预应力超静定结构的平衡荷载计算

本文根据砼结构设计规范的抗裂验算规定,提出了计算预应力超静定结构平衡荷载的办法,并据此平衡荷载计算所需预应力钢筋的面积,避免了预应力超静定结构设计中按经验估算平衡荷载值引起的返工重算或不合理配筋。文中附有计算实例。     

部分预应力混凝土超静定结构的试验及分析

预应力混凝土超静定结构在极限状态的性能是人们所关心的问题，预应力混凝土框架结构的内力重分布与弯矩调幅一直是争论的热点。但内力重分布与弯矩调幅不仅会影响预应力混凝土超静定结构的经济性，还会影响预应力混凝土结构的可施工性。弯矩调幅既与超静定结构的极限状态...     

预应力混凝土超静定结构弯矩调幅设计建议

通过对国内外混凝土设计规范和各研究机构对预应力超静定结构考虑塑性内力重分布的弯矩调幅设计建议的介绍,深入讨论了影响预应力超静定结构弯矩调幅的三个主要因素：截面相对受压区高度ξ、次弯矩Mscc和水平荷载作用,提出了适用于无侧移和有侧移预应力超静定结构的弯矩调幅设计建议。试验证明,本文提出的调幅设计建议是合理和安全的。     

预应力混凝土梁弯矩调幅值研究

从延性理论出发，得到了满足塑性铰转动能力的截面延性条件，结合结构在承载能力极限状态所需的转角，导出了满足承载能力要求的弯矩调幅值公式，具有一定的工程使用价值。     

钢筋混凝土延性框架设计中梁端弯矩调幅的探讨

阐明了钢筋混凝土梁在弹塑性工作状况下梁端弯矩调幅的原理,分析了钢筋混凝土超静定结构采用弯矩调幅方法进行设计的条件,说明了采用弯矩调幅法进行结构设计对提高结构的抗震性能的必要性,并结合现行规范的相关规定提出了采用该方法进行设计应该注意的问题。     

苏联装配整体式结构的计算方法

一、概述 设计装配式结构时,加强构件间的共同工作,使单跨简支构件变成装配整体式超静定结构,能提高其承载力、刚度和抗裂度。 实践证明,保证结构良好的整体性和装配接头的连续性,必须研究装配与整浇部分新旧混凝土接触面的弯曲强度,使构件接头能可靠的传递荷载,且考虑结构应变状态下混凝土收缩和蠕变影响。     

钢筋混凝土框架非弹性分析及试验研究

在钢筋混凝土结构中,由于混凝土应力应变关系的非线性、杆件受拉区混凝土可产生裂缝及软钢有明显的屈服台阶等性质,钢筋混凝土结构从加荷到破坏的全过中杆件刚度均处于不断变化状态,超静定结构各杆件的实际内力与习用的线性弹性分析有显著差别。这种相对于弹性分析所得内力的差别,可视为结构的内力重分布。在满足静力平衡、杆件受压区混凝土的极限变形和截面转动要求的前提下,结构内力可人为地进行调整。近年来各国多采用在线性弹性分析的基础上对结构内力进行调幅的方法。但是,调整幅度差异较大,更主要地     

变形协调条件在超静定结构中的应用

在日常施工中,经常会遇到超静定结构,因超静定结构求解方法比较麻烦,不能简单用静力平衡理论来求解,所以一般的方案计算中,因要求较低,且精确度不高,通常将超静定结构简化成静定结构来求解。如果对计算精确度要求较高,或是在做施工设计时精确考虑材料的用量,从成本控制的角度来考虑的话,将超静定结构简化计算是不合适的,因此可采用变性协调条件来进行求解,文章就以工程实例来介绍该方法的应用。     

部分预应力砼的实际应用与强度计算

在预应力砼结构内配置非预应力钢筋的问题,我国《砼结构设计规范》GBJ10中仅提出如下规定:“当受拉区部份钢筋施加预应力已能使构件符合抗裂或裂缝宽度要求时,则承载力计算所需的其余受拉钢筋允许采用非预应力钢筋”,并未对此向题进行深究。但在国外,却把此类结构命名为部份预应力砼,以区别于普通钢筋砼和全预应力砼,并在很多工程中应用,取得了较好的效果。例如: 1.一座公路桥的超静定箱形梁,中跨41.6m、边跨32m。使用全预应力砼时,需沿梁的全长配置18根钢丝束,其中6根分别自肋板弯入顶板及底板,工序复杂而困难。改用部份预应力砼结构,取预应力度系数K=0.68,预应力及非预应力钢筋的配筋率各为0.32％及0.     

