纵向焊接铝合金压杆承载力研究

大多数结构用铝合金通常要经过热处理或加工硬化以改善其力学性能。当这种合金焊接后除了产生残余应力外,在焊缝附近还将产生强度明显降低的热影响区(HAZ)。而对于钢结构,由于其热导率比铝材小得多,因此只有高强钢才可能产生强度降低的热影响区,而且其强度的降低没有铝合金显著,热影响区的宽度也比铝合金小得多。这将使得铝合金受压杆件的屈曲性能变得更为复杂。对贴角焊和剖口焊这两种焊接方式的工字型铝合金中心受压杆件进行试验研究,并将试验结果同即将颁布的国标《铝合金结构设计规范》(送审稿)及欧洲规范9(EC9)进行比较。结果表明,通常情况下,对于贴角焊构件,规范结果与试验结果吻合较好;而对于剖口焊构件,规范结果偏保守。     

纵向焊接铝合金压杆承载力研究

大多数结构用铝合金通常要经过热处理或加工硬化以改善其力学性能.当这种合金焊接后除了产生残余应力外,在焊缝附近还将产生强度明显降低的热影响区(HAZ).而对于钢结构,由于其热导率比铝材小得多,因此只有高强钢才可能产生强度降低的热影响区,而且其强度的降低没有铝合金显著,热影响区的宽度也比铝合金小得多.这将使得铝合金受压杆件的屈曲性能变得更为复杂.对贴角焊和剖口焊这两种焊接方式的工字型铝合金中心受压杆件进行试验研究,并将试验结果同即将颁布的国标<铝合金结构设计规范>(送审稿)及欧洲规范9(EC9)进行比较.结果表明,通常情况下,对于贴角焊构件,规范结果与试验结果吻合较好;而对于剖口焊构件,规范结果偏保守.     

焊接铝合金压杆承载力研究

铝合金作为一种新型结构材料,在现代建筑中得到了越来越广泛的应用.国内目前关于挤压型材已经进行了大量研究,但有关焊接铝合金构件的研究很少.由于铝合金焊接后受焊接热影响较大,试件中除了产生残余应力,在焊缝附近的局部区域材料强度还将大大降低,该区域被称为热影响区（HAZ）.而对于钢结构,由于其热导率比铝材小得多,因此,只有高强钢才可能产生强度降低的热影响区,而且其强度的降低没有铝合金显著,热影响区的宽度也比铝合金小得多.这将使得铝合金受压杆件的承载力研究变得更为复杂.为此,对贴脚焊工字型铝合金中心受压杆件进行了试验研究,并将试验结果同即将颁布的国家标准《铝合金结构设计规范》及《欧洲铝合金结构设计规范》（EC9）进行了比较.研究表明,通常情况下,对于贴脚焊构件,《规范》计算值和试验结果吻合较好.     

铝合金焊接节点力学性能的试验研究

为满足国家标准“铝合金结构设计规范”编制的需要,对铝合金焊接节点的力学性能进行系统的试验研究。试验内容包括铝合金对接焊缝节点和角焊缝节点。通过试验得出对接焊缝临界失效面距焊缝中心及焊缝边缘的距离、焊接热影响区及折算强度区的范围;确定临界失效面强度折减系数的取值大小;分析焊件厚度、焊丝型号、焊接工艺对焊缝强度、临界失效面强度折减系数、焊接热影响区范围及折算强度区范围的影响;验证角焊缝强度计算β公式。部分试验结果同欧洲及英国铝合金结构规范值进行对比分析。研究成果为我国首部铝合金结构规范相应章节的制定提供必要依据,是国内首次对铝合金焊接节点力学性能完成的基础性试验研究。     

