Key Construction Monitoring Technology for Long-Span Continuous Girder Bridge

This paper integrates a monitoring practice for the construction of a long-span continuous girder bridge to explore strain measurement and geometric shape control technology. In doing so, the actual stress of the bridge in the cantilever-construction stage is identified, and the influence of ambient temperature on the geometric shape control of the main girder is eliminated. According to linear creep theory, a strain correction method based on the superposition principle is proposed to remove the strain induced by concrete shrinkage and creep. By identifying the pattern of the solar thermal effect on the main girder geometry, a double in-situ measurement interpolation method is proposed to predict the adjusted value of formwork erection elevation. The results show that the deviation between the measured and corrected stress values on the root section of the main girder under the maximum cantilever state of the main girder is 16%–23%, which verifies the necessity of strain correction. The corrected values of measured stress on each controlled section are essentially identical to the calculated values, and both have consistent change patterns throughout the construction process, which verifies the validity of the strain correction method. During the cantilever-construction stage, the vertical deformation of the main girder owing to the solar thermal effect is parabolic and significant; hence, the main girder geometry should be measured prior to sunrise. The double in-situ measurement interpolation method can effectively eliminate the adverse effects of solar thermal when lofting the vertical formwork elevation in a non-ideal period.