Research On The Seismic Performance Of The Prefabricated Frame-bridge

In the current highway construction process,prefabricated frame-bridge is a new structure in facing the problem of difficult soil acquisition,large land occupation,poor environmental protection,and so on.It effectively realizes the industrial construction and green construction concept of “design standardization,manufacturing industrialization,and construction assembly”.It has been popularized and applied in many provinces due to its good economy,practicability,and durability.Prefabricated frame-bridge is different from both traditional bridges and ordinary subgrades,and its seismic performance research is still in its infancy.From the perspective of a structural system,the prefabricated deck and high-strength concrete prestressed pipe pile are generally connected by consolidation,with small span,a large number of connected spans.The stiffness of the overall structure is large,especially in the transverse direction,which is similar to the frame structure,and there may be transverse pounding with the original subgrade under the seismic excitation.Moreover,the seismic performance of high-strength concrete prestressed pipe piles is poor.Therefore,it is necessary to reveal the seismic response law and seismic damage mechanism of prefabricated frame-bridge.For the seismic safety and application of this type of structure,seismic reduction and isolation measures are needed.The project relies on an expressway reconstruction and expansion project in Anhui Province,the research on the seismic response law and seismic fragility of prefabricated frame-bridge is carried out.The key problems such as transverse pounding effect,seismic performance of connection between the pile and deck are deeply discussed,which will contribute to the development and application of prefabricated frame-bridge in different regions of China.The main research contents and conclusions of this paper are as follows:(1)Master the engineering application and research status of prefabricated frame-bridge at home and abroad,and systematically summarize the mechanical properties of prefabricated frame-bridge.Then the seismic pounding effect and seismic performance of the connection between the superstructure and the substructure are investigated;(2)Through the full-scale model test and seismic fragility analysis of prefabricated frame-bridge,it is clear that the mechanical properties,such as stiffness and bearing capacity of elastoplastic column-deck joint are better than prestressed pipe pile.Under the action of horizontal force,the main failure mode is the failure of high-strength concrete prestressed pipe piles.Based on the comparative analysis of test data and finite element results,the nonlinear seismic finite element model of prefabricated frame-bridge,which can consider the transverse pounding effect between the structure and subgrade is established,and its correctness and effectiveness are verified;(3)The influence of transverse pounding on the seismic response of prefabricated frame-bridge is revealed: when the seismic intensity is low,the influence of transverse pounding on the seismic response of prefabricated frame-bridge is small.With the increase of seismic intensity,the seismic response of the structure will be reduced,and the hysteretic energy dissipation of the structure will increase due to pounding;(4)The damage indexes of elastoplastic column-deck joint and prestressed pipe pile corresponding to four failure states of slight damage,moderate damage,severe damage,and complete damage are defined.Then the damage indexes are reasonably quantified by using curvature ductility coefficient,and the seismic vulnerability curves of prefabricated frame-bridge are obtained.On this basis,the influence of elastoplastic column-deck joint and its key parameters(including steel ratio,section size,and reinforcement ratio)on the seismic performance of prefabricated frame-bridge is clarified,and the design parameters of elastoplastic column-deck joint are optimized.