不锈钢螺栓连接中净截面失效的数值分析

不锈钢和碳素钢力学性能不同,但不锈钢连接设计规范只是在碳素钢规范基础上做一些修正。对于净截面承载力,欧洲不锈钢连接规范EN1993-1-4沿用欧洲冷弯碳素钢规范EN1993-1-3及SCI/Inox设计手册中的规定。对不锈钢连接净截面的破坏性能进行研究,建立奥氏体及马氏体不锈钢数值模型,用试验结果进行验证;并利用此模型对影响螺栓连接净截面破坏的主要参数进行研究,包括边缘距离e2和螺栓构造。通过研究不同e2和螺栓布置时净截面的应力分布,可发现不锈钢具有足够韧性,保证断裂前内力重分布。因此,提出基于EN1993-1-3的净截面承载力修正公式,并通过静力分析验证其可靠性。     

不锈钢节点板连接件数值分析

尽管不锈钢和碳素钢的力学性能有本质区别,然而,现行规范规定不锈钢连接设计时仍基本遵循碳素钢的设计准则,仅在此基础上稍作修改。对于常见的角钢单肢与加固板连接的情况,EN1993-1-4以及SCI/欧盟不锈钢设计手册对不锈钢的设计规定,直接采用了EN1993-1-8对碳素钢净截面承载力的设计规定,且未作任何修改。对单肢与加固板采用单排螺栓连接的L型不锈钢的净截面承载力进行了研究。建立奥氏体不锈钢的数值模型,并利用现有的试验结果对其进行了验证。这些模型随后用于进行参数研究。最后,基于研究结果对L型不锈钢净截面承载力的设计方程进行了修正,并通过统计分析验证了该方程可靠性。     

常温和高温下钢板螺栓连接的设计

通过自攻螺钉可以将冷弯压型钢板与钢屋架的上弦杆直接连接。常温下,无论是EN1993-1-8规范还是EN1993-1-3规范都可以直接作为此类连接的设计规范。此外,在EN1993-1-2规范中,没有针对火灾中螺栓连接的设计条文。利用ABAQUS软件,建立了一个单剪螺栓连接的三维有限元模型。通过试验证实此模型的有效性之后,采用该模型计算常温和高温下螺栓连接的极限承载力。并且,分析了边缘效应和末端距离对连接承载力的影响。根据EN1990规范,考虑了分项系数,在试验和有限元分析结果的基础上,确定承载力设计值。     

静剪切力作用下薄壁不锈钢板螺栓连接的有限元建模

最近的试验研究表明,日本现行钢结构设计标准(AIJ)不能准确预测薄壁(冷加工)SUS304不锈钢板的螺栓连接在静剪力作用下的极限状态,因此本文提出极限强度计算公式,说明不锈钢和薄壁钢板的机械特性。以现有试验数据作为参数研究的基础,采用ABAQUS程序对三维实体单元进行有限元分析,以探究薄壁不锈钢板中螺栓剪切连接的结构性能。采用材料非线性和几何非线性分析法以预测螺栓连接的荷载-位移曲线。试验中试件发生的卷曲等连接板端部的平面外变形在不考虑几何缺陷的有限元模型分析中同样可观察到;在对卷曲对极限强度的影响进行量化检验外,提出适合于预测螺栓连接破坏模式的破坏准则。此外,有限元分析结果与以前试验结果相比可知,破坏模式和有限元推荐步骤预测的极限强度与试验结果具有良好的相关性,数值方法可提供具有合理精度的评估。     

Q550钢材高强螺栓连接承压性能研究

高强螺栓承压型连接是钢结构中常用的节点连接方式,采用经验证可靠的Marc有限元计算模型对Q550高强度钢材高强螺栓承压型连接的承压性能进行数值模拟。分别对影响极限承载力的端距、边距、螺栓预紧力以及连接板件间的抗滑移系数等因素进行研究。研究结果表明:端距和边距二者共同影响Q550高强螺栓承压型连接的破坏模式和极限承载力,当端距和边距值分别取2. 0d0(d0为螺栓孔径)和1. 5d0时连接发生承压破坏并可以得到较高的承载力;对螺栓施加预紧力可以适当提高接头的极限承载力;抗滑移系数对极限承载力的影响不大。     

