3种不同梁端构造的H型钢梁-柱节点抗震性能试验研究

为了研究不同梁端构造对H型钢梁-柱节点抗震性能影响,选用3个不同构造形式的节点,在相同的加载准则下对节点的破坏形式、滞回性能、骨架曲线、极限荷载、刚度退化、耗能等多项抗震性能指标进行比较和分析。试验研究表明,尽管3个H型钢梁-柱节点梁端构造不同,但均表现出良好的抗震性能;梁端局部的碳纤维布横向缠绕约束以及填充混凝土的构造,可以使节点延性提高约30%,节点强度提高约10%,且翼缘的屈曲远离焊缝位置;梁柱间采用端板-螺栓连接的节点耗能与采用焊接的节点较为一致,说明梁端-螺栓连接的构造对节点耗能的影响不显著。     

BJ200无缝伸缩缝在桥梁维修施工中的应用

桥梁伸缩缝是组成桥梁的一个部分,在构造中十分重要。桥跨结构会在多种因素影响下产生形变和梁端的位移,如活载作用、温湿度变化、墩台沉降、混凝土收缩和徐变等。为使车辆能够在梁端位移和形变的情况下也能够在桥上平稳行驶,需在梁端、桥面梁端、桥台背墙间加设伸缩缝。     

某办公楼预应力大梁裂缝成因分析与处理

某办公楼预应力大梁张拉完成后出现较多的贯穿性裂缝.通过现场检测与复核计算,裂缝主要是预应力钢筋配置过多,张拉力相应增大,混凝土受压区高度和梁端纵向受拉钢筋配筋率大于相应的规定值等因素引起的,锚固端构造措施处理不当加剧了裂缝的发展.该裂缝为受力引起的有害裂缝.采用粘贴碳纤维加固方案对大梁的裂缝进行处理.梁端斜裂缝宽度大于...     

连续性倒塌工况下钢管柱框架节点的破坏模式与鲁棒性

采用双半跨单柱型梁柱子结构,通过静力加载试验考察了圆钢管柱外环板节点与方钢管柱内隔板节点在中柱失效连续性倒塌工况下的破坏模式,并以梁柱子结构竖向抗力来评估梁柱节点的鲁棒性。试验参数包括连接方式、螺栓布置、梁端构造与跨高比。试验结果表明,在柱顶施加竖向位移的过程中,梁柱子结构的破坏均出现在梁柱节点部位,不同的连接构造呈现出不同的损伤演化机制。节点破坏模式可分为梁端连续性破坏、梁端间断性破坏与柱身破坏三类。当节点破坏发生在梁端,采用全焊连接的节点发生梁端连续性破坏,采用栓焊混合连接的节点发生梁端间断性破坏。柱身破坏模式的发生前提为下层内隔板与柱身脱离,与腹板连接方式无直接关系。在梁端间断性破坏或柱身破坏的演化过程中,节点在初始断裂后仍可保持有效的梁柱拉结作用,悬索机制得以开展并为梁柱子结构提供稳定的后期承载力,节点具有较好的鲁棒性。节点若发生梁端连续性破坏,梁端截面面积逐步减小导致梁柱拉结作用削弱,梁柱子结构无法有效开展悬索机制,节点鲁棒性能较差。     

RC框架结构梁端楼板设缝后的设计方法及构造措施研究

框架结构梁端楼板设缝可以减少现浇板对梁端刚度和承载力的影响,因此该方法有利于实现"强柱弱梁"机制。本文在研究梁端楼板设缝后梁柱的合理线刚度比基础上,通过构造设计,并建立有限元模型进行模拟分析,据此提出RC框架结构梁端楼板设缝的合理建议。     

墙体对梁端约束的试验研究与有限元分析

多层混合结构房屋承重纵墙计算模式中关于砌体对梁端的约束作用这一问题一直未能得到较好的解决。针对此问题,制作了一榀两层单跨混合结构模型,进行了墙体对梁端约束作用的试验研究,考察了构件的破坏过程和破坏特征,分析了梁端约束弯矩和转角、跨中挠度和弯矩随荷载的变化规律,并与按现行规范计算结果进行了比较;同时采用有限元分析软件对梁端约束情况进行了非线性分析,并将分析结果与试验数据进行了比较,此外,探讨了梁端插入墙体长度以及墙体应力等因素对梁端约束的影响。试验研究和有限元分析结果表明:多层混合结构房屋梁端存在约束力矩,并随荷载的增加呈抛物线变化,反映了框架性质,多层混合结构房屋不能简单地按铰接简图计算内力,现有规范计算公式误差也较大;梁端约束力矩与梁的刚度、砌体的刚度、梁端插入墙体的长度、墙体上部荷载、梁上荷载、梁与墙体连接处的节点构造等因素有关。     

预应力梁张拉端加腋处混凝土劈裂事故分析

本文通过介绍后张预应力混凝土梁张拉端加腋处混凝土劈裂的工程事故实例,深入分析了破坏产生的原因,给出了建议性的加固处理措施及预应力梁加腋处的施工构造要求,为今后预防后张预应力梁加腋处混凝土破坏和改善梁端受力性能提供了参考依据。     

钢结构梁柱刚性节点的抗震设计

通过学习现行《建筑抗震设计规范》(GB 50011-2010)关于抗震节点设计的条文,总结出了钢结构房屋梁柱刚性连接节点设计的几个要点,针对具体梁端消弱式节点和梁端加强式节点,提出了相应的构造措施和应用特点.     

