Experimental Study On Flexural Behavior Of RC Bridge Beams Strengthened With Stranded-wire Ropes

The strengthening technique using prestressed high strength steel wire ropes has been widely applied in the strengthening of existing building structures for it’s obvious superiority: it put little weight to the structure with excellent performance in durability,fire resistance,environmental-protection and convenience in operation.Compared to the strengthening technique in building structures,bridge strengthening need more rigorous requirements: outdoor conditions,larger span and higher need in standard.To apply this technique in bridge strengthening field properly,An innovative technique with distributed anchorage was presented,and several works had been operated based on the strengthening technique.(1)An improved strengthening technique was proposed based on the traditional method,apart from the angle iron at end anchorage,two box irons with steel pipes inside were designed to make the steel wire rope better combined with the beam,similar to the end anchorage,the box irons were attached to the beam with high-strength rods along the beam.Besides,the conduction of the approach turned out to be convenient.(2)To verity the effectiveness of the proposed technique,three beams strengthened with high strength steel wire ropes and one comparative beam were tested,the paraments involved the variation of the diameter and the prestress attached to the steel wire ropes.The enhancement of the flexural capacity,section rigidity and the propagation of flexural cracks(specifically observe the width of cracks during the period from the presence of cracks to the yielding of tensile rebar)were assessed.The results showed that:(1)The bond performance between the steel wire ropes and the anchorage showed good cohesiveness during the experiment,hence prove the technique to be applicable;(2)The bearing capacity enhanced apparently with the increasement of steel wire ropes amount,specimens with the reinforcement rate of 0.056% and 0.079% were 35.51% and 63.94% higher than the comparative beam,respectively;while the prestress played a limited role in bearing capacity,specimens with the prestress of 0.25 and 0.35 were 63.94% and 70.89% higher than the comparative beam,respectively,with the discrepancy less than 7%;(3)The capacity improved with the increasement of reinforcement rate and prestress among those retrofitted beams;(4)The strengthened beams could reduce the increasement of stresses in reinforcement and steel wire ropes,thus suppress the propagation of cracks,decrease average crack spacing and maximum crack width.Anticracking ability had been improved with the increasement of reinforcement rate and prestress.(3)A computational formula of bearing capacity had been put forward according to plan cross-section assumption,the calculation results and experimental values showed coherence.(4)Three-dimensional nonlinear finite element model was established with ABAQUS,The simulation results presented a good agreement with experiment datas.