钢筋混凝土双向板肋梁楼盖挠度计算方法研究

对现浇钢筋混凝土双向板肋梁楼盖中的中区格板、边区格板和角区格板,分别进行了均布荷载作用下的静力加载试验,测试了梁板的挠度值;考虑区格板边界支承条件的影响,建立了双向板挠度计算公式,并将公式的挠度计算值与试验值进行比较。结果表明:按线弹性理论所得的挠度值与试验值之间存在较大误差;按挠度计算公式计算所得挠度值与试验结果比较吻合。     

梁板刚度比变化对板内力的影响

整浇钢筋混凝土楼盖中,梁板协同工作,梁的竖向变形和刚度对楼板的内力分布有着较大的影响。本文采用大型有限元分析程序ANSYS对楼盖进行纯SOLID块体单元建模分析,并与静力手册计算结果比较,分析了梁板刚度比对楼板内的影响。     

简支双向钢-混凝土组合楼盖的弹性分析

用梁格法、拟板法、有限元法对四边简支双向钢-混凝土组合楼盖弹性阶段的变形及内力进行分析。通过与试验结果的对比可以看出,拟板法和有限元法计算简支双向组合楼盖比梁格法更经济且计算结果更全面。改变梁格数及板厚跨比进行算例分析可知,拟板法可用于分析常见结构布置的简支双向钢-混凝土组合楼盖。     

考虑梁板相互作用的现浇混凝土肋梁楼盖静力试验与理论分析

为研究现浇混凝土双向板肋梁楼盖梁板的相互作用,对柱支承混凝土双向板肋梁楼盖中的中区格板和边区格板模型进行了竖向加载试验,观测了这两种区格板模型中板、梁及柱的裂缝发展及破坏过程;分析了梁、板的荷载-挠度曲线以及板、梁和柱的荷载-钢筋应变曲线;采用线弹性理论、塑性理论和等效框架法分别计算了板控制截面的弯矩值并与试验值进行比较。根据试验与分析,对楼盖结构中梁与板的相互作用进行了分析。结果表明：这两种区格板肋梁楼盖模型均发生梁 板破坏模式;按线弹性理论和塑性理论（板破坏模式,不考虑梁板相互作用）所得板控制截面弯矩值与试验值差别较大,而按等效框架法和塑性理论（梁-板破坏模式,考虑梁板相互作用）所得弯矩值与试验值吻合较好。按塑性理论的梁 板破坏模式,分析了这两种区格板楼盖的极限荷载,分析结果与试验结果比较吻合。     

混凝土空腹夹层板静力性能的有限元参数分析

混凝土空腹夹层板可以看作是通过剪力键连接的双重密肋楼盖,为了解其静力性能,考虑组成构件的刚度和结构高跨比影响,采用8节点弹性块体单元有限元模型在四点支承条件下进行25个算例分析.结果表明:结构内力分布与空腹网架类似,但剪力键变形时表现了整体转动的特点,肋及剪力键的承载力设计应计及弯矩影响;增加支承梁(框架梁)刚度有利于降低楼盖的挠度、改善梁边肋的内力分布,建议框架梁在满足楼盖刚度控制前提下采用较小的高跨比;增大结构总厚度可以有效提高其整体刚度及跨中截面承载力,当高跨比在1/30~1/20之间并采用现行规程的实用方法时,应重视楼盖角区上肋的承载力设计;表层薄板对结构刚度和承载力改善的意义不大,可按网格尺寸的1/40~1/30确定其厚度;楼盖的内力分布对肋刚度较为敏感,上、下肋截面高度可按网格尺寸的1/15~1/10确定,实用方法对肋承载力的调整措施需进一步研究;剪力键刚度对楼盖整体刚度的影响较小,工程设计需增大剪力键截面时,应提高楼盖角区和边节间肋的承载力,并应对角区剪力键予以加强.     

钢筋混凝土整体楼盖中梁的刚度对板的弯矩的影响分析

根据对钢筋混凝土整体楼盖设计方法的理论分析 ,提出了支承结构的刚度对板的最大弯矩的影响问题 ,通过用ANSYS有限元软件对某一实际电厂厂房的钢筋混凝土整体楼盖内力计算以及调整尺寸后结构内力计算的结果比较 ,得出了支承结构的刚度增大 ,板内最大弯矩将减小的分析结论。     

关于拟梁法计算现浇混凝土双向板楼盖内力和挠度的讨论

在计算楼盖结构内力和挠度时,可用拟梁法考虑梁板的协同工作。为了验证拟梁法的可靠性,应用SAP2000对6 m×6 m的单区格现浇混凝土双向板分别用有限元方法和拟梁法进行分析对比,拟梁数量由5根变化到10根。分析结果表明,与有限元法计算结果相比,当拟梁数量为5根时,用拟梁法计算所得的板跨中弯矩误差为7.2%,支座弯矩误差为12.48%,跨中挠度误差为4.1%;当拟梁数量为10根时,用拟梁法计算所得的板跨中弯矩误差17.56%,支座弯矩误差11.75%,跨中挠度误差为5.2%。直接用拟梁法计算混凝土双向板内力和挠度会产生较大误差,工程设计时应慎重使用。     

梁板刚度比变化对板内力的影响

在整浇钢筋混凝土楼盖中,梁板协同工作,梁的竖向变形和刚度对楼板的内力分布有着较大的影响。本文采用大型有限元分析程序ANSYS对楼盖进行纯Solid块体单元建模．分析梁板刚度比对楼板内力的影响。     

