Structural Characteristics Of Pile Slab Subgrade Based On Multi-scale Finite Element Model

Pile slab roadbed is a new subgrade structure put forward in recent years.It also has two functions of foundation treatment and roadbed structure.It is mainly composed of reinforced concrete pile foundation,bridge deck(or cap plate)and so on.Compared with the soil roadbed,it has the advantages of small settlement after construction,high rigidity and high smoothness.Because of the innovation of bridge panel and pile plate joint structure,the traditional modeling strategy has become no longer applicable to the analysis of the structural characteristics of the subgrade,so multi-scale modeling becomes a better choice of modeling.In this paper,the pile slab subgrade is selected as the research object.According to the corresponding simplified model and working condition,the suitable multi-scale connection method is chosen to apply it to the multi scale model of different categories.The static stress characteristics of the bridge deck and pile plate joints are compared longitudinally,the dynamic characteristics of the whole model and the difference of the elastic stability calculation results are compared,and the calculation results of the refined model are taken as the comparison datum,finally the most suitable multi-scale modeling method is selected.The main research work and conclusion of this paper are as follows:1.At first the connection principle of all kinds of multi-scale connection methods is expounded.Based on the design drawings,a refined model of roadbed entity with 54 m length is established.According to the structural characteristics,the corresp-onding simplified models can be intercepted and compared.Based on the idea of control variables,the stress and displacement of the multi scale interface and the maximum equivalent stress on the cross section of the multi-scale interface are compared when the multi-scale connection method is applied under the same working condition.Taking the entity refinement model as the comparison benchmark,because of the least error under each working condition,the CERIG method is finally selected as the most reasonable multi-scale connection method.2.Under the action of the standard combination condition,the local stress condition of the structure is judged and the entity refinement model is simplified accordingly.The most concentrated entity unit is retained,and the rest is replaced by the plate and shell element or the beam bar element.Then the optimal multiscale connection method CERIG is applied to connect different elements to establish several multi-scale finite element models.3.By using several established multi-scale finite element models,the stress characteristics of the local bridge panel and the pile structure under the normal use limit state are analyzed.The differences are compared with the solid model,and the multi-scale finite element model of the local structure calculation results closest to the base model is selected.The results of the stress and strain calculation of the whole structure determine whether the optimal model in the local structural analysis is the same as the optimal model in the overall structural analysis,and compares the calculation errors of several models and analyzes the cause of the error.4.Further modal analysis and linear elastic stability analysis are made for several finite element models to determine the applicability of the above optimal model in dynamic calculation and stability analysis.Finally,an optimal multi-scale finite element model is selected,which can not only ensure the accuracy of subgrade structure,but also improve the calculation efficiency of subgrade structure.