Seawater sea-sand engineered cementitious composites contribution to shear performance of beams reinforced with BFRP bars

Abstract

The combination of seawater sea-sand engineered cementitious composites (SS-ECC) and fiber reinforced plastic/polymer (FRP) bars to make structural beams is promising to mitigate the shortage of raw construction materials and improve shear performance. To better understand the shear behaviors of such kind of structural form, an experimental program was conducted to figure out the effects of longitudinal reinforcement ratio, shear span ratio and stirrup ratio. A total of eleven beams reinforced by basalt FRP (BFRP) bars were tested by four-point loading. The test results showed that the stiffness and ultimate shear capacity of SS-ECC beams without stirrups are higher than that of seawater sea-sand concrete (SSC) beams with a stirrup ratio of 0.67%. SS-ECC exhibits much lower compressive strength compared with ultra-high performance concrete (UHPC), but SS-ECC beam and UHPC beam have close ultimate shear capacity. The shear load contribution of fibers is above 70% in SS-ECC beams without stirrups, and it decreases significantly because of using BFRP stirrups. Furthermore, the modified deformation-based approach is proposed to characterize the ductility index of SS-ECC beams. Based on the calculation model of ultimate shear capacity in codes, the modified calculation model considering the shear load contribution of fibers is proposed and verified.