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一、问题的由来根据某些施工部门和建设单位的反映,预应力钢筋混凝土屋架端部截面扩大部分的水平段,当预应力钢筋放张后会产生通长的、有规律性的纵向水平裂缝,或由于施工不精心,漏放了沿预应力孔道的螺旋箍筋(仪端部400mm范围),因而预应力钢筋放张后,同样也产生了纵向水平裂缝,前者是按钢筋混凝土结构设计规范(TJ10—74)进行设计的,并按要求在屋架端头设置了垫板及五片钢筋网片(间距为50mm),施工中出现了纵向水平裂缝,后者是由于未按设计图集要求造成的。从解决这类工程问题的过程中,本人体会到预应力钢筋混凝土屋架端部截面扩大部分(即预应力钢筋锚固区)之所以出现水平纵向裂缝,必然有横向拉力,否则不会普遍产生纵向水平裂缝。为了弄清楚这个
First, the origin of the problem According to the reflection of some construction departments and construction units, the horizontal section of the enlarged section of the end section of the prestressed reinforced concrete roof, when the prestressed steel bars are stretched, they will produce a long, regular longitudinal horizontal crack. Or, due to poor construction, spiral stirrups along the pre-stressed channels (in the range of 400 mm at the end of the instrument) were leaked. After the prestressed tendons were laid, horizontal longitudinal cracks were also produced. The former is based on the design specifications for reinforced concrete structures. (TJ 10-74) was designed, and as required, a backing plate and five pieces of reinforced mesh (with a spacing of 50 mm) were installed at the end of the roof truss. Vertical horizontal cracks occurred during construction. The latter was due to failure to meet the requirements of the design atlas. Caused. From the process of solving such engineering problems, the human body will be able to reach the horizontal longitudinal cracks in the enlarged section of the prestressed reinforced concrete roof (ie, the prestressed steel anchorage zone). Therefore, there must be lateral tensile forces, otherwise horizontal levels will not generally occur. crack. To figure this out