高强度螺栓连接抗剪性能研究

为解决试验和实体模型有限元方法在研究高强度螺栓连接抗剪性能上的局限性,寻找一种简单准确的高强度螺栓连接抗剪性能的简化模型十分必要。采用通用有限元软件ABAQUS建立高强度螺栓连接的非线性有限元模型,对单元选取、螺栓受力行为、材料本构以及接触模型等方面进行详细说明;结合典型高强度螺栓抗剪试验,验证了所建立有限元模型的准确性和适用性,对高强度螺栓连接抗剪性能进行深入探讨。通过参数分析,确定了高强度螺栓连接抗剪简化模型的3个特征点,提出了此类螺栓抗剪简化模型以及循环荷载作用下的滞回模型。实例计算分析表明：建议的抗剪简化模型以及循环荷载作用下滞回模型能准确地模拟此种连接的受力性能,其构造形式简单,计算准确,为工程分析提供依据。     

论高强度螺栓连接的分类和抗拉连接的计算

高强度螺栓连接分为摩擦型和承压型两类,是依照受剪螺栓连接的两种不同极限状态划分的。《钢结构设计规范》(GB 50017—2003)(简称03规范)不恰当地把受拉螺栓连接也纳入这两种分类,造成混乱。对此进行讨论,并提出改变分类的建议。受拉螺栓连接中螺栓通常要承受撬力。03规范不直接计算撬力,而是采用降低螺栓抗拉承载力设计值的方法,计算不够精确。《钢结构高强度螺栓连接技术规程》(JGJ 82-2011)虽然给出撬力计算方法,但存在值得商榷之处。在分析的基础上推出撬力的简化计算公式,并提出梁、柱之间抗弯连接的计算方法。最后,还提出了提高高强度螺栓抗拉承载力设计值的建议。     

中欧钢结构规范螺栓连接承载力比较

根据欧洲钢结构设计规范的EN1993-1-8∶2005和GB50017-2003《钢结构设计规范》及JGJ82-2011《钢结构高强螺栓连接技术规程》对单个螺栓的设计承载力进行比较,包括抗剪连接、抗拉连接、剪拉连接和抗滑移连接的单栓承载力。比较分析可知:国标与欧标钢结构设计规范中的抗剪螺栓连接承载力二者基本一致;欧标的高强螺栓预拉力取值比中国的约高10%;抗拉螺栓连接与剪拉螺栓连接主要区别在于螺栓的抗拉承载力如何考虑撬力的影响。     

钢结构抗拉高强度螺栓设计方法比较分析

抗拉高强度螺栓具有强度高,施工便捷,且避免现场焊缝带来的不利影响等优点,在钢结构连接节点中广泛采用.目前我国现行《钢结构设计规范》(GB 50017—2003)、《钢结构高强度螺栓连接技术规程》(JGJ82—2011)关于抗拉高强度螺栓拉力计算模型及撬力计算的设计方法略有差异,一些文献对以上两规范的抗拉高强度螺栓拉力及撬力计算方法进行了研究分析.针对以上抗拉高强度螺栓设计方法的特点及异同进行了比较分析,并通过有限元、试验、算例结果进行比较验证.研究结果可给工程设计人员提供直观的参考.     

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。     

中美摩擦型连接高强度螺栓承载力计算方法对比分析

对比分析了中美两国常用摩擦型连接高强度螺栓的力学性能,以及两国摩擦型连接高强度螺栓抗剪承载力和剪拉承载力的设计方法。探讨了按AISC 360-2010《美国钢结构设计规范》对中国高强度螺栓进行设计时的预拉力转换问题,根据两种规范的比较结果,提出了预拉力转换建议。根据中美两国规范的计算方法,讨论得出抗剪承载力和剪拉承载力比较结果,供设计人员参考。     

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。     

各国规范高强度螺栓抗剪连接设计方法比较分析

高强度螺栓抗剪连接作为钢结构连接的一种有效方法得到了广泛的应用,而各国规范对高强度螺栓抗剪连接设计方法的规定有所差异。尤其是随着高强度钢材在实际工程中的推广和应用,各国规范规定的适用性有待进行深入探讨。本文对中国钢结构设计规范GB50017-2003、欧洲钢结构设计规范Eurocode 3、美国钢结构设计规范ANSI/AISC360-05、英国钢结构设计规范BS5950和澳大利亚钢结构设计规范AS4100中高强度螺栓抗剪连接设计方法进行对比,其中包括承压型连接和摩擦型连接,并给出了相关实例计算。     

