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An investigation of liquefaction effects on piers and piles of segmental precast balanced cantilever bridges

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2019
Gündüz, Özer
In this thesis, the seismic behavior of a typical segmental precast balanced cantilever bridge over liquefiable soils is investigated. Liquefaction is a phenomenon that is triggered by large movements of the sand layer during earthquakes and cause damage to structures. The subject is still under investigation, approaches for liquefaction induced lateral spreading calculations can be found in the literature. Inertial and kinematic effects of the lateral spreading were studied with a total of four different approaches which are the non-liquefied scenario, liquefied scenario for inertial analysis, force-based method case and displacement-based method for kinematic analysis. The focus of this study is given to identify the changes in the structural response of case study bridge using different approaches. In inertial analysis, liquefaction effect on acceleration response spectrum was estimated via one-dimensional site response modeling. Some specifications have offered p-y curves for soil-pile interaction. Also, they suggest that the design response spectrum can be used in the case of liquefaction. Therefore, the liquefied and non-liquefied configuration was set up in this thesis for inertial analysis of this kind of bridge. In kinematic effects of soil, lateral spreading which is one of the major damaging mechanism of liquefaction also investigated. In this purpose, different soil profiles having different peak ground accelerations, the shear strain of the soil were analyzed. P-y curves belonging to the soil profile had been modeled and their effects on superstructure and infrastructure were discussed. It was observed that the structure period is highly important in considering inertial analysis. Pier seismic design forces are critical in liquefied response-spectrum models than non-liquefied one which is design spectrum. Also, pile forces were more critical in displacement applied lateral spreading. Then other methods, liquefaction effects on the spectrum can significantly alter the structural response for long period structures.