Introduction

Designers who practice in seismically active developing countries face numerous unique issues with respect to earthquake-resistant design and construction. Situations where widespread poverty coexists with aspirations to advance technologically and economically lead to many extremes. Adjacent to a building project employing state-of-the-art seismic resistance, such as seismic isolation, basic engineered or non-engineered construction in all likelihood lacks any intentional earthquake resisting features. Although all of the content of previous chapters is applicable to developing countries, this chapter bridges between technologies and practices commonplace in so-called developed countries and what is rarely encountered and possibly resisted in developing countries.

Developing countries are characterized by rapid urbanization, most of which is uncontrolled or poorly controlled. Weak or non-existent regulatory environments, a subsequent lack of enforcement of design and construction standards, and a lack of effective technical and professional leadership, have led to seismically vulnerable building stocks. Polat Gulkan's description of the situation in Turkey applies elsewhere: ' [the] quality of the country's building stock is highly variable and control and supervision of design and construction seem to have been pre-empted in the interest of a fast-paced rural to urban conversion' ' 1 Sudhir Jain's insight into India's construction industry prompts him to assert that 'a huge number of unsafe buildings continue to be built every day in different cities and towns ' . By way of illustration, he notes how approximately three-quarters of 6000 pre-cast concrete school buildings constructed between 1999 and 2000 collapsed or were seriously damaged during the 2001 Bhuj earthquake (Fig. I6.I).2

▲ 16.2 Seismically vulnerable buildings in Mumbai.

(Reproduced with permission from R. Sinha).

Developing country researchers who assess the seismic vulnerability of their own cities come to similarly troubling conclusions. After noting that almost 50 per cent of Mumbai's population inhabits informal slum houses, Sinha and Adarsh conclude that ' the occurrence of a code-level (MSK Intensity VII) at Mumbai may lead to massive loss of life and damage of buildings. Depending on the time of day, between 25,000 and 42,000 people may perish due to structural collapse and damage in the earthquake. The numbers of serious injuries may also range between 71,000 to 118,000, possibly placing a very severe strain on the emergency relief and health-care infrastructure. Similarly, a very large number of buildings (in millions) may be damaged or lost' 3 (Fig. 16.2). Although not as dramatic in its findings, a report on the vulnerability of Tashkent, the capital of Uzbekistan states that, ' About 43 per cent of the inhabitants of the Tashkent city live in buildings that were not adequately designed and constructed to meet current standards of seismic resistance' .4 In this case, the most hazardous buildings are not so-called ' informal ' buildings, but engineered nine to sixteen-sto-rey frame-panel buildings (Fig. 16.3). They were prefabricated and connected by field welds of poor quality.

It comes as no surprise that informal or non-engineered buildings are seismically deficient. Built from heavy, brittle and often weak materials they lack any tension elements to tie walls together, or walls to floors or roofs, and that might strengthen walls against in-plane shear failure. Unfortunately, this seismically vulnerable construction, which may be new, has in many cases replaced traditional building types which have demonstrated better seismic performance during past quakes. However, it i s unexpected that engineered buildings, which may also be designed by architects, are so vulnerable. The reality is that the seismic performance of many engineered buildings in developing countries is compromised by configuration, design and construction defects. In most countries a sound earthquake-resistant building can be achieved only by going well beyond their conventional practice, to the extent of introducing quite different design and building techniques.

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