Yi Qie, Lecture Notes in Civil Engineering, 804, 811, May 2022, [Peer-reviewed]
Springer International Publishing, English, Meeting report, 31428741

Numerical Response Estimations of a Frame-Spine-FLC System Prior to Experimental Dynamic Testing
Bryam Astudillo, David Rivera, Barbara Simpson, Larry Fahnestock, Richard Sause, James Ricles, Masahiro Kurata, Taichiro Okazaki, Yohsuke Kawamata, Zhuoqi Tao, Jessica Duke, Yi Qie, Lecture Notes in Civil Engineering, STESSA 2022: Proceedings of the 10th International Conference on Behaviour of Steel Structures in Seismic Areas, 370, 378, May 2022, [Peer-reviewed]
Springer International Publishing, English, Meeting report, 31428741

A Database for Steel Braces with Respect to Inelastic Strength and Ductility Capacity
Ryota Matsui, Zhang Yiyue, Taichiro Okazaki, Toru Takeuchi, Lecture Notes in Civil Engineering, STESSA 2022: Proceedings of the 10th International Conference on Behaviour of Steel Structures in Seismic Areas, 216, 223, May 2022, [Peer-reviewed]
Springer International Publishing, English, Meeting report

Residual Performance of Structural Steel After Cyclic Plastic Deformation and Strain Aging
Haruka Nakagawa, Kayo Taniguchi, Shaoqi Yang, Tetsuhiro Asari, Taichiro Okazaki, Lecture Notes in Civil Engineering, STESSA 2022: Proceedings of the 10th International Conference on Behaviour of Steel Structures in Seismic Areas, 157, 165, May 2022, [Peer-reviewed]
Springer International Publishing, English, Meeting report

Report on Future Direction Sessions in the 17th World Conference on Earthquake Engineering　　　　　　　　　　　　　　　
Masayuki Kohiyama, Taichiro Okazaki, Mitsuyoshi Akiyama, Tsuyoshi Ichimura, JAEE Newsletter, 11, 1, 18, 23, Apr. 2022
English, Introduction scientific journal

STUDY ON FRAGILITY FUNCTION UPDATING FOR PARTITION WALL USING IMAGE PROCESSING AND MONITORING SYSTEM
Mai UMEBAYASHI, Noriyuki TAKAHASHI, Hiroyuki CHIDA, Takuya NAGAE, Taichiro OKAZAKI, Tomohiro MATSUMIYA, Koichi KAJIWARA, Hiroshi NAKAZAWA, Yoshikazu KANZAKI, Journal of Structural Engineering B, 68B, 261, 270, Apr. 2022, [Peer-reviewed]
Architectural Institute of Japan, Japanese, Meeting report, 31428741

修業時代を振り返って　　　　　　　　　　　　　　　
岡崎太一郎, 日本免震構造協会会誌MENSHIN, 115, 1, 3, Jan. 2022, [Invited]
Japanese, Introduction scientific journal

米国のブレース構造 ―日本と違った設計法・構造計画・考え方―（特集：ブレース材・制振部材を活かした構造デザイン）　　　　　　　　　　　　　　　
岡崎太一郎, 鉄鋼技術, 33, 389, 48, 51, Oct. 2020, [Invited]
Japanese, Introduction commerce magazine

Computational study on the seismic behavior of steel chevron braced frames in Japan　　　　　　　　　　　　　　　
Ilanildo Dias, Akiri Seki, Taichiro Okazaki, 17th World Conference on Earthquake Engineering, Paper No. C001293, Sep. 2020
English, Summary international conference

Residual performance of structural steel beams after plastic deformation and strain aging　　　　　　　　　　　　　　　
Kayo Taniguchi, Shaoqi Yang, Taichiro Okazaki, Tetsuhiro Asari, 17th World Conference on Earthquake Engineering, Paper No. C004120, Sep. 2020
English, Summary international conference

Numerical simulation of fracture propagation in high-rise buildings subjected to long period-long duration earthquakes.　　　　　　　　　　　　　　　
Taichiro Okazaki, Akiri Seki, Hashini Herath, Takuya Nagae, 17th World Conference on Earthquake Engineering, Paper No. C004008, Sep. 2020, [Lead author]
Summary international conference

主題解説 (1) 学会規準・指針の成立経緯　　　　　　　　　　　　　　　
緑川光正, 松井良太, 岡崎太一郎, 『日本の鋼構造設計を世界に知ってもらうために』構造部門（鋼構造）パネルディスカッション資料、2019年度日本建築学会大会（北陸）, 4, 11, Sep. 2019
Japanese, Lecture materials

主題解説 (6) 世界に知ってもらうために　　　　　　　　　　　　　　　
岡崎太一郎, 『日本の鋼構造を世界に知ってもらうために』構造部門（鋼構造）パネルディスカッション資料, 49, 57, Sep. 2019
Japanese, Lecture materials

A computational study on the cyclic loading behavior of steel chevron braced frames　　　　　　　　　　　　　　　
Ilanildo Dias, Akiri Seki, Taichiro Okazaki, 15th Japan Earthquake Engineering Symposium, 777, 784, Dec. 2018
English, Summary international conference

Experimental behavior of chevron braced frames designed according to current practice　　　　　　　　　　　　　　　
Akiri Seki, Taichiro Okazaki, Ilanildo Dias, Hayato Asada, 15th Japan Earthquake Engineering Symposium, 795, 803, Dec. 2018
English, Summary international conference

Experimental performance of chevron steel braced frames using I-section braces.
Akiri Seki, Shuhei Usesugi, Taichiro Okazaki, Hayato Asada, Tetsuhiro Asari, Proceedings of Constructional Steel, Japan Society of Steel Construction, 26, 196, 203, Nov. 2018
Japanese, 11746797

