Experimental Study And Analysis On The Diagonal Shear Property Of Corroded Reinforced Concrete Beam

The durability of reinforced concrete structures is one of the problems widely concerned in engineering. The corrosion of reinforcement is the most dominating factor that influences the durability of reinforced concrete structures, since the corrosion may cause deterioration of mechanical properties for the reinforcement, damage of sectional performance for the concrete and reduction of the bond between steel bars and concrete, so as to change the failure mode of members, decrease their load capacity, and consequently affect the security of structures.Considering the fact that less study has been made on the characteristics of diagonal section in corroded reinforced concrete beams, this thesis investigates the influences of complete or partial bond failure between steel bars and concrete, due to severe corrosion of longitudinal reinforcement, on the characteristics of diagonal section in reinforced concrete flexural members. Nine reinforced concrete beams with longitudinal bars of different corrosion levels were designed and tested under concentrated loading to study the shear performance of beams. According to the comparisons and analyses of test results on crack distribution, deflection and ultimate load capacity, the effect of bond reduction, resulted from corrosion of longitudinal bars, on the characteristics of diagonal section in reinforced concrete beams were investigated for different corrosion ranges, extents and positions of reinforcement. Simulation analyses were also carried out for beams with partial bond failure, using FEA software ANSYS. The factors that influence the shear strength of flexural members were finally analyzed. Based on the truss and arch theories, the effect of longitudinal and lateral reinforcement on the shear strength of flexural member elements was analyzed, and in combination with test results a shear strength formula for corroded reinforced concrete beams under concentrated loading was proposed.In this research, the test results show that:1 .The corrosion of longitudinal bars reduces the rigidity of beam, and the rigidity decreases with the increase in the corrosion extent and range. The rigidity is also influenced by the corrosion position of longitudinal bars, with more severe reduction of rigidity for corrosion near supports than that in the midspan under the same corrosion ranges.2. The severe corrosion of longitudinal bars in the midspan make the occurrence of normal cracking of beam earlier but rarely changes the time of occurrence of diagonal cracking; the severe corrosion of longitudinal bars in the shear span however makes the diagonal cracks appear much earlier.3. The severe corrosion of longitudinal bars in the midspan may vary the distribution of cracks in that the umber of cracks within the area of severe reinforcement corrosion decreases together with the increase in the crack spacing. The corrosion of longitudinal bars in the midspan increases the width of diagonal cracks under service loads.4. If the longitudinal bars are anchored reliably, the extensive corrosion of longitudinal bars in the shear span may change the failure mode of beams. The weakening of bond between longitudinal bars and concrete in the midspan does not show remarkable effect on the shear strength of beams. The analytical results indicate that the corrosion of reinforcement will decrease the shear strength of diagonal section in flexural members.