Seismic Response And Uncertainty Quantification Of Pile-supported Bridges In Frozen Soil

In the 21 st century,with the rapid development of China’s economic,regional coordinated and sustainable development is on the agenda.In order to balance development of the central and western regions,infrastructure construction has become the top priority for the development of the central and western economy.Economic development,traffic first.The construction and operation of the Qinghai-Tibet Railway provide a solid foundation for the development of the western economy.The Qinghai-Tibet Railway runs through the permafrost regions of Qinghai and Tibet,and is the longest plateau railway in the world.In order to overcome the problems caused by the construction and operation of railway in frozen soil regions,engineers often employ pile foundations for undesirable geology.However,earthquakes in China’s are widely distributed and large intensive.The seismic activity of the Qinghai-Tibet Plateau is the first in China.Therefore,the seismic problems of pile-supported bridges in frozen soil are becoming increasingly importance.Based on the above,this study the seismic response of piles-supported bridge in frozen soil,and takes the pile-supported bridge of typical frozen soil as the research object.Firstly,based on the result of low temperature dynamic triaxial experiment,the conventional p-y curve is modified.Secondly,a three-dimensional finite element numerical model of pile-supported bridge in frozen soil is established to simulate the seismic response of pile-supported bridge considering the effect of frozen soil.Finally,the Gaussian process surrogate model is used to replace the model,and the statistical variables of the seismic response of the pile-supported bridge in frozen soil are calculated,and then the uncertainty quantitative is carried out.The specific research contents are as follows:(1)Experimental study on dynamic characteristics of sandy gravel in frozen soil regions.Through a series of low-normal temperature triaxial experiment,the backbone curve,dynamic shear modulus and damping ratio of sandy gravel at different temperatures,different confining pressures and different gravel and sand percentage were discussed.Based on the average and standard deviation of computed tomography scan(CT scan)numbers obtained from CT scan images of sandy gravel specimen,the damage evolution process and characteristics of sandy gravel specimens were analyzed based on the changes of dynamic shear stress,dynamic shear strain,and the internal microstructure images.(2)Based on the low-normal temperature dynamic triaxial experimental data,the conventional p-y curve is modified to make it better applicable to the modeling of soil-pile interaction in frozen ground.The experimental basis is provided for constructing the p-y curve of frozen soil.The finite element numerical model of the pile-supported bridge in frozen soil was established by using the interface-friendly MSBridge program.The simulation technique in the numerical model were introduced in detail.Finally,the open-source finite element numerical computing platform Open Sees is used to perform the corresponding numerical simulation to analyze the seismic response characteristics of the pile-supported bridge in the frozen soil.(3)Using Gaussian Process Surrogate Model to replace the model,the statistical variables of seismic response of pile-supported bridges in frozen soil is calculated,and then the uncertainty quantification is performed.Based on the main parameters affecting the response of the pile-supported bridge in frozen soil,the distribution characteristics of these parameters are determined from the related references,and the input samples are obtained.Secondly,based on the nonlinear time history response analysis,the response of the model under different sample inputs are obtained,and the input-output training samples are obtained.Finally,combined with Gaussian Process Surrogate Model,the uncertainty quantification of seismic response of pile-supported bridge are performed.Based on the low-normal temperature triaxial experiment and the three-dimensional finite element analysis,this study focuses on the dynamic characteristics of the sandy gravel material in frozen soil and the seismic response characteristics of the pile foundation bridge.On this basis,the Gaussian Process Surrogate Model is used to calculate the statistical variables of the seismic response of pile-supported bridges in frozen soil,and then the uncertainty quantification is carried out.The above work will provide some reference for the dynamic soil characteristics related to test,and the three-dimensional finite element modeling and seismic response characteristics of bridge pile-supported bridge.