温度作用和索长误差对采用定长索设计的张拉结构影响研究

Influences of temperature changes and cable length errors on tension structures using un-adjustable cable length design

对于较复杂的张拉结构,可采用定长索进行设计与张拉,即将索头设计成不可调节的形式,通过精确设计索长,在施工现场直接张拉到位,避免现场为满足预应力分布的要求对索长进行反复调节。张拉结构属于柔性结构,温度变化和索长制造误差对其影响很大,必须在设计施工中予以考虑。尤其对于使用定长索设计的张拉结构,由于各构件的尺寸在制作完成后不能再改变,因此必须在设计与制造时考虑温度作用和索长误差的影响。本文首先将张拉结构在全生命周期内可能受到的各种温度作用进行分类,之后讨论不同温度作用对结构的影响与边界支承条件的关系。然后提出计算温度作用控制范围的方法,并对一实际索穹顶结构算例进行实例计算,得出温度作用的控制值。此外,研究当实际加工制造中温度不满足控制要求时,通过补偿构件长度尺寸以抵消温度作用影响的方法。同时,基于可靠度理论与非线性规划方法,亦给出了索长误差对张拉结构的影响及计算索长误差控制限值的方法。

For complicated tension structures, un-adjustable cable length design could be used, in which cable length could not be adjusted by fixing cable ends. When using un-adjustable cable length design, cable length must be well determined and cables can be directly tensioned to anchorage or connecting points at the construction site. For tension structures, temperature changes and manufacturing errors of cable length have great influences on the structural performance and must be considered in design, especially for tension structures using un-adjustable cable length design as the cable length cannot be changed after manufacturing. In this work, all temperature changes in the full life cycle of tension structures were analyzed firstly, and were classified into two different categories. Based on this classification, the relationship between the influences of temperature changes and the boundary conditions were analyzed. Then, a method of analyzing the control criteria of different temperature changes was proposed based on an example of an actual cable dome. Furthermore, the method of compensating the length of different members when temperature changes exceed the control criteria was studied. In addition, the influences of cable length errors and the control criteria of cable length errors were analyzed based on the reliability theory and the non-linear programming method.