Toshikazu Kabeyasawa

New Concept on Fail-Safe Design of Foundation Structure Systems Insensitive to Extreme Motions

Owing to systematic and dense seismic observation networks, extreme ground motions have been recorded in recent major earthquakes with high velocity or high acceleration far exceeding the conventional design code level. At the same time, most of reinforced concrete (RC) building structures in Japan survived these severe motions, probably because of higher capacity than design requirements or of input loss at the base. The authors have conducted shake table tests on full-scale RC buildings with flexible foundation at E-Defense to verify the input loss at the base. The test results are outlined in this paper, where the obvious reduction of damage to the building structure was observed owing to the slip behavior at the base. The results show that it is feasible to and apply in practice a fail-safe system against possible and yet unseen future extreme motions, by incorporating the slip behaviour positively to control damage or ensure safety.

Effective Slab Width for Evaluating Ultimate Seismic Capacities of Reinforced Concrete Buildings

A series of static and seismic loading tests of reinforced concrete frame assemblies were conducted in 2010, 2012, 2013 and 2014 to identify the effects of slab for evaluation of seismic capacities of reinforced concrete buildings as part of national research projects for review of the technical standards on seismic design practices in Japan. Two-fifth or half scale seven specimens were tested representing three-dimensional reinforced concrete beam-yielding frames with floor slab. A special loading set-up was invented and used to simulate the boundary conditions of the medium-story frame so that the axial elongation of the beams would not be constrained by the reaction supports consisting of pin-fixed and pin-roller. It was generally found from the series of tests and analyses that the slab reinforcing bars were increasing almost uniformly through the whole slab width and was fully effective to the flexural strength of the beams at around one percent story drift. The observed and calculated beam strengths with the full width of slab was much higher than those with the effective slab reinforcing bars assumed in the current design practice.

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.