Mechanical performances and evolution of stiffness of thin-walled strain hardening cement-based composites pipes during cyclic loading

Four series of pipes such as reinforced strain hardening cement-based composites (SHCC) pipe (RSHCCP), plain SHCC pipe (SHCCP), reinforced cement mortar pipe (RMP) and plain cement mortar pipe (MP) were investigated by means of Three-Edge Bearing Testing (TEBT) under monotonic and cyclic loading. Results show that RSHCCP had the highest load-carrying capacity and deflection ratio among them. The synergy reinforced effect of PVA fiber and reinforcing steel to improve load-carrying capacity and deflection ratio of pipe was validated. Under cyclic loading, the irreversible deflection at the crown of pipe increased gradually. The envelope of the load-deflection response of cyclically loading pipe was consistent with the load-deflection curve of monotonically loading pipe. The pipe stiffness of concrete pipe under TEBT was characterized using the ratio of load to the reversible deflection at the crown of pipe during cyclic loading. The pipe stiffness of RSHCCP decreased continuously after the applied load exceeded the elastic range while the pipe stiffness of SHCCP, RMP, and MP remained stable unless the imposed load was close to the ultimate load. The pipe stiffness of RSHCCP could satisfy the requirements for the installation flexural stiffness ratio of semi-rigid pipe as the applied load was more than 70% of its ultimate load. The deflection ratio of RSHCCP was greater than the minimum deflection ratio level (i.e. 3%) of semi-rigid pipe.