预应力混凝土受弯构件长期反拱和挠度的合理估算方法
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预应力混凝土受弯构件长期反拱和挠度的合理估算方法徐金声,薛立红(中国建筑科学研究院,北京 100013)[摘要]回顾了对预应力混凝土构件长期反拱变化规律的研究及认识过程;提出了一个经验公式,大大简化了预应力混凝土构件长期反拱的精确计算工作。该经验公式既能适用于“全”预应力,也能适用于“部分”预应力混凝土构件长期反拱值的计算。同时,对预应力混凝土构件长期挠度的估算也提出了一个经验公式。长期反拱和挠度的两个经验公式都考虑了四个主要影响因素作为自变量(即钢筋的配筋率及其位置与混凝土的徐变和收缩)。用试验数据全面地进行了对比,给出长期反拱系数θp(t→∞)的终极值的可变范围为-3~+3.5,其通常变动范围是-0.5~+2.8,而不是固定的值+2.0。长期挠度也不能简单地简化为短期挠度的2倍。给出了实际工程的检测结果和计算例题并提出了对现行《混凝土结构设计规范》第8.2.5条和第8.2.6条的修改建议。[关键词]预应力混凝土;长期反拱系数;长期挠度系数;试验数据;经验公式;非预应力筋;配筋率;钢筋位置中图分类号:TU378文献标识码:A文章编号:1002-848X(2011)01-0095-08Rational method for estimating long-term camber and deflection of prestressed concrete flexure membersXu Jinsheng, Xue Lihong(China Academy of Building Research, Beijing 100013, China)Abstract:The historical understanding of long-term camber and deflection of prestressed concrete members was described. An empirical formula, which greatly simplifies the calculation for long-term camber of prestressed concrete members was presented. It not only applies to the calculation of long-term camber in prestressed concrete members, but also in partial-prestressed concrete members. An empirical formula for estimating long-term deflection was presented. The two empirical formulas of long-term camber and deflection had considered four important independent variables(steel ratio and its position, creep and shrinkage of concrete). A comprehensive comparison of experimental data of long-term camber and results predicted by the formula was also carried out. The range of variation of long-term camber coefficient θp(t→∞) is -3 to +3.5, its normal range is -0.5 to +2.8 and not a constant value+2.0. Even long-term deflection cannot be simplified with a multiplication factor of 2 over short-term deflection. Suggestions were presented for revisions of section 8.2.5 and 8.2.6 of Code for design of concrete structures.Keywords:prestressed concrete; long-term camber coefficient; long-term deflection coefficient; testing data; empirical formula; non-prestressed steel; steel ratio; steel position作者简介:徐金声,研究员,Email:xujinsheng@cabrtech.com。参考文献[1]GB50010—2002 混凝土结构设计规范[S]. 北京:中国建筑工业出版社,2002.[2]BRANSON D E. Deformation of concrete structures[M].New York:Mcgraw-Hill International Book Company,1977.[3]徐金声. 预应力混凝土梁的长期变形[J].土木工程学报,1988,21(3):59-70.[4]徐金声,洪婉儿.预应力混凝土混合配筋结构长期反拱的研究[C]//混凝土结构基本理论及工程应用(全国第三届学术讨论会论文集).湖南:湖南科学技术出版社,1993:325-332.[5]徐金声,薛立红.现代预应力混凝土楼盖结构[M].北京:中国建筑工业出版社,1998.[6]ГОЛЫШЕВ А В. Расчет Предварительно Напряженных Железобетонных Конструкций с Учетом Длительных Процессов,Издательство литературы по строительству,Москва-1964:105-146.[7]NEVILL A M,DILGER W H,BROOKS J J. Creep of plain and structural concrete[M]. London and New York:Construction Press,1983.[8]徐金声,林春哲.预应力混凝土混合配筋结构的徐变理论与应用研究[C]//混凝土结构基本理论及工程应用(全国第三届学术讨论会论文集).湖南:湖南科学技术出版社,1993:317-324.[9]徐金声,陈永春,高红旗.混合配筋预应力梁的截面长期应力分析[J].建筑结构学报,1985(5):16-28.[10]徐金声,高红旗.钢筋砼构件的收缩应力与翘曲[J].建筑结构学报,1988(2):32-44.[11]徐金声,薛立红,洪婉儿,等.混合配筋预应力混凝土框架扁梁楼盖结构长期挠曲的变化规律[J].建筑结构学报,1997,18(3):11-21.[12]董建伟,聂永明,叶林,等.预应力转换梁的理论计算及测试分析[J].建筑结构,2006,36(S1):(5-37)-(5-40).[13]徐金声,薛立红,洪婉儿,等.预应力混凝土楼盖结构长期水平方向的变形[J].建筑科学,1997(5):18-23.[14]徐金声,薛立红,王向东. 18m×21m跨度预应力交叉梁配夹层板结构的设计与施工(北京军区总医院门诊楼多功能厅)[C]//第十二届全国混凝土及预应力混凝土学术会议论文,兰州,2003(10):173-180.[15]JTGD64—2004 公路钢筋混凝土及预应力混凝土桥涵设计规范[S]. 北京:人民交通出版社,2004.[16]European Standard, Eurocode 2: Design of concrete structures·Part 1: General rules and rules for buildings[S].2002.[17]CEB-FIP model code 1990(混凝土结构,1991年7月最终稿,1991年9月维也纳第28届全体会议批准)[S].1991.