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A tendon system to re-center steel moment frames with weak stories

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Earthquake Engineering and Engineering Vibration 2024年第04期 1057-1072页

作者： Wang Tao Wang Fei masayoshi nakashima Institute of Engineering Mechanics China Earthquake Administration Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake Administration Disaster Prevention Research Institute Kyoto University

A wide open bottom story of a frame building is often expected by owners for use as a garage or ***, this leads to weak stories due to abrupt changes in lateral stiffness and often results in unexpected story collapse as observed in many previous earthquakes. To retrofit frame buildings that have experienced weak story damage, a tendon system is proposed in this study, which consists of a set of swaying columns and tendons. The swaying columns are used to uniformly redistribute the lateral deformation along the height, while the tendons provide extra lateral stiffness and renders the entire structural system a re-centering capability. To avoid unnecessary forces to swaying columns, pin-connections are used at the bottom. Tendons are placed over the entire story to gain large elastic displacements. Parametric analysis reveals that the swaying column, with a stiffness of about 0.9 times that of the weak story, and the tendons attached at the roof, with a stiffness of 0.04 times that of the weak story, can provide the optimal performance with a maximum residual story drift angle of less than 0.5%. Online hybrid tests were carried out, which demonstrated that uniformly distributed story drifts and acceptable residual deformation could be achieved by the proposed tendon system.

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Application of headed studs in steel fiber reinforced cementitious composite slab of steel beam-column connection

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Earthquake Engineering and Engineering Vibration 2012年第1期11卷 11-21页

作者： Yao Cui masayoshi nakashima Center for Urban Earthquake Engineering Tokyo Institute of Technology Japan Disaster Prevention Research Institute Kyoto University Gokashyo Uji Kyoto Japan

Steel fiber reinforced cementitous composites （SFRCC） is a promising material with high strength in both compression and tension compared with normal concrete. The ductility is also greatly improved because of 6% volume portion of straight steel fibers. A steel beam-column connection with Steel fiber reinforced cementitous composites （SFRCC） slab diaphragms is proposed to overcome the damage caused by the weld. The push-out test results suggested that the application of SFRCC promises larger shear forces transferred through headed studs allocated in a small area in the slab. Finite element models were developed to simulate the behavior of headed studs. The failure mechanism of the grouped arrangement is fiarther discussed based on a series of parametric analysis. In the proposed connection, the SFRCC slab is designed as an exterior diaphragm to transfer the beam flange load to the column face. The headed studs are densely arranged on the beam flange to connect the SFRCC slab diaphragms and steel beams. The seismic performance and failure mechanism of the SFRCC slab diaphragm beam-column connection were investigated based on the cyclic loading test. Beam hinge mechanism was achieved at the end of the SFRCC slab diaphragm by using sufficient studs and appropriate rebars in the SFRCC slab.

关键词： multi-directional transmitting artificial boundary viscous-spring artificial boundary saturated soilfoundation Biot's equations

Flexible substructure online hybrid test system using conventional testing devices

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Earthquake Engineering and Engineering Vibration 2013年第3期12卷 341-350页

作者： Wang Tao masayoshi nakashima Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering Mechanics China Earthquake Administration Disaster Prevention Research Institute Kyoto University

This paper presents a substructure online hybrid test system that is extensible for geographically distributed tests. This system consists of a set of devices conventionally used for cyclic tests to load the tested substructures onto the target displacement or the target force. Due to their robustness and portability, individual sets of conventional loading devices can be transported and reconfigured to realize physical loading in geographically remote laboratories. Another appealing feature is the flexible displacement-force mixed control that is particularly suitable for specimens having large disparities in stiffness during various performance stages. To conduct a substructure online hybrid test, an extensible framework is developed, which is equipped with a generalized interface to encapsulate each substructure. Multiple tested substructures and analyzed substructures using various structural program codes can be accommodated within the single framework, simply interfaced with the boundary displacements and forces. A coordinator program is developed to keep the boundaries among all substructures compatible and equilibrated. An Interuet-based data exchange scheme is also devised to transfer data among computers equipped with different software environments. A series of online hybrid tests are introduced, and the portability, flexibility, and extensibility of the online hybrid test system are demonstrated.