纵向焊接铝合金构件的试验和设计研究

大多数结构用铝合金通常要经过热处理或加工硬化以得到比退火状态更高的力学性能。这种合金焊接后,焊接热会使焊缝附近局部区域(称为热影响区HAZ)强度降低。而对于钢结构,由于其热导率比铝材小得多,因此只有高强钢才可能产生强度降低的热影响区,而且其强度的降低没有铝合金显著,热影响区宽度也比铝合金小得多。这将使焊接铝合金构件的设计变得更为复杂。由于我国目前还没有关于铝合金结构的设计规范,为此本文通过试验研究及对已有试验数据的分析,并在参考国外规范的基础上,提出了纵向焊接铝合金构件的设计建议公式,并将公式计算结果与试验结果进行了比较,两者吻合较好,从而验证了建议设计公式的适用性。     

大截面铝合金轴压构件整体稳定试验研究

随着大跨度铝合金结构的兴起,大截面铝合金构件的应用越来越广泛。为研究大截面铝合金轴心受压构件整体稳定性能,针对4个工字形6061-T6铝合金轴心受压构件和3个箱形6061-T6铝合金轴心受压构件进行了试验研究。试验中,以长细比为变量研究了构件的稳定承载力、破坏形态和荷载-位移曲线。并将试验结果与中国规范、欧洲规范和美国规范进行了对比。所有构件均发生典型的整体失稳破坏形态,中国规范与欧洲规范均对构件的承载力有明显低估,而美国规范较为准确地预测了试验结果。试验结果可为GB 50429—2007《铝合金结构设计规范》的修订提供建议。     

铝合金矩形开孔柱轴压性能试验研究

采用试验研究的方法,对6061-T6系列和6063-T5系列的铝合金矩形开孔柱的轴心受压性能进行了试验研究。试验主要研究了材料的力学性能、试件的初始几何缺陷、变形性能、破坏模式、轴压承载力、孔洞的存在及数目对铝合金轴心受压构件承载力和屈曲模式的影响等,并将试验所得结果与各国铝合金设计规范中相关公式计算所得结果和北美冷弯型钢轴心受压开孔构件的有效宽度法公式的计算结果进行了对比。通过试验和对比发现:中国规范关于铝合金轴心受压构件极限承载力的计算结果偏大,欧洲规范更贴近试验结果,孔洞的存在降低了构件的承载力,北美冷弯型钢轴心受压开孔构件的计算公式不适用于铝合金开孔构件。     

纵向焊接铝合金柱设计方法研究

大多数结构用铝合金通常要经过热处理或加工硬化以得到比退火状态更高的力学性能。这种合金焊接后,焊接热会使焊缝附近局部区域(称为热影响区HAZ)强度降低。而对于钢结构,由于其热导率比铝材小得多,因此只有高强钢才可能产生强度降低的热影响区,而且其强度的降低没有铝合金显著,热影响区宽度也比铝合金小得多。这将使焊接铝合金柱的设计变得更为复杂。由于我国目前还没有关于铝合金结构的设计规范,为此本文通过试验研究及对已有试验数据的分析,并参考国外规范,提出了纵向焊接铝合金柱设计方法的建议,并将计算结果与试验结果进行比较,两者吻合较好,从而验证了建议设计公式的适用性。     

异形截面轴心受压铝合金构件屈曲性能试验研究

采用试验与数值模拟相结合的方法,研究了异形截面铝合金受压杆件的屈曲破坏模态和屈曲承载力问题,并将试验结果、数值模拟结果以及《铝合金结构设计规范》中相关公式的计算结果进行了对比.结果表明,数值模拟结果与试验结构吻合较好,证明了有限元模型的正确性,并可采用该模型进行异形截面铝合金构件屈曲性能参数分析;规范所研究异形截面铝合金构件没有区分屈曲破坏类型的影响,屈曲承载力的计算结果偏小.     

