Cracks On Reinforced Concrete Bridge Deck Rockfall Resistance Study On The Influence Of Impact Performance

Since the roads and bridges in the mountainous areas of western China are invariably built along the mountains,this leads to frequent accidents of rockfalls hitting bridges.Rockfalls caused by rockfalls in mountain rocks are easy to cause damage to bridges,which will affect the normal use of the bridge to a certain extent.Furthermore,in the use of reinforced concrete bridge deck,due to external loads such as vehicles,cracks will appear on the surface of concrete slabs.If the bearing members of the bridge also work with cracks,the impact load will be more serious.Therefore,it is of great practical significance and engineering value to study the dynamic response of reinforced concrete bridge deck with cracks.Based on this,this paper uses the numerical simulation software LS-DYNA to establish a numerical simulation model of reinforced concrete slabs.The finite element simulation of the existing drop hammer test in the literature is carried out.By comparing the peak impact force,the maximum deflection,the peak reaction force and the failure state in the test,and the hourglass energy control to ensure the accuracy of the numerical simulation method and parameters,the reinforced concrete bridge deck model with longitudinal cracks and transverse cracks in the middle of the bottom of the slab is established respectively.The influence of the length,width,depth of the crack,the impact velocity of the rockfall and the change of the diameter of the rockfall on its dynamic mechanical properties is explored.The main conclusions are as follows:(1)As crack size develops,the peak impact force of the plate with longitudinal and transverse cracks decreases.On the contrary,the peak mid-span displacement of the plate increases as crack size develops.For the bridge deck with longitudinal cracks,the impact force is most sensitive to the crack depth,while for the bridge deck with transverse cracks,the impact force is most sensitive to the crack length.(2)The analysis of two plates with longitudinal and transverse cracks shows that the peak value of impact force and the peak value of mid-span displacement are proportional to the impact velocity and diameter of rockfall.The influence of impact velocity and rockfall diameter on mid-span displacement is greater than that on impact force.The sensitivity of impact force and mid-span displacement to rockfall diameter is greater than that to impact velocity.(3)Under the effect of impact load,the bottom of the plate with longitudinal and transverse cracks will appear positive " cross " cross cracks,while the bottom of the plate without cracks appears oblique " cross " cross cracks.The crack does not expand at a constant speed,and the propagation rate of the crack is faster in the early stage,and then decreases.