Experimental And Theoretical Research On Flexural Behavior Of Reinforced Concrete Beams With HRB500 Bars

HRB500 bar is a new hot-rolled ribbed bar with strength of 500MPa, which will be listed in the modifying Chinese Code for design of concrete structures. However, there is not enough experiment about the properties of HRB500 reinforced concrete members, such as ultimate bearing capacity, cracks, rigidity etc. Entrusted by the Code for Design of Concrete Structure Management Committee of Ministry of Construction, we have been conducted the research to the HRB500 reinforced concrete structural member stress performance.Based on the test of 11 flexural R.C. beams with variant ratio of reinforcement, the phenomenon of the development of flexural cracks, deflection, damage property and the ultimate bearing capacity were observed and recorded in detail. And whether the design values of =420MPa, 430MPa and 450MPa of tensile strength of HRB500 reinforcement bars in calculating can be met the limit of the maximum crack width and deflection of the active Code GB50010-2002 are also be discussed. The reasonable design value of tensile strength of HRB500 reinforcement bars used in calculating the flexural bearing capacity was also suggested.A modulusαBfor the calculation of flexure rigidity using active Code which named Relative bearing capacity adjusting factor has been introduced in this thesis. The computed deflection which with using the adjusted flexure rigidity from the state of concrete cracking to reinforcement yield could be got satisfied.Based on the classical analogy truss model, an improved analogy truss model that considered the tension stiffening effect was developed to calculate the flexure rigidity of RC beams. The short-term deflections in serviceability state of 169 test beams have been calculated.A computer program which named SectionForce was written in FORTRAN90 language in use for calculate the forces acting on the cross section and bond stress around the reinforcing bars in iterative procedures. Iterative procedures are used for the above calculation because of the non-linear nature of the constitutive relationship for concrete and the bond stress-bond slip relationship which has been assumed. The cracking moment, ultimate bearing capacity, and steel stress on just before or just after cracking also can be calculate correctly. Finally, based on the results of the program SectionForce, a finite element model and software ANSYS have been used for the analysis of the stress and strain distribution of the concrete between adjacent cracks.