Blind bolted moment connection to sides of hollow section columns

This paper presents the results of an experimental programme for a new blind bolted connection to unfilled hollow section (HS) columns under static loading. In this connection, channels with side plates connect beam flanges to the side face of HS columns. This is a simple alternative connection to typical face connections, i.e. the extended endplate connection or the T-stub connection (with T-stubs connecting the top and bottom flanges of the beam to the face of the column). The channel side plate connection was found to be much stiffer than a typical face connection and has the potential to achieve a rigid connection status for braced frames according to the EC3 classifications. Comparison of the test results and three dimensional finite element (FE) modelling indicates that the FE analyses can be used to predict the connection behaviour with sufficient accuracy. The preliminary investigation for the channel side plate connection shows promising results and forms the basis for the development of other blind bolted side connections for applications in the low rise construction industry.     

钢结构梁柱梁翼内侧加劲板补强接头耐震试验及有限元素分析

本研究主要探讨钢结构梁柱补强接头之耐震行为,补强接头的主要方式是采取避免破坏既存建筑物楼板且不会减低楼层净高度要求下,在钢梁翼板内侧与箱形柱间焊加劲板增加梁端近柱面之弯矩强度。为证明此补强接头之耐震行为,共进行六组大尺寸之梁柱接头试验,其中一组为传统未补强之梁柱接头,另外五组为梁翼内侧加劲板补强接头,未补强之梁柱接头及一组补强接头之梁柱焊接工作于1996年前工地现场完成后,于2006年由既存34层大楼切除后运至实验室进行试验,另四组梁柱补强接头之焊接工作均于2006年在实验室内完成。补强接头试体加劲板与梁翼及柱板接合均采用全渗透焊接,梁上下翼板之背垫板均未移除,亦未与柱面进行填角焊接。二组补强接头试体在实验时的韧性行为极佳,试体在历经第一次反复载重测试至超越美国规范AISC(2005)规定之4%弧度层间侧位移角的要求下,并未发生梁柱接头焊道断裂及强度递减的情形。因此将此二组试体分别进行第二次AISC(2005)反复载重测试,在历经第二次反复载重测试至4%弧度的层间侧位移角时,发生较明显之梁挫屈及强度递减,但梁柱界面焊道未断裂。而另外三组补强接头因梁翼板内侧加劲板所提供的劲度及强度不足,与未补强之梁柱接头试体同样在未能达到AISC(2005)所订定之4%弧度层间侧位移角前而发生破坏。本研究并利用非线性有限元素分析程序ABAQUS(2003)仿真梁柱接头试体,以进一步了解梁翼板内侧加劲板传递梁弯矩的贡献,和可能发生接头破坏的区域。根据实验及有限元素分析结果提出设计方法及范例供工程师补强既有钢结构梁柱接头参考。     

Experimental investigation of extended end plate joints to concrete-filled steel tubular columns

An experimental programme to obtain the behaviour of blind bolted extended end plate joints to circular or square concrete-filled steel tubular (CFST) columns under monotonic loading has been conducted. In order to enhance the strength and stiffness of the connections, the anchorage extensions are provided to the blind bolts to link the connection back into the concrete with the tubular. This paper investigated the effect of the end plate thickness and the column section type on the static behaviour and failure modes of the tested connections. The structural performance of the blind bolted extended end plate connections was evaluated in terms of the moment–rotation relationship, connection rigidity, the deformation pattern and the strain response. The test results showed that the blind bolted extended end plate connection to CFST columns exhibits high strength and stiffness, while its connection rotation capacity satisfies the ductility requirement for earthquake resistance in aseismic region. The experimental studies also demonstrated that the strength and stiffness of the connections can be improved by providing anchorage extensions to the blind bolts, and utilising moderately thick end plates leads to joints approaching full strength for the extended end plate connections.     

