Damage Analysis of Segmental Dry Joint Full-Scale Prestressed Cap Beam Based on Distributed Optical Fiber Sensing

Distributed fiber optic sensors (DFOS) can detect structural cracks and structural deformation with high accuracy and wide measurement range. This study monitors the segmental prestressed bent cap, assembled with a large key dry joint, based on optical fiber technology, and it allows the comparison of its damaging process with that of a monolithic cast in place counterpart. The obtained results, comprising cross-section strain distributions, longitudinal strain profiles, neutral axis location, crack pattern, and the damage process, show that the DFOS technology can be successfully used to analyze the complex working stress state of the segmental beam with shear key joints, both in the elastic range and at the ultimate load, and to successfully identify the changing characteristics of the stress state of the segmental capping beam model when elastic beam theory no longer applies. The DFOS data confirm that the shear key joint, as the weak point of the segmental cap beam, results in the high stress concentration area, and the damage rate is higher than that of the cast-in-place beam. The accurate monitoring by the DFOS allows for the realization that the damage occurs at the premature formation of a concentrated compression zone on the upper part of the shear key.

Automated summary

Distributed fiber optic sensors can accurately and extensively detect structural cracks and deformation. This study used optical fiber technology to monitor a segmental prestressed bent cap with a large dry joint, comparing it with a monolithic cast-in-place counterpart. The results showed that DFOS technology can successfully analyze the stress state of the segmental beam with shear key joints, including strain distributions, crack patterns, and damage processes. The DFOS data confirmed that the shear key joint is a weak point causing high stress concentration and higher damage rate compared to cast-in-place beams.