Integrated biomechanical-thermomechanical approach for hydration heat management in hollow concrete piers: Balancing structural integrity and construction ergonomics

This study investigates temperature field variations and associated risks in tall hollow concrete bridge piers caused by cement hydration heat during construction. Integrating field measurements and numerical simulations, we analyzed the dynamic evolution of internal temperature distribution and its structural implications. Field experiments involved continuous temperature monitoring using high-precision sensors embedded in critical zones (core, surface, and varying depths) of a representative pier. Concurrently, a 3D finite element model was developed in ANSYS, incorporating nonlinear thermal properties, the Priestley temperature-dependent hydration model, and realistic boundary conditions. Transient thermal analysis simulated hydration-induced temperature evolution, validated against experimental data. Results revealed significant temperature gradients, with core temperatures rising rapidly due to restricted heat dissipation in large-volume piers. Hydration heat peaked at approximately 70% of maximum temperature within 28 h post-pouring, reaching full intensity at 50 h. Key influencing factors included concrete mix design, cement type, environmental conditions, and cross-sectional dimensions. Post-formwork removal, surface cracking risks escalated due to abrupt temperature differentials, inducing tensile stresses exceeding early-age concrete strength. Mitigation strategies emphasized optimized formwork removal timing, low-heat cement blends (e.g., incorporating fly ash or slag), and enhanced curing techniques (moisture retention, insulation) to regulate thermal gradients. Furthermore, the study highlighted occupational health risks from concentrated heat release, proposing measures such as adjusted work schedules, cooling systems, and protective equipment to safeguard workers. These findings provide actionable insights for balancing structural integrity, construction efficiency, and labor safety in large-scale concrete infrastructure projects. The environmental chamber testing results showed that in a hot environment, the mean skin temperature (35.8 ℃ vs. 36.59 ℃), heart rate (110 beats/min vs. 116 beats/min) and core temperature of the subjects with NCV were significantly lower than those with the control (without NCV). The intelligent monitoring system equipped with sensors has an early warning response time of one minute and a false alarm rate of less than 1%.