Study On Bending-torsion Bearing Performance Of CFRP Strengthing Reinforced Concrete Box Beams

CFRP as a high-performance material with the advantages of excellent physical properties, light weight, corrosion resistance, easy construction and small footprint, etc., have become the main material of Strengthing Reinforced Concrete structures, strengthening design methods and theoretical analysis study is the hot issues of concern to engineers. the bridge structures, most of them in a state of combined loadings, bridge structure of combined loadings cause people's attention.In recent years, Our country and foreign researchers on experimental and theoretical study of reinforced concrete structures under combined loadings has obtained excellent results, The strengthening process has promulgated the corresponding technical specifications, but for the use of CFRP reinforced box beam,the combined loadings mechanism is influenced by many factors, still lack a more in-depth study. However many of the reinforcement project use of CFRP materials due to its advantages and highly favored by civil engineers, therefore, experimental and theoretical study of CFRP reinforced composite box beams under the combined loadings have great significance.In this paper, CFRP reinforced concrete box beams torsional capacity under combined loadings test. Making five tests of reinforced concrete box beams,one box beam is not reserved for a comparison test as a reinforcement beam, and the remaining four box beams in a different way pasting CFRP reinforcement, and through each box beam carries on the step by step load test, obtaining each test section's the deflection and the strain of steel bar, CFRP and concrete.And the crack of the beam body surface is observed and recorded during the loading process. Analysis of the test results, that the use of the outer surface of the CFRP sheets can be pasted on the box beams torsional capacity increased by about 45%, of the U-shaped box girder reinforcement method is the primary factor in improving the torsional capacity, its wrapping effect is to improve the structure of the torsional capacity factors; increase the rigidity of the torsion beams, inhibit the development of cracks, and reduces the crack width.Based on variable Angle space truss theory,put forward torsion strength of concrete box beams calculating method under combing loading. According to the static equilibrium condition establish the equations,inferred the capacity formula of Reinforcement of box beams under bending-torsion.In the current design of concrete structures in that twisted component capacity based on the relevant formulas, combined with the complex bending stress under twist dimensionless correlation between the structural resistance of the CFRP contribution into account, derived pure torsion and bending-torsion two kinds torsional capacity mode component calculation formula.Using ANSYS finite element analysis software,Each box beam under different loading situation was simulated,the calculated curve box beam stiffness, deflection curve with the experimental results closer.It is feasible to use CFRP to analyze the reinforced concrete beams with ANSYS.