六十年代以来,从国际上预应力混凝土桥梁的发展来看,以钢绞线为预应力筋束的张拉体系,随着大型现代化桥梁的增多,越来越广泛地被采用,而以钢丝为预应力筋束的张拉体系已不能适应桥梁发展的要求。如美、英、意等许多国家,在预应力混凝土梁结构中,钢绞线已成为一种主要的预应力筋材料。我国早在1966年成昆铁路推广使用串联梁时,就采用了7φ4钢绞线为预应力筋,但在那时以后的一段时期,由于钢绞线的生产供应和张拉锚固体系(当时采用的为YC—60千斤顶和JM—12锚具)没有完满解决。故采用钢绞线为预应力筋的张拉体系未能推广应用。近年建筑科学研究院 Since the 1960s, from the perspective of the international development of prestressed concrete bridges, the tension system using strand as prestress tendons has been adopted more and more widely with the increase of large-scale modern bridges. However, The prestressed tendons tension system can not meet the requirements of bridge development. Such as the United States, Britain, Italy and many other countries, in the prestressed concrete beam structure, the strand has become a major prestressed tendons material. As early as 1966, Chengdu-Kunming Railway promoted the use of tandem beams, 7φ4 steel strands were used as prestressing tendons, but at some time after that time, due to the production and supply of strands and the tensioning anchoring system For the YC-60 jack and JM-12 anchors) is not fully resolved. Therefore, the use of prestressed steel strand tensioning system failed to promote the application. In recent years, Academy of Building Research