Dynamic Evaluation of Structure using Shock Table

Abstract

Masonry is one of the most popular construction material for Public and Residential Buildings due to its easy availability and cheaper cost. Apart, it is locally available. For low cost housing, people prefers masonry structures. In hilly areas people prefer to use stone masonry structures instead of Reinforced Cement Concrete (RCC) structures and Load Bearing masonry structures to reduce transportation cost of concrete, steel and masonry. Most hilly area of Northen India is seismically active and suffered many earthquake in past. Stone masonry structures being massive in nature, behavior of such structures under dynamic force like earthquake is important from safety point of view. Apart, innovative and cheap earthquake resisting features plays vital role to enhance earthquake safety of such massive stone masonry structures. Present study aims towards understanding behavior of stone masonry structure with different earthquake resisting features. Various earthquake resisting features like use of vertical containment reinforcement, cross bracing, cross links, welded wire mesh at various stage of stone masonry wall were used. Before implementing earthquake resisting features to scaled stone masonry building, efficiency of earthquake resisting feature are studied through freely standing stone masonry walls. Two full scale stone masonry walls, one made from stone with mud mortar while other made from stone with mortar with Vertical Containment reinforcement, Cross links connected through out height of wall and have welded wire mesh of two layers, one at 1 3 of height and other at top of wall are constructed. Both stone masonry walls, with and without earthquake resisting features are tested under impact load applied through freely swinging pendulum formed using sand begs through A-frame loading system. Peak acceleration at point of impact and at top of walls are captured using Uni-axial Accelerometer , Data Acquisition System and Computer system. It has been found that stone masonry wall with earthquake resisting features like Vertical Containment, Cross-links and Welded Wire Mesh outperform stone masonry wall without such features. Mode of failure observed for stone masonry wall with earthquake resisting feature is much controlled as compared to other stone masonry wall. Efficacy of earthquake resisting features is further access by conducting dynamic test on half scaled one and half story stone masonry building and half scaled two and half story stone masonry building using Shock table facility. Apart, comparative study to understand effectiveness of individual earthquake resisting features vertical containment reinforcement with cross links and welded wire mesh at different level of wall at different part of wall along with wall with stone in mud mortar and stone in lime mortar are also under taken on shock table. It has been found that, both half scaled models of one and half story and two and half story of RR stone masonry building resist dynamic load sufficiently with local damage at few places and do not completely collapse. Comparative study of four walls reveal that performance of wall with stone in mud mortar is at par with stone in lime mortar. However they both fails in brittle mode. Stone masonry wall with welded wire mesh at varies level improves performance as compared to wall with stone in mud mortar and stone in lime mortar. However RR stone wall with Vertical Containment with cross links shows ductile behavior and perform best amongst all four wall.