環境配慮設計の現状と課題　　　　　　　　　　　　　　　
岡崎太一郎, 『東京五輪を契機に鋼構造環境配慮設計をどのように次世代に引き継ぐか』構造部門（鋼構造）パネルディスカッション資料, 4, 9, Sep. 2018
Japanese, Lecture materials

Cyclic loading behavior of steel chevron braced frames with round-hollow-section or I-section braces　　　　　　　　　　　　　　　
Taichiro Okazaki, Akiri Seki, Hayato Asada, 16th European Conference on Earthquake Engineering, Paper No. 11271, Jun. 2018, [Lead author]
English, Summary international conference

Now Available: English Translation of the 2005 AIJ Design Standard for Steel Structures　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Steel Construction Today & Tomorrow, 52, 3, 4, Dec. 2017
English, Introduction other

An Experimental study of adhesively joined steel beam splices subject to combined shear and flexure Part 2　　　　　　　　　　　　　　　
Yosuke Watanabe, Haruna Takano, Taichiro Okazaki, Hisakazu Hori, Tetsuhiro Asari, Proceedings of Constructional Steel, Japan Society of Steel Construction, 25, 602, 609, Nov. 2017, [Peer-reviewed]
Japanese, Summary national conference

An Experimental Study on the Application of Structural Adhesive in Steel Connections　　　　　　　　　　　　　　　
Haruna Takano, Yosuke Watanabe, Taichiro Okazaki, Tadayoshi Okada, Shinpei Terada, Proceedings of Constructional Steel, Japan Society of Steel Construction, 25, 594, 601, Nov. 2017, [Peer-reviewed]
Japanese, Summary national conference

Experimental Performance of Chevron Steel Braced Frames　　　　　　　　　　　　　　　
kiri Seki, Shuhei Usesugi, Taichiro Okazaki, Hayato Asada, Tetsuhiro Asari, 鋼構造年次論文報告集、日本鋼構造協会, 25, 841, 848, Nov. 2017, [Peer-reviewed]
Japanese, Summary national conference

Seismic response of structures that permit foundation uplift　　　　　　　　　　　　　　　
Kasushi Nakata, Tetsuhiro Asari, Taichiro Okazaki, Mitsumasa Midorikawa, Journal of Structural Engineering, Architectural Institute of Japan, 63B, 351, 358, Apr. 2017, [Peer-reviewed]
Japanese, Summary national conference

Failure mode, overstrength ration in compression, and energy dissipation capacity of buckling-restrained braces　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Journal of Structural Engineering, Architectural Institute of Japan, 63B, 543, 552, Apr. 2017, [Peer-reviewed]
Japanese, Summary national conference

Cyclic loading performance of full-scale special truss moment frame with innovative details for high seismic activity　　　　　　　　　　　　　　　
Chatchai Jiansinlapadamrong, Sanputt Simasathien, Taichiro Okazaki, Shih-Ho Chao, 16th World Conference on Earthquake Engineering (16WCEE), No. 2914, Jan. 2017
English, Introduction international proceedings

Seismic Diagnosis and Damage Prediction of Existing Building in Hokkaido
山﨑 翔, 緑川 光正, 岡崎 太一郎, 麻里 哲広, 北海道地区自然災害科学資料センター報告 = Bulletin of the Natural Disaster Science Data Center, Hokkaido, 29, 35, 58, Mar. 2016
北海道地区自然災害科学資料センター (北海道大学大学院工学研究院), Japanese

An Experimental study of adhesively joined steel beam splices subject to combined shear and flexure　　　　　　　　　　　　　　　
Keisuke INOUE, Taichiro OKAZAKI, Hisakazu HORII Mitsumasa MIDORIKAWA, Tetsuhiro ASARI, Proceedings of Constructional Steel, 23, 262, 269, Nov. 2015, [Peer-reviewed]
Japanese, Summary national conference

013 Survey on the design of steel concentrically braced frames in Hokkaido
Okazaki Taichiro, Midorikawa Mitsumasa, Asari Tetsuhiro, 日本建築学会北海道支部研究報告集, 88, 55, 60, 27 Jun. 2015
Architectural Institute of Japan, Japanese

Modified structural layouts for Staggered Truss Framing systems used in seismically active areas
S. Simasathien, S. H. Chao, K. Moore, T. Okazaki, NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering, No. 1126, 2014
The steel Staggered Truss Framing (STF) system is a highly economical and efficient steel framing system that accommodates generic architectural and structural requirements for mid- to high-rise buildings. Due to the attributes of enabling small floor-to-floor height, large column-free spaces, reduced number of columns, efficient use of material, light weight, reduced size and load requirements for the foundation, high lateral stiffness, rapid construction, and low overall cost, STFs have become a popular system in regions of low seismicity. Although STFs were originally developed for low seismic regions, the high lateral stiffness and light weight make this system attractive for use in high seismic regions. However, very limited studies have been conducted on the behavior of STFs under strong earthquake ground motions. A key to the lateral-load resisting mechanism of STFs is the active participation of the floor diaphragms (typically consists of prestressed hollow-core planks) to transfer the inertial forces cumulating in a staggered manner across the height of the structure. The increasingly large diaphragm shear force in the lower stories brings concerns regarding the cyclic behavior of diaphragm-to-truss connections, local stress demand in the diaphragms under in-plane force and out-of-plane displacement. The stability of the system needs to be investigated if the trusses are designed to take inelastic action since the trusses serve as both the gravity and lateral-load resisting systems. In this paper, limitations of the conventional STF for use in seismically active areas are discussed. Subsequently, an alternative structural layout was investigated in which the conventional diaphragms composed of precast concrete panels are replaced by horizontal steel trusses to transmit the large diaphragm shears in the lower stories. A prototype mid-rise STF building was designed according to the spectrum specified in ASCE-7 and the seismic performance of the 3-D model was evaluated by nonlinear time-history analyses., Earthquake Engineering Research Institute, English, Introduction international proceedings

