ASSESSMENT ON THE EFFECTS OF SPAN TO DEPTH RATIO ON COMPOSITE BEAMS UNDER FATIGUE LOADING

Abstract

Composite beams are structural members composed of two or more dissimilar materials joined together to act as a unit. This thesis work studies the behavior and use of structural steel and reinforced concrete combination as a composite material subjected to fatigue loading. Fatigue loading is a non-static or cyclic loading. It is a process of a cycle-by-cycle accumulation of damage in a material undergoing fluctuating stresses and strains. A significant feature of fatigue is that the load is not large enough to cause immediate failure. Experimental results are used for validation analysis using ANSYS nonlinear finite element analysis (FEA) software and further parametric studies on the span to depth ratio, the configuration of shear studs, and the ratio of reinforcement bars is performed to investigate the behavioral response of composite beams under fatigue loading. FEA results showed span to depth ratio of composite beams has significant effect on fatigue strength of the composite beam whereas shear stud configuration and transverse reinforcement have negligible effect. To be specific, increasing span to depth ratio of composite beams under fatigue loading by 41.71% reduced the fatigue strength of the beam by 83.06% where as a single shear stud arrangement in comparison with a double shear stud arrangement reduced the fatigue strength of composite beam by 1.75% and an increase in transverse reinforcement bar ratio by 45.01% increased the fatigue strength by 0.684%. Increasing span to depth ratio of composite beams under fatigue loading by 41.71% reduced the shear stress of the beam by 97.93%. Stiffness degradation which causes major fatigue cracks initiation and propagation is observed to be as a critical concern in the configuration of shear studs.