胶合木梁柱螺栓-钢填板节点转动性能研究

通过4组22个胶合木梁柱螺栓-钢填板足尺节点试件的单调和低周反复加载试验以及有限元数值模拟研究梁柱螺栓-钢填板节点的转动性能。试验研究表明,胶合木梁柱螺栓-钢填板节点性能主要取决于螺栓和螺孔周边木材的承压能力;节点加载初期的螺孔间隙和加载后期木材横纹裂缝张开均会导致节点刚度显著下降;同等条件下,节点初始刚度和极限弯矩随螺栓直径的减小而减小,节点初始刚度随螺栓边距的增加而减小。对试件进行有限元分析结果表明,基于有限元分析软件建立的节点三维实体模型对于节点的初始刚度和极限弯矩有较好的模拟精度(误差20%以内)。此外,模型参数分析表明,在更大取值范围内(螺栓直径12~28 mm,螺栓边距30~70 mm),螺栓直径和边距对节点性能的影响与试验结果一致。     

Study on rotational behavior of bolted glulam beam-to-columnconnections with slotted-in steel plates

通过4组22个胶合木梁柱螺栓-钢填板足尺节点试件的单调和低周反复加载试验以及有限元数值模拟研究梁柱螺栓-钢填板节点的转动性能。试验研究表明,胶合木梁柱螺栓-钢填板节点性能主要取决于螺栓和螺孔周边木材的承压能力;节点加载初期的螺孔间隙和加载后期木材横纹裂缝张开均会导致节点刚度显著下降;同等条件下,节点初始刚度和极限弯矩随螺栓直径的减小而减小,节点初始刚度随螺栓边距的增加而减小。对试件进行有限元分析结果表明,基于有限元分析软件建立的节点三维实体模型对于节点的初始刚度和极限弯矩有较好的模拟精度（误差20％以内）。此外,模型参数分析表明,在更大取值范围内（螺栓直径12~28mm,螺栓边距30~70mm）,螺栓直径和边距对节点性能的影响与试验结果一致。     

不同螺栓边距对角钢连接性能影响的研究

角钢在土木工程中应用广泛。为研究不同螺栓边距对角钢连接性能的影响,设计了角钢在不同螺栓边距下的连接试验,通过改变螺栓孔边距研究角钢螺栓连接的抗剪性能,建立ABAQUS有限元模型与试验结果对比验证。并运用有限元建模方法,改变角钢型号进行参数分析。结果表明,有限元分析的荷载-位移曲线、极限承载力和破坏模式与试验结果吻合较好,为做参数分析提供依据;对《钢结构设计手册》中螺栓边距进行修正,便于实际工程应用。     

AISC设计指南中不锈钢结构设计准则的进展

介绍了AISC(美国钢结构协会)设计指南中热轧和焊接不锈钢结构设计准则的进展。不锈钢性能与碳素钢类似的,设计指南仅简要引用了ANSI/AISC 360-10《美国钢结构建筑设计规范》的相关章节。AISC规范中设计准则用于不锈钢时计算结果不保守,给出了与AISC 360中等效表达式类似、适用于不锈钢的特定准则。通过大量构件和连接节点的试验结果对不锈钢设计准则进行了验证。为计算LRFD抗力系数,进行了可靠性分析;结果表明,在多数情况下,碳素钢的抗力系数也适用于不锈钢。     

双剪高强螺栓连接研究

对用3个或4个螺栓连接的受拉节点进行26组承载力试验,节点板所用钢材等级为S690。对试验进行数值模拟,研究螺栓间的剪力分布。对文献中由高强型钢制作的类似节点进行试验,并进行数值模拟。数值结果与试验数据非常吻合,以此对规范EN1993-1-8中的承载力公式进行评价。     

Bearing failure in stainless steel bolted connections

Although the mechanical behaviour of stainless steel and carbon steel differs significantly, design provisions for stainless steel connections in current standards are essentially based on the rules for carbon steel. For bolted connections, the design resistances in EN 1993-1-4 and the SCI/Euro Inox Design Manual for Structural Stainless Steel are based on those in EN 1993-1-8 and EN 1993-1-3 with only some minor modifications. In this paper, an investigation into the bearing behaviour of stainless steel connections between both thick and thin plates has been conducted. Numerical models for previously tested specimens in austenitic and ferritic stainless steel have been developed and validated. The validated models were then used to perform parametric studies to investigate the key variables affecting the bearing failure of bolted connections; these include edge distance e₂, end distance e₁ and plate thickness t. The investigation showed the deformation behaviour of stainless steel connections to be somewhat different from that of carbon steel connections, with stainless steel exhibiting pronounced strain hardening. However, the locations of fracture initiation obtained from the numerical models matched those observed during experimental studies of both carbon steel and stainless steel connections and this feature has been used as the basis for defining a consistent, strength based criterion of failure. The results of the parametric studies have been utilised as the basis for design provisions for bearing failure in stainless steel bolted connections that cover both the ultimate and the serviceability limit states and which are both more economic and more straightforward than the present EC3 provisions.     