工程起重机械高强度螺栓计算方法

为提高螺栓连接设计的可靠性,针对工程起重机械行业普遍采用的高强度螺栓,分析摩擦型高强度螺栓与承压型高强度螺栓两种连接类型的性能、特点及抗拉、抗剪承载力设计值的计算方法,并对两种类型螺栓连接的计算方法进行研究和分析,以实际算例验证了计算方法的有效性。     

考虑孔周应力集中的摩擦型高强度螺栓抗滑移性能分析与设计方法研究

抗滑移性能是摩擦型高强度螺栓受剪连接的重要力学性能之一。为研究抗滑移性能的影响因素,设计并完成了单个高强度螺栓抗滑移性能试验和高强度螺栓群抗滑移性能试验,连接试件均为双面剪切且表面进行了抛丸处理。基于试验结果,建立了准确、可靠的有限元验证模型,据此对高强度螺栓受剪连接进行了参数分析,主要研究参数包括：螺栓预紧次序、连接板件厚度、垂直于内力方向的螺栓间距与边距以及顺内力方向的螺栓间距与边距。分析结果表明：连接板件最危险截面的塑性区分布对摩擦型高强度螺栓的抗滑移性能有着显著影响,设计时应考虑孔周应力集中现象对抗滑移承载力的折减;不同的截面受力情况对应的孔周应力集中系数存在明显差异。通过计算分析给出了螺栓抗滑移承载力折减系数建议值。相关研究成果可为摩擦型高强度螺栓受剪连接的设计提供改进思路。     

钢管混凝土柱螺栓连接钢梁节点的抗震性能分析

为了改进施工过程,同时确保房屋的抗震性能,提出了一种新型的连接类型,用于钢管混凝土柱和钢梁的连接处设计。该连接具有外伸端板的特性,出厂前与钢梁焊接在一起,然后在现场用高强钢将其与钢管混凝土柱螺栓连接。对这种螺栓连接端板节点的抗震性能进行试验研究,并通过对3个足尺节点模型进行试验,评估了混凝土楼板和削弱型梁截面对其的影响。试验结果表明:楼板对节点强度的作用显著,削弱型梁截面能有效地将屈曲区域转移到远离焊接点的位置。同时,螺栓连接端板节点的分析模型也采用OPENSEES1.7.3模拟了试验结果。     

Seismic behavior of exterior connections with steel beams bolted to CFT columns

In order to improve the constructability and meanwhile ensure satisfactory seismic behavior, an innovative type of connection for concrete filled circular steel tube (CFT) column-to-steel beam composite structures was conceived and studied. The proposed connection details are characterized by an extended endplate that is welded to a steel beam in factory and then bolted to a CFT column using high-strength steel rods in the field. An experimental investigation on seismic behavior of the proposed bolted endplate connection and evaluation of the effect of concrete floor slabs and reduced beam sections was conducted by testing three full scale joint models. The experimental results indicated that the presence of floor slabs contributed to the strength of joints significantly and reduced beam sections were effective in moving the buckling zone away from the welds. Analytical models for the bolted endplate connections were also constructed using OPENSEES1.7.3 to simulate the experimental results.     

Shear slotted bolted connection

Slotted bolted connections (SBCs) have been developed and used as an axial friction damper in braced frames since 1980s. To employ the benefits of SBCs in moment resisting frames (MRFs), rotational slotted bolted connections have been developed more recently with limited application in members that flexural behavior is dominated to shear. In this paper, shear slotted bolted connection (SSBC) is introduced as a new type of friction dampers to employ the benefits of SBCs in lateral load resisting systems with predominant shear behavior members that dissipate energy by traditional yielding mechanisms. The SSBC is a modified bolted connection that dissipates energy through friction in which friction is activated by shear force. The applications of the proposed system as a shear link in link beams of eccentrically braced frames (EBFs), in the beams of MRFs, and coupling beams of coupled concrete shear walls are introduced. To show the efficiency of SSBC, an existing EBF with tubular link beam is equipped with SSBC, and its behavior is studied via models created in general purpose finite element program ABAQUS (SIMULIA, The Dassault Systèmes, Realistic Simulation, RI, USA) verified thoroughly against relevant test results. Also, three MRFs with different beam lengths are modified using SSBC, and their monotonic and cyclic behavior are investigated using validated finite element models. The results show that, as expected, SSBC is capable of working as a mechanical shear fuse dissipating energy effectively in both MRFs and EBFs without any material yielding.     

