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.
