Papers by Author: Chengqing Wu

Abstract: Currently, there are adequate guidelines available for FRP retrofitting RC structures against static and seismic loads. However, there is still limited information on retrofitting RC structures against short-duration dynamic loading effects such as blast loading. Due to the increasing threat of terrorism in recent years, retrofitting of RC structures against blast loading is of paramount importance in structural engineering. In this paper, a dynamic model that is based on single-degree-of-freedom (SDOF) approach is developed for the analysis of the response of retrofitted fixed end supported RC slabs subjected to blast loads. A previously validated layered capacity analysis method is used to determine the yielded and ultimate blast resistant capacity of a cross-section of a RC slab which allows varying strain rates with time along the depth of the member. The corresponding deflections are determined by plastic hinge analysis. To simplify the calculation process, a tri-linear resistance-deflection function which consists of elastic, elasto-plastic and plastic region for fixed end supported RC slabs is converted to an equivalent bilinear function. This developed model can adequately predict the retrofitted members’ response to blast loading. It is then is used to conduct a parametric study to optimise the retrofitting of RC slabs subjected to blast loading by varying the quantity, material type and technique of retrofitting.

Abstract: Displacement-controlled design method is now being used by current guidelines such as TM5 and ASCE to design RC members against airblast load. If the maximum deflection of the designed member under airblast loads is less than the allowable deflection, the designed member is considered to be safe. Although the displacement-controlled design method is easy to use, it may not result in a design having maximum energy-absorption capacity against airblast loads, especially for a design of a reinforced ultra-high performance fibre concrete (RUHPFC) member which is of both high strength and high ductility, that is, high energy-absorption capacity. In this paper, a layered analysis model allowing for varying strain rates with time as well as along the depth of the member was used to calculate energy-absorption of a simple supported RUHPFC slab under airblast loads. An optimal reinforcement ratio of the slab was achieved by maximizing the energy absorption of the slab under different reinforcement ratios. The energy-controlled design method was validated by field blast tests. Using the validated design method, a designed slab with the optimal reinforcement ratio was also tested and the effectiveness of the design was demonstrated.