Study On The Influence Of The Thickness Of The Pile Cap Under The Failure Condition Of The Curved Beam Bridge

The construction of bridge usually last long with complex stress change process, especially for the lower pile foundation(covert project) which is the key point of engineering quality.Compared withstraight bridges,the pile cap(pile group) of curved beam bridge are usually confronted with uneven pressure because of "bending-torsion coupling" effect. Once foundation failure occurs, corresponding disease will be reflected in the subsequent construction processes.One super-long bridge in Guangxi Province is adopted as an example to discuss the mechanical behavior ofpile foundation when the invalidation or partially invalidationoccurs and figure out the practicability of reducing foundation failure by enlarging the thickness of pile cap.Specific research methods and main conclusions are as follows:(1) In order to select a more reasonable approach, several pile capacity calculation theories and methods which are widely adopted in the bearing capacity calculation for the pile foundation are summarized and compared systematically.Through comparison, it can be concluded that method in specification is the most specific and detailed of all and allowable value isconservative. Therefore, the method proposed in current specification, which is alsothe most widely usedmethod in practical engineering, is adopted to calculate bearing capacity.(2) The numerical analysis model of one curved bridge is constructed on MIDAS CIVIL software to calculate the reaction force of the roots of pier foundationsin different construction stages and figure out the most hostile load combination.According to the numerical analysis, the load combination(1.2~*dead load+1.4~*live load) is selected for the study of reaction force of the roots of pier foundations(3) The solid model of curved bridge pile cap is established to study the mechanical behavior of pile capin different failure model and load cases. The maximal tensile stress and the maximum vertical displacement, corresponding to different construction stages, are obtained respectively.(4) In order to investigate the influence of thickness variation, several finite element analysis models of pile caps with different thickness are constructed.The studies show that increasing the thickness of the bearing platform can effectively improve the bearing capacity of pile caps and this method is beneficialto resist the impact of the pilefailure.