# Research on the Fatigue Performance of Composite Girders with CSW and ST Truss
###### Abstract  
To study the fatigue performance of a composite girder with corrugated steel web (CSW) and steel tube (ST) truss, based on an engineering object, a test and finite element (FE) analysis were carried out. The fatigue failure mode and the sensitivities of the hot spot stress to the geometric parameters of the composite girder above were studied. The position with the maximum hot spot stress and the fatigue crack position were discussed and determined. Furthermore, a fatigue life evaluation method was discussed. properties by replacing the truss web members in composite girders with CSW, a kind of improved composite girder has been put forward. The new structure above is referred to as the composite girder with CSW and ST truss [10] and has been widely adopted over the last decade [11], as shown in Figure 1d. As for the studies on the fatigue performance of the composite girders with CSW, to obtain the fatigue performance of web-flange weld of corrugated web girders, model tests and theoretical analysis have been conducted. The influence of web corrugation geometry and flange on web-flange weld toe stress was acquired; meanwhile, the calculation method for the fatigue performance of web-flange weld of corrugated web girders was also put forward [12; 13]. By carrying out the fatigue performance test, the fatigue life of steel bridge I-girders with trapezoidal web corrugations was acquired. Moreover, combining the test results and the stipulation given in AASHTO specification [14], the Category \(B^{\prime}\) was suitable to be used in designing the fatigue life of the girders above [15]. To study the fatigue performance of the welds between the steel plate and the CSW, model tests and FE analysis have been carried out. By combining the results obtained from model tests and FE analysis, the fatigue performance of the welds between the steel plate and the CSW with different types was acquired. Meanwhile, the calculation method for the fatigue life has been put forward [16; 17; 18]. The research results above mainly focused on the welds between the steel plate and the CSW of composite girders, and whether the research results above are suitable to evaluate the fatigue performance of the welds between the steel tube and the CSW should be discussed in detail. There were many studies on the mechanical properties of composite girders with CSW [19; 20], however, existing studies on composite girders with CSW and ST truss were very limited. Based on the engineering case, model tests have been conducted to study the flexural performance of the composite girders with CSW and ST truss, and the calculation method for the flexural bearing capacity of the composite girders above under positive and negative bending moments has been put forward [11; 21]. To analyze the shear lag effects, both model tests and FE analysis were carried out, and the calculation method  
Figure 1: Types of composite girders: (**a**) steel girder-concrete slab girders; (**b**) steel web-PC girders; (**c**) truss girders; and (**d**) composite girders with CSW and ST truss. for the shear lag effects of the composite girders above have been put forward [22]. By combining the results obtained from the test and FE analysis, the influence of the geometric parameters on the torsional behavior of the composite girders has been studied [23]. Taking the Maluanshan Park Viaduct in Guangdong Province, China as an object, the fatigue performance test has been conducted on the composite girders with corrugated steel web and concrete-filled steel tubular (CSW-CFST) truss chords, but its chord was filled with concrete, and the evaluation method on the composite girders with CSW-CFST truss chords was not established [24]. As a result, there exists a relatively mature static theory for the composite girders with CSW and ST truss.