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前言本结构具有显著的徐变性能,在长期荷载作用下变形有较大发展,因此过去在确定连续上弦的计算弯矩时,按两个工作阶段考虑。一是在载荷初期阶段,近似地把屋架看做是刚性的,节点不产生沉降,认为上弦是支承在固定铰支座上的连续梁,按此来计算支座(节点)处的弯矩。另一是在荷载长期作用阶段,考虑到节点随屋架的整体变形产生沉降,把上弦看成为弹性支座上的连续梁,而近似的按简支梁来计算其跨中弯矩。上述这种考虑方法是否符合连续上弦的实际工作状态呢?本文试图从理论分析和实验结果两方面来探讨这个问题。(一)屋架连续上弦在短期荷载作用下的实际工作结合1974我院进行载荷试验的一个屋架的实例来进行分析。
Foreword This structure has significant creep properties, and the deformation is greatly developed under long-term loading. Therefore, in the past, when determining the calculated bending moment of continuous winding, two working stages are considered. First, in the early stages of the load, the roof truss is considered to be rigid, and no settlement is generated at the joints. The upper chord is considered to be a continuous beam supported on a fixed-hinge bearing. Based on this, the bending moment at the bearing (node) is calculated. The other is that during the long-term loading stage, taking into account the joint settlement caused by the overall deformation of the truss, the upper chord is viewed as a continuous beam on the elastic support, and the approximate mid-span bending moment is calculated by simply supporting the beam. Does the above consideration method accord with the actual working state of continuous winding? This article attempts to discuss this issue from both theoretical analysis and experimental results. (a) The actual work of the roof truss on a continuous winding under short-term load is combined with an example of a truss carried out in 1974 by our institute.