木结构钢板螺栓连接节点承载力计算分析及试验研究

为便于木结构工程设计,提出了钢板螺栓连接承载力计算式,并提出了受弯螺栓连接节点承载力上限和下限的计算方法。设计制作了钢填板螺栓连接节点试件,并进行了复合受力节点承载力试验研究。试验结果表明,各受力工况下试验节点的承载力平均值均介于所计算的承载力上、下限之间,且基本等于所计算的承载力上、下限的平均值。从而验证了所提出的钢板螺栓连接承载力计算式和连接节点承载力计算方法的正确性和适用性,为设计提供了可靠依据。     

常温和高温下冷成型薄钢板抗剪连接件的性能

冷成型钢屋面板可以通过粉末冶金射钉或自攻螺钉直接与钢桁架上弦杆连接。对常温和高温下射钉和螺栓连接的剪切性能进行了试验研究和有限元分析。螺栓连接的研究中对承载能力的4个部分(包括薄钢板与螺杆间的承载能力、垫圈与薄钢板之间摩擦力、薄板与厚板之间的摩擦力、薄板倾斜的承载力)进行了定性和定量分析。射钉连接的研究表明,垫圈、射钉、薄板材和支承板之间具有较强的相互作用。在射钉推入过程中出现的隆起,将导致材料中厚钢板承载力提高,对连接的承载能力提高有积极作用。     

钢结构螺栓连接的有限元数值模拟

螺栓连接是钢结构连接的主要方式之一,具有施工简单、拆装方便等优点。现行钢结构规范中对螺栓连接的计算都是在一定的假设条件下进行的。本文以钢结构规范中的计算公式为基础,运用有限元数值分析的方法,采用ABAQUS来分析普通螺栓群在受剪和受拉条件下的各个螺栓的受力情况。将有限元软件模拟的结果与公式计算结果进行比较,证明规范公式的正确性。文中分别模拟分析了普通螺栓群在受剪的情况下承受轴心力、扭矩,和普通螺栓群在受拉的情况下承受拉力、弯矩的受力情况。     

拉力作用下高强螺栓连接的有限元模拟

采用大型有限元分析软件ANSYS，对钢结构高强度螺栓连接的受力分布规律进行了计算和分析，得出了该构件堂警窖分布图，从理论上对高强度螺栓连接的破坏形式和受力变化进行了分析研究，为进一步改进高强螺栓连接构件的受力状况和结构设计提供了必要的理论依据。     

高强度螺栓连接在高温下极限承载力的试验研究

高强度螺栓连接在高温环境下力学性能及极限承载力的研究文献不多,《钢结构设计规范》(GB50017-2003)也尚未涉及。以8.8级高强度螺栓连接为对象,通过试验研究了在不同温度环境下,螺栓的抗剪、抗拉极限承载能力,总结了承载力与环境温度之间的相互关系。     

循环荷载下高强度螺栓连接摩擦系数试验研究

高强度螺栓摩擦型连接在承受循环剪力时,螺栓拉力和接触面的摩擦系数会随加载过程发生变化,因此,使用抗滑移系数进行分析和设计不安全.为研究高强度螺栓受剪连接中未处理轧制表面直接接触、轧制表面间垫设紫铜片以及螺栓垫圈与轧制钢板接触的摩擦系数,对不同栓杆直径、不同孔形的4组(12个)高强度螺栓连接试件开展了循环加载试验和有限元数值模拟研究,分析了循环荷载下连接滑移过程中高强度螺栓拉力及摩擦系数的变化情况,以及数值模拟中摩擦系数的取值方法.结果 表明:改变螺栓直径或孔型对未处理轧制表面直接接触的摩擦系数影响较小;增大螺栓直径,螺栓垫圈与轧制钢板接触的摩擦系数显著降低;采用大螺栓孔时,轧制表面间垫设紫铜片对摩擦系数有一定幅度提高;有限元模拟中,双剪试件输入摩擦系数结果与试验结果较为吻合,而单剪试件输入抗滑移系数结果与试验结果吻合程度更高.     

