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钢筋混凝土屋架在扶直阶段的验算,目前有两种方法:一种是将屋架上弦视为连续梁,将屋架两端支垫点及吊点视为支座,用弯矩分配法计算上弦弯矩;另一种是将屋架上弦视为简支梁,将屋架两端支垫点视为支座,把吊索拉力视为集中荷载,用普通分析静定结构的方法计算上弦弯矩。两种方法均验算屋架上弦刚离地时(即屋架平面与地面夹角α=0时)的裂缝宽度或抗裂度。现举一例,分别用两种方法计算如下。【例】某18m 跨度的钢筋混凝土折线形屋架的外形和各杆件尺寸如表1及图1所示,试计算并绘出上弦在四点扶直中的弯矩图。
There are currently two methods for the checking of the reinforced concrete truss during the straightening phase: One is to treat the truss chord as a continuous beam, and the two sides of the roof truss are regarded as bearings, and the bending moment distribution method is used to calculate the upper chord. Moment; the other is to treat the truss chord as simply supported beam, and regard the support points at the two ends of the roof frame as the bearings. The pull force of the sling is regarded as the concentrated load. The bending moment of the winding string is calculated by the ordinary method of analyzing the static structure. Both methods check the crack width or crack resistance of the roof truss just above the ground (ie when the angle between the roof plane and the ground is α=0). As an example, the calculation is as follows using two methods. [Example] The outline and bar dimensions of a 18-m-span reinforced concrete polygonal roof truss are shown in Table 1 and Figure 1, and the bending moment diagram of the upper chord at four-point erection is calculated and plotted.