Toko Hitaka

Seismic resistance capacity of high-rise buildings subjected to long-period ground motions: E-defense shaking table test

A series of large-scale shaking table tests is conducted for a high-rise building structure subjected to long-period ground motions. A test method is developed to preserve the original dimensions of structural members of a prototype building that has 21 stories with a total height of 80 m. The test specimen consists of a four-story, two-span by one-bay steel moment frame and three substitute layers placed on top of the moment frame. The substitute layers, which consist of concrete slabs and rubber bearings, are arranged to represent the upper stories of the prototype. From preliminary vibration tests, equivalence between the test specimen and the prototype is verified in terms of the lower mode natural periods and corresponding mode shapes. The test specimen when subjected to long-period ground motions exhibits cumulative ductilities more than four times those expected in Japanese seismic design, while the maximum story drifts remain nearly the same as those considered in the design. A number of cyclic in...

Using Steel Fiber Reinforced Cementitious Composite (SFRCC) in Shallow Embedded Column Base

Exposed column bases in Japan are commonly covered with lightly reinforced concrete (RC) slab, whose effect is neglected in seismic design so far. However, many experimental investigations showed that the strength, stiffness and energy dissipation are increased by the contribution of the RC slab. In this study, steel fiber reinforced cementitious composites (SFRCC) is employed for the covered slab to further improve the behavior of exposed column base. Here, 0.4 mm×12.0 mm and 6% volume fraction straight steel fibers were adopted for SFRCC. Eight specimens, one exposed, three concrete and four SFRCC specimens, are tested. The test parameters included slab material and reinforcement ratio (size and strength of steel bars).

Cyclic Tests on RC-Steel Shear Plate Composite Wall System Applicable in Beam Spans with Large Openings

A new hysteretic damper system utilizing slit steel shear plates and out-of-plane restraining wood panels is proposed. In this system, the upper half of the damper is a slit shear plate, whereas the lower half is a base wall. The slit shear plate and the wooden restraining panels are attached through bolts designed to prevent shear force transfer to the wood panels. Cyclic loading tests were performed to investigate seismic performance of the proposed system. The restrained specimens mostly behaved in stable manner. While the local out of plane deformation around the slit ends were not restrained, the wood panels were effective to restrain global out-of-plane deformation of shear plates.

Compressive and Flexural Behavior of RC Columns Laterally Prestressed by High-strength Steel Bars

A dry column confining method using high-strength steel bars proposed by one of the authors is applied to a total of 24 reinforced concrete (RC) columns. Two series of tests were conducted on these columns. Hoop steel ratio of the columns was 0.1%, typical of RC columns designed before the Japanese Building Code in 1981. These RC columns were laterally reinforced using 19 sets of four high-strength steel bars and L-shaped steel blocks that were attached around the column by tightening the high-strength steel bars. Five specimens were exposed to concentric compression. Uniform bending test was conducted on 9 specimens under constant axial load. High-strength steel bars were pre-tensioned before testing. The amount of pre-tension was controlled by strain in the bars. It was found that the new confining method is effective to increase ductility of the RC columns. Strength of a RC column increases in a proportional manner to the amount of pre-stress in high-strength steel bars. Strength estimation method is proposed. The measured strength varied between 93% to 116% of the calculated strength.