铝合金结构螺栓连接的抗剪计算方法

铝合金建筑结构在工程中的应用已逐渐增多,但对于铝合金结构螺栓连接的计算方法还缺乏系统的研究,相关的规程规范还有待于完善。本文采用有限元数值计算方法探讨了铝合金螺栓连接的受剪破坏模式,并采用已有试验资料对计算模型进行了验证,研究了在各种连接长度的情况下,剪力在各个螺栓之间的分布规律,并与钢结构螺栓连接的情况进行了对比。在参数分析的基础上,本文建议了螺栓连接的抗剪计算公式,并给出了长连接的抗剪承载力折减系数。     

摩擦型高强螺栓抗剪连接的螺栓单排数量和间距因素分析

在已有试验结果的基础上合理地建立数值模型,对摩擦型高强螺栓的抗剪连接性能进行分析计算,探讨螺栓的数量、间距等对滑移荷载的影响。     

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.     

高温下耐火钢材梁柱抗弯连接的应用

介绍了使用耐火钢材的一个新方法,以提高钢结构中梁柱抗弯连接的耐火性。按照ISO-834标准,对两个足尺梁柱抗弯连接构件在高温条件下进行试验,以验证该方法的可行性。此外,采用一个详尽的三维有限元模型模拟梁柱抗弯连接在火中的结构性能。耐火试验结果表明:该方法可以有效延长构件的耐火时间,减小结构变形,同时提高梁柱抗弯连接破坏时的临界温度。三维有限元分析得到的数值结果也与试验结果具有很好的一致性。     

高温下受约束钢梁的一般非线性模型

基于一般钢截面的弹塑性非离散半解析公式,提出一个新颖的数值方法,对受约束钢梁在高温下的非线性性能进行描述。模型与较大的变形位移效应以及材料的非线性相结合,用于评估曝露在室内火荷载下钢梁的性能。在温度增加时,模型考虑了屈服和悬链线作用。公式中考虑了梁截面受各种热作用情况下沿梁长方向的热梯度影响。采用经验函数,对随着温度的变化所引起的刚度退化和屈服强度进行模拟,这种方法隶属于工程力学中传统边界值问题。研究中所提出的方法与ABAQUS有限元模拟结果吻合,所提出的计算公式优于商业有限元软件包,公式可用于结构设计和评估平台。     

升温下钢构件的强度设计标准

通过与非线性有限元模拟比较,对结构钢构件在升温下的设计公式进行了评估。比较美国钢协与欧洲标准委员会对温度在800℃侧向无支撑的Ⅰ型柱、梁、柱-梁的设计规定。欧洲规范3的规定与有限元模拟的结果相差10%～20%。另一方面,美国钢协的规范预测的强度与模拟结果相差高达2倍。对于温度超过300℃的中细构件,相差最大。提出了对美国钢协规范计算公式的修正建议,修正后的精度与模拟的结果误差在20%～30%。最后讨论了结构防火工程基于构件评估的局限性、未来的研究以及发展方向。     

高强钢S690的高温力学性能

由于火灾下钢结构力学性能退化将导致承载能力减小,因此将其作为钢结构设计的主要内容。为了解高强钢S690高温下的力学性能,使用稳态和瞬态方法对温度范围20～700℃的试样进行了试验研究。将试验结果与欧洲、美国、澳大利亚和英国设计规范进行对比,结果显示,现有规范均无法安全指导S690钢结构的耐火性设计。因此,研究高温下S690的力学性能具有重要意义。     

高温下冷弯薄壁型钢的力学性能分析

由于火灾中冷弯薄壁型钢结构的力学性能参数(如:屈服强度和弹性模量)的急剧下降,引起承载力的下降,使得力学性能成为冷弯薄壁型钢结构设计的重要指标。因此需要掌握高温下冷弯薄壁型钢的力学性能(屈服强度和弹性模量)。尽管有高温下冷弯薄壁型钢力学性能的相关试验数据,但是该数据不能涵盖各种不同等级和厚度的冷弯薄壁型钢。针对在澳大利亚经常使用的两种厚度的高强和低强冷弯薄壁型钢进行高温试验研究。拉伸试验的温度控制在20～700℃。将试验结果与已知的降低屈服强度、弹性模量和应力-应变曲线的因素进行比较,以确定哪个因素可以被提高。在昆士兰工科大学,很多不同的冷弯型薄壁型钢的试验结果用于同样类似的研究中。改进后的方程用于分析一定范围内不同等级和厚度的冷弯型钢屈服强度和弹性模量降低的因素及应力-应变曲线。给出试验结果及与之前研究结果的比较、钢的设计标准和新的计算方程。     

