word文档，中文2400字，英文1400字

一 导言
根据美国认证协会的定义，钢筋混凝土是有导致的内应力平衡到理想程度，是由于外表上应用的荷载的材料。混凝土作为一种建筑材料，主要缺点之一就是抗拉的能力很弱。当混凝用于存在受拉区的构件时，比如用于受拉构件或受弯构件时，受拉区的混凝土在很小的拉应力作用下就会开裂，造成构件裂缝宽度超出许可或构件刚度达不到要求。为解决混凝土抗拉能力低带来的一系列问题，人们设想对在荷载作用下的受拉区混凝土预先施加一定的压应力，称为预压应力，使其抵消部分或全部由荷载产生的拉应力，这就是预应力混凝土的概念。
这样尽管有优势，但我们必须考虑到较高的成本，更强的材料，需要昂贵的配件，有必要检查和控制质量。

一、 INTRODUCTION
According to the ACI definition,prestressed concrete is a material that has had internal stresses induced to balance out,to a desired degree,stresses due to externally applied loads.Since tensile stresses are undesirable in concrete members,the object of prestressing is to create compressive stresses (prestress) at the same locations as the tensile stresses within the member so that the tensile stresses will be diminished or will disappear altogether.The diminishing or elimination of tensile stresses within the concrete will result in members that have fewer cracks or are crack-free at service load levels.This is one of the advantages of prestressed concrete over reinforced concrete,particularly in corrosive atmospheres.Prestressed concrete offers other advantages. Because beam cross sections are primarily in compression, diagonal tension stresses are reduced and the beams are stiffer at service loads.In addition,sections can be smaller, resulting in less dead weight.