Shear bearing capacity calculation method for UHPC beams with steel bottom plate

To investigate the shear performance and the calculation method for the shear bearing capacity of ultra-high performance concrete (UHPC) beams with steel bottom plates, seven test UHPC beams were designed and fabricated for shear-resistance testing by test research and theoretical analysis, with test parameters including joint configuration, longitudinal web reinforcement layout, and shear span ratio. Combined with limit equilibrium theory and sub-item linear superposition, a recommended formula for calculating the shear bearing capacity of UHPC beams with steel bottom plates was established. Shear contributions from stirrups, steel fibers, UHPC matrix, and steel plates were considered in this formula. It was subsequently compared with the calculation formula prescribed by the French code. Test results show that the failure mode of joint beams is characterized by shear failure with joint malposition, with primary cracks progressing diagonally along the joint side near the mid-span. In contrast, the failure mode of intact beams is related to the shear span ratio, shifting from shear-compression failure to flexural-shear failure as the shear span ratio increases. The presence of joints reduces the shear bearing capacity of UHPC beams with steel bottom plates, and it decreases with the increase of the shear span ratio. The layout of longitudinal web reinforcement can improve the shear bearing capacity and deformability of these beams effectively. The average ratio of the calculated value of shear bearing capacity via the proposed method to the test value is 0. 91, with a coefficient of variation of 0. 16. In comparison, the average ratio of the calculated value of shear bearing capacity via the French code method to the test value is 1. 08, with a coefficient of variation of 0. 29. Therefore, the proposed calculation method exhibits lower discreteness and is applicable for the shear bearing capacity calculation of UHPC beams with steel bottom plates. 5 tabs, 10 figs, 31 refs. © 2024 Chang'an University. All rights reserved.