Seismic Response of Laterite Masonry Structures

Abstract

Laterite is the most favored masonry material in south-west coastal areas of India due to its availability in abundance. However, not much research has been carried out so far on the structural performance of laterite masonry. The studies addressing the seismic performance of laterite masonry buildings are almost nil and hence there is a need for research in this area. The strength and elastic properties of laterite masonry are influenced by the individual properties of laterite blocks and mortar used and the nature of bond between them. Experimental investigations were carried out on the strength characteristics of laterite blocks, cement mortar specimens and stack-bonded laterite masonry prisms under uniaxial compression. From these studies laterite masonry may be classified as weak-soft unit and strong-stiff mortar masonry. Stack bonded laterite masonry prism was modeled using commercially available finite element software and analyzed to understand the stress distribution pattern. Parametric studies were also conducted. In south-west coastal areas of India masonry structures are normally box-type structures with either a light roof or a rigid roof. Efficiency of different types of seismic strengthening measures like lintel band, roof band etc. were studied on both these types of structures. A method of reinforcing laterite masonry with vertical reinforcement called ‘containment reinforcement’ has also been tried. Different configurations of box-type laterite masonry structures with these strengthening measures were modeled. Free vibration studies were conducted to find the natural frequencies and mode shapes of boxtype laterite masonry structures without and with roof. Response of single storeyed boxtype laterite masonry structures, to El-Centro acceleration input was obtained using timehistory analysis. The effect of strengthening factors like lintel band, roof band and containment reinforcement on the natural frequencies, mode shapes and time-history responses were analyzed. Responses of some of these structures to Kobe and Koyna accelerations were also studied