Behaviour of composite high performance concrete slab on steel I-beams subjected to static hogging moment

This paper investigates the behavior of composite girders made of high performance concrete (HPC) slab connected to steel I-beam through stud shear connectors subjected to hogging moment. Such girders are widely used in bridge construction. However, reinforcing steel bars in the negative moment region contribute significantly to the moment resistance and is found to be ineffective due to cracking of ordinary concrete. This research proposes the use HPCs containing fibers (with better crack resisting and strain hardening characteristics) in the deck slab to enhance both cracking and yield load carrying capacity of such girders at the negative moment region. Four composite girder specimens made of different types of concrete and having variable slab continuity were tested to failure under monotonic loading simulating negative moment. Three types of concrete were employed in the first three girder specimens, namely: Normal Concrete (NC), Steel Fiber-Reinforced Concrete (SFRC) and engineered cementitious composite (ECC). The fourth girder specimen was constructed using two SFRC end slabs connected together with an Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) closure strip located at the maximum negative moment mid span region. This specimen represents the case of full width -full depth deck slabs resting over steel girders with transverse joints filled with UHPFRC used to accelerate bridge construction. The SFRC and ECC composite girders showed better performance in terms of cracking characteristics (multi-cracking and smaller crack width), higher pre-cracking linear stiffness, higher cracking load, higher concrete strain development during cracking and higher strength compared to their NC counterparts.