梁端弹簧自复位框架耗能节点试验研究

梁端弹簧自复位框架耗能节点是一种新型自复位节点形式,通过在梁端布置弹性恢复装置和节点阻尼器,使得节点具有确定的转动刚度和阻尼,可以同时实现结构的自复位和地震能量耗散。为了验证节点的可行性、研究其抗震性能,选择钢板弹簧作为弹性恢复装置、腹板屈服耗能金属阻尼器作为耗能装置进行节点构造,并对足尺梁端弹簧自复位框架耗能节点进行拟静力试验,得到无控节点和有控节点的试验滞回曲线和骨架曲线。试验结果表明,梁端弹簧自复位耗能框架有控节点试验的滞回曲线饱满、具有良好的耗能能力,通过无控节点试验的骨架曲线求得的节点转动刚度与预设设计值一致,表明采用梁端弹簧耗能节点构造自复位框架是可行的,为进一步研究整体框架抗震性能提供依据。     

钢筋混凝土悬臂梁的构造设计

介绍了即将颁布的《混凝土结构设计规范》(GB5 0 0 10 )中悬臂梁的构造设计 ,分析、探讨了钢筋混凝土悬臂梁细部构造问题 ,包括纵筋的截断、锚固、梁端小立柱、截面承载力的计算要点 ,提出了设计原则     

Free vibration of shear beams with finite rotational inertia

Free vibration of shear beams is studied when rotational motion is taken into account, while classical shear beams do not consider rotational motion. From a single governing equation of Timoshenko beams, we analytically derive Rayleigh beams and shear beams as two limiting cases of the ratio of reduced shear stiffness to bending stiffness being sufficiently large and small, respectively. Emphasis is placed on the analysis of free vibration of nonclassical shear beams without damping effect. Under the condition of general end restraints, a characteristic equation for nonclassical shear beams with finite rotational inertia is derived in explicit form. A condition that the nonclassical shear beams reduce to the classical ones is found, and classical shear beams may be understood as nonclassical ones with infinite large rotational inertia. Nonclassical natural frequencies and mode shapes are calculated for a standing shear beam on an elastic foundation. Previous results of pinned-free, and free-free shear beams can be taken as special cases of the present analysis. The effects of finite rotational inertia, material properties, geometrical conditions and end restraints on the natural frequencies of shear beams are discussed.     

CFS-GFS混杂预应力加固梁界面性能数值分析

通过非线性有限元方法对CFS加固混凝土梁界面性能进行数值分析,并与解析解进行了对比,吻合较好.建立了CFS-GFS混杂加固梁界面有限元模型,将计算结果与双层CFS加固梁进行了数值对比研究.结果表明混杂加固可以有效的控制纤维布末端界面剪应力大小,并且界面正应力也有所降低,这种加固方式具有优良的界面混杂效应.在此基础上,通过模拟CFS-GFS施加不同大小的预应力,研究预应力界面性能,结果表明在粘贴端部施加锚固可以有效降低界面处混凝土及胶层应力,提高纤维布强度的实际利用率.     

非弹性侧向屈曲的悬臂钢梁强度

两端支承钢梁的设计方法不适用于抗侧向屈曲的悬臂梁。悬臂梁与两端支承梁的约束不同,其最大位移和转角发生在自由端,而不是在跨中附近。因此,它们的屈曲模态不一样。这些方法考虑了弯矩分配法对两端支承梁弹性及非弹性屈曲的影响,但不适用于悬臂梁。悬臂梁的侧向屈曲设计法是对端支承梁设计法的修正,但其精度不高,有时过于保守,某些情况下,不能用于设计。使用弯矩分配法进行结构的屈曲分析,总结了该方法对悬臂梁弹性屈曲的影响。改进两端支撑梁的非弹性屈曲设计方法,使其能考虑弯矩分配法对悬臂梁非弹性屈曲的影响。改进的方法与简支梁的设计法是一致的。以某工程为实例,演示了此方法的应用。     

腹板开洞的钢与混凝土组合梁承载力计算方法综述和探讨

介绍了三种钢与混凝土组合梁腹板开洞处承载力的计算方法 ,讨论了其存在的不足 ,提出了修正的方法。并通过一悬臂开洞组合梁的试验资料对修正方法进行验证 ,证明其是可行的。同时 ,简要说明了腹板开洞组合梁设计中的其他需要注意的问题。     

Lateral-torsional buckling resistance of coped beams

The lateral-torsional buckling resistance of beams depends on the support conditions. In floor structures for buildings coped beams are often used. A numerical model was developed to investigate the influence of copes on the lateral buckling resistance. This model is described in a companion paper [Maljaars J, Stark JWB, Steenbergen HMGM, Abspoel R. Development and validation of a numerical model for buckling of coped beams. Journal of Constructional Steel Research 2005;61(11):1576-93]. In this paper results of a parameter study carried out with the numerical model are presented. Based on these results recommendations for design rules are given. The study is restricted to (coped) beams with end plates.     

