与有粘结相协调的无粘结预应力混凝土梁刚度及裂缝宽度计算方法
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摘要
由于无粘结筋相对于其周围混凝土可发生纵向相对滑动,因此受弯构件中的无粘结筋对构件抗弯刚度的贡献及其对裂缝开展的抑制作用小于有粘结预应力筋。为了实现无粘结与有粘结预应力混凝土受弯构件刚度及裂缝宽度计算方法的协调和统一,提出了受弯构件中无粘结筋等效折减系数的概念,通过对无粘结预应力混凝土受弯构件的变形试验数据和按已有公式对设计试件的变形试算数据进行分析,得出了无粘结筋等效折减系数的建议取值(α=0.23)。用等效纵向受拉钢筋配筋率代替有粘结预应力混凝土受弯构件刚度计算公式中纵向受拉钢筋配筋率,用等效纵向受拉钢筋面积代替用于计算有粘结预应力混凝土受弯构件裂缝宽度的纵向受拉钢筋等效应力计算公式中的纵向受拉钢筋面积,就可分别得到与有粘结相协调的无粘结预应力混凝土受弯构件刚度及裂缝宽度计算公式,两公式计算结果与试验结果均吻合良好,可用于工程设计。
Because unbonded tendons can slip along the surrounding concrete, their contributions to flexural stiffness and restraint to growth of crack are smaller than those of bonded tendons in flexural member. To unify the calculation methods of stiffness and crack width of unbonded prestressed concrete (UPC) flexural member with those of bonded prestressed concrete (PC) flexural member, the conception of the equivalent reduced coefficient of unbonded tendons is presented, moreover, the recommended value (α=0.23) is proposed by analyzing the deformation data of model tests and simulated tests according to the existing formulas. The stiffness formula and crack width formula of UPC flexural member in accordance with bonded PC flexural member can be developed if the ratio of longitudinal tension reinforcement in the stiffness formula of bonded flexural member is replaced by the ratio of the equivalent longitudinal tension reinforcement, and the area of total longitudinal tension reinforcement in equivalent stress formula in calculating crack width formula of bonded flexural member is replaced by the equivalent area of longitudinal tension reinforcement. The calculated results by using these two formulas are in good agreement with test results and therefore they can be used in the design of civil engineering.
Because unbonded tendons can slip along the surrounding concrete, their contributions to flexural stiffness and restraint to growth of crack are smaller than those of bonded tendons in flexural member. To unify the calculation methods of stiffness and crack width of unbonded prestressed concrete (UPC) flexural member with those of bonded prestressed concrete (PC) flexural member, the conception of the equivalent reduced coefficient of unbonded tendons is presented, moreover, the recommended value (α=0.23) is proposed by analyzing the deformation data of model tests and simulated tests according to the existing formulas. The stiffness formula and crack width formula of UPC flexural member in accordance with bonded PC flexural member can be developed if the ratio of longitudinal tension reinforcement in the stiffness formula of bonded flexural member is replaced by the ratio of the equivalent longitudinal tension reinforcement, and the area of total longitudinal tension reinforcement in equivalent stress formula in calculating crack width formula of bonded flexural member is replaced by the equivalent area of longitudinal tension reinforcement. The calculated results by using these two formulas are in good agreement with test results and therefore they can be used in the design of civil engineering.
引文
[1]GB50010—2002混凝土结构设计规范[S].
[2]无粘结预应力混凝土结构技术规程编写组.无粘结预应力混凝土结构技术规程(征求意见稿)[R].中国建筑科学研究院,2002:23-29.
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[5]刘超英,陈永春,杜拱辰.无粘结预应力矩形截面受弯构件短期刚度的试验研究[J].土木工程学报,1988,21(3):37-46.
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[9]郑文忠.无粘结部分预应力混凝土矩形截面梁裂缝、开展和闭合的试验研究[D].哈尔滨建筑工程学院,1992:50-52.
[10]赵国藩,文明秀.无粘结部分预应力混凝土梁裂缝宽度的试验研究[J].建筑结构学报,1991,12(3):24-34.
[11]杨志勇,龙炳煌,董晓峰.部分预应力无粘结混凝土梁短期裂缝宽度的计算[J].福州大学学报,1996,24(增刊):242-247.
[2]无粘结预应力混凝土结构技术规程编写组.无粘结预应力混凝土结构技术规程(征求意见稿)[R].中国建筑科学研究院,2002:23-29.
[3]陶学康.无粘结预应力混凝土设计与施工[M].北京:地震出版社,1993:55-63.
[4]陶学康,王逸,杜拱辰.无粘结部分预应力混凝土的变形计算[J].建筑结构学报,1989,10(1):20-27.
[5]刘超英,陈永春,杜拱辰.无粘结预应力矩形截面受弯构件短期刚度的试验研究[J].土木工程学报,1988,21(3):37-46.
[6]冯德刚.无粘结部分预应力混凝土受弯构件短期刚度的试验研究[J].东北电力学院学报,1996,16(4):36-43.
[7]喻伟,蔡运来.无粘结部分预应力混凝土梁短期刚度的试验研究[J].人民长江,1996,27(12):21-24.
[8]蓝宗建,严欣春,夏保国,冯志祥.无粘结部分预应力混凝土梁裂缝宽度的计算[J].东南大学学报,1991,21(4):67-72.
[9]郑文忠.无粘结部分预应力混凝土矩形截面梁裂缝、开展和闭合的试验研究[D].哈尔滨建筑工程学院,1992:50-52.
[10]赵国藩,文明秀.无粘结部分预应力混凝土梁裂缝宽度的试验研究[J].建筑结构学报,1991,12(3):24-34.
[11]杨志勇,龙炳煌,董晓峰.部分预应力无粘结混凝土梁短期裂缝宽度的计算[J].福州大学学报,1996,24(增刊):242-247.
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