Assesment of Soil Structure Interaction on Dynamic Response of A Masonry Structure

Abstract

This thesis presents the effect of Soil Structure Interaction on dynamic behavior of an unreinforced braced masonry structure under railway traffic vibrations which is never studied before. For this purpose, an instrumented unreinforced braced masonry signal cabin near railway track was investigated under eighteen various railway traffic vibrations. A structure was instrumented with four triaxial accelerometers and a free field accelerometer to consider soil structure interaction effects. The first part discusses in detail, the vibrations measured at free field, base and the roof level of the structure. The amplification effects from the free field to base and from base to roof are compared and discussed thoroughly. The variation in wave amplification in soil and structure shows that they vibrate with their own natural frequency and wave amplifications vary with varying excitations. In the second part of thesis, N4SID time domain system identification technique is applied to calculate and compare mode shapes, modal frequencies and modal damping ratios of fixed and flexible base models. The results showed that modal properties of the structure for fixed and flexible base systems changed. In the third part, two Finite Element Models were developed, one with considering soil flexibility and other with the rigid constraints at the base. After that, the dynamic analysis of the structure was carried out and the effect of soil in modifying the dynamic response was studied in detail. The results showed that even for a single storey braced structure, base input force, base moment, peak displacement were increased.