Research On Stiffness And Crack Of Concrete Beam Reinforced With High-Strength Rebars

The application of high-strength rebars has positive significance for economizing, which can promote sustainable development. However, high rebar stress and strain caused by high-strength rebars will lead to wider crack width, so the ratio of rebars may be controlled by serviceability limit states, and the excellent performance of high-strength rebar will be wasted. Based on the research on high-strength concrete beams reinforced with HTRB600 rebars, including bearing capacity of flexural, crack width and stiffness, evidence of HTRB600 rebars applicability has been provided.Based on experiment of 5 high-strength concrete flexural beams reinforced with HRB400 rebars and 5 reinforced with HTRB600, comparison of flexural cracks, deflection, damage properties and bearing capacity is carried out. The results show that there is sufficient safety margin in terms of bearing capacity when design tensile strength of HTRB600 is 500MPa according to the calculation methods in GB50010-2010. Also, on the basis of the calculation model on short-time crack width adopted in the code according to test date obtained from the experiment and collected from some previous experiments about flexural members reinforced with 400MPa and 500MPa rebars, the comparison is carried out. The results show that the calculated value is agreed with the experimental when the stress of rebar is low, but the former is obviously conservatism when the stress is high. Consequently, limit of rebar stress during calculation is proposed to be set. Meanwhile, according to the test data and some previous experiments, based on the calculation model on short-time stiffness adopted in the code, revised stiffness formula for concrete beams reinforced with high-strength rebars is proposed because of the formula adopted in the code seems unsafe.Compared with three different indicators, the change of ductility of flexural members due to the strength of rebars was studied by ABAQUS. At the same time, for members reinforced with high-strength and high-ductility prestressed rebars such as HTRB600, the influence of the effective prestress level was also be discussed. From the viewpoint of energy, the energy dissipation performance affected by rebar strength was studied, so as the influence of prestressing on the hysteresis loop, though the stress-strain analysis of steel bars under cyclic load according to the criteria of loading and unloading after yielding.With HTRB600 in the precast concrete square piles and prestressing some of them, crack of pile will be restrained during transporting and using. Based on bending experiment of 2 prestressed precast concrete square piles, cracks of the piles were obviously improved. In the basis of 5 piles reinforced of different rebars, prestress loss was analyzed, prestress of rebar was proposed not too low. A computer program written in Fortran 90 based on iterative procedures because of non-linear nature of the constitutive relationship for concrete was used for calculating the crack moment. The energy dissipation performance of piles was studied by Opensees for the usage of high-strength rebars and no significant impact showed.