Abstract:

This study investigates the effect of prestressing tensioning in the negative moment zone on the force performance of wet joints in the flange slabs against the background of an under-construction simply-supported and then continuous T-girder bridge.The stress distribution law of wet joints is analysed through construction process monitoring and parametric numerical simulation. In order to facilitate the construction, the prestressing bundles were firstly tensioned and the longitudinal wet joints were poured afterwards in the background project. In addition to the original construction sequence (first type), the parametric analysis considered two additional conditions: the joints were poured first and then prestressed (second type), and the negative moment zone was partially poured with joints, then prestressed and finally poured with the remaining joints (third type). Monitoring showed that: the difference in prestressing tensioning level during construction exceeded 10%, but the wet joints were not significantly affected due to post-casting; the transverse direction of the joints was basically compressed after casting, and the longitudinal direction was only tensed at a low level in the beams (15 με); the monitoring showed that the prestressing tensioning did not directly increase the risk of cracking of the joints. Parametric analyses show that there is a certain degree of stress redundancy in the joints under all three construction sequences. The maximum main tensile stresses under constant load were 0.2 MPa, 1.9 MPa and 0.8 MPa in order; and the first two tensile stresses continue to be significant after the second period of constant load; while the third one, casting wet joints in stages still has lower tensile stress after the second stage of constant load, but the construction process is more complicated. The above results can provide support for the force analysis and process optimisation of the construction process of similar structures.

Key words: assembly, wet joints, monitor, construction process, finite element