预应力混凝土超静定梁的预应力筋布置分析

针对预应力混凝土超静定梁 ,采用结构力学方法 ,推导了在均布及集中荷载作用下 ,二跨及三跨连续梁的次弯矩表达式 ;在满足混凝土设计规范中规定的预应力混凝土构件在施工阶段预拉区抗裂要求的条件下 ,得到了预应力筋布置偏心距的表达式。可作为超静定梁进行预应力筋布置的依据。     

Requirements for moment connections in statically indeterminate timber structures

In statically indeterminate structures, connections play a vital role in the moment distribution. Demonstrated here is a method to evaluate the conditions, taking full advantage of the benefits offered by the indeterminate nature of the structures, and using the well-established, graphical beam-line method. This method shows how important the immediate load take-up is, the stiffness, the moment capacity of the connection and how it all affects the structural behaviour. The examples considered here use both the traditional non-reinforced dowel-type fastener connections and also timber connections reinforced with steel plates. They show that the minimum rotation requirements to achieve an effective structure are satisfied easily in contrast to requirements on stiffness. In this respect, timber connections with local reinforcement glued at the interface of the connection area offer more prospects.     

结构力学中反对称荷载作用下对称刚架的弯矩图规律

在结构力学的学习过程中,绘制弯矩图是基本功,属于重点考查内容,也是结构内力分析的起始性关键环节。超静定结构的弯矩图比较复杂,严重影响了学生对基本内容的理解和掌握。文章旨在通过对比静定对称刚架的弯矩图,分析反对称荷载作用下超静定对称刚架的弯矩图特点,从而找出对称刚架弯矩图的一般性规律。     

部分预应力混凝土超静定结构的设计方法

本文提出了部分预应力混凝土超静定结构的一种新的设计方法──单位次弯矩法。该法以结构中所有部分预应力混凝土构件同时满足两类极限状态为设计原则。另外，基于有效利用次内力的思想，对预应力筋的配置以及利用非吻合束等问题提出了可供实践应用的设计建议。附有设计实例。     

预应力超静定结构的等效荷载计算

预应力对超静定结构的作用,除产生主弯矩外还产生次弯矩。等效荷载法是计算次弯矩的最简便方法,但现有等效荷载的计算公式是通过预应力沿预应力筋不变的静定梁求得的,而在实际结构中,尤其是在多跨曲线配筋的预应力超静定结构中,预应力沿预应力筋有明显的变化,因而按现有方法计算等效荷载存在较大的误差。本文提出预应力沿预应力筋变化的超静定结构的等效荷载计算方法,以供设计应用。文末并附有计算实例。     

Shear and bending flexibility in closed-form moment solutions for continuous beams and bridge structures

Shear deformations can affect final member-end-moments for statically indeterminate continuous beams and frame structures, though for typical civil engineering structures their effect is small and moments can be based on flexural deformations only. When a member is deep relative to span length, however, shear deformations should be considered in the analysis. This can be included in the stiffness method and in a modified form of moment distribution where the carry-over factor is less than one-half due to the added flexibility from shear. In a prior paper the first author presented a new approach for solving statically indeterminate beams and bridge frames, with final end moments given in closed-form expressions. The advantages of this new approach are that no simultaneous equations are required as in the stiffness method, moments are not distributed back and forth as in moment distribution, and manual calculations may be used which give exact results for as many spans as desired. While only flexural deformations were considered in the original paper, this paper presents a closed-form approach that has been modified to include shear deformations. Final expressions are given for continuous beams and bridge frames, providing exact member-end-moments that match results from the stiffness method when shear deformations are included in the analysis.     

