INTRODUCTION
  1. GENERAL
Earthquake is an uncontrollable natural phenomenon that can damage even the most well designed structure. The common perception for resisting a seismic force is by strengthening the structure. The traditional engineering design strategy for seismic protection is based on increasing the design capacity and stiffness to accommodate foreseeable lateral forces. It may not be the most efficient solution. The problem of the conventional approach is that all seismic forces from the foundation will be absorbed by the superstructure. Moreover, to make sure that the capacity exceeds the seismic demand for a concrete structure, a large amount of concrete and reinforcement is needed, which in turn increases the cost of construction. The seismic base isolation technique is precisely the opposite approach to the conventional design strategy. It is not possible to control the earthquake itself but it is possible to modify the demand that it creates on the structure by preventing the seismic motions being transmitted from the foundation into the structure above. It reduces the demand to make sure that it is less than the capacity. Seismic base isolation is a part of a structure’s seismic protection systems that reduces the effect of ground shaking on the superstructure. It is a design technique that uncouples a structure from its base or ground and thereby protecting it from damaging effects of ground motion[1]. The concept of base isolation is that the structure is separated from the ground during an earthquake, the ground will be moving but the structure will be dormant. It actively damps the seismic energy thereby preventing the seismic energy to be transferred to the superstructure and damage it. This ingenious strategy not only meets all serviceability and functional requirements but also reduces the requirement of concrete and reinforcement needed to increase the capacity of structure to resist being damaged by ground motion. Thus, construction cost is reduced.
The concept of seismic base isolation is more than a century old[1]. However, not until the 1970’s it evolved into the practical strategy for seismic-resistant design. Modern concept of shock absorbing by base isolation with a bi-linear force-displacement characteristic was inspired from the shock-absorbing soft first story concept developed by Mark Fintel and Fazlur R. Khan, 1969[2]. In 1976, the Earthquake Engineering Research Centre (EERC), now known as the Pacific Engineering Research Centre (PEER), of the University of California at Berkeley, was the first institution in the United States to conduct a study on the feasibility of using raw rubber bearings as base isolators to defend buildings from earthquakes[3]. Among all types of base isolation system actually the rubber bearings are the most effective isolators as they are comparatively effortless to manufacture, can survive for a long time, do not require external restoring force and are outstandingly resistant to ecological degradation.
  1. BACKGROUND
  2. MOTIVATION
  3. LIMITATION
  4. PRESENT CONDITION IN BANGLADESH
  5. SCOPE AND OBJECTIVES
The motivation behind this dissertation paper is twofold. First, it is meant to provide a concise point of departure for researchers and practitioners alike wishing to assess the current state of the art in the control of civil engineering structures. Second, and perhaps more important, it provides a link between structural control and other fields of control theory, pointing out both differences and similarities and where future research and application efforts are likely to prove fruitful.
The paper is organized in the following way: section 2 deals with passive energy dissipation; section 3 deals with active control; section 4 deals with hybrid and semi-active control systems; section 5 discusses sensors for structural control; section 6 deals with smart material systems; section 7 deals with health monitoring and damage detection; and section 8 deals with research needs. An extensive list of references is provided in the references section.
Given the very broad and interdisciplinary nature of the field of structural control and monitoring of civil infrastructure systems, it is not feasible to discuss or cite all relevant publications and applications. The writers have done their best to present a balanced view of the developments in the field of structural control and monitoring, however, only a limited number of references could be cited. Consequently, absence of a citation of a particular work should not be construed as implying anything about the publication’s merit. Where appropriate, publications in technical journals were preferred for inclusion over related publications in proceedings. Also, when discussing control theory, emphasis was placed on those issues related to the physical behavior of civil structures as opposed to sophisticated developments in control system theory.
Chapter 2