Journal of Earthquake and Tsunami

By taking building structures as systems, the difference between the safety margins of a structure and that of its element is clarified and the robustness of the structure to resist unexpected disasters is discussed. The system concept is further used to introduce the concepts of importance levels and functionality levels in structural systems, the designability of structural systems is then pointed out. The local and global failure mechanisms of building structures under earthquake are summarized, and the failure mechanism control method is discussed based on the concepts of system and designability. For global failure mechanism, the desirable seismic performance is put forward, and at last some practical methods to control the seismic failure mechanism and the failure procedures are proposed based on the hierarchy concept of the structural system.

To reduce casualties and troubles due to earthquakes, Japan Meteorological Agency introduced earthquake early warning (EEW) to general public on 1 October 2007. However, the possibility that EEW induces traffic accidents exists because EEW through car radio may not be transmitted to all the expressway drivers. Hence, the effects of EEW were investigated based on driving simulator experiments. Two kinds of experiments were performed in this study. First, single driving simulator was employed to reveal the effects of EEW on expressways. The reactions of drivers with/without warning are compared in avoiding an obstacle induced by seismic motion. Second, three synchronized driving simulators, simulating three cars running together on an expressway, were employed. When EEW was transmitted to only one car, some drivers reduced speed suddenly, and accidents occurred in two cases out of 14 tests. These experiments show the necessity of public education how to react an EEW on expressways. Turning on the hazard lights after receiving an EEW and then reducing speed gradually is suggested to avoid traffic accidents.

The height of 101-storey Shanghai World Financial Center Tower is 492 m above ground. According to the philosophy of performance-based seismic design, the seismic performance design objectives and corresponding parameters were proposed for the structure under various seismic actions from frequent to rare earthquake levels. Analytical studies including refined finite element analysis, nonlinear time-history analysis, and stress distribution analysis on the important joint have been conducted to evaluate the structural seismic performance. Along with the analytical studies, shaking table model test and the important joint tests have been carried on in order to verify the accuracies of the analytical results as well as to complement the analytical studies. The results obtained from the studies demonstrate that the structural system meets the performance-based design objectives presented in the paper.

The bearing capacity and ductility of confined concrete can be greatly increased by the confinement of confining material. To better study the mechanical behavior of confined concrete, this paper presents the yield criterion of confined concrete, based on the static equilibrium condition, the unified compressive strength model of confined concrete is established. The model captures the character of confined concrete, the effects of confinement effect ratio, the compressive strength of unconfined concrete, and the mechanical properties of confining material on the compressive strength of confined concrete were carefully analyzed.

Stochastic equivalent linearization (SEL) method has gained wide popularity because of its versatility in application to multiple-degree-of-freedom (MDOF) nonlinear systems. It is restricted in the random vibration analysis of flexible structures because of the implicit nonlinear system. This paper presents a new method for the equivalent nonlinear system of flexible structures. Using this method, the implicit geometrically nonlinear system can be represented as an explicit equivalent nonlinear system. According to the modal analysis method, the geometrically nonlinear force is replaced by a high-order moment of modal coordinate. The MDOF physical system is translated into a modal system, which could be solved easily. Based on the equivalent nonlinear system, the nonlinear random vibration method is presented by using SEL technology. By using the pseudo-excitation method, the efficiency of the nonlinear random vibration method is increased obviously. The rapid calculation makes it possible to analyze the nonlinear random vibration of MDOF flexible structure. The validation shows that the method has reasonable precision and high efficiency and it could be used in the random vibration analysis of practical flexible structures.