单层超长预应力平板-柱结构侧限分析

预应力平板柱结构在张拉预应力筋时将受到侧向约束影响,通过对-实际工程的检测分析这种侧向约束影响的规律;根据变形协调关系建立单层多跨框架在两端部集中力作用下求解侧向约束影响系数的方程组,根据基本假定得到计算柱次剪力的简化计算公式,并结合公式分析实际工程受侧向约束影响的规律。文中给出的求解侧向约束影响系数方程组可以较准确地计算水平构件的侧限影响。     

受拉翼缘约束下梁整体稳定的计算

通过利用能量法对受拉翼缘存在均布侧向约束的工形截面梁的弹性整体稳定进行了分析.分析了不同荷载情况下,连续侧向约束对梁整体稳定承载力产生的影响.运用有限元法分析计算,得出了在实际设计中考虑受拉翼缘均布侧向约束有利作用的计算方法.     

体外预应力加固混凝土框架梁侧向约束影响理论分析

通过4根体外预应力混凝土框架梁加固的试验研究,分析框架柱的侧向约束对体外预应力梁的受力性能影响：研究框架梁体外预应力加固时梁柱相互约束的受力机理,并讨论侧向约束对梁上预应力有效量的影响等;用有限元软件进一步分析不同参数的变化以及侧向约束对体外预应力框架梁力学性能的影响。     

竖向支撑对连续梁中预应力值影响分析

分析了预应力框架结构中侧向约束对连续框架梁中预应力值的影响,以及这种影响对竖向构件本身的影响,得出了侧限系数的计算公式。并通过工程实例,提出了考虑侧向约束影响的应用条件,可供设计人员参考使用。     

FRP约束方形混凝土柱轴心受压强度模型

FRP约束方形混凝土柱的侧向约束力受截面形状的影响较大，与圆形柱相比，由于拐角的应力集中导致的侧向约束应力不均匀等，使得FRP包裹方形柱的侧向约束效果明显降低。基于FRP约束圆柱体的强度公式，考虑方形柱的有效核心区、拐角效应以及等间距包裹的影响，引入对应的影响系数，建立了FRP约束方形混凝土柱轴心抗压强度新模型并与试验数据对比分析，结果表明，该模型具有良好的精度。     

侧向约束对超长结构预应力施加的影响分析

超长混凝土结构施加预应力时,侧向刚度会约束梁、板构件的轴向变形,从而影响预应力在水平构件中的传递,导致轴向预应力的损失。本文分析了侧向约束对超长结构预应力施加效果的影响,并在理论分析和工程实测数据的基础上,提出了减小次内力的措施。     

预应力混凝土结构侧限影响分析

考虑预加力对预应力混凝土结构侧向约束的影响,利用矩阵位移法分析了框架结构预应力梁在预加力等效荷载及梁端转角影响下的侧向约束影响,提出了预应力混凝土结构在预加力影响下的侧限影响系数计算公式。并通过工程实例得出预加力对侧限影响系数的影响随预加力的增大而减小,且这种影响较小,并且为有利影响。为合理设计有侧向约束的预应力混凝土结构提供了参考。     

考虑下部支承结构协同变形的椭圆形弦支穹顶结构温度效应研究

空间结构周边约束刚度是影响结构温度变形和温度应力的主要因素之一。周边约束刚度与支座刚度、下部支承结构侧向刚度有关,而目前大部分研究中忽略了下部混凝土支承结构侧向刚度的影响,使得分析结果不能准确反映结构的实际状态。以天津宝坻体育馆椭球形弦支穹顶结构为背景,建立包含下部混凝土支承结构的整体模型,研究了下部支承结构侧向刚度对结构温度效应的影响,发现合理考虑下部支承结构的侧向刚度可有效降低结构的温度应力、温度变形和支座反力。     

非对称侧向约束结构的受力特性分析

非完整地下室的结构受不对称的侧向约束,目前常用计算软件不能方便地计算分析这类结构。运用ETABS软件对这类结构的计算表明,相对不考虑侧向约束的结构而言,这类结构刚度增大,在有侧向约束的楼层结构内力减小,但又可能导致结构楼层刚度突变而形成薄弱层、结构局部内力增大、竖向构件塑性铰位置发生转移等不利影响。     

