Earthquake Resistant Features in Stone Masonry Buildings.

 

Earthquake Resistant Features in Stone Masonry Buildings.

Low strength stone masonry buildings are weak against earthquakes, and should be avoided in high seismic zones. The Indian Standard IS 13828-1993 states that inclusion of special earthquake-resistant design and construction features may raise the earthquake resistance of these building and reduce the loss of life. However, in spite of the semic features these buildings may not become totally from from heavy damage and even collapse in case of a major earthquake. The contribution of the each of these features is difficult to quantify, but qualitatively these features have been observed to improve the performance of stone masonry dwellings during past sarthquakes. These features include the following.

(a) Ensure proper wall construction: The wall thickness should not exceed 450 mm. Round stone boulders should not be used in the construction Instead, the stones should be shaped using chisels and hammers Coursed rubble (CH) may is preferred. Use of mud mortar should be avoided in higher seismic s Instead,  cement-sand mortar should be 1.6 for richer) and lime-kand mortar 1:3 (or richer) should be used.

 

(b) Ensure proper bond in masonry courses: The masonry walls should be built in construction lifts not exceeding 600 mm. Through stones (each extending over full thickness of wall) or a pair of overlapping bond-stones (each extending over at least the thickness of wall) must be used at every 600 mm along the height and 4 at a maximum spacing of 1.2 m along the length.

(c) Provide horizontal reinforcing elements: The stone masonry dwellings must have various horizontal bands such as plinth, lintel, roof and gable bands. These bands should be constructed out of reinforced concrete. It is important to provide at least one band (either lintel band or roof band) in stone masonry construction.

(d) Control on overall dimensions and heights: The unsupported length of walls between cross-walls should be limited to 5 m; for longer walls, cross supports raised from the ground level called buttresses should be provided at spacing not more than 4 m. The height of each storey should not exceed 3.0 m. In general, stone masonry buildings should not be taller than 2 storey’s when built in cement mortar, and 1 storey when built in lime. The wall should have a thickness of at least one-sixth its height