Generally, when an extreme natural event occurs, emergency shelters, often school buildings, house affected people and keep them out of harm's way. Unfortunately, our school buildings seemed more vulnerable than residential buildings. So the lives of affected people after the earthquake were precarious. Thousands of tents were not enough to house disaster victims because public building likes schools and government offices which could be used to shelter large number of victims suffered significant damages.
This author worked as an engineer to retrofit school buildings in eastern Nepal after 2011 Nepal-Sikkim earthquake. I had visited hundreds of public school. Based on this experience, this article tries to analyse the nature of school buildings that made them so vulnerable.Many school buildings are constructed by funding agencies using local material. These funding agencies do not always take into consideration natural hazards and the schools, therefore, may not be built with hazard vulnerability in mind. Many school buildings built before the 1980s are unreinforced masonry buildings. Masonry building in Nepal were not designed and constructed in accordance to the National building Code (NBC) Nepal. School buildings in remote areas are constructed of stone, and adobe. Stone-masonry buildings suffer damages primarily because of undressed stones used without proper bonding between adjacent courses of masonry. The mud mortar used as bonding material further weakens the strength of the structure.
Earthquake resistant features such as horizontal bands and stones at the corners are generally not provided. This resulted in severe cracks near the corners when subjected to even mild shaking.
Money allocated/distributed by Department of Education (DoE) is not enough to construct disaster-resilient buildings. In addition, schools are often built on marginal pieces that are unsuitable for commercial or agricultural use. All too often, school buildings are situated in vulnerable areas because proper site-selection criteria were not applied.
Most school buildings were built a few decades ago when electricity was limited to urban areas. Natural light and cross ventilation is still prime factor in designing school building in remote areas. Natural light and cross-ventilation requirements lead to construction of school buildings that are long but which have very narrow width, making them vulnerable to earthquake. In hilly areas with limited flat land, this results in buildings with irregular shapes. Building with irregular shapes such as L, H and T have vulnerable corners. Classrooms often have large windows on one side to provide natural light and ventilation. Large class room ventilation or window restricts the height of masonry wall below them.
In order to accommodate large number of students per class, classrooms tend to be large, without interior supports. Classrooms also tend to be placed next to each other with a corridor and exterior windows on the other two sides, meaning that there are few, if any, cross walls outside class rooms. As mentioned, school buildings were built few decades ago. Most of them have load-bearing wall system. Longer walls without cross walls make the buildings vulnerable to earthquakes. This is the reason school buildings are more vulnerable than similarly-built residential houses. School buildings have fewer walls for the same plinth area because of larger room and opening (window, door and ventilation).
In Nepal, school buildings are often constructed on hilltops, filled land and riverbank. Soft soil in filled land, near the river and hilltops can amplify earthquake tremors. School built on filled land are susceptible to liquefaction, a phenomenon in which saturated sandy soil flows like liquid.
In urban areas, school buildings are often concrete cement structures. However, most of these buildings have been designed either prior to enforcement of building code or have been designed by flouting the building code. More than half of private school buildings are not functionally designed as school buildings.
Inadequate exits are problematic in schools if there is an earthquake or fire. Many classrooms have only one small door which opens inward rather than outward. Additionally, windows also have iron bars that prevent from being used as alternate escape routes. Corridors and staircases are often too narrow and used for storage.
Government forces communities to build schools but does not provide any technical support. District Education Office has one or two engineer to provide technical support to all schools in the district. Lack of inspection during construction removes the incentive to follow plans and adhere to specifications. Construction quality in most community built schools is poor due to poor quality of both engineered and locally available materials and lack of skills. A structure that is not properly maintained is more vulnerable to natural disasters. Unfortunately, school buildings are often poorly maintained and little money, if any, is typically set aside for maintenance. Corruption, low bid contracting, informal engineering lead to poor quality of construction.
There have been catastrophic failures of unreinforced masonry structures in previous earthquakes, but based on the author's experience, this kind of construction is still the norm in suburban and remote areas of Nepal. Unreinforced masonry buildings with walls not properly connected to the foundations, floors, roof, and interior or exterior transverse walls constitute a major threat because the walls start to collapse as soon as the building is subjected to even moderate shaking.
The author is a PhD candidate in civil engineering at University of Alberta, Canada
kesehab@ualberta.ca
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