Cyclic loading performance of special truss moment frame with double-channel chord members
S. Simasathien, C. Jiansinlapadamrong, T. Okazaki, S. H. Chao, NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering, No. 1109, 2014
Special truss moment frame (STMF) is a relatively new type of steel framing system for use in high seismic areas. STMFs dissipate earthquake energy through ductile special segments located near the mid-span of the truss girders, while the other members outside the special segment, including truss members, columns, and girder-to-column connections, are designed to remain elastic. When an STMF is subjected to seismic forces, the induced shear force, V<
inf>
ne<
/inf>
, in the middle of the truss girder is resisted primarily by the chord members in the special segment. One of the major advantages of using the STMF system is that the truss girders can be economically used over longer spans, and greater overall structural stiffness can be achieved by using deeper girders. In addition, the open-webs can easily accommodate mechanical and electrical ductwork. As a consequence, this system offers a wide range of structural, architectural, and economical benefits due to their ability to achieve a large column-free floor. Research work carried out on STMFs with angle sections as chord members during the 1990s led to the formulation of design code provisions. However, previous tests on STMFs did not adequately reflect the current practice in design and detailing where much heavier sections are needed for chord members. Substantial improvement in design methodology and confidence could be gained for STMFs by further research. In this paper, preliminary test results of a National Science Foundation (NSF) Network for Earthquake Engineering Simulation (NEES) project on two of the full-scale STMF specimens with double-channel chord members are discussed. The goals of the experiments are to verify the behavior of STMFs designed and constructed according to recommendations from the latest American Institute of Steel Construction (AISC) Seismic Provisions as well as to investigate the innovative detailing used in designing the truss members., Earthquake Engineering Research Institute, English, Introduction international proceedings

Performance of triple-pendulum bearings observed in a full-scale shake-table test program
T. Okazaki, E. Sato, K. Ryan, T. Sasaki, S. Mahin, NCEE 2014 - 10th U.S. National Conference on Earthquake Engineering: Frontiers of Earthquake Engineering, No. 114, 2014
A full-scale, steel moment-frame building, whose base was seismically isolated using nine triple-pendulum bearings (TPBs), was subjected to a number of horizontal and horizontal-plus-vertical ground motions using the E-Defense shake table. The tests demonstrated excellent performance of the base-isolation system against ground motions with different characteristics ranging from large high-frequency content, large vertical acceleration, to long duration. After experiencing 20 severe ground motions, the TPBs exhibited the same performance as they did in the first ground motion. Large variation in vertical forces, produced by overturning moment in the building and vertical ground acceleration, caused instantaneous disturbance to individual TPBs but had limited influence on the performance of the isolation system. Motions with extremely large vertical acceleration caused uplift in the TPBs of up to 20 mm. The uplift was followed by an impact that produced a large compression spike in the TPBs. The impact did not damage the TPBs and caused little influence on the hysteretic behavior of the TPBs. A height difference as large as 7 mm was recorded between the TPBs, but the difference reduced to below 3 mm when the horizontal displacement receded., Earthquake Engineering Research Institute, English, Introduction international proceedings

第15回世界地震工学会議参加報告　　　　　　　　　　　　　　　
小檜山雅之, 岡崎太一郎, 日本地震工学会誌, 18, 88, 91, Jan. 2013
Japanese, Introduction other

鉄骨造の接合部を設計する III章 接合部のディテール 柱脚のディテール 露出柱脚の設計と性能
岡崎太一郎, 建築技術, 754, 122-123, 159, 01 Nov. 2012
建築技術, Japanese

Japanese research on super-high-strength structural steel　　　　　　　　　　　　　　　
Taichiro Okazaki, Fukami Hidenori, Masato Ohata, Masayoshi Nakashima, North American Steel Construction Conference (NASCC), Apr. 2012, [Invited]
English, Introduction international proceedings

Damage to Buildings Observed from the March 11, 2011 Tohoku Earthquake
緑川 光正, 岡崎 太一郎, 北海道地区自然災害科学資料センター報告, 25, 30, 75, Mar. 2012
北海道大学大学院工学研究科北海道地区自然災害科学資料センター, Japanese

鋼構造建物の大型振動実験の今とこれから : 鋼構造設計施工の高度化と合理化に向けて(構造部門(鋼構造),パネルディスカッション,2010年度日本建築学会大会(北陸)の概要)
岡崎 太一郎, 建築雑誌, 126, 1614, 43, 43, 20 Feb. 2011
社団法人日本建築学会, Japanese

Out-of-plane stability of buckling-restrained braces
T. Hikino, T. Okazaki, K. Kajiwara, M. Nakashima, Structures Congress 2011 - Proceedings of the 2011 Structures Congress, 938, 949, 2011, [Peer-reviewed]
English

Reduced link sections for improving the ductility of eccentrically braced frame link-to-column connections　　　　　　　　　　　　　　　
Jeffrey W. Berman, Taichiro Okazaki, Heidrun O. Hauksdottir, 9th US National and 10th Canadian Conference on Earthquake Engineering 2010, 3546, 3555, Jul. 2010, [Peer-reviewed]
English, Summary international conference

On the interface of stability and seismic design requirements for steel buildings　　　　　　　　　　　　　　　
Taichiro Okazaki, Larry A. Fahnestock, Matthew Parkolap, Structural Stability Research Council - Annual Stability Conference, 271, 290, May 2010
English, Summary international conference

