火灾下焊接空心球节点的温度场分析

基于火灾高温下网格结构的应力特征和火灾性能,按照EuroCode 3和国际标准升温曲线(ISO834 ),对焊接空心球节点火灾高温下的性能进行了非线性有限元数值模拟.研究了焊接空心球节点火灾高温下温度场的分布规律和影响因素.研究结果表明,通过降低焊接空心球节点实际承受的荷载比和外焊钢管的厚度可以有效延长其极限耐火时间,并且焊接空心球节点在受拉时的极限耐火时间比受压时的长.     

网架结构超大直径焊接空心球节点破坏机理分析及其承载能力的试验研究

本文首次对超大直径焊接空心球节点进行了系统的理论分析及试验研究。以弹塑性分析为基础,运用非线性有限元方法,揭示了超大直径焊接空心球节点表面的应力、应变及位移的分布规律;按冲剪模型理论建立了超大直径焊接空心球节点在受拉时的承载力计算公式;基于能量法原理建立了受压节点承载能力的理论表达式,得到了其极限载荷的上限理论解。同时本文还对6组超大直径焊接空心球受压节点进行了试验研究,试验结果与理论结果进行了比较,二者符合较好。     

不锈钢网架结构试验研究

对奥氏体不锈钢网架结构的物理力学性能、焊接性能加以分析，并进行了不锈钢焊接空心球节点承载力试验，确定了该种节点的受拉和受压承载能力。在此基础上，又做了不锈钢组合扭网壳模型的破坏性试验研究，试验结果与理论计算值比较，吻合较好。     

某钢框架栓-焊节点施工缺陷影响分析及处理

对某钢框架结构的栓-焊节点焊接缺陷进行了调查,发现翼缘焊缝存在明显错台和未熔透现象。计算分析表明,焊缝错台高度低于板厚的20%时,对节点承载力影响不明显;超过板厚的20%后,翼缘的弹性拉压承载力会逐渐降低,错台达到板厚的70%时,承载力降低约20%。但是考虑地震时结构塑性变形,翼缘的受拉弹塑性承载力会显著降低,错台超过板厚1/3,受拉承载力降幅可达50%以上;翼缘的受压弹塑性承载力也有降低,但相对弹性承载力降低不显著。如果焊缝熔透深度不足,则翼缘的弹性和弹塑性拉压承载力都将显著降低。采用加劲肋对栓-焊节点进行补强,计算结果表明,采用该措施可以满足节点承载力要求。     

手弧焊板状试件仰焊单面焊双面成型操作方法探讨

本文针对板状试件仰焊单面焊双面成型操作工艺难度大,很容易在焊件正面出现焊缝中间高,两侧有夹角,焊件背面出现凹陷、未焊透等缺陷问题,认真分析产生缺陷的原因,并结合自己的实践经验,在使用碱性低氢钠型焊条时,可以通过合理选择电源极性,正确掌握焊接方法来克服和消除缺陷,获得满意的焊接接头并保证焊接质量。     

T型接头焊缝中未焊透宽度对钢结构质量的影响

通过对T型接头焊缝中未焊透缺陷存在时剪应力的计算 ,找出了钢结构焊缝所受剪应力随此类缺陷宽度df的增加而增大 ;并且 ,当它们宽度达到一定数值时 ,焊缝所受剪应力就会大于焊缝容许剪切力 (τht) ,从而降低焊缝的有效承载能力 ,影响焊缝质量和性能 ,减小钢结构寿命的规律。还提出了在钢结构的检测和验收时 ,应该考虑到未焊透等缺陷宽度对焊缝质量的影响等问题。     

重型大管径长输管道焊接技术及应用

通过香港屯门海底排污管工程的现场组对焊接，总结了一套行之有效的焊接工艺，克服了重型大管径长输管道焊接时易出现裂纹和未焊透等缺陷。     

加肋焊接空心球节点高温下轴心受压性能分析

为研究高温对加肋焊接空心球节点受压承载能力的影响,采用数值模拟方法,对单向轴心受压的加肋焊接空心球节点在高温下的受压性能进行研究,分析焊接空心球节点在轴心受压荷载作用下的破坏模式,得到不同温度下焊接空心球的承载能力。分析结果表明:高温下焊接空心球节点的薄弱部分为钢管与球节点连接处;高温对加肋焊接空心球节点的承载能力有着很大影响,随着温度的升高,承载力逐渐降低,当温度超过400℃以后节点承载力下降迅速,尤其是在节点温度达到700℃时,节点的极限荷载只有常温下的20%左右;随着温度升高,球节点越来越早进入弹塑性阶段。不同厚度的加劲肋在不同温度下呈现不同的变形。     

