Effect of Fatigue Loading and Precracking on the Interface Shear Transfer of Cold Joints

This paper investigated the shear strengths (that is, the ultimate strength, post-ultimate residual strength and failure strength) and shear transfer mechanism of cold joints after experiencing high-cycle fatigue loading and/or precracking. Twelve cold joint push-off specimens with naturally smooth interfaces were cast and tested. Six of these specimens were directly subjected to push-off tests without any prior treatment, serving as control specimens. Two specimens were intentionally precracked, while the remaining four specimens underwent two million constant amplitude load cycles, before the push-off test. Push-off test results indicate that the effect of fatigue loading on shear strengths can be disregarded. Precracking has very little influence upon the residual strength and the failure strength, but it significantly reduces the ultimate strength to a level comparable to the residual strength. Moreover, this paper identified a new interface failure mode and presented complete interface shear load-displacement curves, revealing the shear transfer mechanism at the interface. This mechanism provides a clear explanation for the aforementioned effect on the shear strengths. Besides, building upon this mechanism and through a force-balance analysis, the equations are proposed for predicting the residual strength and failure strength of cold joints, which are found to reliably yield accurate calculation results.