Fe-SMA prestressed strengthening of damaged transverse hinge joints in hollow slab bridges

The hinge joint is crucial for enabling transverse load transfer between slab beams in hollow slab concrete
bridges. However, cracking damage in hinge joints is a common issue. This study proposes a novel transverse
local prestress strengthening method using self-prestressing iron-based shape memory alloy (Fe-SMA) bars to
repair damaged hinge joints. To validate the method, a scaled model (1:4) comprising six hollow slab beams was
constructed, with artificial damage introduced into one hinge joint. Load tests were conducted to evaluate lateral
load distribution patterns before damage, after damage, and post-repair using the proposed method, followed by
an ultimate failure test. A finite element parametric analysis was also performed. Results indicated that before
damage, transverse load transfer between slab beams was efficient. After hinge joint damage, load transfer efficiency
dropped significantly, and the lateral load distribution factor (LLDF) and strain transverse distribution
factor (STDF) exhibited irregular variations under different loading conditions. Following repair, LLDF and STDF
distributions became more uniform, exceeding the initial state. Moreover, the transverse connection stiffness of
the repaired hinge joint surpassed its original condition, and the relative displacement between slab beams
decreased by 20.1–85.4 % under loading. Finite element parametric analysis revealed that reducing Fe-SMA bar
spacing and increasing recovery stress could further improve repair effectiveness. The findings confirm that the
proposed Fe-SMA-based transverse local prestress method effectively restores and strengthens damaged hinge
joints, significantly enhancing the transverse connection in hollow slab bridges.