STRENGTHENING OF EXISTING BUILDINGS AGAINST EARTHQUAKE WITH CONSIDERATION OF ECONOMIC CONSTRAINTS IN DEVELOPING COUNTRIES

摘要

Developing countries located in earthquake prone areas of the world can anticipate huge life and property loss during major earthquakes. The study that was recently conducted for the city of Tehran indicates that the economic loss due to a scenario earthquake with intensity IX (MMI) will amount to tens of billion US dollars, not mentioning the loss of many lives and the chaos following the event. Obviously such loss may exceed the GNP of the nation. There are many old buildings of various types in Iran that have the potential for strengthening to withstand earthquakes with lower Intensity, say VI or VII (MMI). For developing or poor nations it would be unreasonable and economically unfeasible to demolish old buildings that do not meet the requirements of their respective seismic codes. This is a luxury that developing countries cannot afford. Building strengthening should be gradual process in order to be acceptable to their owners and the authorities and at the same time feasible to implement. One philosophy that may be adopted for developing countries is to survey, identify and categorize the buildings based on their inherent lateral load resistance levels. The strengthening can be a gradual process and therefore be planned for different levels of earthquake intensity. Therefore, the extent of damage during earthquakes of different intensities can be controlled without imposing sudden major economic impact on the nations. The survey of several hundred buildings of different structural types and usage was carried out for the entire city of Tehran recently. Earthquake resistance level for those buildings was determined. Based on the above philosophy and the knowledge gained about the existing buildings, several levels of appropriate strengthening methods were established. This paper presents the established strengthening methods and their respective cost savings for different levels of earthquake intensity, compared with full-fledged strengthening complying with the code requirements.