Temperature and structural properties of prefabricated pipe gallery during whole fire process

To investigate the effects of different variables on the temperature and structural response of assembled superimposed single-compartment pipe galleries during the entire fire process, as well as the differences in damage, single-compartment pipe galleries with varying haunch heights and reinforcement ratios were designed for a full-process fire study. This included static tests under normal temperature, thermal-mechanical coupling tests during the fire, and post-fire static tests. Model tests and finite element simulations were employed to analyze the temperature gradient across the pipe gallery cross-section, longitudinal temperature distribution patterns, structural failure modes, displacement responses, strain responses, and residual bearing capacity evolution. Results indicate that the significant temperature difference between the inner and outer surfaces of the pipe gallery's top slab generates thermal stress, leading to the degradation of concrete performance. Fire exposure causes severe damage to the pipe gallery, while increasing haunch height and reinforcement ratio effectively enhances its bearing capacity and ductility throughout the fire process. Based on observed residual bearing capacity phenomena, a calculation method incorporating high-temperature material degradation and structural shear failure modes is proposed. Experimental data were compared with numerical simulations and validated through finite element analysis. Considering the temperature characteristics and structural performance of the pipe gallery, practical engineering improvement recommendations are provided. The research outcomes offer theoretical support for the study and application of assembled superimposed pipe galleries.