Abstract: Based on the shear test data of 50 beams with bonded tendons and 25 beams with unbonded tendons, this paper studies the influences of shear force, degree of prestress, shear span-depth ratio, stirrup, content and curved tendon on the development of diagonal cracks of P.P.C. beams with unbonded tendons. It is proposed that the calculation of the diagonal crack width under the influences of the above factors be transferred into determining the equation of the curve in shear-crack width coordinate system. Combined with the statistical analysis on the test data, a formula with a simple form is obtained to predict diagonal crack widths of P.P.C. beams with unbonded tendons.

Key words: diagonal crack, unbonded tendon, cracking shear, ultimate shear, degree of prestress

摘要： 本文依据50片后张有粘结部分预应力砼梁和25片无粘结部分预应力砼梁的抗剪试验实测资料,研究了荷载剪力、预应力度、剪跨比、配箍率和弯起预应力钢筋对斜裂缝开展宽度的影响,提出在考虑上述诸因素影响下的斜裂缝宽度计算可转化为一个解析几何问题——求剪力斜裂缝宽度坐标系中的曲线方程,据此建立起计算模式,并结合对试验资料的统计分析得到斜裂缝宽度的计算公式,该式形式简单,计算方便,可供设计和研究参考。

关键词: 斜裂缝, 无粘结预应力, 开裂剪力, 破坏剪力, 预应力度