The Advances and Prospects of Research on Earthquake Engineering at IEM

This paper describes briefly the recent advances and achievements of the research projects conducted by the Institute of Engineering Mechanics (IEM) in the period of the Ninth Five-Year Plan (1995～2000) with the support of the China Seismological Bureau (CSB). These projects are related with key problems in the field of earthquake engineering. They are: development of the methods for determining earthquake resistant design load level, study on mechanisms of earthquake damage to buildings; development of new technology of base isolation, and study on earthquake damage prediction and seismic loss assessment methods. Through these studies, quite a number of problems have been solved and some of them have been applied in earthquake engineering design and practice.

Stochastic Response Analysis of Piled Offshore Platforms to Earthquake Load

In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to earthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis.

Large, moderate, small earthquakes and seismic fortification criterion

This paper discusses the relation between two-step seismic design and the standard of probability of exceedance, and the relation of three-levels seismic ground motion parameters given by probability method and comprehensive probability method. The relative size relations of the ground motions with 2%, 10%, 63% probability of exceedance in 50 years, namely large earthquake, moderate earthquake, and small earthquake, are discussed through a practical example of seismic hazard analysis. The methods to determine seismic fortification criterion are discussed.

Behaviors of Rural Structures during Destructive Earthquakes

This article deals with the results of the research on the behaviors of the rural buildings made up of local materials during earthquakes. This article reveals the mechanical properties of masonry detected based on experimental research results on wall samples made of local materials such as mud bricks, clay and straw mixture, rubble stones and limestones cut in standard sizes. In addition, the constructive measures prepared for the earthquake resistance of rural structures and the application techniques of these buildings in common construction are also generalized in this article.

Adaptive base-isolation of civil structures using variable amplification

Semi-active dampers are used in base-isolation to reduce the seismic response of civil engineering structures. In the present study, a new semi-active damping system using variable amplification will be investigated for adaptive baseisolation. It uses a novel variable amplification device （VAD） connected in series with a passive damper. The VAD is capable of producing multiple amplification factors, each corresponding to a different amplification state. Forces from the damper are amplified to the structure according to the current amplification state, which is selected via a semi-active control algorithm specifically tailored to the system＇s tmique damping characteristics. To demonstrate the effectiveness of the VAD-damper system for adaptive base-isolation, numerical simulations are conducted for three and seven-story base-isolated buildings subject to both far and near-field ground motions. The results indicate that the system can achieve significant reductions in response compared to the base-isolated buildings with no damper. The proposed system is also found to perform well compared to a typical semi-active damper.

APPLICATIONS OF FRACTAL AND CHAOTIC LAWS IN SEISMIC DISSIPATED ENERGY IN AN ENERGY SYSTEM OF ENGINEERING STRUCTURES

Based on the intrinsic characters of the fractal and chaotic dynamic systems of seismic dissipated energy active intensity E d and active intensity of seismic dissipated energy moment I e,the evolutional laws of the long term system and short term system behavior are discussed respectively.Active and passive earthquake control parameters,maintenance decision and inputted energy optimization of system are discussed by means of the predictive results of short term behavior in practical engineering structures; earthquake resistant design probability,maintenance probability,seismic risk analysis and seismic hazard analysis are also discussed by means of the predictive results of long term behavior probability in practical engineering structures.The content might be valuable for the practical applications of earthquake resistance theory and method,and for earthquake control and earthquake reduction problems in practical engineering structures.

Probability-Based Seismic Performance Evaluation for Buildings

Recent developments in earthquake engineering indicate that probabilistic seismic risk analysis (PSRA) is becoming increasingly useful for the evaluation of structural per-formance in accordance with building codes. In recent years, the field of seismic resis-tance design has been undergoing a critical shift in focus from strength to performance. However, current earthquake resistant design procedures do not relate building performance to probability. A lack of sufficient empirical data has highlighted gaps in this research. This study integrated results from the analysis of structural fragility and seismic hazard in Taiwan to perform PSRA to examine the effectiveness of building code in mitigating the risks associated with earthquakes. Factors taken into account included the effect of construction materials, building height, and building age. The results of this study show that the probability of exceeding damage associated with the CP level in buildings of light steel, pre-cast concrete, and masonry, exceeds 2%. These buildings fail to meet the performance objectives outlined in FEMA-273.