钢筋接触电渣焊

十七冶机电公司广大革命职工在伟大领袖毛主席关于“我们必须打破常规,尽量采用先进技术”的光辉指示指引下,开展了群众性的技术革新运动,在建筑工程上试验和推广了“钢筋接触电渣焊”新工艺。这是利用电流通过渣池所产生的电阻热,将钢筋端部熔化,然后施加压力,使粗钢筋焊接起来的一种新型焊接工艺。它比通常工地采用的绑条焊、剖口焊、熔槽焊具有设备简单,     

Aluminum alloy tubular columns—Part II: Parametric study and design using direct strength method

A parametric study of aluminum alloy columns of square and rectangular hollow sections was performed using finite element analysis (FEA). The columns were compressed between fixed ends. The parametric study included 120 columns with and without transverse welds at the ends of the columns. An accurate and reliable finite element model was used for the parametric study. Design approaches for aluminum alloy tubular columns with and without transverse welds were proposed. Column strengths predicted by the FEA were compared with the design strengths calculated using the current American, Australian/New Zealand and European specifications for aluminum structures. In addition, the direct strength method (DSM), which was developed for cold-formed carbon steel members, was used in this study for aluminum alloy columns. The design strengths calculated using the DSM were compared with the numerical results. Furthermore, design rules modified from the DSM were proposed. It is shown that the proposed design rules accurately predicted the ultimate strengths of aluminum welded and non-welded columns. The reliability of the current and proposed design rules was evaluated using reliability analysis.     

Design formulations for non-welded and welded aluminium columns using Continuous Strength Method

Aluminium members are used in structural applications due to their high strength-to-weight ratio, corrosion resistance, attractive appearance, recyclability, ease of production and availability. Thin aluminium sections are susceptible to buckling at a relatively low stress and welding makes it even worse; the design stress i.e. 0.2% proof stress is almost halved in the vicinity of the heat affected zones (HAZs). Currently available design codes have their guidelines both for welded and non-welded aluminium columns, but the predictions for welded aluminium columns are often quite inconsistent. The current research exploits a newly developed strain based design approach the ‘Continuous Strength Method’ (CSM) to predict the behaviour of aluminium members with SHS and RHS cross-sections subjected to compression. A new design curve is proposed herein to predict the cross-sectional resistance in compression; this concept is further extended to propose a new Perry type buckling curve to predict the flexural buckling resistance of aluminium columns. A simplified technique is proposed to include the effect of heat affected zone (HAZ) in CSM formulations. The CSM predictions for aluminium columns are compared against those obtained using available guidelines proposed by the European, American and Australian/ New Zealand standards of aluminium structures. The CSM predictions for non-welded columns are in line with the code predictions, whilst the proposed simple technique for transversely welded columns seems to produce significantly improved predictions.     

Effects of transverse welds on aluminum alloy columns

This paper investigates the effects of transverse welds on aluminum alloy columns. The materials of the specimens were 6063-T5 and 6061-T6 heat-treated aluminum alloys. Various coupon tests were performed to obtain the non-welded and welded material properties of aluminum alloys. An accurate and reliable finite element model (FEM) was used for the simulation of aluminum alloy stub columns of square and circular hollow sections (SHS, CHS) in this study. The stress–strain relationships obtained from the coupon tests were incorporated in the FEM. A parametric study was conducted that included 48 columns of different section shapes with and without transverse welds at the ends of the columns. This study focused on the effects of transverse welds on column strengths with respect to the section slenderness. Hence, the parametric study was performed on stub columns of SHS and CHS in constant column length. The European Code for aluminum structures uses the heat-affected zone (HAZ) softening factor to consider the weakening effects of transverse welds on column strength. The HAZ softening factors obtained from the parametric study were compared with the corresponding values specified in the European Code. HAZ softening factors were proposed in this study.     

Experimental investigation and design of aluminum columns with longitudinal welds

This paper presents an experimental investigation of longitudinally welded aluminum alloy I-section columns subjected to pure axial compression. The specimens were fabricated using 6061-T6 heat-treated aluminum alloy. The test program included 20 column tests which were separated into 2 test series of different types of welding sections. Each test series contained 10 columns. All the specimens were welded using the Tungsten Inert Gas welding method. The length of the specimens ranged from 442 to 2433 mm in order to obtain a column curve for each test series. The observed failure mode for the column tests includes mainly flexural buckling around the minor axis and the major axis by applying support except for one column (ZP1217-1) which buckled in the local zone and some columns which failed in the weld. The test strengths were compared with the design strengths predicted by the European Code and China Code for aluminum structures. The purpose of this paper is to present the tests results of two typically longitudinally welded I-section columns, and to check the accuracy of the design rules in the current specifications.     

