Use of UHPC Slab in Continuous Composite Girders

The concrete slab at the negative moment region of continuous composite steel-concrete girders will be under tension and consequently loses its contribution to the composite action. The American Institute of Steel Construction (AISC) code ignores the contribution of concrete slab at negative moment region for continuous composite girders or considers the steel reinforcements of concrete slab to act compositely with steel section. For both options of AISC code, the section capacity at negative moment region greatly reduced. This proposal intends to investigate the use ultra-high performance concrete (UHPC) slab at negative moment region for continuous composite girders to maintain the composite action at service load. The concrete slab cast in two stages: first stage will be casting normal concrete (NC) at positive moment region followed by casting UHPC at negative moment region. The girders designed to have full composite action at positive and negative moment regions. This new construction approach will maintain the composite action at the negative moment region for service load and consequently improves the strength and stiffness of the continuous composite girder. An experimental testing needed to verify this construction approach of using UHPC slab at negative moment region for continuous composite girders. Several girders will be prepared and tested to failure to evaluate the performance of UHPC slab through all stages of loading. Evaluate numerically the behaviour of the continuous composite girder using ABAQUS software and verify the numerical results with the experimental results. A parametric study will be conducted to evaluate in depth the effects of some parameters on the behaviour of the continuous composite girder. These parameters include thickness and length of UHPC slab and shear stud spacing at the negative moment region. Finally, utilizing both experimental and numerical results to develop analytical solution to evaluate the capacity of the girder at service and ultimate load