受拉焊接空心球节点火灾高温下的性能分析

基于火灾高温下空间网格结构的性能,本文根据欧洲规范了中高温下的钢材特性和国际标准升温曲线(ISO834),对单轴受拉焊接空心球节点高温下的性能进行了数值模拟,分析了空心球的温度场分布规律和极限耐火时间的影响因素。通过分析高温下空心球的应力和位移变化特征,确定了其破坏模式;结果表明钢管根部和赤道处是其高温下受拉承载力的薄弱环节。     

海洋钢结构常见裂纹形式及预防措施

在钢结构焊接时由于主观、客观因素的影响,经常会出现裂纹、气孔、夹渣、未熔合、未焊透、咬边、焊瘤、烧穿、凹坑和弧坑、飞溅等缺陷,在这些缺陷当中,裂纹是焊接生产中比较普遍而又最危险的缺陷,它不仅减少承载截面,产生严重的应力集中,还会在使用中逐渐扩大,最后导致构件的破坏,造成废品,严重的还会带来灾难性的事故。预防裂纹或其它缺陷的产生和焊后外观检验发现缺陷是我们焊接检验工程师义不容辞的责任和使命。     

某钢结构梯架火灾后的性能分析与鉴定

根据钢结构火灾后性能分析与鉴定的一般程序、内容及方法,针对一受火钢结构梯架进行了火灾后钢材现场取样拉伸试验以及化学锚栓拉拔试验,记录了现场结构外观测量结果以及火灾后的结构变形.发现结构焊缝处有多处裂缝以及有部分构件因受火出现局部屈曲.随后采用测得的火灾后结构变形数据,建模分析了该火灾后的结构受力性能并与火灾前结构受力进行了对比,结合现场取样拉伸试验和锚栓拉拔试验结果对结构承载能力进行了验算.并对原结构中出现的构件局部屈曲与焊缝裂缝给出了修复意见.最后对火灾后钢结构的分析与鉴定中需注意的问题做了探讨,强调火灾后钢结构的检测不能忽视节点区域焊缝裂缝的检查.     

The strength of planar fillet weld groups subjected to a shearing force applied outside their planes

The method of analysis previously proposed for calculating the strength of fillet welded connections subjected to a shearing force only is now extended to analyse the strength of fillet welds which all lie in one plane and are subjected to a shearing force applied along a line of action which is parallel to, but outside, this plane and is so positioned as to give rise to a couple acting in a plane normal to the plane of the welds. The welds are assumed to have equal leg lengths. The effect of longitudinal residual stresses in the welds is allowed for. Analytical expressions, which depend upon the weld metal ultimate tensile strength and the weld geometry, are developed for predicting the strength of the welds; these expressions are simple enough to be used in design. The predictions of these formulae are compared with published experimental results, and agreement between the two is shown to be reasonable.     

H形梁翼缘与端板非全熔透焊接的节点性能试验研究

对H形梁翼缘与端板分别采用全熔透焊接和非全熔透焊接的节点进行了对比试验。选择板件宽厚比、端板厚度、翼缘板与端板平面的夹角等设计参数,对24个试件进行了单调加载试验,6个试件进行了反复加载试验。试验结果表明:节点无一例发生焊缝破坏,焊缝形式对连接的最大荷载、翼缘近焊缝端应变以及滞回性能等无明显影响;在以局部屈曲为主要控制模式进行设计的轻型门式刚架中,无论对单调静力荷载还是反复荷载,H形梁翼缘与端板的连接都可采用非全熔透焊接。     

X形方圆汇交钢管节点的焊缝轴拉性能试验研究与承载力计算

为了研究X形方圆交汇钢管节点（主管为方形截面钢管、支管为圆形截面钢管）的焊缝轴拉承载力,对5个非刚性连接和3个刚性连接试件进行静力加载试验。采用硅橡胶印模技术对焊缝几何特性进行精细化测量,考察焊缝全周的应变分布、破坏模式和承载力。试验结果表明：刚性连接试件在轴拉荷载作用下的焊缝全周应变分布均匀,而非刚性连接试件的焊缝全周应变分布则呈现明显的不均匀性;非刚性连接的焊缝承载力相对于刚性连接的焊缝承载力有较大程度的降低,主要原因是焊缝应力的不均匀分布以及热影响区材料的脆性破坏无法与非刚性连接主管管壁的塑性变形协调,从而先于熔敷金属发生断裂。采用有限元分析方法对焊缝的受力性能进行分析,得到不同节点参数下的焊缝有效长度,通过试验和有限元参数分析,提出了基于焊缝有效长度,且满足规范可靠度要求的非刚性连接焊缝轴拉承载力计算式。     

