This paper proposes different optimization schemes for enhancing the performance of conventional continuous composite girder bridges with corrugated steel webs. In particular, for the positive moment region, the substitution of a ribbed steel plate for the reinforced concrete bottom flange is proposed for optimizing such bridges. Three-dimensional finite-element analysis was used to preliminarily validate this optimization scheme based on the background project, Dongbaohe Xinan Grand Bridge. An experimental study revealed that the optimization scheme can afford advantages, such as reduced self-weight, avoidance of cracking in the bottom flange, and convenient construction. If the steel plate with proper thickness is used, higher flexural stiffness and load capacity can be achieved as additional advantages due to the enhanced steel ratio of the cross section. For the negative moment region of the bridge, the optimization scheme was implemented in two parts identified as Optimization Schemes I and II. In Scheme I, corrugated steel plate–concrete composite webs were used, whereas a steel–concrete composite bottom flange was further adopted in Scheme II. Compared to the conventional scheme, both Optimization Schemes I and II significantly reduced the shear stress in the corrugated steel web and at the steel–concrete interface due to the lined concrete in the web. Thus, it can be deduced that the applied load corresponding to the yield of the corrugated steel web will be enhanced; namely, the shear capacity will be enhanced. Because shear connection failure was prevented in both optimization schemes, there were remarkable improvements of the load capacity and ductility of the girder. The confining effect of the lined concrete decreased the prestress lead-in ratio, but not significantly. In addition, Optimization Scheme II afforded much greater construction convenience compared to both Optimization Scheme I and the conventional scheme.
In this paper, a beam-truss model is introduced for the design analysis of composite box-girder bridges. An integrated research program for beam-truss models, including modeling implementation, analysis, and application, has been performed to exploit this powerful research and design tool. First, beam-truss models of composite box-girder bridges are implemented, and then corresponding model strategies are formulated based on classical shear–flexible grillage analysis. The calculation accuracy of the beam-truss models is then verified through comparative studies on the structural behavior of straight and curved composite, simply supported, and continuous box-girder bridges obtained using elaborate beam-truss finite-element (FE) models. Numerical analyses include modal analysis; static analysis under gravity load, prestressing load, and lane live load; and whole-process analysis considering the construction method and the long-term behavior of concrete. Finally, beam-truss models are employed for the analysis of field tests on two actual composite box-girder bridges, one straight and the other curved. It is concluded that the beam-truss model provides a reliable and powerful tool for the design analysis of composite box-girder bridges.
Numerical stability and computational accuracy are required for the nonlinear full-process shear analysis of reinforced concrete (RC) structures and members. For this requirement, the planar membrane element is implemented and employed based on the rotating crack model. First, the complex plane stress conditions of RC members are classified into three groups of principle strain states in the principle strain space. Then, the computational methods for the three different principle strain states to update stress and calculate Jacobian Matrix are given. Third, the flowchart for programming is developed and the program of the planar membrane element is implemented based on the large generic finite element package, ABAQUS 6.9. Finally, tests of a group of classic RC beam and a series of typical RC shear wall are selected for the application and validation. Good agreement is found between the test and predicted curves and ultimate capacities. Comparison results also demonstrate that, by integrating the flowchart given in this paper into the program of the planar membrane element, good numerical stability and computational accuracy can be gained.
Experimental results of eight reinforced concrete beams under 3-month's sustained load, with the ratio of shear span to depth equal to 2.5, are reported. It is shown by tests that the diagonal crack develops in width and length with time for RC beams dominated by shear. Semi-empirical formulae are proposed for predicting the time-dependent growth of diagonal crack width and the long-term diagonal crack width. The calculated values are generally in good agreement with the measured results.
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