Hitoshi Shiohara

DESIGN IMPLICATIONS OF A LARGE-SCALE SHAKING TABLE TEST ON A FOUR-STORY REINFORCED CONCRETE BUILDING

A full-scale, four-story, reinforced concrete building designed in accordance with the current Japanese seismic design code was tested under multi-directional shaking on the E-Defense shake table. A two-bay moment frame system was adopted in the longer plan direction and a pair of multi-story walls was incorporated in the exterior frames in the shorter plan direction. Minor adjustments to the designs were made to bring the final structure closer to U.S. practice and thereby benefit a broader audience. The resulting details of the test building reflected most current U.S. seismic design provisions. The structure remained stable throughout the series of severe shaking tests, even though lateral story drift ratios exceeded 0.04. The structure did, however, sustain severe damage in the walls and beam-column joints. Beams and columns showed limited damage and maintained core integrity throughout the series of tests. Implications of test results for the seismic design provisions of ACI 318-11 are discussed.

Seismic Retrofit of Reinforced Concrete Beam-column Joints with CFRP Composites

ð This is an experimental study on a new seismic retrofitting method for longitudinally over reinforced concrete beam-column joints. The objective of the retrofit is to increase the story shear capacity with externally placed CFRP composite to ensure a strength of beam-yielding mechanism by shifting the critical section from the joints to the beam ends. Four one third scale reinforced concrete interior beam- column joint subassembleges were constructed and subjected to statically cyclic lateral loading simulating an earthquake. The main parameter of the test is with and without a retrofit. Externally placed CFRP composite for seismic retrofit of beam- column joints has been considered as challenging because the presence of transverse beams and floor slab that limit the accessibility to the joint in actual three- dimensional frame. The method in this study overcomes the difficulty by placing only four CFRP bundled strands vertically at the four corners of a column. Due to its simplicity it is applicable to most types of three dimensional beam-column joints with transverse beams and floor slab despite of architectural restrictions. Test result shows that a joint shear failure was altered to a beam-hinging mechanism and the story shear increased to the shear at flexural capacity of beams. It is verified that the new retrofitting method is one of the practical solutions for seismic retrofits of critical beam-column joints.

Damages to Reinforced Concrete Buildings

Typical damages to reinforced concrete buildings, both by the ground motions and the tsunami waves, are outlined in this section. The report herein is based primarily on the field survey of the AIJ members and collected through the members of the Reinforced Concrete Steering Committee of AIJ. The typical damages to reinforced concrete buildings are described below through the reports on the buildings selected and available for detailed survey. The damage reports below are translated selectively from the Chap. 6, Sect. 6.2 of AIJ report in Japanese version, which contains more photos and figures, especially on the structural plans as well as the damage rate evaluation of members. The reports on the buildings below are arranged as from the Japanese version: (1) school buildings located from north to south (Iwate, Miyagi, Fukushima and Kanto areas), (2) government offices, (3) residential buildings.

Development of a New Precast Concrete Panel Wall System Incorporated with Energy Dissipative Dowel Connectors

Conventional methods of earthquake resistant design rely on the ductile behavior of the structural member for energy dissipation. It is required that the structure yields and experiences damage without collapse under a catastrophic event. For newly built structures, ductility requirement can be achieved by providing special detailing where inelastic deformation expected. However, the situation is not straightforward and complex for the existing or poorly detailed structures. In most case, rehabilitation becomes impossible due to insufficient techniques, high costs and long down-time. As a response to these shortcomings, a new Precast Concrete Panel Wall (PCPW) system with dowel connectors is introduced herein. In a moderate event, proposed system relies on the energy dissipated by the dowel connectors at panel attachments. The hysteretic energy dissipation will be concentrated on specially designed connectors and this will reduce the inelastic demand on existing elements. However, under the action of a major event, panels will intact with the frame and contribute stiffness by a diagonal strut action. This will prevent from total collapse of the structure. The dual response mechanisms of PCPW systems inspire us considering them as an alternative passive control system that would be used in strengthening works.