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为较严密地计算预应力混凝土箱梁桥实时温度应力场,有效防止单箱双室箱梁桥零号块施工中由于水化热过大产生裂缝。为了有效防止单箱双室箱梁桥零号块施工中由于水化热过大产生裂缝,对易开裂部位采用现场埋设温度传感器的实时监测测试方法,从混凝土浇注开始,每隔0.5h实时采集各个测点的温度,分析箱梁混凝土浇注后早期的温度变化,通过采集得到的混凝土温度时程曲线分析箱梁中混凝土的水化热应力。同时基于箱梁表面热交换平衡理论、综合考虑环境条件、物理材料特征、几何性质采用热瞬态分析热-结构耦合求解技术,实现任意时刻箱梁零号块的温度应力场的仿真。研究结果表明:采用普通硅酸盐混凝土,箱梁零号块在第一层浇注后3天时,混凝土的主拉应力超过抗拉设计强度的区域较大。为了防止箱梁零号块横隔板由于水化热应力过大而开裂,建议横隔板的两侧增设防裂网。
In order to more closely calculate the real-time temperature and stress field of prestressed concrete box girder bridge, cracks in the construction of No. 0 block of single box and double-chamber box girder bridge are effectively prevented due to excessive hydration heat. In order to effectively prevent cracks in the zero block construction of single box double chamber box girder bridge due to excessive hydration heat, a real-time monitoring test method of on-site buried temperature sensors is adopted on the easy cracking site, and real-time monitoring is conducted every 0.5h from the concrete pouring The temperature of each measuring point, analyzing the early temperature change of the concrete after the pouring of the box girder, and analyzing the hydration thermal stress of the concrete in the box girder through the collected time-history curve of the concrete temperature. At the same time, based on the heat balance theory of the box girder, considering the environmental conditions, the characteristics of the physical materials and the geometrical properties, the thermo-structural coupling solution of the thermal transient analysis is used to simulate the temperature stress field of the zero block of the box girder at any moment. The results show that the area where the main tensile stress of concrete exceeds the tensile strength is larger than that of the tensile strength of concrete by ordinary silicate concrete. In order to prevent the box girder zero block of the diaphragm due to hydration thermal stress is too large and cracking, it is proposed to add crack protection mesh on both sides of the diaphragm.