| Bridge is an important part of traffic network.With the service time of bridges increases,the structure and material undergo aging and damage,which would result in the degradation of bearing capacity and durability.Strengthening of the deck slab is necessary in these cases.As a novel method,pre-stressed BFRP grids can be adopted to strengthen reinforced concrete(RC)deck slab.Strengthening with pre-stressed BFRP grids can be bonded smoothly,while the strengthening methods with BFRP sheets,plates or cloth are difficult to construct under water.Strengthening with pre-stressed BFRP grids can enhance the utilization efficiency of grids compared to that without pre-stress.This technology corresponds to the current domestic policy,which advocates green energy and emissions reduction.The researches include:1.A static tensile test on BFRP grids was conducted.The test parameters are the thickness of grid(1mm and 3mm).The fundamental behavior of BFRP grids like elasticity modulus and ultimate tensile strength were acquired.Furthermore,a creep test was conducted on 1mm and 3mm BFRP grid.In each test group,the BFRP grid was subjected to a sustained load for 1000 hours.The sustained load is about fifty percent of its ultimate stress.No creep rupture occurs on the specimens.2.A flexural test on the RC deck slab strengthened by BFRP grids was conducted,which include three slabs strengthened by BFRP grids with different pre-stress levels,two slabs strengthened with BFRP grids without pre-stress and one control slab without strengthening.A special tension and anchor system was developed for prestressing.The performance of reinforced concrete slabs strengthened by BFRP grids with different pre-stress levels of was studied.Test results show that at the same pre-stress level,the slab strengthened with thicker BFRP grids possesses larger bearing capacity.The slab strengthened with higher pre-stress level BFRP grids possesses larger bearing capacity,with the same thickness of BFRP grids.The slab strengthened with non-prestressed BFRP grids possesses larger ultimate capacity and higher yield load than the control slab,but their cracking loads are identical.The slab strengthened with pre-stressed BFRP grids possesses higher cracking load than the control slab,but its ultimate load and yield load are similar with the slab strengthened with non-prestressed BFRP grids with the same thickness.3.The performance of RC deck slab strengthened with pre-stressed BFRP grids was simulated by the finite element analysis software ABAQUS.A small error of simulated value compared with experimental is observed in the load-strain curve.It is proved that the test result of this performance was reliable and it can be used as basic data for further researches.According to the concrete standard,a formula calculating the cracking load and ultimate load of the RC deck slab was derived.The error between calculated value and experimental value is small.Thus,the formula is trustworthy and can be used as a design reference.Pre-stressed BFRP grids strengthening can avoid some defects like strain lag,debonding failure and poor utilization efficiency of material strength.It is a green,energy-efficient technology,which has a wide application prospect. |
