Abstract: Based on the test data of 25 beams,this paper studies the shear strength of partially preetressed con-crete beams with unbonded tendons.A new calculative model for the shear strength of beams withoutweb reinforcemnt is estabiislied by means of equilibrium equations and failure theory,The shearCayyied by stirrupe and the ultimate stress of unbonded curved tendons are also discussed,A formulawhich agrees well with test results is proposed for predicting the shear strength of beanms with unbondedtendons.A comkparison is also made between the beams with and without bended tendons。

Key words: unbonded tendon, shear compression failure, failure theory, shear span-depth ratio, strrupcontent

摘要： 本文依据25片无粘结部分预应力砼梁的抗剪试验结果，从梁发生剪压破坏时剪压区砼的应力分析入手，应用砼在复合应力状态下简化的强度准则和静力平衡条件建立起抗剪强度的计算模式，并据试验资料的统计分析确定了其中的计算参数，由此得到的公式既简单适用，又具有较好的精度和一定的理论依据，可供设计和研究参考，文中还将无粘结预应力砼梁与有粘结预应力砼梁作了对比分析。

关键词: 无粘结预应力筋, 剪压破坏, 强度准则, 剪跨比, 配筋率