Mechanical behavior analysis of concrete girder bridges widened by partial splicing method

This study focuses on long‐connected concrete continuous girder bridges where the superstructures of new and old bridges are integrated while their substructures remain separate. A three‐dimensional Finite Element model was developed to analyze the effects of long‐term loads such as concrete shrinkage, creep, and temperature variations along both longitudinal and transverse directions. To expedite construction, a novel partial splicing method and a new structural splicing type were introduced and tested through full‐scale model experiments. Concrete shrinkage, creep, temperature gradients, and overall temperature changes were identified as the most influential factors affecting the displacement of long‐connected bridges. Concrete shrinkage contributes the largest proportion to transverse displacement in widened long‐connected bridges' supports, accounting for up to 68.58%. The new partial splicing method, designed to reduce widening time effectively, involves symmetrically splicing main girders of new and old bridges through in situ wet joints from the middle towards both sides, leaving the ends non‐splicing. In the full‐scale model experiment of rectangular steel plate, under medium and biased vehicle loads equivalent to 140 kN (twice the weight of Class I‐highway vehicles in China), no cracking or crushing occurred at the connection between the steel plate and girder flange throughout the loading process, with or without bridge deck pavement, confirming the rationality and effectiveness of the proposed rectangular steel plate for the non‐splicing section.