Cost increases due to earthquake resistant detailing of concrete structures

Abstract

There are two major factors that discourage the use of earthquake resistant design and detailing of structures constructed in Sri Lanka. They are the belief that the earthquake resistant structures will cost a lot more than the normal structures and the misconception that Sri Lanka is located at an area where no earthquakes will occur. On many occasions, the assumption that a particular area is seismically inactive has been proven wrong at the cost of human life and severe destruction to the infrastructure of an area. This is true for Sri Lanka as well since a number of earthquakes have been reported in the recent past in Central India and one event close to Sri Lanka which have hitherto be considered as seismically inactive. British Standard Codes of Practice used in Sri Lanka for structural design does not cover earthquake design and some of the reinforcement details widely adopted are not desirable with respect to earthquake performance. Earthquakes are among the most awesome of natural forces. They occur suddenly, generally without warning, and within 10-20 seconds can turn cities into wasteland. Most earthquakes around the world occur on well defined tectonic plate boundaries, and are known as inter-plate earthquakes. Earthquakes within a tectonic plate are called intra-plate and are spread across the whole of the plate rather than being confined to the boundaries. These occur less frequently. Since Sri Lanka is located away from well known plate boundaries, any earthquake occurring in Sri Lanka is intra-plate type. In an intra-plate area, it is almost impossible to predict the location or likely time of an earthquake event (Hutchinson et al., 1995). However, it is now widely accepted that the risk of earthquakes and their potential for damage especially in heavily populated areas can no longer be ignored. In summary an earthquake event in Sri Lanka may be considered to be low risk but of high consequence