The excessive deflection of large-span cantilever cast prestressed concrete (LCCPC) box girders has always been a complex problem to be solved in bridge engineering. To analyze the effect of shear deformation at segmental joints on the deflection of LCCPC box girders, comparison tests were carried out on three prestressed concrete (PC) I-girders with joints and a PC I-girder without joints, and a finite element simulation method of segmental joints was proposed based on the tests. Subsequently, finite element analysis was conducted on a test girder and the Assistant Shipping Channel Bridge of Humen Bridge (a PC continuous rigid frame bridge with a main span of 270 m) using this method. The experimental and theoretical analysis results showed that the effect of the shear deformation at joints compared to the deformation at midspan of the girder specimens was negligible. Deformation at midspan of the specimens would not significantly increase, even if shear rigidity at the joints was significantly reduced or there were more joints in the girder specimen. The effect of shear deformation at segmental joints on the deflection of LCCPC box girders was quite small and thus insignificant.

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.