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大跨度的预应力钢筋混凝土屋架、吊车梁等构件,由于运输条件限制,只能在施工现场预制,因此都采用后张法张拉工艺。后张工艺必须通过埋管、拔管、穿筋、张拉、锚固、喷浆等多道工序,而且需要专用设备。大跨度钢筋混凝土门式刚架,在折角部位无法进行埋管、拔管、穿筋等工序,因此发展了无粘结预应力筋这项新工艺(图1)。
The large-span prestressed reinforced concrete roof truss, crane girder and other components can only be prefabricated at the construction site due to the limitation of the transportation conditions. Therefore, the post-tensioned tensioning process is adopted. The post-cardinal process must pass through many processes such as burying pipes, extubating, threading, tensioning, anchoring, and spraying, and requires special equipment. Long-span reinforced concrete gantry rigid frame can not be buried, extubated, and ribbed in the corners. Therefore, a new process of unbonded prestressed tendons has been developed (Figure 1).