部分约束下组合梁柱子结构抗连续倒塌机理

为研究部分约束钢框架组合梁柱子结构的抗连续倒塌机理,对其进行数值模拟研究。利用ABAQUS软件建立了1:3缩尺的部分边界约束组合梁柱子结构的精细化数值模型,模型计算结果与试验结果吻合较好,验证了有限元建模方法的正确性。在此基础上建立足尺模型,分析边界约束侧向刚度、边柱尺寸、边柱轴压比对部分边界约束下组合梁柱子结构的抗连续倒塌性能的影响。结果表明:当弹簧约束系数n<1时,边界约束侧向刚度对组合梁柱子结构的抗连续倒塌性能影响显著,增大侧向约束刚度可有效提高组合梁柱子结构的抗连续倒塌性能; 当弹簧约束系数n>1时,增大侧向约束刚度对组合子结构的抗连续倒塌性能影响较小; 边柱尺寸过大或过小均不利于组合梁柱子结构抗连续倒塌性能的发挥,当梁柱线刚度比处于0.6～1.1区间时,边柱尺寸越大,悬链线机制发挥越充分,组合梁柱子结构的抗连续倒塌性能越好; 边柱轴压比对不同机制抗力的占比影响不大,但会影响组合梁柱子结构的承载能力,当边柱轴压比取0.3时,组合梁柱子结构的抗连续倒塌性能发挥最佳。     

Elastic flexural-torsional buckling of steel beams with rigid and continuous lateral restraints

A simple model of the elastic buckling of steel beams with rigid and continuous lateral restraints has been developed. It is based on a method of displacements that associate lateral restraint conditions. A numerical procedure for resolving the resulting partial differential equations is proposed in which rotations are approximated by trigonometric functions. The effects of moment distribution and continuous restraints on the elastic flexural-torsional buckling of beams are also studied and design approximations and procedures developed. This study also highlights that the restraint of the tensioned part of the beam is not sufficient to limit lateral buckling. The use of these solutions is demonstrated by two examples.     

Zur Aussteifung von Biegeträgern durch Drehbettung und Schubsteifigkeit

Beams in bending restraint by rotational spring stiffness and shear stiffness of adjacent members. An exact but more extensive design check for lateral torsional buckling can be avoided if values for minimum restraints are fulfilled. Well known are values for minimum torsional restraints in the actual codes DIN 18800‐2 and DIN EN 1993‐1‐1. The values of DIN EN 1993‐1‐1 table BB‐1 are originally given in DIN 18800‐2 table 6 based on the lateral torsional buckling curve of DIN 18800‐2. They are newly calculated on the basis of the curves given in DIN EN 1993‐1‐1 chapte 6.3.2.3 and more load cases are taken into account. Different details are given in codes and literature concerning lateral restraints given by trapezoidally sheeting. Additional investigations are carried out with regard to the minimum shear stiffness (lateral restraint) S_min which limit the applicability of values S corresponding to eq. (5a) which is recommended in literature.     

Design of steel beams with discrete lateral restraints

Discrete lateral restraints offer an effective means of stabilising beams against lateral-torsional buckling. Design expressions for simply-supported beams braced regularly along their span with elastic restraints, based on analytically-derived formulae, are presented herein. These include the minimum restraint stiffness required to force the beam to buckle in between the restraint nodes and the forces induced in the restraints, along with a brief treatment of the critical moment of the beam. It is demonstrated that there is close agreement between the values obtained from the design formulae and their original analytical counterparts. These are also compared with the results from design formulae based on analogous column behaviour, an approach commonly used in design codes. It is found that the column rules used by design codes return values that, when compared with the results of the current analysis, are overly conservative for cases where the restraints are positioned at the compression flange of the beam but unsafe for restraints positioned at the shear centre.     