关键词： substructure online hybrid test conventional loading device displacement-force mixed control coordinator program Interuet-based data exchange scheme

Earthquake engineering research needs in light of lessons learned from the 2011 Tohoku earthquake

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Earthquake Engineering and Engineering Vibration 2014年第S1期13卷 141-149页

作者： masayoshi nakashima Oren Lavan Masahiro Kurata Yunbiao Luo Disaster Prevention Research Institute (DPRI) Kyoto University Professor Disaster Prevention Research Institute (DPRI) Kyoto UniversityGokashoUjiKyotoJapan Faculty of Civil and Environmental Engineering Technion–Israel Institute of TechnologyHaifaIsrael Assistant Professor Post Doctoral Fellow

Earthquake engineering research and development have received much attention since the first half of the twentieth century. This valuable research presented a huge step forward in understanding earthquake hazard mitigation,which resulted in appreciable reduction of the effects of past earthquakes. Nevertheless,the 2011 Tohoku earthquake and the subsequent tsunami resulted in major damage. This paper presents the timeline of earthquake mitigation and recovery,as seen by the authors. Possible research directions where the authors think that many open questions still remain are identified. These are primarily based on the important lessons learned from the 2011 Tohoku earthquake.

关键词： research needs earthquake engineering quick recovery 2011 Tohoku earthquake

Quantitative investigation on collapse margin of steel high-rise buildings subjected to extremely severe earthquakes

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Earthquake Engineering and Engineering Vibration 2018年第3期17卷 445-457页

作者： Lin Xuchuan Mikiko Kato Zhang Lingxin masayoshi nakashima Key Laboratory of Earthquake Engineering and Engineering Vibration Institute of Engineering MechanicsChina Earthquake AdministrationHarbinChina Nikken Sekkei LTD. OsakaJapan Kyoto University KyotoJapan Kobori Research Complex TokyoJapan

Reponses of structures subjected to severe earthquakes sometimes significantly surpass what was considered in the *** is important to investigate the failure mechanism and collapse margin of structures beyond design,especially for high-rise *** this study,steel high-rise buildings using either square concrete-filled-tube（CFT） columns or steel tube columns are designed.A detailed three-dimensional（3 D） structural model is developed to analyze the seismic behavior of a steel high-rise towards a complete *** effectiveness is verified by both component tests and a full-scale shaking table *** collapse margin,which is defined as the ratio of PGA between the collapse level to the design major earthquake level（Level 2）,is quantified by a series of numerical simulations using incremental dynamic analyses（IDA）.The baseline building using CFT columns collapsed with a weak first story mechanism and presented a collapse margin ranging from 10 to *** significant variation in the collapse margin was caused by the different characteristics of the input ground *** building using equivalent steel columns collapsed earlier due to the significant shortening of the locally buckled columns,exhibiting only 57% of the collapse margin of the baseline *** influence of reducing the height of the first story was quite *** shortened first story not only enlarged the collapse margin by 20%,but also changed the collapse mode.

关键词： collapse quantification steel high-rise building numerical models local buckling collapse mechanism

H_(∞)control in the frequency domain for a semi-active floor isolation system

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Frontiers of Structural and Civil Engineering 2013年第3期7卷 264-275页

作者： Yundong SHI Tracy C BECKER Masahiro KURATA masayoshi nakashima Graduate School of Engineering Kyoto UniversityKyoto 611-0011Japan Disaster Prevention Research Institute Kyoto UniversityKyoto 611-0011Japan

A floor isolation system installed in a single floor or room in a fixed base structure is designed to protect *** this configuration,the input motions to the floor isolation from the ground motions are filtered by the structure,leaving the majority of the frequency content of the input motion lower than the predominant frequency of the *** floor isolation system should minimize the acceleration to protect equipment;however,displacement must also be limited to save floor space,especially with long period ***-active control with an H_(∞)control was adopted for the floor isolation system and a new input shaping filter was developed to account for the input motion characteristics and enhance the effectiveness of the H_(∞)control.A series of shake table tests for a semi-active floor isolation system using rolling pendulum isolators and a magnetic-rheological damper were performed to validate the H_(∞)*** control using an oil damper was also tested for *** test results show that the H_(∞)control effectively reduced acceleration for short period motions with frequencies close to the predominant frequency of the structure,as well as effectively reduced displacement for long period motions with frequencies close to the natural frequency of the floor isolation *** H_(∞)control algorithm proved to be more advantageous than passive control because of its capacity to adjust control strategies according to the different motion frequency characteristics.