ミネソタの一面
岡崎 太一郎, 尾上 博一, コンクリート工学 = Concrete journal, 46, 11, 66, 67, 01 Nov. 2008
Japanese

ミネソタ大学MAST装置を使った研究　　　　　　　　　　　　　　　
岡崎太一郎, 震災予防, 216, 26, 31, Sep. 2007
Japanese, Introduction scientific journal

Finite element simulation of link-to- column connections in steel eccentrically braced frames　　　　　　　　　　　　　　　
Taichiro Okazaki, Michael D. Engelhardt, 100th Anniversary Earthquake Conference commemorating the 1906 San Francisco Earthquake (Eighth National Conference on Earthquake Engineering), Aug. 2006, [Peer-reviewed]
English, Summary international conference

22349 Cyclic loading behavior of link members constructed of ASTM A992 steel
Okazaki Taichiro, Engelhardt Michael D, Summaries of technical papers of Annual Meeting Architectural Institute of Japan. C-1, Structures III, Timber structures steel structures steel reinforced concrete structures, 2005, 0, 697, 698, 31 Jul. 2005
Architectural Institute of Japan, Japanese

Impact of recent research findings on eccentrically braced frame (EBF) design　　　　　　　　　　　　　　　
Paul Richards, Chia-Ming Uang, Taichiro Okazaki, Michael D. Engelhardt, Structural Engineers Association of California (SEAOC) Convention 2004, Aug. 2004
English, Summary national conference

Experimental study on link-to-column connections in steel eccentrically braced frames　　　　　　　　　　　　　　　
Taichiro Okazaki, Michael D. Engelhardt, Masayoshi Nakashima, Keiichiro Suita, The Thirteenth World Conference on Earthquake Engineering, Aug. 2004, [Peer-reviewed], [Lead author]
English, Summary international conference

Recent research on link performance in steel eccentrically braced frames　　　　　　　　　　　　　　　
Taichiro Okazaki, Gabriela Arce, Michael D. Engelhardt, The Thirteenth World Conference on Earthquake Engineering, Aug. 2004, [Peer-reviewed], [Lead author]
English, Summary international conference

Behaviour of link-to-column connections in steel eccentrically braced frames
Taichiro Okazaki, Michael D. Engelhardt, Masayoshi Nakashima, Keiichiro Suita, K.-C. Tsai, Fourth International Conference on Behavior of Steel Structures in Seismic Areas (STESSA 2003), 351, 356, Jun. 2003, [Peer-reviewed], [Lead author]
English, Summary international conference

Experimental behaviour of shear and flexural yielding links of ASTM A992 steel
Gabriela Arce, Taichiro Okazaki, Michael D. Engelhardt, Fourth International Conference on Behavior of Steel Structures in Seismic Areas (STESSA 2003), 107, 113, Jun. 2003, [Peer-reviewed]
English, Summary international conference

UC Berkeley - CUREE Symposium in Honor of Ray Clough and Joseph Penzien　　　　　　　　　　　　　　　
岡崎太一郎, 中島正愛, 震災予防, 185, 1, 2, Jul. 2002

Elasto-Plastic Behavior of Thin-Walled Members under Repeated Axial Loading
OKAZAKI Taichiro, NONAKA Taijiro, Summaries of technical papers of Annual Meeting Architectural Institute of Japan. C-1, Structures III, Timber structures steel structures steel reinforced concrete structures, 1996, 0, 817, 818, 30 Jul. 1996
Architectural Institute of Japan, Japanese

2055 Elasto-Plastic Behavior of Thin-Walled Members under Repeated Axial Loading
OKAZAKI Taichiro, NONAKA Taijiro, 日本建築学会近畿支部研究報告集. 構造系, 0, 36, 233, 236, 03 Jul. 1996
Architectural Institute of Japan, Japanese

AIJ Standard for Allowable Stress Design of Steel Structures　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Chapters 1 to 6
Maruzen, Oct. 2019, [Joint work]

AIJ Design Standard for Steel Structures ― Based on Allowable Stress Concept― (2005 Edition)　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Chapers 1 to 4
Architectural Institute of Japan, Oct. 2017, [Joint translation]

AIJ Recommendations for Plastic Design of Steel Structures　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Chapter 7
Maruzen, Feb. 2017, [Joint work]

Recommendations for Sustainable Steel Building Construction (Draft) ―Member Reuse―　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Sections 2.2 and 4.1
Maruzen, Dec. 2015, [Joint work]

JSSC Sets of Torshear Type High-Strength Bolt, Hexagon Nut and Plain Washer for structural Joints (English translation)　　　　　　　　　　　　　　　
Taichiro OKAZAKI, 全体
Japanese Society of Steel Construction, [Joint work]

Possibilities of Structural Adhesives in Steel Building Construction
Taichiro Okazaki
2024年度第33回構造接着・精密接着研究会シンポジウム, 26 Nov. 2024, Japanese, Invited oral presentation
26 Nov. 2024 - 26 Nov. 2024, 31428767, [Invited]

Possibility of Member Reuse in Steel Building Structures　　　　　　　　　　　　　　　
Taichiro Okazaki
69th Structural Engineering Symposium, 15 Apr. 2023, Japanese, Invited oral presentation
15 Apr. 2023 - 16 Apr. 2024, [Invited]

Seismic Performance of Steel Beam-to-Column Moment Connections in Japan　　　　　　　　　　　　　　　
Taichiro Okazaki
Tianjin University / National Facility for Earthquake Engineering Simulation, 16 Nov. 2020, English, Public discourse
[Invited]