预应力混凝土框架梁次轴力计算及其影响因素分析

现行国家规范(规程)仅对预应力次内力中的次弯矩和次剪力的计算方法做了规定,而对次轴力的计算并未做明确规定,只给出了相应的施工技术措施以减小超静定结构中次轴力对预应力构件的不利影响。推导了超静定结构中预应力次轴力的计算方法,并分析了柱截面刚度、梁的弹性模量和截面面积、梁跨度、层高、不同张拉方式等对其的影响。     

地基不均匀沉降时超静定框架应力场的还原及应用

针对发生地基不均匀沉降的超静定框架结构应力场的还原问题,给出了基于结构力学矩阵位移法还原超静定框架结构体系应力场的计算原理。基于包含上部钢框架、独立基础和多维弹性地基支承的整体超静定结构体系的静力平衡条件和变形协调条件,建立了超静定结构的有限元计算模型。以实际监测工程为算例,采用MIDAS/Gen有限元软件计算还原了包含上部钢框架、基础和基底弹簧支座的整体超静定结构第二平衡状态下的应力场; 由实测的钢框柱柱脚位移值反算出基底弹簧支座各方向的弹性刚度,得出整体超静定结构第二平衡状态下的刚度矩阵及位移矩阵,从而求得监测初期和终期上部超静定钢框架结构各构件的内力计算值。最后,对比钢框架各构件内力的理论计算增量值与监测增量值。结果表明:构件各项内力理论计算增量值与监测增量值的相对误差均不超过40%,且构件各项内力理论值与监测值的增量变化方向一致,验证了基于矩阵位移法的超静定框架结构应力场还原方法的合理性和可行性。     

Closed-form moment solution for continuous beams and bridge structures

Moment distribution continues to be a valuable structural analysis tool for spot-checking member-end-moments of continuous beams and frame structures from computer results. Prior to the widespread use of mainframe and, later, personal computers in the 1980s and 1990s, moment distribution provided a simple hand method for practicing civil engineers to analyze and design statically indeterminate structures, since its public introduction in the early 1930s by Hardy Cross, directly leading to new types of designs and construction. The chief benefits of this method of analysis over the other available methods are that (1) member-end-moments are found directly from the applied loads without first determining various displacement components, (2) no simultaneous equations need to be formed and solved, (3) it is easy to remember and apply, (4) an approximate solution can be obtained at any stage in the analysis and (5) a remarkable variety of statically indeterminate structures can be solved by hand. While the development and introduction of moment distribution represents a great advancement in the history of structural engineering, the distribution process can be tedious, especially if only a few final member-end-moments of a multi-redundant structure are desired. Additionally, when results are wanted to a greater accuracy, the number of distribution cycles required and the number of significant figures that must be carried through the process make it a daunting procedure. In this paper, a new method is presented that gives exact member-end-moments for continuous beams and bridge structures, without the need to distribute moments back and forth as in moment distribution or to set up and solve simultaneous equations, as with the stiffness method. It is anticipated that the primary application of the proposed method will be to spot-check computer results.     

利用位移互等定理改进的超静定结构位移计算方法

结构力学中,超静定结构的位移计算常使用单位荷载法,即利用超静定的实际位移状态与虚拟单位力状态相配的传统方法计算位移。该方法用于计算承受复杂荷载的超静定结构时,计算工作量巨大。利用位移互等定理改进的单位荷载法——位移互等算法,将原结构承受的荷载作用于静定的任一力法基本结构上所得的状态,与作用于原结构的虚拟单位力状态相配计算位移。由于荷载转为作用在静定基本结构上,有效降低了计算工作量。该方法在结构力学教学中有一定的实际应用价值,为师生提供了一种可选的新方法,丰富了结构力学的教学内容。     

关于预应力混凝土结构设计规范若干问题的建议

作者在预应力混凝土工程施工实践及理论分析的基础上，对现有预应力混凝土结构技术规程中有关次内力及摩擦、锚固损失的计算问题提出了进一步完善的建议。