Spring 2007

 Numerical and Experimental Study of Structures with Soft Stories

Himadree Roy


This thesis presents results of numerical and experimental works performed on the seismic response of structural models with soft stories. Part of the work concentrates on the numerical work on nonlinear two-dimensional RC frames with brick infills, which show the potentially destructive effect and significant permanent deformation of structures with soft stories caused by a major earthquake.

The experimental facilities described in the latter part of the work are developed at The University of Asia Pacific (UAP), which includes a small shake table capable of generating defined earthquake motion (scaled El Centro earthquake) using an indigenous and inexpensive approach. It is the first such work reported in Bangladesh and this concept can be used for developing larger shake tables, the cost of which would otherwise be prohibitive. Arrangements for ground shaking are made from the combination of mechanical and electrical equipments. The structural model used for the experiments is a model multi-storied structure made of springs (as columns) and timber plates (as floors). Floor vibrations are recorded with time using mechanical devices. The data acquisition system is found to be very accurate as the recorded ground motions match very well with the scaled El Centro earthquake data.

Several experimental scenarios are created by changing the structural mass and stiffness at different floors and subjecting the structural model to scaled El Centro ground vibrations of different time durations. The resulting modifications to the structural behavior are quite significant. The experimental results match very well with the numerical predictions from computer programs using nonlinear dynamic analysis.