预应力混凝土框架结构的侧向约束分析

在预应力混凝土框架结构梁中张拉预应力筋时,柱侧向约束将造成梁中设计预加轴力的损失,梁中达不到设计预加应力值,同时也会在柱中产生次剪力和次弯矩,并进一步在梁中产生次剪力和次弯矩作用。对于有明显侧向约束的超长超宽多跨预应力混凝土框架结构,若不合理考虑侧向约束对预压力传递的影响,不仅裂缝控制得不到满足,而且承载力计算也是偏于不安全的。建立了不同张拉顺序下次内力计算模式并推导出了计算公式,提出了设计、施工运用中注意的问题,为合理进行结构设计提供了依据。     

Biegedrillknickmomente und Eigenformen von Biegeträgern unter Berücksichtigung der Drehbettung

Critical bending moments and modal shapes for lateral torsional buckling of beams under consideration of torsional restraints. The design for lateral torsional buckling according to DIN 18800 and EC 3 is based on the elastic critical bending moment. Because of economical reasons it is favourably to consider the stabilizing effects of adjacent structural members. This paper is dealing with the determination of M_Ki considering the influence of torsional restraints. Beyond that one shows the corresponding modal shapes because they are necessary for the verifications considering equivalent geometrical imperfections. As alternative to computations by EDP programs for selected structural systems approximation formulae are indicated to enable the determination of M_Ki by means of manual calculation.     

连续组合梁侧向失稳的弹性地基压杆稳定解

连续组合梁负弯矩区的侧向稳定可等效为弹性地基上的压杆稳定问题。为研究这一问题，分析了变轴力分布对压杆稳定解的影响，探讨采用变轴力弹性地基压杆稳定理论连续组合梁形变侧向失稳的实用设计方法。     

不同边缘构件约束剪力墙抗震性能试验研究

针对剪力墙结构在实际应用过程采用不同边缘构件约束方式的特点，对一组1／4缩尺比例的三种不同边缘构件（暗柱、明柱、翼缘）的剪力墙模型进行了低周反复水平荷载作用试验研究。通过试验研究分析了不同形式边缘构件与墙体的共同工作性能，对比研究了不同边缘构件约束条件对中高剪力墙受力特点、破坏和耗能机理的影响，并从承载力、延性、恢复力特性和耗能能力等方面来综合评价三种不同边缘构件约束条件下剪力墙的抗震性能。研究结果表明，随着边缘构件约束作用的加强，剪力墙的平面外稳定性增强，剪力墙承载能力有一定的提高，但延性系数和耗能能力则相应有所降低。     

不同屈曲约束形式的钢板剪力墙往复剪切性能试验

为研究不同冷弯薄壁型钢屈曲约束形式的钢板剪力墙的往复剪切性能,剥离框架对钢板剪力墙结构抗侧力的贡献,单独对3个不同屈曲约束形式的钢板剪力墙结构试件和1个纯钢板剪力墙结构试件进行了拟静力试验研究,并通过试验与理论分析揭示了不同屈曲约束形式的钢板剪力墙在往复剪切作用下的力学性能与失效机理。结果表明:冷弯薄壁型钢对钢板剪力墙的面外变形具有较好的约束作用,显著提高了钢板剪力墙的耗能能力、延性和承载力; 竖向屈曲约束构造形式对钢板剪力墙的耗能能力提高效果最好,其次是水平约束形式,最差是45°斜向约束形式; 对于带45°斜向约束的试件而言,由于约束形式非轴向对称,其承载力在推、拉方向上表现出明显的差异,即在拉力带垂直于冷弯薄壁型钢约束时,其承载力更高。     

Ultimate behaviour of continuous steel beams with discrete lateral restraints

Through a programme of experiments, numerical modelling and parametric studies, the implications of allowing for strain-hardening in the design of laterally restrained continuous steel beams are investigated with particular emphasis on the performance of the bracing elements. A total of six tests were performed on continuous beams considering two basic scenarios: discrete rigid restraints and discrete elastic restraints of varying stiffness. In the latter case, the forces developed in the restraints were measured and compared to the design forces specified in EN 1993-1-1 (2005) for members containing rotated plastic hinges. Two different restraint spacings were considered in the tests to give non-dimensional lateral torsional slenderness values of 0.3 and 0.4 for the unrestrained lengths. In all tests, bending resistances predicted by the deformation-based continuous strength method (CSM) were exceeded. Using a standardised numerical model validated against the laboratory test data, a series of parametric studies were conducted; it was concluded that elastic restraints for members containing rotated plastic hinges should be designed to sustain higher forces than required for traditional plastic design if the full CSM collapse load is to be achieved.