Dynamic Buckling Analysis And Engineering Application Of Group Piles In Vertical Elastic Compression Wave

Pile foundations, especially with high pile cap, are widely used in modernconstruction such as bridge engineering, harbor engineering and dock engineeringdue to its high bearing capacity, small settlement, high strength, good ant-seismicperformance and other merits. This pile-group foundation with high pile cap is likelyto undergo flexural buckling destruction on the multiple applications of static loadsincluding the upper structure loads and the self-weight of pile foundation, anddynamic loads induced by the vehicle vibration, the seism wave. This destruction ismostly characterized by sudden and brings serious consequence. It is of greatsignificance in the practical engineering application to analyze the dynamic responseof pile-group foundation, particularly the dynamic buckling stability.To this end, based on the review of the published literatures relating to thebuckling stability of pile foundation and the interaction among the pile-soil-capsystem, a systematic summary for the available analytical methods of pile-soil-capinteraction and the corresponding analytical models was given in this work.Furthermore, the theoretical analysis of the displacement influence for pile-soil-pilewith characteristic of fluctuation was introduced to the dynamic Winkler beammodel. By simplification, the kinematical differential equation for pile-soilinteraction under the action of dynamic loads was formulated and the correspondingcalculation method for the solution of the dynamic interaction factor was given.Additionally, a solid model of22pile-group foundation considering thecontact of pile-soil-cap and the nonlinear characteristic of the surrounding soil wasestablished by using dynamic finite element software ANSYS/LS-DYNA to comparewith the test results and the applicability of the finite element simulation wasverified. According to the corresponding contours of displacement and internalforces resulted from the FEM, the development and the distribution of thedisplacement and internal force of pile was discussed. The influence of pile space,pile-soil stiffness ratio, the pile length and other parameters on the horizontaldisplacement at pile top for pile group foundation was investigated by varying thegeometric and material parameters of the pile-soil system.Eventually, a practical project of Lizigou Bridge of large-span was selected todemonstrate the proposed approach in this work. A three-dimensional solid model of the pile-group foundation under the12#cap was constructed to perform the staticand dynamic analysis considering the pile-soil interaction. The results of the staticanalysis were used to compare with the measured data in field, and the distributionsof the vertical displacement of pile end and the horizontal displacement of pile topfor the central pile and corner pile of the pile-group foundation under varied seismicacceleration were discussed respectively. Taking the cooperation of static anddynamic loads into account, the dynamic characteristic variation of pile-soil-capsystem under the actions of different seismic waves was analyzed, and the influencevariation of dynamic loads on the displacement amplitude and the critical loading offailure for pile group foundation were obtained subsequently. All above worksdeepen the cognition of the dynamic response of pile-group foundation on the actionof seismic loads, and generates the two optimal design proposals by changing pilespace and by changing pile length for this engineering pile foundation.