Experimental Response of Irregular Building Under Dynamic Loading

Abstract

Advancement to new construction technologies and invention of newer and more efficient material made possible to construct lighter and flexible structures with irregular geometry. Due to unsymmetrical distribution of mass and stiffness of irregular structure, it is expected to behave differently as compared to regular geometry structure when subjected to dynamic loading. Typically when irregular structures undergoes torsion, inducing additional shear to vertical structural elements. It has been found that many irregular structures are used for important building like school, hospital, industrial and commercial. This offers seismic hazard hence it is important to study the behaviour of irregular structures under dynamic loading. In the present study, Irregular structures with irregularities plan geometries like L- and T- shape are studied through Single Degree of Freedom Systems (SDOF) and Multi Degree of Freedom System (MDOF) scaled building model through shake table. SDOF and MDOF building model are fabricated using Aluminium material and satisfies the planer irregularities provisions defined in IS 1893 (part -1)-2002.Apart SDOF model with material irregularity is also fabricated with three columns are made out of aluminium while fourth is made of mild steel. Also SDOF and MDOF building modes are subjected to free as well as forced vibrations to determine its behaviour in terms of Natural Frequency, Damping constant and Acceleration response of the mass. It has been observed that L- shape building model shows larger acceleration response as compared to T-shape building model. Apart damping coefficient ζ is observed to be highest for building model with material irregularity followed by T-shaped building model and least is building with L- shape geometry. Forced vibration study on SDOF and MDOF systems indicates that for both the types transmissibility ratio is highest for L-shape building model. Transmissibility ratio for T shape building model is smaller than transmissibility ratio for L shape building model, but is slightly higher than transmissibility ratio of material irregularity building model.