某厂反应釜支撑梁开裂原因分析

对某厂反应釜支撑梁体内的裂缝进行检测 ,从两个方面分析了支撑梁开裂原因 ,采用ANSYS有限元软件对该工况下的梁进行了仿真分析 ,分析结果与实际相符 ,并为预防同类梁开裂提出了几点建议     

复杂荷载作用下单向受弯简支钢梁的弹性临界弯矩

为了研究单向受弯简支钢梁的弹性弯扭屈曲理论,尤其是复杂荷载作用下的临界弯矩计算,针对端弯矩和任意集中荷载共同作用下的简支梁,首先给出了能够模拟复杂变形并满足边界条件的侧向弯曲变形函数和扭转变形函数,以及任意荷载下的构件弯矩表达式,然后采用Rayleigh-Ritz法推导出了简支梁临界弯矩及其参数的通用计算公式,临界弯矩计算公式与传统公式在形式上完全相同,便于应用。算例分析表明：该通用公式不仅适用于端弯矩、任意集中荷载、满跨均布荷载单独作用下的简支梁,也适用于端弯矩和任意集中荷载共同作用下的简支梁,具有广泛的适用性,且精度较高。     

Analysis of catenary action in steel beams using a simplified hand calculation method, Part 1: theory and validation for uniform temperature distribution

This and the companion papers present, in detail, the development and validation of a simple analysis method of catenary action in steel beams at elevated temperatures, which may be adopted as the basis of a design calculation method. Although the analysis is suitable for beam behaviour over the entire temperature region, the present discussions will emphasize on catenary action. The main assumptions of the analytical model are the beam’s deflection profile and interaction between axial load and bending moment. The beam’s deflection profile depends on its loading condition and end rotational restraint. For simply supported beams under distributed load or beams with complete end rotational restraint, the beam deflection profile may be assumed to be a polynomial that satisfies the beam’s geometric boundary conditions. For simply supported beams under point loads, the beam’s deflection profile may be assumed to take the shape of its free bending moment diagram. For flexible end rotational restraints, linear interpolation may be adopted as a function of the degree of end rotational restraint. For combined axial load and bending moment, the proposed analysis allows the beam’s axial load to change in isolation and the beam’s bending moment is then calculated from the axial load-bending moment interaction equation. This is a simplifying assumption that does not comply with stress distribution in the beam. It will be found that this method will predict higher catenary forces, which is on the safe side. This paper will present validation studies, by comparing results of the proposed method and numerical simulations using ABAQUS, for beams with uniform temperature distribution. The companion paper will give additional equations to be used in the proposed method and validation examples for beams with non-uniform temperature distributions.     

外贴碳纤维布加固混凝土梁的抗剪设计方法

在对 2 0根碳纤维布 (简称CFRPs)加固混凝土梁进行抗剪试验及国内外相关试验研究的基础上 ,对采用碳纤维布加固后梁的破坏机理进行了分析研究 ,针对两种不同的破坏特征提出了相应的受剪极限承载力计算方法 ,并对两者做了比较分析 ,最后给出了采用CFRPs对混凝土梁进行抗剪加固的一些设计建议。     

Composite steel-framed structures in fire with protected and unprotected edge beams

The structural behaviour of a steel-concrete composite frame subject to a natural fire is analysed using a numerical model. The behaviour is compared when fire protection is applied to only the external beams and when no beams are fire protected. The behaviour of the structure in the two cases is significantly different. When the edge beams are protected the floor slab tends to span in 2 directions because the edge beams provide sufficient support around the perimeter of the floor for tensile membrane action to develop. When the edge beams are unprotected the slab tends to span in only one direction in a manner similar to a beam in catenary action. Catenary action is a weaker load carrying mechanism than tensile membrane action. As a consequence of the weaker mechanism, when the edge beams are unprotected, the columns displace inwards towards the end of the fire indicating the possibility of imminent runaway collapse.The pattern of mechanical strains in the floor slab reinforcement depends on the load carrying mechanism and therefore on whether edge beam protection is included. Although the average mechanical tensile strains are higher when the edge beams are protected the highest strains occur when the beams are unprotected. Conversely, an instability in the primary beam occurs at much lower temperatures when the edge beams are protected.It is concluded that fire protecting the edge beams of the structural layout studied has a number of effects on the fire resistance of the structure, some beneficial, some detrimental, however, in general, fire protecting the edge beams provides an increased level of fire resistance.