钢拱架在升温状态下的非线性弹塑性分析

提出了一种新型的非离散化方法,用于分析钢拱架在升温状态下的性能。钢拱架中单轴对称的横截面上具有弹性和塑性区域,经受着任意方向的热效应,如沿拱的长度方向和沿横截面的深度方向。公式中考虑了高温时可能产生的几何及材料非线性,以及潜在的悬链线效应的影响。采用ABAQUS对几何模型进行了非线性分析,通过与分析结果的对比验证了该模型的有效性与准确性。所提出的方法也给出了一些重要参数,如温度加载时钢拱架横截面底部纤维的温度分布,横截面顶部纤维与底部纤维的温差。所提出的模型也使有限元程序能更加准确地进行计算,并为钢拱架的抗火设计提供了一个计算的平台。     

Design of high strength steel columns at elevated temperatures

The main objective of this paper is to study the behaviour and design of high strength steel columns at elevated temperatures using finite element analysis. In this study, equations predicting the yield strength and elastic modulus of high strength steel and mild steel at elevated temperatures are proposed. In addition, stress-strain curve model for high strength steel and mild steel materials at elevated temperatures is also proposed. The numerical analysis was performed on high strength steel columns over a range of column lengths for various temperatures. The nonlinear finite element model was verified against experimental results of columns at normal room and elevated temperatures. The effects of initial local and overall geometrical imperfections have been taken into consideration in the analysis. The material properties and stress-strain curves at elevated temperatures used in the finite element model were obtained from the proposed equations based on the material tests. Two series of box and I-section columns were studied using the finite element analysis to investigate the strength and behaviour of high strength steel columns at elevated temperatures. Both fixed-ended stub columns and pin-ended slender columns were considered. The column strengths predicted from the finite element analysis were compared with the design strengths predicted using the American, European and Australian specifications for hot-rolled steel columns at elevated temperatures by substituting the reduced material properties. In addition, the direct strength method, which was developed for the design of cold-formed steel columns at normal room temperature, was also used in this study to predict the high strength steel column strengths at elevated temperatures. The suitability of these design rules for high strength steel columns at elevated temperatures is assessed. Generally, it is shown that the American and European specifications as well as the direct strength method conservatively predicted the column strengths of high strength steel at elevated temperatures. The European Code predictions are slightly more conservative than the American Specification and the direct strength method predictions.     

Corner properties of cold-formed steel sections at elevated temperatures

This paper presents the mechanical properties of the corner parts of cold-formed steel sections at elevated temperatures. Light-gauge structural members are cold-formed which results the mechanical properties of the corner parts being different from the flat parts. However, previous research has focused on the investigation of the corner parts of cold-formed steel sections at normal room temperature and the performance of the corner parts at elevated temperatures is unknown. An appropriate model for fire resistant design of steel structures necessitates a correct representation of mechanical properties of structural steel at elevated temperatures. Therefore, experimental investigation on corner coupon specimens at different temperatures ranged from approximately 20 to 1000 °C was conducted to study the behaviour of the corner parts of cold-formed steel sections at elevated temperatures. Two kinds of corner coupon specimens, namely the inner corner coupon specimens and outer corner coupon specimens having the steel grade of G500 (nominal 0.2% proof stress of 500 MPa) and nominal thickness of 1.9 mm were tested. The test results were compared with the flat coupon specimens taken from the same cold-formed steel sections as the corner coupon specimens. A unified equation to predict the yield strength (0.2% proof stress), elastic modulus, ultimate strength and ultimate strain of the corner parts of cold-formed steel sections at elevated temperatures is thus proposed in this paper. Generally, it is shown that the proposed equation adequately predicts the test results of the corner coupon specimens. Furthermore, stress–strain curves at different temperatures are plotted and a stress–strain model is also proposed for the corner parts of cold-formed steel sections.