As one important branch of post-tension prestressing system, external prestressing system is a system that tendons are located outside of structure.
　　The concept and technique of external prestressing technology came from French. External prestressing technology was used to bridge construction at 1950’s, but it was almost given up in the subsequent 20 years because of the technical limitations at that time, in particular the protection tech. of external prestressing cable and the structure design was not solved well.
　　At the end of 1960’s, the unbonded prestressing tech. and construction tech. of cable-stayed bridge were came into being and applied, the problem of protection tech. of cable and concrete structure design were solved. Based on these technologies, external prestressing tech. was reused.
External prestressing application has promoted the development of prestressing structures to some extent, which has led to the breakthrough of the conventions in the bridge design, and has broadened the applications of prestressing technology. No duct exists in the webs of external prestressing concrete box beams, so the webs are simplified and the widths are also decreased, then the structural deadweights are lightened, the structural costs are substantially cut down. The constructions of precast segmental structures in casting yards only need to assemble precast box segment sin mobile brackets, which can greatly save constructional faculty, and improve efficiency, then speedup bridge constructions. No concrete construction exits in sites due to the application of precast segments, which can solve all problems of concrete constructions in precast yards, and improve constructional quality of concrete. Only communications and circumstances near constructional bridges are affected when the precast segments are being assembled, which is an important factor in constructions of urban bridges. External prestressing system can be detected at any time, tendon stress can be adjusted after grouting, corrosion of tendons also can be inspected, and tendons can even be maintained and replaced when needed, but internal prestressing system can not.
　　External prestressing system is also ideal for existing structures needing maintaining and strengthening. Because most of the strengthening have to be carried out through outside of sections of existing structures, it implies prestressing tendons should be located outside of concrete sections of structure members, so strengthening by external tendons have become a primary and positive strengthening way for bridges.
Cost can be reduced if the Filled Epoxy-Coated Strands are used as tendons of external prestressing system because of its perfect anti-corrosion performance. The external prestressing systems of FECS carried out by FASTEN, have obtained the social verifications. External prestressing system of FECS and relevant equipments have been successfully applied to some domestic and foreign engineering projects.