In this thesis, the earthquake response of building structures with foundation uplift are investigated. The effect of vertical ground acceleration, P-δ effect and the effect of soil conditions on the seismic response of building structures with foundation uplift are investigated.
Lumped mass matrix with story masses associated to horizontal displacement at each floor level was used to maintain the consistency with the stiffness matrix, with one degree of freedom per floor, obtained by matrix condensation technique. Two spring-damper system is used to model the interaction between foundation mat and soil.
The dynamic eqiulibrium equations are established considering the equilibrium in horizontal and vertical direction and the overturning of total system. These nonlinear equations are replaced by three sets of linear equations according to uplift criteria.
Foundation uplift during earthquake resulted in the decrease of the base shear of building structures. The difference in soil properties had minor effects on the dynamic behavior of building structures when foundation uplift was allowed while significant effects were observed when foundation uplift was prevented. The effect of vertical ground acceleration appeared to incense when the foundation uplift occured for longer time.
Beams are assumed to be rigid in the shear building models resulting in the increased lateral stiffness and the shorter fundamental vibration period. Therefore it is recommended to use condensed models or modified shear building models with correct vibration periods for seismic analysis of building structures with foundation uplift. P-δ effect has more significant influence on the dynamic response of structures when foundation uplift was not prevented.