地震と鋼材―阪神・淡路大地震から25年を過ぎて―　　　　　　　　　　　　　　　
岡崎太一郎
第71回白石記念講座, 28 Nov. 2019, Japanese, Public discourse
[Invited], [Domestic Conference]

Contribution of Academic Research to the Seismic Safety of Steel Structures in Japan.　　　　　　　　　　　　　　　
Taichiro OKAZAKI
16th Symposium on Earthquake Engineering (India), 22 Dec. 2018, English, Keynote oral presentation
[Invited], [International presentation]

Seismic Design Procedure of Steel Structures in Japan: Past, Present, and Future　　　　　　　　　　　　　　　
Taichiro OKAZAKI
Nagoya Institute of Technology International Symposium (2018), 10 Sep. 2018, English, Invited oral presentation
[Invited], [International presentation]

Japanese Research on Super-High-Strength Structural Steel　　　　　　　　　　　　　　　
Taichiro OKAZAKI, Hidenori FUKAMI, Masato OHATA, Masayoshi NAKASHIMA
NASCC: The Steel Conference, 20 Apr. 2012, English, Oral presentation
[Invited], [International presentation]

SDGs Seminar: International Colearning PBL for Problem Solving　　　　　　　　　　　　　　　
Hokkaido University
Jun. 2022 - Present

Steel Design II　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2020 - Present

Exercise in Building Materials (Team taught)　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2018 - Present

Advanced Structural Analysis　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2018 - Present

Structural Steel Members and Systems　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2017 - Present

Structural Mechanics 2　　　　　　　　　　　　　　　
Hokkaido University
Oct. 2016 - Present

Structural Mechanics 1　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2016 - Present

Introduction to Architectural Engineering (co-taught)　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2012 - Present

Freshman Seminar: Material and Mechanics of Structures (co-taught)　　　　　　　　　　　　　　　
Hokkaido University
Dec. 2019 - Mar. 2021

Structural Mechanics 3　　　　　　　　　　　　　　　
Hokkaido University
Oct. 2012 - Aug. 2019

Structural Analysis I　　　　　　　　　　　　　　　
Hokkaido University
Oct. 2011 - Jan. 2018

Mathematics in Architectural Engineering　　　　　　　　　　　　　　　
Hokkaido University
Oct. 2011 - Jan. 2018

Dynamics of Building Structures　　　　　　　　　　　　　　　
Hokkaido University
Oct. 2011 - Aug. 2017

Seminars in Architectural Engineering II　　　　　　　　　　　　　　　
Hokkaido University
Mar. 2011 - Aug. 2016

Applied Mathematics I (co-taught)　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2011 - Aug. 2013

Exercise in Computing (co-taught)　　　　　　　　　　　　　　　
Hokkaido University
Apr. 2011 - Aug. 2013

Ductile Behavior of Steel Structures (Graduate)　　　　　　　　　　　　　　　
University of Minnesota
Feb. 2007 - May 2009

Linear Structural Analysis　　　　　　　　　　　　　　　
University of Minnesota
Sep. 2005 - Dec. 2008

Steel Design II　　　　　　　　　　　　　　　
University of Minnesota
Feb. 2006 - May 2008

Evaluation methodology and modular systems to enable steel reuse
Grants-in-Aid for Scientific Research
Jun. 2024 - Mar. 2028
岡崎 太一郎
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Pioneering), Hokkaido University, Principal investigator, 24K21220

鋼構造建築物の破壊過程の解明と倒壊余裕度の把握
科学研究費助成事業
Apr. 2024 - Mar. 2028
岡崎太一郎、松井良太、長江拓也
日本学術振興会, 基盤研究(A), 北海道大学, 24H00340

High-Seismic-Performance Building with Sliding Foundation System and Reinforced Non-Structural Components
Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
07 Oct. 2022 - 31 Mar. 2027
長江 拓也, 浅井 竜也, 柏 尚稔, 高橋 典之, 梶原 浩一, 藤原 淳, 岸田 明子, 松宮 智央, 岡崎 太一郎
Japan Society for the Promotion of Science, Fund for the Promotion of Joint International Research (Fostering Joint International Research (B)), Nagoya University, 22KK0063

環境負荷軽減を実現する座屈拘束ブレースの開発
科学研究費助成事業
30 Jun. 2023 - 31 Mar. 2026
松井 良太, 岡崎 太一郎, 丸山 一平
日本学術振興会, 挑戦的研究(萌芽), 北海道大学, 23K17781

Developing rational design metholodogy for chevron braced frames　　　　　　　　　　　　　　　
Grants for Research and Education in Steel Structures
Apr. 2023 - Mar. 2025
岡崎太一郎、松井良太、田川浩、陳星辰
The Japan Iron and Steel Federation, Grants for Specified Research Areas, Principal investigator

Numerical analysis of large deformation and stability response of steel structures under earthquake loading　　　　　　　　　　　　　　　
Researcher Exchange Support for International Researchers
Apr. 2024 - Jun. 2024
Ali IMANPOUR, Taichiro OKAZAKI
The Kajima Foundation

