Shoichi Kishiki

Influence of Isolation Gap Size on the Collapse Performance of Seismically Base-Isolated Buildings

The pounding of retaining walls forms a potential risk of degrading the performance of seismically base-isolated buildings subjected to strong, especially near-fault, earthquake ground motions. Incremental dynamic analysis is employed to generate the so-called gap graph, in which two characteristic gap sizes of a base-isolated building are related with the isolation period of the building and the strengthof the superstructure. Thegapgraph canbe usedto evaluate the required gap size for a base-isolated building to have certain collapse performance. By means of gap graphs, the interdependent relations of gap size with other important factors that influence the seismic performance of the base-isolated building are examined. In particular, the results show that near-fault pulse-like ground motions are likely to impose much higher demand for the isolation gap than far-field ones.

Subassemblage Cyclic Loading Tests of Buckling-Restrained Braced RC Frames with Unconstrained Gusset Connections

AbstractAn unconstrained gusset connection for buckling restrained braces in reinforced concrete frame structures is proposed and tested as an effort to mitigate the complicated and usually harmful interactions between the steel gusset plate and the adjoining reinforced concrete column. Local damage control incorporating the rearrangement of beam flexural strength is also proposed to enhance the reliability of the gusset connection by moving the potential plastic hinge of the beam away from the connection region. Two different connecting methods, one with posttensioned steel rods and the other embedded stud groups, were considered. The results of the cyclic loading tests on reinforced concrete (RC) beam-gusset connection subassemblies confirmed that both connecting methods are available as long as the local damage control is implemented, which is not only helpful in eliminating the unfavorable deformation loss at the connection, but more importantly, can prevent the buckling restrained braces (BRBs) from ...

STRUCTURAL DAMAGE ON SCHOOL GYMNASIUMS DUE TO THE 2011 TOHOKU EARTHQUAKE

In order to clarify structural damage on school gymnasiums due to the 2011 Tohoku Earthquake, total 1611 of school gymnasiums in Iwate Prefecture, Miyagi Prefecture, Fukushima Prefecture, Ibaraki Prefecture, and Tochigi Prefecture were investigated. More than 70% of investigated school gymnasium were slightly damaged or not damaged. On the other hand, about 6% of school gymnasium built in or after 1982 were seriously damaged. Moreover, in this paper, structural elements damaged seriously in the school gymnasiums built in 1982 or afterwards were examined.

RECONNAISSANCE OF DAMAGED STEEL SCHOOL BUILDINGS DUE TO THE 2011 TOHOKU EARTHQUAKE

An outline of a reconnaissance of steel school buildings damaged by the 2011 Tohoku earthquake is presented. In this reconnaissance, a total of 216 facilities have been investigated by the Steel Structure Working Group of the Subcommittee on Seismic Performance of School Buildings, Architectural Institute of Japan. The damage to structural elements, connections, non-structural elements, foundation and surrounding soil, as well as the details including building history and seismic retrofit have been recorded and the overall damage has been evaluated based on the “Standard for Post-earthquake Damage Evaluation of Damaged Buildings” published by the Japan Building Disaster Prevention Association. Not only seismic damage but damage caused by the devastating tsunami are also covered. Detailed analysis of the damage to individual structural and non-structural components are presented in following papers.

PULL-OUT TEST OF ANCHOR BOLT FOR FASTENING LEAD DAMPER TO CONCRETE FOUNDATION

Pull-out tests on anchor bolts for fastening lead damper to concrete foundation were conducted to evaluate factors affecting pull-out behavior of anchor bolts. The main parameters were type of anchor bolt commonly used for anchorage of lead damper and layout of reinforcements around anchor bolt. The following results were obtained : (1) Vertical reinforcements arranged around anchor bolt contribute to increase in concrete breakout strength. (2) For long nut type anchor bolt, long nut length covered anchor bolt must be treated with enough care to avoid slipping anchor bolt. Because slipping failure lead to decrease in tensile strength and increase in pull-out displacement at failure. (3) The slope of the concrete cone was much flatter than 45 degree assuming in design procedure, regardless of the embedment depth, anchor type and reinforcement pattern. (4) Based on test results, simple concrete failure model was proposed. Using this model, effective radius of projected area were assessed 0.81le - 0.96le. These values were close to effective radius 1.0 le in existing design formula according to AIJ.

SHAKING TABLE TEST OF BEAM-END DAMPER FRAME USING MULTIPURPOSE INERTIAL MASS SYSTEM

This paper presents a multipurpose set-up system called “test bed” for large shaking table tests. The test bed is composed of multistory box-trusses with concrete mass of inertia supported by linear slider bearings in each layer. It supports self-weight, and gives horizontal inertial force to the specimen frame when they are connected together and placed on the shaking table. In this paper, shaking table tests with a single-story sample frame with beam-end damper are carried out. Their results are compared with the analytical results and the performances of this set-up is discussed.