现浇钢筋混凝土结构中梁与板协同作用研究

对于现浇混凝土肋梁楼盖结构的内力和挠度计算,一般假定梁为板的不动铰支座,梁、板的内力和配筋分别单独计算,不考虑梁板的相互作用。为了探讨梁板相互作用对楼板内力和挠度的影响,采用有限元分析软件SAP2000对现浇混凝土梁板体系进行了大量的数值计算,分析了梁与板相互作用的内在规律及影响因素,在此基础上,对梁板体系中楼板的设计提出了建议。     

混凝土双向密肋装配整体式空心楼盖挠度计算方法的试验研究与有限元分析

为解决现浇混凝土空心楼盖存在的问题,提出由预制钢筋混凝土空心箱体与现浇钢筋混凝土密肋组合而成的新型楼盖形式。对预制空心箱体进行设计,测定其盖板、底板承载力;进行了一个9m×9m角点支承混凝土双向密肋装配整体式空心楼盖的足尺模型试验,得到其荷载-挠度曲线;通过分析预制空心箱体与密肋共同工作的楼盖刚度,提出了楼盖跨中最大挠度计算公式。采用有限元程序ANSYS9.0进行了楼盖模拟计算,计算结果与试验结果吻合良好;通过数值计算,研究了以试验楼盖尺寸为基准的混凝土双向密肋空心楼盖模型、实心平板无梁楼盖模型、去掉空心箱体底板的密肋楼盖模型以及去掉空心箱体底板与盖板交叉梁楼盖模型的楼盖挠度等值线分布规律,为深入开展该新型楼盖结构性能的研究提供了依据。     

预应力混凝土叠合板与底板(实心、空心)受弯承载力相关关系试验研究

通过理论与试验研究，分析了预应力混凝土底板(实心、空心)与叠合板开裂弯矩相关性、抗弯极限承载力相关性，提出了二者相关关系模式与相应的计算方法，为叠合板与底板结构性能检验提供了新的检验方法与计算手段，弥补了叠合板与底板结构性能现有检验方法的不足，可供有关规范及通用标准图集编制和生产、检验部门参考试用。     

Elastic analysis of slabs

Most building codes permit the use of elastic design methods for concrete slabs. These methods for small deflection theory of slabs are discussed, and then graphically complete distribution of principal bending moment contours and trajectories, and deflections are obtained for simply-supported and encastre slabs subject to uniformly distributed load. Destructive tests on simply supported slabs designed elastically, according to code requirements, and by the yield line method are then described.     

Strengthening existing floor slabs

Whether done as part of general restoration work or to remedy a defect in the original construction, techniques for in situ strengthening of existing reinforced concrete structures have been considerably developed in Czechoslovakia. Here a senior lecturer in the building faculty of the Czech Technical University in Prague summarises the results of tests on old floor slabs which have been strengthened by the addition of a new concrete layer.     

Wall-clamping of floor slabs

In design of floor slabs, insufficient allowance is made at present for the wall-clamping effect. The paper deals with determination of bending moments in different systems, with joint deformability taken into account and structural safety ensured by covering all possible modes of failure. By this means, significant saving can be effected in large-span structures.     

闭口压型钢板-轻骨料屋面板抗弯试验研究

结合闭口压型钢板-轻质混凝土组合板的应用现状,阐述了该新型屋面结构的优点,通过试验对其抗弯刚度性能进行了研究,并总结了抗弯刚度的理论计算公式,得出计算结果与实测值吻合较好的结论.     

冷轧带肋钢筋预应力混凝土叠合板与空心底板受弯承载力相关性分析

通过理论分析与试验研究,提出了冷轧带肋钢筋预应力混凝土叠合板与空心底板受弯承载力相关性模式,为该类叠合板设计与结构性能检验提供了新的方法与计算手段,可供有关规范及通用标准图集编制和预制构件生产、施工、检验部门应用。     

Instantaneous deflection of light-weight concrete slabs

Construction loading before the age of 28 d can have the most significant effects on the slabs, especially for multi-story structures. The changing properties of the young concrete complicate the prediction of serviceability design requirements also. An experimental investigation is performed on four simply supported Light-Weight Concrete (LWC) one-way slabs subjected to immediate loading at 14 d. Effects of aggregate type, loading levels and cracking moment together with the influences of ultimate moment capacity and service moment on the instantaneous deflection of slabs are studied. Comparison of the obtained results with predictions of existing models in the literature shows considerable differences between the recorded and estimated instantaneous deflection of LWC slabs. Based on sensitivity analysis of the effective parameters, a new equation is proposed and verified to predict the instantaneous deflection of LWC slabs subjected to loading at the age of 14 d.     

Shear failures in frames and slabs

A most serious type of failure in concrete construction is a defect in shear resistance. Collapse can come unheralded by prior deflection and cracking. Dr Feld, New York consulting engineer and author of ‘Lessons from Failures of Concrete Structures’, here considers aspects raised by specific instances of failure.     

Shear failures in frames and slabs

A most serious type of failure in concrete construction is a defect in shear resistance. Collapse can come unheralded by prior deflection and cracking. Dr Feld, New York consulting engineer and author of 'Lessons from Failures of Concrete Structures', here considers aspects raised by specific instances of failure.     

Behaviour of GFRP-strengthened RC cantilever slabs

This paper presents an experimental study on reinforced concrete (RC) cantilever slabs bonded with glass fibre-reinforced polymer (GFRP) strips. Ten tests in three series were conducted on such slabs with different amounts of internal steel reinforcement and external FRP reinforcement. All FRP-strengthened test slabs were found to experience debonding of FRP strips from the slab, which started near the fixed end and propagated towards the free end, with the final failure mode being either complete debonding or FRP tensile rupture. The severity or likelihood of debonding is shown to depend on the thickness and width of the bonded FRP strips. It is further shown that debonding in these slabs does not have a serious detrimental effect on the ultimate strength, particularly when the FRP reinforcement ratio is low. Instead, it leads to a more ductile behaviour.