Analysis and assessment technology for seismic collapse safety of steel building structures
Grants-in-Aid for Scientific Research
Apr. 2020 - Mar. 2024
Taichiro OKAZAKI, Ryota MATSUI, Tomohiro MATSUMIYA, Noriyuki TAKAHASHI, Takuya NAGAE
鋼構造建築物の倒壊過程を実験的に解明する研究目的に沿って、国立研究開発法人防災科学技術研究所の大型耐震実験施設で、2020年11月から12月にかけて、縮尺1/2のパイロット試験体による振動台実験を実施した。同研究所の兵庫耐震工学研究センターで、2020年12月に実施された日米共同実験に参加し、次世代型鋼構造システムを開発する研究を推進した。大型耐震実験施設で、2021年12月に、縮尺1/3の4層ラーメン構造の倒壊実験を実施した。一方で、倒壊に至る鋼構造の非線形・動的挙動を追跡するコンピュータ解析技術を確立する研究目的に沿って、数値モデル化技術を種々検討してきた。一連の研究活動で得られた成果は、下記のとおりである。（１）倒壊実験によって、柱や梁が降伏し破断する過程と、損傷と破壊が架構全体に伝播する状況に関する実データを収録できた。（２）複数の実験から得た、鋼構造架構の非線形動的応答に関する実データを、既往の大規模振動台実験のデータと合わせて、数値解析技術の検証を進めてきた。特に、破断を模擬するための現状のモデル化手法では、既往の重層架構実験で観察された、部材破断後の部材力再分配を正しく再現できないことを突き止め、今後の課題を特定した。減衰モデルの選択によって、架構の応答変位や応答加速度が異なることに注目し、定量的な検討を進めた。（３）部材破断の再現方法を含めて、ブレース付鋼構造架構の解析手法に関する知見を蓄積し、現状のブレース付鋼構造架構が保有する耐震性能を検証した。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 20H00269

Fracture of steel connections under very-low-cycle loading　　　　　　　　　　　　　　　
Grants-in-Aid for Scientific Research
Sep. 2022 - Sep. 2023
Taichiro OKAZAKI, WANG YUANZUO
Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 22F22042

Development of a post-earthquake quick inspection method utilizing the movement data and video image of non-structural components in existing buildings subjected to a strong earthquake
Grants-in-Aid for Scientific Research
01 Apr. 2020 - 31 Mar. 2023
長江 拓也, 梶原 浩一, 岡崎 太一郎, 松宮 智央, 高橋 典之, 藤原 淳, 岸田 明子
本提案では，即時応急危険度判定として，地震被災建物の非構造材の動作に関する計測値分析と，屋内外のビデオ映像に基づく外観損傷や部材変形の画像解析を統合し，構造体の安全性はもとより建物機能の健全性を判定する方法を開発することを目標としている。さらに，判定結果を速やかに周囲に伝達することで，人間避難行動を適切に誘導する判定情報伝達技術の開発までを射程とする。本年度も引き続き，鋼構造架構を準備し，間仕切壁，カーテンウォールの加振実験を実施した。部材角を評価するGyro，表示のLEDの適用性について検証した。判定基準整備の一環として，確率論的性能評価の適用性について検討を重ねた。
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Pioneering), Nagoya University, 20K20435

Proposal of Structural Design Method for Steel Structures Based on Ultimate Performance using Collapse Analysis
Grants-in-Aid for Scientific Research
01 Apr. 2020 - 31 Mar. 2023
松井 良太, 岡崎 太一郎, 竹内 徹
本研究課題では，鋼構造物の限界性能を検証できる構造設計手法を提示することを目標としている。2021年度では，鋼構造物の中でも，鋼材ブレースと合成梁の力学的性能を検証することに焦点を当てて研究計画を立てた。
第一に，2020年度に構築したデータベースを参照して製作した鋼材ブレースを対象とした模型載荷実験を実施した。試験体の断面には，H形鋼，円形鋼管，角形鋼管の3種を選定した。接合部には，境界条件の剛柔によるブレースの力学的性能の差異を確認すべく，端部のエンドプレートと溶接接合した形式と，ガセットプレートを介して接合した形式の2種を設定した。細長比を19から28とした太短いブレースを6体，比較のため51から65の比較的細長いブレースを4体用意した。H形鋼のフランジ幅厚比を6，円形鋼管の径厚比を31から39，角形鋼管の幅厚比を22から33となる断面を採用した。全試験体を繰返し載荷し，ブレースの耐力および塑性変形能力を検証した。本研究を計画した時点で予期していなかったブレースの破壊挙動を確認した。
次いで，鋼材の破壊力学の考え方を導入し，代表者が提案してきた繰返し載荷を受ける鋼材ブレースの塑性変形能力を評価する手法を発展させた。有限要素解析により，既往の載荷実験における角形鋼管ブレースの最大圧縮耐力，局部座屈による耐力劣化などの挙動について再現を試みた。他研究者が提案した破壊力学における鋼材の空隙進展モデルに適合する，鋼材ブレースの局部に集中した塑性歪を抽出するため，部材の要素分割，鋼材の材料特性などの条件を調整した。有限要素解析より得られた結果から，要素の歪をブレース軸方向にわたって抽出し，材全体の変形で局所に集中する塑性歪を評価するために必要となる事項を整理した。合成梁については，2020年度に実施した実験を参照し，コンクリート床スラブの有効幅の設定が性能に及ぼす影響を検討した。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 20H02292

Demountable and reusable modular steel construction
Grants-in-Aid for Scientific Research
Nov. 2020 - Mar. 2023
岡崎 太一郎, ZONG LIANG
Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 20F20354

