A study of the opening factor for seismic resistance of earthen buildings
Unreinforced mud-brick (adobe) structures are extremely vulnerable when subjected to seismic forces that can result in human casualties and asset damage. The majority of unreinforced adobe structures are usually found in developing countries as their construction is easy, cheap and requires little skill. There are many adobe buildings located in the northern part of Thailand, an area classified by the Thai government as a seismic hazard area. This research investigated the seismic performance between circular and square construction of unreinforced adobe buildings, both with and without openings. Static tilt tests were carried out to evaluate the seismic performance of square and circular adobe models constructed at a scale of 1: 3. The models were subjected to an increasing lateral load when tilted from the vertical on a tilting table. The lateral component of model weight was used as a parameter to quantify the maximum seismic force for each model and indicated that the shapes and the openings of unreinforced adobe buildings are important factors in the seismic resistant performance. The circular shape indicated a better seismic resistance than the square as did buildings with openings. The lighter weight of the models with openings influenced the ability to resist the lateral forces. Adobe constructions in seismic areas should be built in a circular shape and designed to minimize the overall weight. This will assist in decreasing potential damage to the structures, reduce fatalities and asset losses during any earthquake event.
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