后张法当制作混凝土构件或块体时,在放置预应力钢筋的部位预先留出孔道,待混凝土达到规定强度后,向预留孔道内穿人预应力钢筋并进行张拉,当张拉到设计规定控制的应力后,即借助于锚具把预应力钢筋锚固在构件端部,最后进行孔道灌浆。这种做法称为后张法。后张法一般适用于现场预制或工厂预制块体在现场拼装的中型和大型构件,如生产预应力的屋架、吊车梁、托架、楼层地面等。本节将结合目前工地生产屋架、吊车梁构件、楼层地面等常用的后张法,归纳成锚具和预应力钢筋的制作;张拉机具设备和生产工艺二部份进行介绍。一、锚具和预应力钢筋的制作预应力钢筋的制作与钢筋直径的大小、锚具的型式、张拉设备和张拉工艺有关。目前,常用的预应力钢筋有单根粗钢筋、钢筋束和钢丝束三种。下面介 Post-tension method When making concrete structures or blocks, leave holes in advance at the places where prestressed steel bars are placed. After the concrete reaches the specified strength, wear prestressed steel bars in the reserved holes and stretch them. After designing the controlled stress, the prestressed steel bar is anchored at the end of the component by means of anchorages, and finally the channel grouting is performed. This practice is called post-tensioning. The post-tensioning method is generally applicable to medium-sized and large-scale components that are prefabricated on site or assembled on the site by factory prefabricated blocks, such as prestressed roof trusses, crane girders, brackets, and floor floors. In this section, the commonly used post-tension methods such as the production of roof trusses, crane girder components, floor floors, etc., will be combined into the production of anchorages and prestressed reinforcements; the tensioning machine equipment and production process will be introduced in two parts. First, the production of anchorage and prestressed steel production of prestressed steel bars and the size of the diameter of the bar, the type of anchorage, tensioning equipment and tensioning process. At present, there are three types of commonly used prestressed steel bars: single coarse steel bar, reinforced beam, and steel wire bundle. Below