Calculation Method for Reinforcement Stress in Ultra-High Performance Concrete Beams Considering Bond-Slip Effect
Four-point bending tests were conducted on six ultra-high performance concrete T-shaped(UHPC-T)section beams to establish a reinforcement stress calculation method for reinforced UHPC beams and study the variation law of reinforcement stress.Based on the mechanism of force balance and deformation coordination between reinforcement and UHPC,a reinforcement stress calculation formula was derived using the differential equations of equilibrium,deformation,and bond-slip established by micro elements,which could comprehensively reflect the influence of bond-slip between reinforcement and UHPC interfaces and the contribution of steel fibers to tensile strength.By simplifying the calculation of the strain non-uniformity coefficient and the reinforcement stress in cracked sections,a simplified formula for reinforcement stress suitable for engineering applications was proposed.The results show that the increase in reinforcement stress under unit load decreases with the increase in reinforcement ratio,but it is not related to the change in steel fiber volume fraction.Compared with ordinary concrete beams,the reinforcement stress in UHPC beams is relatively small in the cracked section,but the uneven distribution of reinforcement stress between adjacent cracks is intensified.The calculation value of the suggested formula for reinforcement stress is in good agreement with the experimental values in this article and existing literature.The average ratio of the calculated value of the simplified formula for reinforcement stress to the experimental value is 1.03,and the coefficient of variation is 0.06,indicating that this simplified formula can be used for calculating reinforcement stress in UHPC beams.
ultra-high performance concrete(UHPC)reinforcement stressbond-slipstrain non-uniformity coefficientmicro elements
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