Deformation Performance And Stiffness Analysis Of Corroded RC Beams Strengthened With Bolted Steel Plate

Corrosion will cause steel area to weaken,mechanical performance degradation and concrete cover cracking,led to the reduction of bond behavior between steel bar and concrete,bearing capacity and stiffness degradation of the structure of the bridge.In the case of serious corrosion,the bridge operation will appear safe hidden dangers,so,it is urgent to repair and strengthen the old bridges in danger.By conducting tests on 9 corroded RC beams strengthened by bonded steel plates,this paper analyzes the different thickness steel plate and protective layer thickness on the influence of reinforcement beam deformation performance.By introducing steel strain lag coefficient of m(?s),steel strain uneven coefficient of n(?s)and coordination coefficient of ? between steel plate and concrete,put forward the short-term flexural stiffness model of corroded RC beams strengthened by bonded steel plates.By experimental study on 3 “corrosion-reinforcement-corrosion” RC beams,combining with the aforementioned part of the test beams,this paper analysis the deformation behavior,strain and failure mode of the corroded RC beams,corroded RC beam strengthened with bolted steel plates and strengthened beams had experience secondary corrosion.At the same time,the influence of thickness protective layer thickness on deformation behavior of corroded reinforcement beams which corroded again is discussed and the stiffness model of“corrosion-reinforcement-corrosion” RC beams is given.The main contents can be drawn as follows:(1)12 reinforced concrete beams are divided into 3 groups according to the thickness of the protective layer,each group with one contrast beam.After the electrochemical corrosion test and preloading work,the nine corroded RC beams which beyond contrast beams will be reinforced with a thickness of 3mm,4mm,5mm steel plate,then do the beam single point load test and record the test data.(2)Experimental study show that the average strain distribution of corroded reinforcement beam is generally consistent with the assumption of plane cross section,reinforced steel plate significantly improve the normal performance of the beam,stiffness of the strengthenedbeams are evidently improved.When the protective layer thickness and corrosion rate are close,the deflection of the strengthened beams decreases with the increase of the thickness of the steel plate,and the stiffness increases and the ductility decreases;protective layer thickness on the deformation capacity of the strengthened beams is not obvious.(3)Based on the experimental results and the stiffness calculation theory of RC beams,the formula of stiffness strengthening RC beams by bolting and affixing steel plates is given in this paper and the comparation between the tested results and the theoretical results indicates that the formula provides a good reliability and applicability.(4)By experimental study on 3 “corrosion-reinforcement-corrosion” RC beams,combining with the aforementioned corroded reinforcement beams,this paper analysis the deformation behavior,strain and stiffness rule between them.The experimental study show that the deflection of the corroded RC beam strengthened with bolted steel plates is smaller than the strengthened beams had experience secondary corrosion when beams have the same thickness of concrete cover and the same loading condition,so the stiffness is lager;The average strain distribution of the strengthened beams had experience secondary corrosion isn't consistent with the assumption of plane cross section,protective layer thickness on the deformation capacity of the strengthened beams had experience secondary corrosion is not obvious.