The Impact Caused By Uplift Phenomenon On Dynamic Response Of Superstructure

In the earthquake engineering, there are many cases showing that it is easy for buildings with big high-width ratio to uplift during strong earthquakes. This geometrical nonlinearity phenomenon gives some powerful proofs about the soil- structure interaction. Compared to the non-uplift ones, the moment, shear force and the storey displacement in structures are changing lots, resulting in the unusual dynamic response. So the more accurate analysis is stressed in the building design according to the performance in the earthquake. So it is necessary and meaningful to put up with a proper and accurate foundation uplift model and make some detailed analysis based on that model.With the help of the previous study, a new spatial coupling foundation uplift model is put forward which can take the horizontal, rocking, vertical and torsional response into account. Then put forward a new uplift model which is based on Sway-Rocking model. At last, derive force equilibrium equations of the uplift model and investigate the earthquake response while cons idering foundation uplift with the method of numerical analysis. The research results are shown as below:(1) Match the simplified formula of foundation impedance with the help of TLM. Compare the results calculated by simplified formula with that obtained by TLM to verify the accuracy and propose a new spatial coupling foundation uplift model.(2) Derive the dynamic equilibrium equations of the new spatial coupling foundation uplift model and calculate the equilibrium equations with Newmark method. What’s more, the problem of geometric nonlinearity caused by foundation uplift is settled with the help of force correction method.(3) The uplift model is established by FORTRAN 95 and a structure of water tower is applied in the uplift model. Compare the results obtained in the uplift model and that obtained in Sway-Rocking model. It reveals that the foundation uplift not only influence the response in the direction where uplift phenomenon happens but also the response in the direction where the foundation does’ s uplift.