Research on end-plate connection with non-completely penetrated welds

A series of tests were executed for H-shaped beams whose flanges were connected to end-plate by non-completely penetrated welds. The welds were designed by equal capacity rule and the beams were mainly composed of non-compact or slender elements. The parameters introduced are width-thickness ratios of beam flange and web, end-plate thickness, angle between flange plane and end-plate plane and so on. 24 pieces of specimens were tested to failure under monotonic loading and 6 under cyclic loading. For comparison, a few of the specimens are those with completely penetrated groove welds. Finite element (FE) analysis was also carried out to study the effect of parameter change on the resistance of the welds. The parameters involved end-plate thickness, weld size, column flange thickness and bolt gauge. The results show that thinner end-plate and greater bolt gauge will deteriorate the resistance of weld. As long as the components are properly designed, as done in tests, the connections will not fail at the welds no matter what kind of weld form is adopted. In addition, weld form has no obvious effect on the ultimate loads and cyclic behavior of specimens. It is confirmed that the non-completely penetrated welds connecting flanges of H-shaped beams and end-plates can be used both under static loading and seismic loading in low-rise building structure where local buckling of the member is the predominant factor.     

A new analysis of the strength of some simple fillet welded connections

The strength of some simple fillet welded connections is investigated. The connections considered are those made using (a) tension fillet welds, (b) shear fillet welds, and (c) a combination of types (a) and (b), the welds having equal leg lengths. The strength of the welds is determined as a function of the weld geometry and the ultimate tensile strength of the weld metal by considering the forces acting on the welds. The sets of forces for which the welds are analysed are not the actual ones present but they are ‘equivalent’ to the actual forces. The effect of longitudinal residual stresses, which are locked into the weld metal when the weld is deposited, is allowed for. The predictions of the various strength formulae developed are compared with experimental results published by other workers and agreement between the theoretical and experimental results is found to be reasonable. The strength formulae turn out to be so simple that they could easily be used in design. The effect of unequal leg lengths on the strength of the welds is investigated and it is shown that the strength of tension fillet welds is markedly affected by the shape of the weld cross-section. The way in which the proposed method can be applied to more complex loading conditions is described and an example is given to show that the predictions of the method are in reasonable agreement with experimental results.     

钢结构工程的焊接检测

考虑到钢结构焊接检测的针对性和适用性,主要就焊缝抗拉试验、焊缝尺寸和焊缝外观质量的检测进行了分析和讨论。     

砂岩动静态拉伸力学性能试验与对比分析

通过对皖北矿区3个煤矿砂岩岩样加工成厚径比为0.5的圆盘试件,利用变截面分离式Hopkinson压杆(SHPB)试验装置,采用不同加载冲击气压驱动撞击杆高速运动,对圆盘试件实施不同加载速率下的动态劈裂拉伸试验,得到了3种砂岩试件的动态拉伸应力和应变率等力学参数,并与静态劈裂拉伸试验结果进行对比,分析了砂岩圆盘试件动静态劈裂破坏形态、动态拉伸应力与加载速率相关性规律;得到了试验冲击气压范围内砂岩动态拉伸应力强度与平均应变率之间近似为乘幂函数关系,比其静态拉伸应力强度提高2～3倍。对砂岩动静态拉伸力学性能研究做了一些有益的探索。     

The strength of inclined fillet welds

The strength of a fillet weld which is required to transmit a shearing force only and which is inclined to the line of action of the applied force is investigated theoretically. A very simple expression based on the weld geometry and the weld metal ultimate tensile strength is developed. Results previously published by the author for longitudinal and transverse fillet welds can be obtained as special cases of the general solution presented in this paper. The residual stresses that are present in welds when they are loaded in the as-welded condition are allowed for in the theory. The predictions of the theory are compared with the few experimental results that are available and are found to provide reasonable estimates of the strength of welds inclined at 30° and 60° to the line of action of the applied force.     

管板连接轴心受拉构件极限承载力试验研究

对6个管板连接构件进行了受拉极限承载力试验研究和有限元分析。试验表明,试件的破坏均为长槽孔末端钢管横截面被拉断,其中,用板补强的试件GPT-3和GPT-6在破坏前钢管出现了明显的颈缩。分析表明,试验结果和有限元分析结果吻合良好,现行美国规范(ANSI/AISC 360-05)和加拿大规范(CAN/CSA-S16-01)中未补强的管板连接受拉承载力设计公式安全适用。研究表明,管板连接构件在受拉过程中,剪切滞后现象非常严重;长槽孔末端绕焊的焊缝质量对构件的受拉极限承载力有很大的影响。