Experimental Study And Analysis Of Force Transmission Path Of GFRP-RPC Composite Double Deck Traffic Beam Bridge

This paper is based on the National Natural Science Foundation of China’s FRP-concrete composite box-section double-layer traffic structure research project(project number:51578236)on the mechanical mechanism and design method.On the basis of the study of the concentrated load loading test under the working conditions,within the linear elastic range,the multi-working condition uniform wiring load loading test and the base plate concentrated load loading test and their analysis were carried out.The deflection of each section position of the combined double-deck traffic girder bridge model and the strains of members and bridge decks are tested under two types of tests and under different working conditions,and some data are analyzed and compared by finite element.The test and analysis have explained the mechanical characteristics of the structure to a certain extent,and laid a foundation for the theoretical calculation of the simplified model in the later stage.The main conclusions of this paper are as follows:(1)In the comparison test of concentrated load loading on the top and bottom plates,the vertical deflection of each measuring point in the bottom plate loading test is larger than that in the top plate loading test.In the load-loading test of the uniform wiring of the roof,changing the rail spacing,the vertical deflection changes less,the vertical deflection distribution of the beam bridge cross-section is relatively uniform,the overall stiffness of the beam bridge is better,and the lateral stiffness distribution is uniform.In the finite element simulation,the deviation is basically controlled within 5%,and this influence can be ignored,and the simulated value of deflection is in good agreement with the experimental value.(2)Under each working condition of the test and analysis,the upper and lower chords are in the form of compression bending and tension bending respectively.The maximum compressive strain value of concrete material appears in the upper chord,and the maximum tensile strain value of GFRP material appears in the lower chord.Considering the overall effect,in the test and analysis of the uniform line load,the inclined web members are all in tension,the side diagonal web members are in greater tension,the straight web members are in compression,and the side straight web members are in compression.Under the concentrated load loading conditions of the bottom and top plates,the straight web members at the edge are subjected to compressive stress along the members.In the upper loading,the mid-span straight web rod is subjected to compressive stress,and when the lower part is loaded,the force form of the mid-span straight web rod changes and is subject to tensile stress.(3)The top and bottom plates in the bridge deck are spliced with multiple one-way GFRP-RPC composite boards,and the bridge deck is designed according to one-way boards.The GFRP-RPC composite plate and the GFRP chord at the support of the bridge deck are connected by rubber bolts,and the boundary conditions at the support of the plate are between the simply supported and the fixed support.In the calculation of the composite plate,the fixed support design at both ends of the one-way plate is referred to at the support,and the bending moment adjustment coefficient at the support position is taken as 0.25.Refer to the design of hinge supports at both ends of the one-way plate at the mid-span position,and the bending moment adjustment coefficient at the mid-span position is taken as 0.85.(4)The chord at the connection node between the chord and the web has a large strain value along the height,and there is a bending moment stress.In the simplified calculation of the truss beam system,the upper and lower chords are considered as a single whole beam respectively.The width of the T-beam flange is usually taken as one-third of the web width or the calculated span of the beam plate,and the plate span of 0.23 times of the composite plate is taken as the chord flange.In the test,the strains on both sides of a single web member are basically the same,which can be considered as a two-force member,and the connection node between the web member and the chord member is simplified as a hinge node.Under the simplified calculation,the force of the chord and the web is in good agreement with the test,and the strain value is larger than the test value as a whole,which confirms the safety and applicability of this simplified method in structural design.