Hiroki Tamai

Evaluation of Cumulative Damage of RC Members under Repeated Impact Loading

In the civil and structural engineering field, there are so many problems regarding act of impact loading against some structures due to natural disaster. So it is important to evaluate the damage condition of them after impact loading, and to estimate the residual performance of them. This study is focused on a reinforced concrete (herein after called RC) structure such as caisson breakwater and rock-shed. In order to quantitatively evaluate the dynamic behavior and cumulative damage of RC members under low-velocity single and repeated impact loading, we conducted numerical approach by using the theory of Continuum Damage Mechanics (herein after called CDM). At the result, we clarified not only impact behavior of the members but also the relationship between cumulative kinetic energy of repeated impact loading and cumulative damage of the members. In addition, applicability limit of our model based on scalar damage modeling was clarified.

A Fundamental Study on the Shock Cushioning Characteristics of a Novel pin-Fixed Aseismatic Connector for Bridges

This paper presents a novel pin-fixed aseismatic connector for bridges. A feature of this device is that the anchorage areas of both ends are connected with hinges; thus, there are no restrictions with respect to their mounting angles. Additionally, the PC cable of this device is given an appropriate amount of sag; thus, within the range of the sag the structure is capable of absorbing the amount of displacement because of temperature changes and live loads. In addition, this device has a certain shock-cushioning effect because of the rubber material surrounding the hinge pins. However, there is no quantitative evaluation method on the shock-cushioning effect of this device. Therefore, in this study, the shock-cushioning effect of the novel pin-fixed aseismatic connector for bridges is investigated using impact load tests and numerical analysis. It is found that the shock-cushioning effect of this device is almost equal to similar aseismatic connectors. Furthermore, it is also confirmed that their effects can be quantitatively evaluated using impact response analysis.

A Numerical Study on Impact Damage Assessment and Dynamic Behaviour of Concrete Bridges by Pounding Effect

The South Hyogo prefecture earthquake indicated that various kind of damage was incurred under severe ground motion. Some of the reported damage cases are caused by pounding between bridge girders and between a superstructure and an abutment. To establish the reasonable and safe seismic design for bridges, it is necessary to evaluate the damage level of bridge abutment under impact of bridge girder and to clarify dynamic behaviour of whole bridge under pounding. So the main objective of this study is to evaluate the damage level of an abutment by pounding. To achieve this, impact response analyses of pounding effect were conducted by using 3-dimensional FEM. Furthermore, to clarify dynamic behavior of whole bridge under pounding, frame analyses were conducted.

Numerical studies on cumulative damage of RC members under repeated impact loading

We have tried to develop the simple FE analysis method based on continuum damage mechanics to quantitatively evaluate the impact behaviour and the cumulative damage of RC beam under repeated impact loading. As a result, it has been found that the cumulative damage and residual displacement of RC beam under repeated impact load can be properly evaluated, but the crack propagation cannot be evaluated by using the proposed method. This paper presents the following matters: (1) Numerical investigation on the impact behaviour and cumulative damage of RC beam under repeated impact loading by using the proposed method. (2) Numerical investigation of the relationship between cumulative kinetic energy of repeated impact loading and cumulative damage of RC members. (3) Investigation on improved points of our existing proposed method to evaluate the crack path of RC member under repeated impact.