The Numerical Simulation Research Of Pre-cracked RC Slab And Repaired Pre-cracked Rc Slab Under Explosive Loads

This paper summarizes the development of antiknock performance of RC structure and the future trend in recent years firstly, and then uses ANSYS / LS-DYNA finite element software to study the dynamic response of normal RC slab under explosive loads by the numerical simulation. In succession, the blast response of the cracked RC slabs with several different crack parameters(e.g. orientation, width and depth) under the blast loading is also studied. Finally, to improve the blast resistance, the cracked RC slabs are stiffened by the carbon-fibre reinforced plastic(CFRP) composite patches and then the influences of layer number and thickness of the CFRP patch on the blast resistance of the repaired model are further analyzed. The main research results are as follows:(1) The dynamic response of normal RC slab under explosive loads is analyzed. It is shown that the explosion shock wave forms strong tensile wave in the bottom face of the RC slab and then repeatedly stretched, which will make the normal RC slab mainly occur flexural failure on the bottom surface. On the upper face of the RC slab, there is a main through crack along the longitudinal direction, while on the bottom surface, there are a plastic zone appeared in the middle part as well as some tensile cracks. The verify of our numerical model is examined by comparing calculation results with published experiment data which indicate that the destruction mode of our numerical simulation of the normal RC slab is good agreement with that of the test specimen. Finally on the basis of the above analysis, several different factors that may affect the destruction mode of RC slab under the explosive loads, e.g., the explosive charge, the initiation distance and the plate thickness, etc.,are studied.(2) The dynamic response of pre-cracked RC slab under explosive loads is analyzed. The research results show that the initial crack in the RC slab makes the slab break easily and occur an obvious stress concentration ring on the crack area under explosion load. The failure of the cracked RC slab initiates from the initial crack tip and expand to around. Compared with the normal RC slab, it’s found that the initial crack on the RC slab make the occurrence of normal cracking of slab earlier and the maximal displacement is increased by about 17.45%under the same conditions, which indicates the damage degree and deformation of the pre-cracked RC slab is more serious than normal slab. Then on this basis, the blast response of the pre-cracked RC slabs with several different crack parameters(e.g. orientation, width and depth) under the blast loading is studied and conclude that there is insigni?cant in?uence in the dynamic response and failure behavior of these cracked RC slabs when varying the orientation, width and depth of the crack. Finally, the dynamic response of pre-cracked RC slab under different quantity TNT mass and distance are also analyzed, and find that the maximum displacement of the mid-span is increased with the increase of the amount of TNT and decreased with the increase of distance.(3) The dynamic response of the pre-cracked RC slab repaired with CFRP is simulated.It is shown that the repaired patches can delay the cracking time of concrete and prevent the development of cracks. This situation has an inhibitory effect on the improvement of the anti-explosive performance and extends the service life of the RC structure. With the increase of the layer number and size of the repaired patch, the anti-explosive performance of pre-cracked RC slab continuously strengthened. In terms of considering the safety and economy, it is found that there are optimal value for both the patch layers and size.