Behaviour of flush end plate joints to concrete-filled steel tubular columns

This paper presents the results of an experimental program for bolted moment connection joints of circular or square concrete filled steel tubular (CFST) columns, and H-shaped steel beams using high-strength blind bolts. In order to investigate the static performance and failure modes of the blind bolted connection, an experimental program was conducted involving four sub-assemblages of cruciform beam-to-column joints subjected to monotonic loading. Moment-rotation relationships of the tested connections were obtained and their performance was evaluated in terms of their stiffness, moment capacities and ductility. The test parameters varied were the column section type and the thickness of the end plate. The results showed that the proposed blind bolted connection, which behaves in a semi-rigid and partial strength manner according to the EC3 specification, displays reasonable strength and stiffness. The rotation capacity of this type of connection to square or circular CFST columns exceeds 70 mrad and this satisfies the ductility requirements for earthquake-resistance in most aseismic regions. The blind bolted connection is shown to be a reliable and effective solution for moment-resisting composite frame structures.     

火灾后栓接Q690角钢净截面受拉承载力研究

对栓接Q690角钢在火灾后的净截面受拉承载力展开研究,参考过火后高强钢Q690材性试验结果,利用ABAQUS建立栓接Q690角钢的有限元模型,分析面外偏心距、螺栓连接长度、过火温度对火灾后栓接Q690角钢净截面受拉承载力的影响; 将已有相关公式及规范公式的计算结果与模拟得到的角钢支撑受拉极限荷载进行比较; 基于最小二乘法,提出了Q690角钢净截面受拉承载力的有效截面系数公式,对比了数值结果及其他文献试验结果; 基于数值模拟数据库,进行了可靠度分析。结果表明:有效截面系数随着螺栓连接长度的增大而增大,随着面外偏心距的增大而减小,而过火温度对有效截面系数几乎没有影响; 美国规范AISC 360-16对不同过火温度下Q690角钢净截面受拉承载力预测结果偏于不安全,中国现行《钢结构设计标准》预测结果偏于离散; 提出的计算公式对于不同过火温度下的栓接Q690角钢净截面受拉承载力均能进行较好预测; 推荐所提出公式计算火灾后栓接Q690角钢净截面受拉承载力的抗力分项系数为1.061。     

Shear Behaviour of Novel T-Stub Connection between Steel Frames and Precast Reinforced Concrete Shear Walls

The paper investigates the performance of a new connection between steel frames and precast reinforced concrete shear walls subjected to cyclic and monotonic loading. The connection is designed as a typical bolted T-stub connection to ensure the reasonable load-transferring mechanics and integrity of the two main components. In the study, two experimental programs with two 1/3-scale specimens tested under the monotonic and cyclic loading are performed to examine the performance of the proposed connection. Furthermore, finite element analysis on the behavior of the bolted T-stub connection is conducted using software ABAQUS and finite element models are created corresponding to the experimental specimens. The results of finite element analysis are verified against those obtained from the experiment. With the findings, behavioral aspects of the bolted T-stub connection are evaluated including failure modes, load-displacement curves, ductility, stiffness, and energy dissipation capacity. The results demonstrate that the bolted T-stub connection presents the favorable monotonic and cyclic performances to meet the requirements of the codes in China. The parametric analysis is then performed to demonstrate the effects of several parameters on the performance of the connection including friction coefficient, bolt preload, thickness of the steel plate embedded in the wall, and diameter of the bolt. The research also provides essential data for the application of the bolted Tstub connection in the engineering projects.     

Finite element modeling of bolted connections in thin-walled stainless steel plates under static shear

The recently performed experimental study indicates that the current Japanese steel design standards (AIJ) cannot be used to predict accurately the ultimate behavior of bolted connections loaded in static shear, which are fabricated from thin-walled (cold-formed) SUS304 austenite stainless steel plates and thus, modified formula for calculating the ultimate strength to account for the mechanical properties of stainless steel and thin-walled steel plates were proposed. In this study, based on the existing test data for calibration and parametric study, finite element (FE) model with three-dimensional solid elements using ABAQUS program is established to investigate the structural behavior of bolted shear connections with thin-walled stainless steel plate. Non-linear material and non-geometric analysis is carried out in order to predict the load–displacement curves of bolted connections. Curling, i.e., out of plane deformation of the ends of connection plates which occurred in test specimens was also observed in FE model without geometric imperfection, the effect of curling on the ultimate strength was examined quantitatively and the failure criteria which is suitable to predict failure modes of bolted connections was proposed. In addition, results of the FE analysis are compared with previous experimental results, failure modes and ultimate strengths predicted by recommended procedures of FE showed a good correlation with those of experimental results and numerical approach was found to provide estimates with reasonable accuracy.     

