Early-Age Thermo-Mechanical Response of a Concrete Spine-Beam Bridge During Construction: Local Heat Accumulation and Restrained Cooling

Early-age cracking assessment requires distinguishing hydration-induced heating from the mechanical effects of restrained cooling. This study examines tensile stress and thermal responses to construction measures in a three-span concrete spine-beam bridge in Shaoxing, China. Temperature and strain were monitored at 34 locations and compared with a three-dimensional sequential model incorporating staged casting, age-weighted deformation increments, shrinkage, and stress relaxation. The baseline represents a 480 h construction window with an 8 d inter-pour interval. The mean absolute peak-temperature error was 3.19 °C; the strain comparison indicated limited agreement at the hourly scale. Thick rib–crossbeam intersections formed the principal thermal hotspots. Under the prescribed cooling boundaries and falsework restraints, the calculated thermal maximum of 87.76 °C occurred at 35 h in an intersection core, whereas the maximum principal tensile stress of 1.66 MPa occurred at 441 h near its lower edge. Lower placing temperatures reduced both maxima, while longer inter-pour intervals reduced temperature but increased tensile stress within 96 h after deck casting. These case-specific results support evaluating tensile stress and thermal indicators together and maintaining attention to restrained cooling after the hydration-temperature peak.