PROVISIONS AGAINST THERMAL AND DRYING SHRINKAGE CRACKING IN CONSTRUCTION OF PRESTRESSED CONCRETE BRIDGE

摘要

This report describes the controlling methods of the thermal and drying shrinkage cracking for a construction of prestressed concrete bridge. In order to control thermal cracking, the following provisions were needed to be considered in each part: modification of cement type, use of expansive additive, insulated curing, cooling concrete with liquid nitrogen and air-cooling with deflection tube for external tendons. Each effect was evaluated through 3D-FE analyses before construction and thermal fitting analyses based on measuring results of temperature inside concrete at first construction. With respect to the drying shrinkage cracking, the following provisions were conducted in all mix proportions of concrete and parts: setting the maximum limit of unit water content, designation of aggregate type and extending wet curing period. These provisions proved the effects in decreasing the thermal and drying shrinkage cracking. As a result, no visible cracks were found to occur in the bridge.