Post tensioned tendons for seismic retrofitting of weak bolted T-stub connections

Current design philosophy for conventional steel moment resisting frames (MRFs) in high seismic regions is that the frames should not collapse for major earthquakes. However, significant structural damage and residual drift due to inelastic deformations in beams and columns may cause loss of building occupancy or operation after major earthquakes. On the other hand, Selecting the optimum technique for rehabilitation of existing structures with weak connections has been a challenge for engineers in the recent years. In this study, the authors proposed using post-tensioned tendons for rehabilitation of bolted Tstub connections with weak bolts or weak T-stub flange as well as a technique for changing pinned connections to moment connections. Six corner connection specimens are made and tested under SAC cyclic loading protocol. The results of this study show that this rehabilitation technique not only modifies the cyclic behavior of weak rigid connections and changes simple bolted connections into moment connections, but also it improves the behavior of the rehabilitated connections in a way that their behavior is more desirable than that of the reference rigid connection designed according to AISC. For example, flexural capacity and rotational stiffness of the retrofitted connections are higher than those of the reference connection by 18 and 26% in average respectively. Besides, rehabilitation using post tensioned tendons add self-centering ability to the retrofitted connection that has a major role in preventing permanent deformations in frame and thus, the possibility of using frictional dampers in self-centering frames for increasing the energy absorption capacity is provided. This rehabilitation technique in bolted connection with weak T-stub flange has better cyclic behavior compared to that of a connection with weak bolts, since the T-stub participates in energy absorption and higher energy absorption is reached.     

胶合木梁柱角钢混合连接静力与抗震性能试验研究

为解决传统的木结构销栓连接刚度低、震后可恢复功能弱等问题,将钢结构梁柱翼缘角钢连接方法应用于木结构,提出了一种胶合木梁柱角钢混合连接形式。为研究此类木结构节点的静力与抗震性能,对节点试件进行了单调与低周反复荷载试验。研究结果表明：当梁柱截面尺寸分别为135mm×420mm和150mm×350mm,连接角钢规格为∟180×110×12时,胶合木梁柱角钢混合连接的极限弯矩达到95.3kN·m,最大转角接近0.096rad,初始刚度达4073kN·m/rad。低周反复荷载作用下,混合连接的变形能力与延性良好,梁端弯矩-转角滞回曲线呈反“S”形,角钢屈服后的大变形使其短肢底部与柱面产生了明显的分离,滞回曲线出现捏缩效应;角钢的短肢翘曲严重,从而使混合连接的耗能能力和等效黏滞阻尼系数均下降。     

State-of-the-art on resistance of bearing-type bolted connections in high strength steel

With the recent development of material science, high strength steel (HSS) has become a practical solution for landmark buildings and major projects. The current codes for design of bearing-type bolted connections of steel constructions were established based on the research of conventional steels. Since the mechanical properties of HSS are different from those of conventional steels, more works should be done to develop the appropriate approach for the design of bearing-type bolted connections in HSS. A review of the research carried out on bearing-type bolted connections fabricated from conventional steel and HSS is presented. The up-to-date tests conducted at Tongji University on four connection types fabricated from three grades of HSS with nominal yield strengths of 550, 690, and 890 MPa are presented. The previous research on failure modes, bearing resistance and the design with consideration of bolt hole elongation are summarized. It is found that the behavior of bolted connections in HSS have no drastic difference compared to that of conventional steel connections. Although the ductility is reduced, plastic deformation capacity of HSS is sufficient to ensure the load redistribution between different bolts with normal construction tolerances. It is also found that behavior of each bolt of multi-bolt connections arranged in perpendicular to load direction is almost identical to that of a single-bolt connection with the same end distance. For connections with bolts arranged in parallel to load direction, the deformation capacity of the whole connection depends on the minimum value between the end distance and the spacing distances in load direction. The comparison with existing design codes shows that Eurocode3 and Chinese GB50017-2017 are conservative for the design of bolted connections in HSS while AISC 360-16 may overestimate the bearing resistance of bolted connections.