Development of Modular Steel Construction to Promote Reclaiming and Reusing Structural Steel
Grants-in-Aid for Scientific Research
Nov. 2019 - Mar. 2022
岡崎 太一郎, XU FEI
建築用鋼材は、建築物の供用期間が終了した時点でも、当初の性質をほとんど維持していると考えられるが、実際の建築物では、解体後に回収された鋼材はスクラップに回される。そこで本研究は、解体される建築物から採取した鋼部材を、新設建築物に再利用するための基礎技術を開発することを目的に掲げる。工学的な課題は、地震等によって塑性変形を受けた鋼材が、時間を経てその力学的特性を変える、ひずみ時効の影響である。2020年度は、代表的な鋼材について、塑性履歴とひずみ時効を受けたあと、力学的特性が変わる過程と要因を分析するための手法を開発した。試行的に、塑性変形と養生時間を経た鋼材において、微細構造が初期状態とどのように異なるかを調査した。微細構造分析には、後方散乱電子回折と透過電子顕微鏡、X線回析の組み合わせが有益であることを確認した。一方で、これまでに蓄積した実験データに基づいて、塑性変形とひずみ時効の影響を関数化して、鋼材の繰返し履歴則に組込む方法を整理した。有限要素法解析において、第一段階目の解析で生じた累積塑性ひずみに応じて、各要素の繰返し履歴則を分布的に更新したあと、第二段階目の解析を実施する方法を考案した。この有限要素法解析の有効性を、過去に実施した実験結果に対して検証した。結論として、過去の地震で塑性変形を受けた構造部材が、次に地震を受けたときにどのように違った挙動を示すかを、提案する解析法で適切に再現できることを示した。
Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Hokkaido University, 19F19360

Rapid post-quake estimation of structural damage and performance based on modern ima ge processing technology
Bilateral Joint Research Project with National Natural Science Foundation of China
Apr. 2018 - Mar. 2022
Japan Society for the Promotion of Science, Hokkaido University, Principal investigator

Experimental study for MEMS sensor monitoring system to assess seismic response of Non-structural element of building
Grants-in-Aid for Scientific Research
01 Apr. 2017 - 31 Mar. 2020
Kajiwara Koichi
In order to maintain and continue normal living and economic activities in our society, preparing for the future large-scale earthquake event, it is necessary to judge the performance of the infrastructures after the earthquake as a matter of course to improve the earthquake resistance before the earthquake. For this reason, many investigations have been conducted on structural health monitoring.
Here, we have researched a system that estimates the structural characteristics of a building after the earthquake by capturing the response of non-structural element installed in the building with MEMS(micro-electro-mechanical systems) sensor. In this research, we have finished the basic investigation for practical use.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), National Research Institute for Earth Science and Disaster Prevention, 17K06666

Towards seismic design of steel buildings addressing collapse risk
Grants-in-Aid for Scientific Research
Apr. 2017 - Mar. 2020
Taichiro OKAZAKI, Tomohiro MATSUMIYA, Noriyuki TAKAHASHI, Tetsuhiro ASARI, Takuya NAGAE
The primary objective of the research was to obtain experimental data on failure of steel components and to advance the technology to numerically simulate the seismic response of steel building structures. The research was planned towards the larger goal of establishing a methodology to assess whether a steel building can safely survive, or maintain usable, after an extremely large earthquake beyond the consideration of building codes. Dynamic loading test of beam-to-column connections was conducted to examine how seismic performance may be affected by connection type and presence of composite floor slab. Numerical modeling techniques were examined to capture the gradual degradation of steel components due to start and propagation of ductile fracture. The model was used to demonstrate that good agreement can be obtained between simulated and experimental behavior of multi-story steel building systems. An additional study was conducted on damping models suited for nonlinear analysis.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 17H03336

Comprehensive study on the 2018 Hokkaido Eastern Iburi Earthquake and its disaster
Grants-in-Aid for Scientific Research
04 Oct. 2018 - 31 Mar. 2019
Takahashi Hiroaki
Comprehensive investigation on the 2018 Hokkaido Eastern Iburi earthquake and its disaster was conducted. Mainshock rupture initiated at deepest part and major slip was occurred in 20-30km deep. Multiple simultaneous landslides in Atsuma town was induced by combination of strong ground shaking and weak sliding layer between pyroclastic fall deposit layers. Halloysite cray minerals was discovered in all sliding layers. Simulation suggested landslides might attack residential houses within 6 seconds. Observed peak ground motions in nearby area were larger than common distance attenuation model. Severe wooden house damage in Mukawa town was due to amplified seismic waves due to site effects. Sounding and boring investigation revealed filled low-density volcanic ash and higher groundwater level in liquefaction area. Electricity blackout caused severe damage in social and economic activities of Hokkaido. These scientific outcomes were explained to residents at public briefing session.
Japan Society for the Promotion of Science, Grant-in-Aid for Special Purposes, Hokkaido University, 18K19952

Substructure Shaking Table Test for Collapse Process of Reinforced Concrete Building
Grants-in-Aid for Scientific Research
01 Apr. 2016 - 31 Mar. 2019
Nagae Takuya, Yenidogan Cem, Takahashi Noriyuki, Matsumiya Tomohiro, Maruyama Ippei, Kajiwara Koichi, Mikoshiba Tadashi, Nakazawa Hiroshi
A method of substructure test was developed by using a shaking table facility. Deformation time histories occurring in prototype buildings were applied to the substructure specimen equivalent to their critical portions. The force-deformation hysteresis was evaluated in the large deformation level significantly exceeding design limit, and compared with a promising numerical model, Krawinkler model. This model was developed in Stanford University, and is now recommended in the newest high-rise building design guideline of the United States. The ultimate energy capacity and other main parameters were tuned according to the test results. The numerical models, which represented substructure test results, were incorporated in the model of a full-scale frame test structure. The adopted method of static cyclic loading frame analysis indicated a new design procedure based on a reasonable performance assessment format.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Nagoya University, 16K06568

