Earthquake Resistant Design: Issues and Challenges

Introduction

Every year thousands or more than that earthquakes are felt by a human being worldwide out of which some range from very small intensity felt only by few persons to great intensities that destroy the whole cities (Federal Emergency Management Agency, 2010). Earthquakes have always been the major potential source of damage and casualties for humankind when compared with other natural hazards such as Tsunami, Cyclone, Floods, and Landslide. Although Places varies but the pattern with which earthquakes will strike remains same, since earthquake strikes without giving any sort of warnings, leaving the whole cities in the wreckage and killing thousands of people (Gioncu & Mazzolani, 2011). The loss of human lives, economical losses depends upon the intensity with which grounds shakes, location and depth of earthquakes and the amount with which buildings get settled (Federal Emergency Management Agency, 2010).

People are killed not due to earthquakes but the buildings or the structure made by them does so. Till date, the number of earthquakes that have occurred yet and damages caused by it weather loss of human lives or financial losses are worse in areas which are densely populated. Where a large number of buildings have been constructed on a seismically active zone and also the due presence of older buildings that have not been properly refurbished (Henkel et. al., 2008). Earthquakes that occurs in isolated areas which are far away from dense populations have experienced rarely any damage so it is not necessary that earthquakes that are of strong magnitude will cause large destructions, even a small magnitude of earthquakes can create a similar scenario when it strikes a densely populated area (Gioncu & Mazzolani, 2011).

Earthquakes, are usually caused by number of factors, such as due to movement of magma within the volcanoes or due to expulsion in the earth crusts, but the earthquakes, which is initiated due to these factors are of very small intensity and causes very less damage, whereas major earthquakes are caused due to sudden movement of tectonic plates over the fault plane deep inside the earth’s mantle because of which ground motion is experienced on the earth surface since transmission of energy waves from the bedrock takes place (Hamburger & Gumpertz, 2009),because of this ground motion earthquake forces are generated as structures dynamically respond to induced ground motion (King, 1998, Lindeburg & McMullin,2014). This action makes earthquake forces completely different from other imposed loads that act on any structures. Thus due the inelastic characteristics of the structures the earthquake forces can be influenced directly which give designer an opportunity to influence the earthquake forces to large extent by properly distributing lateral forces, by maintaining the regularity of building in plan and elevation, by limiting the developments of unwanted response mode and by selecting proper response mode (King, 1998).

Main Purpose Of Design

Structure Design has always been one of the most interesting as well as creative segments in earthquake engineering for many decades. The main purpose of structure design is to create a structure, which is technical, as well as economically sound and it has the ability to resist and transmit the different forces acting on it, and the deformation induced by these forces should be within limits (Kargahi & Anderson, 2004, Rizk, 2010). Therefore, the major purpose of structure design is to construct the optimal structure. According to many authors optimisation not only means to consider the initial cost of buildings but it should focus on the benefits that have to come from structure in its service period, maintenance cost, damage cost and there is always been probabilities that during service period structure will suffer damage and failure (Rosenblueth, 1974, Dalton. et al. 2013). Gallagher pointed that even today in the field of modern analysis technology; optimum design technology, has not been properly accepted in practical design and it is difficult to determine the causes responsible for slow acceptance of design technologies in practical design fields (Gallagher, 1973).