Behaviour of precast reinforced concrete slabs in steel-concrete composite bridge decks with bolted shear connectors

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Due to ease of fabrication and maintenance and speed of construction, precast prefabricated composite deck slabs have gained huge popularity all around the globe. The precast prefabricated structural systems do not require the costly in-situ formworks. Accordingly, the precast prefabricated structural systems can reduce the cost of labour and improve the safety and speed of construction. In addition, the prefabricated composite structures can significantly facilitate application of external reinforcement in lieu of conventional internal steel bars. The reinforced concrete (RC) structures, in general, suffer maintenance and repair difficulties, as internal reinforcements in reinforced concrete (RC) structures are susceptible to corrosion that can be typically accelerated by chloride and other corrosive material ingress. Once the corrosion occurs, reinforcement starts to expand inside the concrete and that in turn causes concrete cracking and spalling. Accordingly, the reinforced concrete member cannot perform its structural role properly. Second generation bridge deck slabs, namely steel-free deck slabs, in which conventional embedded reinforcements are replaced by external reinforcements have proved to be efficient in mitigating the problems associated with corrosion of reinforcing steel bars. The steel-free deck slabs rely on development of arching action to withstand the load. The inherent arching action in longitudinally restrained reinforced concrete members was realised about fifty years ago, however, the beneficial effects of arching action has not been recognised by most of the existing reinforced concrete design standards yet. So far only Northern Island Standard, DRD, NI (1990), and Canadian code, OHBD (1992) takes account of the enhancing effect of arching action in design practice. This intrinsic capacity of laterally restrained RC structures helps the flexural reinforced concrete members to show loading capacity far in excess of flexural resistance predicted by the conventional formulas. Apart from corrosion of reinforcing steel bars, the existing steel-concrete composite deck slabs cannot be repaired and rehabilitated conveniently and without the interruption to the traffic. Although many studies have been conducted examining a wide range of composite deck systems, lack of a practical precast prefabricated steel-concrete deck slab that allow for easy replacement of concrete slabs in case of deterioration is apparent. The restrained steel-free concrete deck provides a practical solution to the corrosion of reinforcement by removing the internal steel bars and replacing them with external steel straps. However, in the meshless slabs proposed by them, the future repair and replacement of concrete slab cannot be conducted easily without a major interruption to the traffic. To take advantage of the intrinsic characteristic of precast prefabricated deck slabs and to overcome the issues associated with corrosion of internal steel bars in RC bridge decks subject to corrosive environment, a novel steel-concrete deck with precast prefabricated concrete slabs is proposed and examined in this study. The results of experimental tests on precast prefabricated slabs with high strength bolts are presented and FE numerical simulation are carried out using ATENA 2D. The novelty of this research project lies in the application of high strength steel bolts for connecting the concrete slabs to steel girders. The high strength bolts are pre-tensioned with a special amount of tensile force induced in them by a torque meter wrench. This new steel-concrete composite deck has two main advantages; firstly, there is no requirement as to design and assemble formworks for constructing cast-in-situ concrete slabs and hence the construction of deck is much faster. Secondly, the high strength bolts can be opened and the precast slab can be easily released and replaced if required. This advantage allows for easy repair and maintenance of the concrete deck slab without causing significant interruption to the traffic during repair and rehabilitation.
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