1969年初,我厂开始采用后张自锚工艺,生产以国产低合金钢为主筋的预应力构件。先后生产过预应力鱼腹式吊车梁、15米和18米长的预应力薄腹梁。但这种工艺存在着生产工序繁杂等缺点。从1973年10月份起,根据Ⅳ级及Ⅴ级钢筋的规格特点,我们设计和制造了新型的张拉夹具,开始用先张法试制并生产预应力薄腹屋面梁。生产实践表明,先张法和后张自锚法相比,具有工序 At the beginning of 1969, our factory began to use post-Zhang Zhang self-anchor technology to produce prestressed components made of domestic low-alloy steel. Has produced pre-stressed fish belly crane beams, 15 meters and 18 meters long prestressed thin-web beams. However, this process has the disadvantages of complicated production processes. From October 1973, according to the specifications of Grade IV and Grade V rebar, we designed and manufactured a new type of tensioning jig, and started trial production and production of prestressed thin-walled roof beams. Production practice shows that the pretensioning method has a process compared with the post-tensioned self-anchoring method.