# Bending Performance of a Prestressed Concrete Composite Girder Bridge with Steel Truss Webs
###### Abstract  
An experiment was conducted on a prestressed concrete (PC) composite girder bridge with steel truss webs to investigate its flexural performance. The mechanical characteristics and failure modes of a PC composite girder bridge with steel truss webs was clarified. Finite element (FE) analysis was carried out, and the influence of the girder height-to-span ratio and eccentric loading effect on the flexural performance of a composite beam bridge with a steel truss web was discussed. The method for calculating the cracking bending moment, the bending moment at the rebar yield stage, and the ultimate bending moment of a PC composite girder with steel truss webs was proposed. Key findings include that, in both the elastic and cracking elastic stages, the strain of the bottom and top conforms to the plane-section assumption. Throughout the loading process, there was no occurrence of joint failure or local buckling failure in the steel truss webs; the composite girder ultimately fails due to excessive deformation, indicating that the overall mechanical performance of the composite beam is good. The deflection and stress in the mid-span section decrease with an increasing height-to-span ratio, and there are significant impacts of eccentric loading on deflection and stress. Compared with the results of the FE analysis and test, the calculation methods of the cracking moment, reinforcement yield moment, and ultimate moment of PC composite girders with steel truss webs presented in this paper have a high accuracy. composite girder bridge; steel truss webs; flexural behavior; experiment; finite element analysis; calculation method +
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At present, there are relatively few research works on composite girder bridges with steel truss webs. Some scholars took an actual composite girder bridge with steel truss webs as the research object to analyze its mechanical performance. [PERSON] [11] studied the Shuianbao overpass and used FEM analysis to investigate the mechanical properties of variable section PC composite continuous rigid frame box girder bridges with steel truss webs. However, this study did not address the overall flexural behavior comprehensively, which this research aims to do. Some scholars use theory and FE analysis to study the shear lag effect of composite beams with steel truss webs. Based on the converted thin-walled box girder method, [PERSON] [12] derived the theoretical formula of the flexural vibration frequency of composite girder bridges with steel truss webs, in which the shear deformation of the bridge and shear hysteresis effect of the box girder section are considered. [PERSON] [13; 14], taking Nanjing Jiangshan Bridge as the engineering background, combined with FE analysis and theoretical derivation, studied the calculation formula of the shear lag coefficient, the variation law of the shear lag coefficient along the longitudinal direction of the bridge, and the calculation method of the effective cantilever width of the composite girder bridge with steel truss webs. [PERSON] [15] carried out FE analysis and theoretical derivation on the deflection calculation method of a composite girder bridge with steel truss webs; the results show that the additional deflection caused by shear deformation and a shear-lag effect of the steel truss web cannot be ignored when calculating the deflection of a composite girder. [PERSON] [16] and [PERSON] [17] adopted the torsion theory of a thin-walled box girder and proposed the calculation method of the torsion warping stress of composite girder bridges with steel truss webs, as well as the constrained torsion control differential equation. [PERSON] [18] used the FE analysis method to study the basic mechanical properties such as the shear lag effect of the concrete top and bottom plates and the stress of the steel web of the typical section in a composite girder bridge with steel truss webs.