Study On Bending Performance Of Prestressed Beams In Simulated Acid Rain Environment

Generally speaking,the durability of the prestressed concrete is better than the reinforced concrete,but while the prestressed concrete structure in corrosive environment(such as chemical corrosion erosion,freeze-thaw,carbonation)under the action,its durability will continue to decline,and make the structure durability failure ultimately.Moreover,compared with ordinary reinforced concrete structures,there are more complex steps in the construction process of prestressed concrete structures,such as corrugated pipe buried,grouting prestressed tension and anchorage,anchorage hole,anti-corrosion treatment,the quality defects of any one of the steps are likely to lead to corrosion of the reinforcement bars,thereby reducing the durability of structures.At present,there are few researches on the durability of prestressed concrete structures in China and abroad.The study on the flexural behavior of corroded prestressed concrete structures under acid rain environment is rarely reported.In order to study the flexural performance of prestressed concrete structure in acid rain environment.In this paper,the chemical composition of acid rain in Jiangxi area was analyzed and simulated acid rain solution was make up,the prestressed concrete beam as the research object,through the experimental study reveals the deterioration law of simulation of prestressed concrete beams under acid rain performance.The main work is as follows:(1)The partial prestressing ratios and the concrete strength is taken as the main production parameters of 8 prestressed concrete beams,one of them was normal beam,and the other were immersed in simulated acid rain solution to accelerate corrosion.In this paper,the test methods of specimen making,steel strand tension and grouting,corrosion method,corrosion rate measurement and crack width measurement are introduced in detail.(2)The pure bending mechanical test is carried out when the corrosion test beam reaches its design corrosion time,In the course of the experiment,the failure process and phenomena of all the test beams were carefully observed,and the development of cracks and corrosion patterns of corroded steel strands were observed,then summarize and compare all of the test beams;and record the deflection,cracking load,ultimate load,concrete strain,steel strain,strain,prestressed reinforcement the crack width,and all the data were collected and analyzed,The bending moment deflection curve of the test beam,the strain curve and the maximum crack width curve in the middle section were plotted.The test results show that the corrosion of prestressed concrete beams in bending process still meet the plane section assumption;the increase of the degree of corrosion gradually reduce the ultimate bearing capacity of prestressed concrete beams;compared with the corrosion test beam,prestressed concrete beam ductility after corrosion decrease;prestress had no effect on the basic strength offlexural performance before cracking,increase the prestressed reinforcement ratio can effectively improve the partially prestressed concrete beams under working load stiffness.(3)Based on bending test results in this paper and the concrete structure design specification formula,the calculation model of bearing capacity of prestressed concrete structures considering corrosion reduce section area of rust and yield strength of prestressed tendons are established,the calculation results of the bearing capacity calculation model are compared with experimental results to verify the accuracy of the calculation model.(4)After the analysis of the corroded steel strand and steel bar,The corrosion of steel wire and steel strain increment ratio of corrosion prestressed concrete beam was take as the starting point,combined with related specifications,the formula for calculating the maximum crack width of prestressed concrete beams is established.