纵向变厚度钢板焊接工字形截面受压短柱的局部稳定试验研究

纵向变厚度(LP)钢板是一种沿轧制方向具有不同厚度钢板的钢材,可用于优化结构的力学性能和提高材料利用率。为研究其局部稳定性能,设计了6根LP翼缘焊接工字形截面短柱,6根LP腹板焊接工字形截面短柱和4根传统等厚度焊接工字形截面短柱,并进行了轴向受压试验。试验研究中确定板临界屈曲荷载的两个主要屈曲准则,同时分析了破坏模式、荷载-侧向变形曲线、荷载-应变曲线和极限荷载,研究LP短柱的局部屈曲行为,得到试件更容易在LP钢板的薄端发生屈曲破坏。将试验结果与现有等厚度板设计规范计算结果进行比较可得,现有等厚度板的设计规范预测腹板变厚度短柱的极限荷载偏于危险,而对于翼缘变厚度短柱欧规EN 1993-1-5能较为准确预测,但需要进一步的数值模拟去验证,从而进一步提出修正公式或者修正系数来指导设计。     

Tragfähigkeit fehlerhafter Schweißnähte

Load bearing capacity of welds with defects. Only welds fabricated according to requirements in execution standards are within the scope of actual design codes. These execution standards do not tolerate imperfections like lack of fusion at the weld root even in case of predominantly static loading. In the recent years, steel products with increasing thicknesses are used for steel constructions. The volume of the weld and thus, the costs for welding increases with about the second power of the thickness. Therefore, partial penetration instead of complete penetration and joint preparations with small angles of bevel are applied, if design aspects allow this. As a consequence, lack of fusion at the weld root cannot always be avoided, especially if thick components are welded. There are no design rules for these welds with defects. Therefore, the effect of imperfections on the load bearing capacity of differently fabricated welds is investigated with tests, numerical and fracture-mechanical calculations.     

Tests and numerical study of ultra-high strength steel columns with end restraints

High strength steels with the nominal yield strength more than 460 MPa have begun to be applied in the construction of many steel structures, but there are short of sound researches on the major axis buckling behavior of such steel welded I-section columns, especially for the ultra-high strength steels having the nominal yield strength more than 690 MPa. In this paper, the experimental research is described on the overall buckling behavior about the major axis of ultra-high strength steel compression I-section columns with end restraints. In this research 8 columns made from 2 kinds of ultra-high strength structural steels S690 and S960, with nominal yield strengths of 690 MPa and 960 MPa, respectively, were tested. Based on the test results, the finite element analysis (FEA) model was validated to analyze this behavior of ultra-high strength steel columns, and the buckling strength of pin-ended columns fabricated from such steels were calculated by the verified FEA model, which were compared with the design buckling strengths according to the Eurocode 3, the American specification for structural steel buildings ANSI/AISC 360–05, and the Chinese codes for steel structures design GB50017-2003 respectively. It shows that the major axis nondimensional buckling strengths of the ultra-high strength steel compression columns, whose buckling curve is type b according to Eurocode 3 and GB50017-2003, are much higher than that calculated according to the column curve b, even higher than the curve a₀ in Eurocode 3 and the curve a in GB50017-2003 on average, and they are also higher than the design values according to ANSI/AISC 360–05. It is therefore indicated that the buckling strength about the major axis of the ultra-high strength steel I-section columns is improved a lot compared with the ordinary strength steel columns on a non-dimensional basis, and the column curve a₀ and curve a can be adopted to design this behavior in Eurocode 3 and GB50017-2003, respectively. Besides, there is no obvious difference between the major axis nondimensional buckling strengths of the pin-ended I-section columns fabricated from these two kinds of ultra-high strength steels: S690 and S960. These research works will provide the test basis to complete the buckling design method and theory of the ultra-high strength steel columns, and also be helpful for the application of ultra-high strength steel structures.