Akira Tasai

Measuring strain and stress distributions along rebar embedded in concrete using time-of-flight neutron diffraction

In modern society, architectural and civil engineering structures such as reinforced concrete buildings require high seismic performance to minimize the ?megarisk? exposed from urban earthquake hazards. In the reinforced concrete structures, the bond resistance between rebar and concrete is one important parameter for discussing its performance and it has been typically evaluated by measuring the strain distribution along the embedded rebar. Here, we present in-situ strain and stress measurements for the rebar in reinforced concrete using time-of-flight neutron diffraction as a novel alternative technique to typical strain gauges. It was demonstrated in this study that the three-dimensional deformation behavior of the embedded rebar in normal-strength concrete, cured in air, can be accurately measured under pull-out loading using time-of-flight neutron diffraction. Wider applications of neutron diffraction in the structural engineering field are expected for advanced understanding of actual phenomena on reinforced concrete structures.

Development of Building Monitoring System to Verify the Capacity Spectrum Method

Due to Kobe Earthquake (1995, M7.3), 6,434 people were killed, and 104,906 buildings were totally collapsed. After Kobe Earthquake , 17 large earthquakes occurred in Japan, which include Niigata Cyuetsu Earthquake (M7.2) in 2005 and the 2011 Off the Pacific Coast of Tohoku Earthquake (M9.0) in 2011. At the same time, a lot of earthquake ground motion data were measured by sensors. Some earthquakes, however, caused only slight damage to reinforced concrete structures although many earthquake records with large PGAs were measured. A monitoring building response is required to find out the reason of disagreement between analysis result and observation. In this paper, a building monitoring system with inexpensive sensors is proposed and the validity of the system is confirmed with an actual response of an instrumented building during the 2011 Off the pacific Coast of Tohoku Earthquake .

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.