施工特大型构件(例如大桥的桥梁等),一般采用后张法施工,技术要求比较高,它的特点是构件大,每件20～80t,而且表面不做装饰。另外,它的断面多为工字形,有的带大翼板,梁内钢筋密,并放有几组钢绞线预留孔波纹管。构件混凝土要求密实并且表面光滑,同时,在构件张拉钢绞线时,构件中部起 Construction of large components (such as bridge bridges, etc.), the general use of post-tensioning construction, technical requirements are relatively high, which is characterized by large components, each 20 ~ 80t, and the surface is not decorated. In addition, it is mostly I-shaped cross-section, and some with large wings, beams within the dense steel, and put several sets of strand pre-made hole bellows. Component concrete requires dense and smooth surface, at the same time, when the member is tensioned strand, the middle part of the member