Numerical investigation of net section failure in stainless steel bolted connections

Despite fundamental differences in the mechanical behaviour of stainless steel and carbon steel, design provisions for stainless steel connections in current standards essentially follow the rules for carbon steel with some limited modifications. For the case of net section capacity, the design rules from EN 1993-1-3 for cold-formed carbon steel have been adopted for stainless steel connections in EN 1993-1-4 and the SCI/Euro Inox Design Manual without any modification. In this paper, an investigation into the behaviour of stainless steel connections failing by net section rupture has been conducted. Numerical models for austenitic and ferritic stainless steel have been developed and validated against existing test results. The validated models were subsequently used to perform parametric studies to investigate the main parameters affecting the net section rupture of bolted connections; these include edge distance e₂ and bolt configuration. By studying the stress distribution along the net section for different edge distances and bolt arrangements, it was found that the ductility of stainless steel is sufficient to ensure extensive redistribution of stresses prior to fracture. Hence, a revised design equation (based on that given in EN 1993-1-3) for net section capacity of stainless steel connections has been proposed and its reliability demonstrated by means of statistical analysis.     

Design of screwed steel sheeting connection at ambient and elevated temperatures

Cold-formed profiled steel roof sheeting can be directly connected to the top chord of a steel roof truss through self-tapping screws. At ambient temperatures, neither EN 1993-1-8 nor EN 1993-1-3 can be used directly for this type of connection. Besides, no design rules are available in EN 1993-1-2 for designing screwed connections in fire. A 3D Finite Element (FE) model for a single-lap shear screwed connection is developed using ABAQUS software. After the validation by tests, the model is used to predict the ultimate resistance of connections at both ambient and elevated temperatures. Further, the effects of edge and end distances on the connection resistance are investigated. Based on the analyses results, revised design equations for predicting the connection resistance are proposed. The design resistance is calibrated by testing and FE analyses results according to the procedure given in EN 1990 and the partial safety factor is derived.     

Numerical modelling of concrete-filled lean duplex slender stainless steel tubular stub columns

Major technological advances in materials processing have led to the development of duplex stainless steels with exceptional mechanical properties. Duplexes have great potential for expanding future structural design possibilities, enabling a reduction in section sizes leading to lighter structures. The duplex grades offer combination of higher strength than austenitics as well as a great majority of carbon steels with similar or superior corrosion resistance. However, high nickel prices have more recently led to a demand for lean duplexes with low nickel content, such as grade EN 1.4162. Extensive work is needed to include the lean duplex grade EN 1.4162, into design standards such as EN 1993-1-4 and ENV 1994-1-1. Accordingly, finite element modelling for concrete-filled lean duplex slender stainless steel tubular stub columns of Grade EN 1.4162 is presented in this paper. The paper is predominantly concerned with two parameters: cross-section shape and concrete compressive strength, which have not yet been investigated. The non-linear displacement analysis of the columns was constructed herein based on the confined concrete model provided by Hu et al. (2003) [15]. The behaviour of the columns was investigated using a range of concrete cylinder strengths (25–100 MPa). The overall depth-to-width ratios (aspect ratio) varied from 1.0 to 1.8. The depth-to-plate thickness ratio of the tube sections varied from 60 to 90. The concrete-filled lean duplex slender stainless steel tubular columns were subjected to uniform axial compression over the concrete and stainless steel tube to force the entire section to undergo the same deformations by blocking action. The ABAQUS 6.6 program, as a finite element package, is used in the current work. The results showed that the design rules specified in the ASCE are highly conservative for square and rectangular concrete-filled lean duplex slender stainless steel stub columns while they are conservative in the case of European specifications. A new design strength is, therefore, proposed that is accurately found to represent the behaviour of concrete-filled lean duplex stainless steel tubular stub columns.     

