Experimental Investigation And Analysis Of Capacity Of Corroded RC Beams Strengthened With Steel Plate In Flexure And U-shaped Strip In Shear

Corrosion of the rebars is seriously restricting the operation conditions of the bridge,the bridge can not meet the requirements of service safety,a large number of existing and future bridge need maintenance and reinforcement.Therefore,in order to study corrosion reinforced concrete beam strengthened with steel plate in flexure and U-shaped strip in shear,13 reinforced concrete beams are designed used to analyze strengthening effect of the plate and U-shaped strip in shear and the mechanical behavior of the beam.Firstly,13 pieces of test beams are designed that strength grade of concrete is C25 and the diameter of the steel bar is 22 mm,Among them,9 pieces of beams divided into three groups according to the thickness of concrete cover which were 25 mm,30mm and35 mm,each group consisted of one piece of corroded RC beam,one piece of corroded RC beam strengthened with bolted steel plates and one piece of strengthened beams experienced secondary corrosion,Remaining 4 pieces of corroded beam strengthened with U-shaped strip in shear,including 1 piece of corroded RC beam strengthened with U-shaped strip in shear without further corrosion(protection layer thickness of 30mm),3 pieces of strengthened beams experienced secondary corrosion(protective layer thickness of 25 mm,30mm,35mm),and three pieces of corroded beam as contrast 4 pieces of strengthened beams.Secondly,strengthened with bolted steel plates: It was shown from the experimental results that the strain distributions along the height of the corroded beam and the strengthened beams at middle-span were in good agreement with the plain section assumption basically,but the strengthened beams had experience secondary corrosion are no longer consistent with this assumption.Strengthened with U-shaped strip in shear: The concrete strain in the cross section of all specimens is basically in line with the assumption of plane cross section and force of U-shaped strip is not equal.Thirdly,Strengthened with bolted steel plates: The ultimate bearing capacity of the strengthened beams had experience secondary corrosion is lower than the corroded beams,the strengthening effect of the steel plate is completely offset When the corrosion rate of the two rebar is relatively balanced,an increase in the secondary corrosion rate of 1% will cause a decrease in bearing capacity about 10~15kN.strengthened with U-shaped strip in shear: U-shaped strip also can improve the bearing capacity,U-shaped strip effect is negligible when beams had experience secondary corrosion,when the protective layer thickness is same,an increase in the secondary corrosion rate of 1% will cause a decrease in bearing capacity about 10 kN.Finally,strengthened with bolted steel plates: according to the theory of truss model,the calculation method of bearing capacity is proposed,and the theoretical model can be used to predict the ultimate bearing capacity of corroded reinforced concrete beams.Strengthened with U-shaped strip in shear: a model for the shear capacity of corroded reinforced concrete beams strengthened with U-shaped strip is proposed,and the correctness of the model is verified by collecting the experimental parameters of the beams in other literatures.