Multi-scale Modeling Method Of Bridge Structure And Its Application

Compared with the beam element macroscopic model.Multi-scale can better analyze the fine parts of the structure.Compared with the detailed model of solid element,it can effectively improve the computational efficiency.However,,this method has been applied to the analysis and calculation of large bridge structures.However,it is not clear how effective the different multi-scale modeling methods are in the calculation of bridge structures.This paper aims at this problem.A three-span reinforced concrete continuous girder bridge is used as the research object.The results of four common multi-scale modeling methods for bridge structures are analyzed.A multi-scale modeling method suitable for bridge structure is found out.The dynamic responses of bridge structures considering pile foundation,pile-soil-structure interaction and different reinforcement ratios of piers are studied by using this method.The main research contents of this paper are as follows:(1)To determine the location of fine modeling.The macroscopic scale model of the whole bridge is established by using beam element.Static analysis was carried out on it.According to the stress concentration and the common failure location of the bridge.Determine the connection between pier top and beam,pier bottom and cap connection and pile foundation to carry out fine modeling;Dimensions for determining fine modeling.Two kinds of multi-scale models,the fine model of 1.5m joint part size and the fine model of plastic hinge length of bridge pier,were established respectively.The dynamic time-history responses of the two models are analyzed and compared.The fine modeling of the connection part at 1.5m was determined as the model for subsequent multi-scale analysis.(2)MPC multi-point constraint method,RBE3 surface constraint method,Cerig surface constraint method and constraint equation method were used to connect the multi-scale model.Static analysis,modal analysis,spectrum analysis and time history analysis were carried out for four kinds of multi-scale models.The results are compared with those of the full-bridge solid model.It is concluded that both MPC method can be well used in multi-scale modeling of bridge structures.(3)Multi-scale modeling of the superstructure of the bridge.Three kinds of multi-scale models with pile foundation,without pile foundation and pile-soil-structure interaction were established respectively.By comparing the natural vibration characteristics and dynamic time-history responses of the structure,it is found that the natural vibration frequencies and modes of the pile foundation with or without the consideration of pile foundation are close to each other.The difference of natural frequencies and modes between pile foundation and pile-soil-structure interaction model is not considered.The time-history response of pile-soil-structure interaction model considering pile foundation and pile-soil-structure interaction model is larger than that without pile foundation.And the time history curve has great difference.(4)The reinforced concrete separated multi-scale model considering pile foundation is established.By changing the pier parts of the different longitudinal reinforcement ratio and stirrup ratio.The influence law of bridge pier reinforcement ratio on seismic response of bridge structure is investigated.The results show that with the increase of pier longitudinal reinforcement ratio.The maximum longitudinal displacement and maximum acceleration of pier top decrease gradually.The maximum lateral displacement increases first and then decreases,and the maximum acceleration increases gradually.The maximum shear stress at pier bottom and pier top increases gradually.With the increase of the piers hoop ratio.The maximum longitudinal displacement and maximum acceleration of pier top decrease gradually.The maximum lateral displacement remains unchanged and the maximum acceleration decreases slightly.The maximum shear stress at pier bottom and pier top increases gradually.The effect of longitudinal reinforcement ratio on bridge pier is greater than stirrup reinforcement ratio.