上海科技馆地下室墙体温度裂缝的控制与监测

CONTROL AND MONITORING OF TEMPERATURE CRACKS OF BASEMENT WALL FOR SHANGHAI SCIENCE MUSEUM

上海科技馆工程采用预应力技术控制超长圆弧形地下室墙体开裂。为了检测实施效果,在试验段墙体中预先埋设钢弦式钢筋应力计,对墙体中预应力变化情况进行了长达8个月的量测。结果表明,墙体中所施加的预应力达到了设计要求。墙体中预应力的变化在时间和空间上表现出一定的规律性。在时间上表现为:同一测点的预应力值先是随着时间逐渐增加,然后趋于稳定;在空间上则表现为:竖向墙体中的预应力在地下室顶板附近较小,而在离开顶板一定距离处最大,然后逐渐减小;在横向,张拉端附近测得的预应力值最大,然后向中间逐渐减小。与此同时,采用裂缝检测仪对墙体表面混凝土裂缝的发展情况进行了监测,墙体表面混凝土裂缝的数量和规模随着墙体中预应力的逐步建立而减小,最终得到了有效控制。实践表明,采用预应力技术来控制超长混凝土结构的开裂,可以达到理想的效果。

In the project of Shanghai Science Museum, the pre-stressing technology was used to control the cracking of the arc shaped ultra-long basement wall. The steel string type steel bar taseometer was installed in the wall in advance to examine the pre-stressing value.The measurement of the change of the pre-stressing value in the wall was lasted for eight month. The results indicated that the pre-stressing exerted on the wall has met the designed requirements. The changing of the pre-stressing value displays certain regularity in the time and the space. In the time, the performance is, the pre-stressing value of identical measuring point is firstly increasing gradually along with the time, finally tends to stability. In the space, the performance is： verticaly, in the wall, the pre-stressing value is small nearby the basement roof, then it will become the biggest at a place with some distance away from the basement roof, after that, it will reduce gradually. In crosswise, the pre-stressing value is biggest in both the tensile ends, it will then reduce gradually to the middle of the wall. Meanwhile, the crack monitoring instrument was used to monitor the cracks, the result showed that the concrete crack quantity and the scale finally were under control. The practice indicated that the pre-stressing technology is an ideal method to control the cracks of ultra-long concrete structures.