BEHAVIOUR OF COMPOSITE HIGH-PERFORMANCE CONCRETE SLAB-ON-STEEL GIRDERS SUBJECTED TO HOGGING MOMENT

摘要

This paper investigates the structural behavior of composite bridge girders subjected to hogging moment. Such composite girders are widely used in accelerated bridge construction. However, the ultimate moment capacity at the negative moment region is highly affected by the contribution of the reinforcing steel embedded in the concrete deck slab that is considered ineffective due to cracking. This paper proposes the use of high-performance concrete in the deck slab to enhance the flexural crack distribution and contribute to both cracking and yield load carrying capacity at the negative moment region. Four reduced-scale composite girders, simulating negative moment region, were constructed and tested to-collapse. The main variables in these specimens were type of concrete and slab continuity. Three types of concrete were considered for the deck slab in each of the first three specimens, namely: Normal Concrete (NC), Fiber-Reinforced concrete (FRC) and Engineered-Cementitious Composite (ECC). The forth specimen was constructed using two slabs made of FRC and connected together using a closure strip acting as shear-key joint located at the maximum negative moment region. The performance of composite girders is analyzed based on load-deflection response, stress-strain characteristics, crack development, failure modes. All specimens exhibited flexure mode of failure with ECC and FRC specimens showing significantly higher load at first crack and better distribution of flexural cracks along the specimen compared to their NC counterpart.