Static Characteristics And Seismic Behavior Of Three Kinds Of Main Jointless Bridges

Jointless bridges cancel expansion joints and expansion devices,and solve the problems which include vulnerability of expansion joints,bumping at bridge end and high maintenance costs.They are favored by the US,Japan and European countries.However,domestic research and application of jointless bridge started late.It is still in exploration.Influenced by climate,natural environment,traffic condition,geological foundation and economic level,the bridge structure forms and jointless methods adopted throughout the country are bound to be different.On this basis,this thesis makes a comparative study on the three most common structural forms of jointless bridges according to No.2 Jinjialing River Bridge in Shaoxing.The purpose of the study is to provide technical guidance for the design of jointless bridges or the jointless transformation of old bridges by considering various main factors,which including safety,durability and use.The main work and contents of this thesis are carried out as follows:(1)The background and development of jointless bridges are introduced,and the classification of different forms of jointless bridges is summarized.(2)The modeling process and simulation method of grillage model are introduced in detail.The stress of main girder,displacement of abutment,displacement of pile foundation calculated by the model are compared with the monitoring data of real bridge.It is found that the trend of the calculated value is the same as the measured value,and the magnitude of the calculated value is close to the measured value.The design checking of the model bridge shows that the checking indexes meet the requirements of the code.(3)Based on the background bridge,the abutment forms of semi-integral bridge and deck extension bridge are drawn up.The static characteristics of the superstructure and the top of pile foundation of four types of bridges(integral bridge,semi-integral bridge,deck extension bridge,common continuous girder bridge)under dead load,temperature load and vehicle load are compared and analyzed.It is found that the internal force of integral bridge pile top is more affected by the combination of heating load than by the combination of cooling load,while the effect of semi-integral bridge and deck extension bridge is less by the combination of heating load than by the combination of cooling load.It is suggested that the concrete pouring of the superstructure and the substructure of the integral bridge should be carried out at relatively high temperature.(4)Comparing the structural responses of two different directions of ground motion input.It is found that the input of seismic wave along the oblique angle direction of integral bridge and semi-integral bridge is more disadvantageous to the force of bridge.Input along the driving direction of extended deck bridge and common continuous girder bridge is more disadvantageous to the force acting on the bridge.Four types of bridges were analyzed by response spectrum analysis of E1 and E2 and time history analysis of recorded wave after amplitude modulation.The displacement of pier top,internal force of pier and pile foundation,displacement of abutment,internal force of pile foundation of abutment and deformation of bearing under earthquake were compared.It is found that the integral bridge has the best seismic performance,and the main girder and abutment are poured as a whole,which improves the overall stiffness.The substructure of abutment and the soil behind the abutment and around the pile participate in energy dissipation,which reduces the huge internal force at the bottom of the pier;the second is the semi-integral bridge,whose soil behind the abutment participates in the seismic action and improves the seismic performance.The seismic capacity of the deck extension bridge and the common continuous girder bridge is weaker than the former two.(5)Based on the good seismic performance of the integral bridge,the type of soil around the pile,the section of pile foundation,the height of abutment and the thickness of abutment are selected as parameters.The dynamic characteristics and structural response peak values of bridge structures with different parameters under E1 earthquake are analyzed and compared,and the reasonable setting of structural seismic parameters is obtained.