关键词： semi-active floor isolation H1 control MR damper shaping filter shaking table test

Statistical evaluation of cluster formation of relapse in neuromyelitis optica spectrum disorder

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Neural Regeneration Research 2024年第9期19卷 1888-1889页

作者： Tetsuya Akaishi Ichiro nakashima Department of Neurology Tohoku UniversitySendaiJapan Department of Neurology Tohoku Medical and Pharmaceutical UniversitySendaiJapan

Evaluating the cluster formation of clinical attacks in chronic relapsing diseases is an important statistical issue because the presence of attack clusters may influence therapeutic strategies for relapse *** recently reported the occurrence of unevenly clustered attacks in patients with anti-aquaporin-4(AQP4)antibody-positive neuromyelitis optica spectrum disorder(NMOSD)(Akaishi et al.,2020a).

关键词： AQP4 relapse

Simple procedure for assessing diffuse subarachnoid hemorrhage successfully created using filament perforation method in mice

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Animal Models and Experimental Medicine 2024年第1期7卷 77-81页

作者： Tatsushi Mutoh Ryota Tochinai Hiroaki Aono masayoshi Kuwahara Yasuyuki Taki Tatsuya Ishikawa Department of Surgical Neurology Research Institute for Brain and Blood VesselsAkita Cerebrospinal and Cardiovascular CenterAkitaJapan Department of Aging Research and Geriatric Medicine Institute of DevelopmentAging and CancerTohoku UniversitySendaiJapan Department of Veterinary Pathophysiology and Animal Health Graduate School of Agriculture and Life SciencesThe University of TokyoTokyoJapan

The murine model of subarachnoid hemorrhage(SAH)is a valuable experimental tool for investigating molecular and cellular mechanisms,and the endovascular filament perforation technique can be used to simulate prominent pathophysiological features observed after human SAH;however,current validation methods for assessing an appropriate SAH model are ***,we introduce a simple procedure for se-lecting a mouse model of diffuse *** was induced in 24 mice using a standard filament perforation *** confirming survival at 24 h,SAH was scored 0-1 based on T2*-weighted images on whole-brain magnetic resonance imaging(MRI)and visual surveillance of the cisterna magna(CM)through the dura *** CM-based SAH grading correlated well with a reference parameter defined by extracted brain(r^(2)=0.53,p<0.0001).The receiver operating characteristic curve revealed a sensi-tivity of 85%and a specificity of 91%for detecting diffuse SAH,with a similar area under the curve(0.89±0.06[standard error of the mean])as the MRI-based grading(0.72±0.10,p=0.12).Our data suggest that confirming an SAH clot in the CM is a valuable way to select a clinically relevant diffuse SAH model that can be used in future experimental studies.

关键词： cisterna magna clot distribution filament perforation mouse model subarachnoid hemorrhage

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屈曲约束支撑体系的应用与研究进展(Ⅱ)

建筑钢结构进展 2005年第2期7卷 1-11页

作者：汪家铭中岛正爱陆烨加州大学圣地亚哥分校建筑工程系京都大学防灾研究所同济大学土木工程学院上海200092

屈曲约束支撑框架体系(BRBF)是新近发明并逐渐得到应用的一种框架体系。因为屈曲约束支撑(BRB)在受拉和受压时都可屈服而不屈曲,因此克服了传统支撑体系的缺点。第二部分简要介绍了SEAOC-AISC提出的反复加载试验要求,介绍了BRB各组成部... 详细信息

屈曲约束支撑框架体系(BRBF)是新近发明并逐渐得到应用的一种框架体系。因为屈曲约束支撑(BRB)在受拉和受压时都可屈服而不屈曲,因此克服了传统支撑体系的缺点。第二部分简要介绍了SEAOC-AISC提出的反复加载试验要求,介绍了BRB各组成部分、BRB构件本身及BRBF体系的性能,以及BRBF的设计方法。

关键词：支撑体系屈曲研究进展应用框架体系试验要求反复加载组成部分设计方法受压