Probabilistic Response of Prestressed Concrete Box Girder Bridges under Stochastic Temperature–Humidity Environmental Conditions

To investigate the evolution of mechanical behavior in concrete box girder bridges during cantilever construction under the coupled influence of stochastic environmental temperature and humidity, a novel simulation method is proposed. This method integrates a temperature–humidity coupling analysis method for the internal fields of concrete and a constitutive model that accounts for multifactor interactions, including temperature-induced stress, drying shrinkage, creep, and the sensitivity of elastic modulus. The proposed method was applied to simulate and analyze the construction process of the Yuanhe Bridge in Jiangxi Province, China. Based on the statistical analysis of nearly two decades of daily historical meteorological data from the region, it was verified through fitting tests and statistical assessments that the probability distributions of temperature, humidity, and wind speed conform to Gaussian (normal) distributions. The results systematically reveal the statistical influences of stochastic environmental factors on the bridge’s camber, shear-lag effect, and prestress loss. The results indicate that the maximum camber and the shear-lag coefficient at the bottom slab–web junction exhibit slightly asymmetric distributions and can be well described by Bigaussian fitting curves, whereas the shear-lag coefficient at the top slab–web junction follows a Gaussian distribution. Increases in the daily temperature range and decreases in relative humidity are found to amplify the camber and the prestress loss. No discernible influence of wind speed on the camber, shear-lag effect, or prestress loss is observed. This study provides a crucial theoretical foundation and technical support for the refined control and optimization of cantilever construction of bridges under stochastic environmental conditions.