Dynamic Interaction of Soil-Isolated Structure:A Systematic Review

Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic performance of isolated structures and revision of relevant isolation specifications,research on dynamic interaction of soil-isolated structure has attracted more and more attention.Based on the basic theory of soil-structure dynamic interaction,we summarize and analyze the research status quo of soil-isolated structure dynamic interaction by means of theoretical analysis,numerical simulation,model test,prototype observation and seismic performance.After reviewing the results of previous research,we reveal that some key issues,which can be used to uncover dynamic interaction mechanism and seismic response characteristics of soil-isolated structures interaction system,should not be neglected.Based on the concept of seismic performance design and the latest research of soil-isolated structure dynamic interaction,we predict the future development of soil-isolated structure dynamic interaction by elastoplastic time history analysis method,seismic performance level and practical analysis method based on energy.

Dynamic Response of Fluid-Single Leg Gravity Platform-Soil Interaction System

An approximate method is presented to investigate the earthquake response of the fluid-single leg (shortened for S. L.) gravity platform-soil interaction system. By assuming a suitable form of the velocity potential of the radiation waves and by using the motion equation and the boundary conditions, the unknown coefficients can be obtained. Thereafter the function of frequency for the interaction system may also be obtained. In this paper, the difference of the system dynamic response between rigid foundation is analyzed and the influences of the various foundation geometric dimension and the various water-depth on the hydrodynamic loading and dynamic response of the system is illustrated.

Approach to Power Spectrum Density Values in Three Dimensional Acceleration of Ground Motions

In this paper, based on the random characteristic analysis of Tianjin Hospital earthquake waves of Tangshan aftershock, the three dimensional acceleration power spectrum density ratio has been presented.

The research of a solution on locating optimally a station for seismic disasters rescue in a city

When the stations for seismic disasters rescue in future or the similars are designed on a network of communication line, the general absolute center of a graph needs to be solved to reduce the requirements in the number ofstations and running parameters and to establish an optimal station in a sense distribution of the rescue arrivaltime by the way of locating optimally the stations. The existing solution on this problem was proposed by Edward (1978) in which, however, there is serious deviation. In this article, the work of Edward (1978) is developed in both formula and figure,more correct solution is proposed and proved. Then the result from the newersolution is contrasted with that from the older one in a instance about locating optimally the station for seismicdisasters rescue.

Design Procedure for Semi Interlocking Masonry

SIM （semi interlocking masonry） is a kind of innovative building system for mortar-less walls. It utilizes a special method of interlocking SIM bricks that allows relative sliding of brick courses in-plane of a wall and prevents out-of-plane relative movement of bricks. It has increased capacity to dissipate earthquake energy through friction between bricks compared with traditional masonry. It can be used in earthquake resistant frame structures as infill panels, which also act as EDD （energy dissipation devices）. However, as a mortar-less system, it is not covered by masonry design standards. The purpose of this paper is to introduce S1M and also to develop an analytical design procedure for this innovative masonry system.

Sturdy,Durable,Fast-To-Build,and Low-Cost Ferrocement Houses

This paper presents the experience in building low-cost houses in ferrocement technology,arched cross-section with on-site construction,using skeletal method combined with steel hollow structural sections.The author wanted to develop a simpler,faster and more cost-effective system of the construction of smaller buildings,retaining their stability and durability,energy-efficiency and resistance to earthquakes and storm winds at the same time.The goal was to enable non-professionals to build houses in quick and simple way using standard,easily accessible materials and tools.Houses such as described in this paper were built in DR Congo(Democratic Republic of the Congo)and have proven to be,fast-to-build,safe,durable and serviceable with practically no maintenance required.In 2016,15 such houses were built in less than four months.The author has promoted the solution for construction of such houses in continent climate conditions too,using stronger frame and much better thermal insulation,without thermal bridges.

HYDRODYNAMIC LOADS ON OIL STORAGE TANKS WITH INTERIOR SEMI-POROUS BARRIERS UNDER EARTHQUAKES

The estimation of the hydrodynamic loading on cylindrical oil storage tank during earthquakes is of fundamental importance in the anti-seismic design. Interior semi-porous barriers are considered being effective to reduce the hydrodynamic response of the inner fluid and the loading on the tank wall. A reduced two-dimensional source distribution method and sub-region matching technique are developed for the prediction of three-dimensional hydrodynamic forces on oil storage tanks of arbitrary sections with interior semi-porous barriers of different configurations under earthquake excitations. Excellent agreement is observed between the present results and the corresponding analytical results for a circular cylindrical oil tank with a concentric interior semi-porous barrier, which shows the validity and effectiveness of the present method. A clear view of the influence of semi-porous barriers on the hydrodynamic response of tanks during earthquakes is obtained by the analyses of computational results, which may offer some guidance to the corresponding anti-seismic design for oil storage tanks and similar structures. The method is also extended to include the effects of the elastic vibrations of the tank.