Experimental Study On The Relationship Between Crack Width And Reinforcement Stress Of Reinforced Concrete Members With High Strength

Crack width is one of the main factors affecting the durability of reinforced concrete structures,and there are many factors affecting the crack width of reinforced concrete members.In this paper,a total of 27 reinforced concrete axial tension members are designed.The main work of this paper includes the following two aspects:(1)Through the axial tensile test of the reinforced concrete members,the cracking condition,crack morphology,distribution and crack width of the specimens under each grade of load were measured.Through the analysis of the test data,the relationship between the reinforcement stress and the crack width is studied.(2)By recording concrete strain measurement with the changing rule of the reinforcement stress,studies of the surrounding of the reinforced concrete range of constraints.Through experimental analysis,the following main conclusions are obtained:(1)When the reinforcement stress increases,the crack width of the reinforced concrete member also increases.When new cracks appear in the member,the original crack width may be reduced.When the crack width of reinforced concrete specimens is 0.25mm and 0.3mm,the corresponding reinforcement stress is respectively in(0.59?0.8)fyk and(0.66?0.86)fyk;(2)When the thickness of concrete protection layer c is the same,the average crack spacing increases with the increase of steel bar diameter and reinforcement ratio,but decreases with the increase of d/?,and the calculated value of "Code for design concrete structures "(GB50010-2010)formula is larger than the test value,the average value of the ratio is 1.431,the variance is 0.185.The measured values of the average crack width of all components are compared with the calculated values of the national standard,and the calculated values are larger than the measured values,indicating that the calculation formula given by the standard has a larger safety factor.(3)Before the cracking of reinforced concrete members,the relationship between the strain of concrete and the stress of steel bar increases linearly.After the cracking of concrete,although the stress of steel bar increases continuously,the strain of concrete increases or decreases,which has no definite rule.(4)With the increase of steel bar stress,reinforcement of the concrete near the constraints of the area also increased,but the scope of this constraint is limited,some is reinforced centroid as the center of the circle,7 d for the steel bar diameter(d)as the radius of the circular area.