Interaction of bending and axial compression of stainless steel members

The paper deals with the buckling behaviour of stainless steel members with the main focus on developing design formulae for use in the latest version of the European Standard EN 1993-1-4: Eurocode 3-Design of steel structures-Part 1-4: General rules — Supplementary rules for stainless steel. Brussels; 2005.It is based on numerical simulations of single span members of various section type, which are subjected to axial compression and bending. Both flexural buckling and lateral-torsional buckling are dealt with so that the buckling behaviour of both I-sections and hollow sections can be covered.On the basis of these numerical results interaction factors have been derived in context with the design model for member design in Eurocode 3-1-1. For statistical evaluation the test results available from other authors have been used.The outcome of this investigation has been incorporated in the present EN 1993-1-4 as a recommendation in restricted form.     

Elevated temperature material properties of stainless steel alloys

Appropriate assessment of the fire resistance of structures depends largely on the ability to accurately predict the material response at elevated temperature. The material characteristics of stainless steel differ from those of carbon steel due to the high alloy content. These differences have been explored in some detail at room temperature, whilst those at elevated temperature have been less closely scrutinised. This paper presents an overview and reappraisal of previous pertinent research, together with an evaluation of existing elevated temperature stainless steel stress-strain test data and previously proposed material models. On the basis of examination of all available test data, much of which have been recently generated, revised strength and stiffness reduction factors at elevated temperatures for a range of grades of stainless steel have been proposed, including four grades not previously covered by existing structural fire design guidance. A total of eight sets of strength reduction factors are currently provided for different grades of stainless steel in EN 1993-1-2 and the Euro Inox/SCI Design Manual for Structural Stainless Steel, compared to a single set for carbon steel. A number of sets of reduction factors is appropriate for stainless steel since the elevated temperature properties can vary markedly between different grades, but this has to be justified with sufficient test data and balanced against ease of design — it has been proposed herein that the eight sets of reduction factors be rationalised on the basis of grouping grades that exhibit similar elevated temperature properties. In addition to more accurate prediction of discrete features of the elevated temperature material stress-strain response of stainless steel (i.e. strength and stiffness reduction factors), a material model for the continuous prediction of the stress-strain response by means of a modified compound Ramberg-Osgood formulation has also been proposed. The proposed model is less complex than the current provisions of EN 1993-1-2, more accurate when compared to test results, and the model parameters have a clear physical significance.     

Design of screwed steel sheeting connection at ambient and elevated temperatures

Cold-formed profiled steel roof sheeting can be directly connected to the top chord of a steel roof truss through self-tapping screws. At ambient temperatures, neither EN 1993-1-8 nor EN 1993-1-3 can be used directly for this type of connection. Besides, no design rules are available in EN 1993-1-2 for designing screwed connections in fire. A 3D Finite Element (FE) model for a single-lap shear screwed connection is developed using ABAQUS software. After the validation by tests, the model is used to predict the ultimate resistance of connections at both ambient and elevated temperatures. Further, the effects of edge and end distances on the connection resistance are investigated. Based on the analyses results, revised design equations for predicting the connection resistance are proposed. The design resistance is calibrated by testing and FE analyses results according to the procedure given in EN 1990 and the partial safety factor is derived.     

Finite element investigation of shear failure of lean duplex stainless steel plate girders

The use of duplex stainless steel material has gained popularity in the last two decades thanks to its nature that combines well the advantages of both austenitics and carbon steel materials. The duplex grades offer a combination of higher strength than austenitics in addition to a great majority of carbon steels with similar or superior corrosion resistance. However, high nickel prices have more recently led to a demand for lean duplexes with low nickel content, such as grade EN 1.4162. Wide-ranging work is needed to include the lean duplex grade EN 1.4162, into design standards such as EN 1993-1-4. Accordingly, a finite element modelling for full-size lean duplex stainless steel plate girders of non-rigid end stiffeners of Grade EN 1.4162 is presented in this paper. The paper is principally concerned with shear failure mechanism characteristics of this type of plate girders, which is not yet investigated. The ABAQUS 6.6 programme, as a finite element package, is used in the current work. The lean duplex stainless steel material is simulated here based on an accepted stainless steel material model available in the literature. A number of transversely stiffened I-section plate girders having equal depth of 1000 mm in span of 4 m is considered and parametric studies regarding flange width-to-web depth ratio, flange-to-web thickness ratio and web plate slenderness are carried out. However, new conclusions on shear strength of lean duplex stainless steel plate girders are presented.