Research On Cooperative Action Mechanism And Effective Distribution Width Of PC Bridge Deck-steel Truss Composite Bridge Girders

PC bridge deck and steel truss girders are important components of steel truss concrete composite girders.The cooperative action between PC bridge deck and steel truss girders is one of the key factors in the whole life construction of steel truss concrete composite girders.In this paper,the collaborative working mechanism of PC bridge decks and steel truss girders and the effective distribution width of PC bridge decks are mainly studied by establishing a numerical simulation model considering the space effect,based on the engineering background of a steel truss concrete composite bridge decks.The main research contents are as follows:(1)The slip characteristics between PC bridge deck and steel truss girders are analyzed,and a numerical simulation cooperative action model of steel truss and concrete composite girder considering the load-slip relationship during the whole process of welding studs is built.The model adopts nonlinear spring element to simulate the welding studs,and different loadslip relationship of welding studs can be defined by F-D curve.(2)A criterion for the synergistic working performance of truss-concrete composite girders was established based on the slip amount of truss-concrete interface and the deflection and stress of composite girders.The influences of three structural parameters,including concrete strength,bridge deck thickness and weld stud diameter,on the synergistic working performance of PC bridge decks and steel truss girders were analyzed.It is learned that the concrete strength grade is between C50 and C55,and the bridge deck thickness is 400mm～420mm.At the same time,appropriately increasing the diameter of the welding studs can effectively improve the cooperative working performance of PC bridge deck and steel truss girders.(3)The influence of load effect on the cooperative working performance between PC bridge deck and steel truss beam is analyzed,and the influence of partial load on interface slip,maximum deflection and stress of steel truss concrete composite girders is revealed.The mechanical responses of steel truss-concrete composite girders under different load forms are studied,and the suggested values of normal stress amplification factor and shear stress amplification factor are given.The influence of temperature effect on the mechanical properties of steel truss-concrete composite beams is analyzed,and the influence laws of the overall rising and cooling on the interfacial slip,maximum deflection and stress of steel truss-concrete composite girders are revealed.The mechanical response of steel truss-concrete composite beams under different temperature gradient modes is studied,and the interface slip,maximum deflection and stress response mechanism are obtained.(4)The shear lag effect of steel truss-concrete composite beams and the effective distribution width of bridge decks under the two models of interface slip and non-slip are studied,and the correction coefficient of effective distribution width of bridge decks calculated by using the model without considering slip is proposed.The effect of bridge deck thickness,concrete strength and width on the effective distribution width of PC bridge deck is studied.It was concluded that the effective distribution width of PC bridge deck can be improved by increasing the concrete strength grade when the concrete bridge deck thickness is 400 mm.