Evaluate collapse margin of medium-low-rise steel buildings
Grants-in-Aid for Scientific Research
01 Apr. 2014 - 31 Mar. 2017
MATSUMIYA Tomohiro
For beam-to-column connection of the steel building, the gradual increase amplitude cyclic loading experiment which assumed loading speed (period 1Hz and 0.01Hz) were carried out. This experiment is fundamental researches for the performance evaluation technique construction that can evaluate the influence that the fracture property of the member end and the yield mechanism of the frame give to the ultimate state of the building. The conclusions obtained from this experiment are (1) The difference in loading speed produced differences of some behavior.(2) In the dynamic loading, beam-to-column connection fracture occur in comparison with static loading earlier, and plastic deformation capacity was inferior. For sliding in the high-strength bolt friction joint, the possibility that it hastened the crack spread started from the welding defect is thought about.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Kindai University, 26420570

Structural Performance and Seismic Design of Steel Building Structures without Base Anchorage
Grants-in-Aid for Scientific Research
01 Apr. 2013 - 31 Mar. 2017
NAKASHIMA, Masayoshi
Japan and many regions in the world keep suffering from large earthquakes, and building collapse is considered to be most responsible for both the human and material losses. Advancement of building technologies for better collapse prevention is a critical societal need. This study proposes a new system in which the base of the super-structure is detached from the foundation, by which shear forces exerted onto the super-structure can be capped to a specified level. A series of dynamic loading test indicates that placing carbon graphite on the surface of foundation RC/mortar beam is found to ensure a friction coefficient of about 0.2 despite the number of sliding cycles. Theoretical equations are formulated to represent the sliding structure, and extensive time-history analyses are implemented for sliding structures subjected to pulse-type ground motions. The results verified that the maximum shear force applied to the super-structure is approximately twice the friction coefficient.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Kyoto University, 25249078

Seismic Performance of Rocking Frames with Column Mid-height Uplift Mechanism at the First Story
Grants-in-Aid for Scientific Research
01 Apr. 2013 - 31 Mar. 2016
Midorikawa Mitsumasa, ASARI Tetsuhiro, AZUHATA Tatsuya, ISHIHARA Tadashi, OKAZAKI Taichiro
The steel frames with column mid-height uplift (CMU) mechanism at the first story are implemented as response-control structural systems that reduce the seismic effects by exploiting the gravity effect generally deteriorating the seismic performance of ordinary structures. In the previous studies, the reduction effect on the seismic response of the column-base uplift (CBU) rocking systems with columns allowed to uplift has been evaluated and examined. The advantages and disadvantages of the systems have also been discussed. This study presents the seismic performance of CMU rocking frames with emphasis on the fundamental mechanical properties of CMU frames based on the simplified analytical models, performance evaluation of CMU mechanism resulted from the cyclically static loading tests and the seismic response behavior of CMU frames. Finally, some suggestions and recommendations are made on the seismic design of the rocking systems.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 25289177

Design and Seismic Performance of Steel Braced Frames
Grants for Research and Education in Steel Structures
Apr. 2014 - Mar. 2016
岡崎太一郎
The Japan Iron and Steel Federation, Principal investigator, Competitive research funding

Economic beam-to-column moment connections in steel structures
Grants-in-Aid for Scientific Research
Apr. 2012 - Mar. 2015
OKAZAKI TAICHIRO
Steel systems using I-shaped columns instead of box-shaped columns was examined to increase the economy of steel building construction. Two full-scale beam-to-column moment connections were tested in the laboratory. One specimen connected the beam to the column flange, while in the second specimen connected the beam to the column web. Both specimens exhibited similar performance to standard connections of a I-shaped beam to a box-shaped column. However, the connections to the web resulted in a 10% loss in stiffness. Out-of-plane deformation of the column web and in-plane deformation of the continuity plates was notable in the post-yield response. The experimental behavior was reproduced successfully by a detailed, nonlinear finite element simulation. Both the experiment and simulation indicated that the connection to the column web is susceptible to fracture in the weld between the beam flange and continuity plate.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 24560676

Development and Application oSfeismically Response-control
Grants-in-Aid for Scientific Research
2010 - 2012
MIDORIKAWA Mitsumasa, ASARI Tetsuhiro, AZUHATA Tatsuya, ISHIHARA Tadashi, OKAZAKI Taichiro
The steel frames with uplift column-bases are implemented as response-control structural systems that reduce the seismic effects by exploiting the gravity effect generally deteriorating the seismic performance of ordinary structures. The reduction effect on the seismic response of the base-plate-yielding (BPY) rocking systems with columns allowed to uplift has been evaluated and examined. The advantages and disadvantages of the systems have also been discussed. This study presents the seismic response characteristics with emphasis on the torsional behavior of the BPY systems and proposes the advanced rocking systems resolving the disadvantage of the BPY systems towards developing and applying widely the rocking structural systems. Finally, some suggestions and recommendations are made on the seismic design of the rocking systems.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 22360219

Steel Connections using Structural Adhesives
Grants-in-Aid for Scientific Research
2010 - 2011
OKAZAKI Taichiro
In order to examine how structural adhesives could be utilized in steel construction, a total of 65 double-splice tension coupons were constructed from two types of adhesives and with various splice proportions. With one of the adhesives, the coupon strength increased with splice length to the point where the splice strength exceeded the yield strength of steel. Three out of 50 specimens exhibited a 25% lower strength owing to the fact that they were governed by interfacial failure rather than cohesive failure. In contrast, with the other adhesive, the coupon strength did not change significantly with splice length and coupon failure was governed entirely by interfacial failure.
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, 22760430

International hybrid simulation of tomorrow's braced frame systems　　　　　　　　　　　　　　　
NEESR-SG
2006 - 2011
Taichiro OKAZAKI
National Science Foundation, Principal investigator, Competitive research funding

Damage investigation and data collection for collapsed I-35WBridge　　　　　　　　　　　　　　　
SGER
2007 - 2009
Taichiro OKAZAKI
National Science Foundation, Principal investigator, Competitive research funding