Numerical simulation of gusset plate connections with rectangular hollow section shape brace under quasi-static cyclic loading

In concentrically braced frames, gusset plate connections to rectangular hollow section braces are fabricated using welds to connect the gusset plate to both brace and flanges of the beam and of the column framing into the brace. The beam-to-column connection at the gusset plate is either welded or bolted. However, past experimental studies have indicated that undesirable failure modes could occur in the gusset plate even when using a linear clearance rule in the design of the gusset plate, especially when connecting hollow rectangular shapes.For these reasons, this study investigates through numerical analyses the local seismic performance of gusset plate connections with fully restrained beam-to-column connections as well as partially-restrained bolted connections. The latter are provided at the outside corner of the gusset plate, away from the face of the column, in order to facilitate the beam rotation at the bolted connection upon continued lateral deformation. The main goal of the study of the local performance of gusset plate connections is to validate the design procedure presented in this paper; to compare the various clearance rules proposed in the literature and to propose an alternative clearance rule to the linear clearance rule.The local performance is examined through detailed finite element models of a braced bay located at the ground floor of a four storey concentrically braced frame using the MIDAS finite element program. Finally, local performance of the models is compared in terms of strain concentrations in gusset plates, beams and columns.     

Bolted large seismic steel beam-to-column connections Part 1: experimental study

Two large bolted steel moment-resisting connections were studied by experiments. These connections were single-sided beam-to-column assemblies that are representative of exterior beam-to-column connections, and they were composed of W36×150 Grade 50 beams and W14×283 Grade 50 columns. T-stubs were cut from W40×264 sections of Grade 50 steel. The T-stub stems were welded to the beams and prestressed by bolts to the beam flanges in the shop. Final beam-to-column assembly required no additional welding: the T-stub flanges were bolted to the column and the column shear tab was bolted to the beam web. The specimens had two symmetrically located T-stubs with different stem geometry: Specimen 1 had rectangular-shaped stems, whereas Specimen 2 had U-shaped stems. During the cyclic testing the beam deformation was minimal controlled by active participation of the T-stub flanges: a separation between T-stub flanges and the column flanges was observed. This separation was caused by bending plastic deformation in the T-stub flanges and plastic deformation in the high-strength bolts. This phenomenon allowed energy dissipation and prevented severe buckling of the beam flanges and beam web.     

Blind bolted moment connection to unfilled hollow section columns using extended T-stub with back face support

This paper presents the results of an experimental and analytical study into a new bolted moment connection between unfilled hollow section columns and open section beams, referred to herein as the extended T-stub connection with back face support. The connection is comprised of T-stubs connecting the top and bottom flanges of the beam to the face of the column and channels connecting the T-stubs to a backplate at the back face of the hollow section column. The addition of the channels to a standard T-stub connection helps to distribute the beam flange tension load to the back face of the hollow section column thus reducing demand on the flexible column face which often will compromise the stiffness of the connection. The extended T-stub connection with back face support was found to be comparable to a previously tested side connection and is much stiffer than a typical face connection. Comparison of the test results and three dimensional finite element (FE) model indicates that FE analysis can be used to predict the connection behaviour with sufficient accuracy. The experimental results and analytical sensitivity analysis demonstrate that this new connection can offer a robust and reliable moment connection for application in the low rise construction industry.     

Blind bolted T-stub connections to unfilled hollow section columns in low rise structures

This paper presents the results of an experimental program investigating blind bolted T-stub connections to unfilled hollow section columns in the tension and compression regions under static loading. The T-stub connection is proposed as an alternative connection to the welded connection currently used as a moment connection for unfilled hollow section columns in the Australian construction industry. The flexural performance of the T-stub connection, in terms of stiffness, has been evaluated in accordance with EC3 classifications and was found to behave as a semi rigid connection under serviceability loading. Results from the experiments have been compared with existing theoretical models that predict the maximum load the flexible column face can carry in the tension region before yielding occurs, and good agreement has been achieved. Furthermore, the experimental results have been used to validate a detailed three dimensional finite element (FE) model which simulates the proposed connection. The developed FE model in turn has been used to perform a sensitivity analysis which is presented in this paper.     

钢管混凝土柱T形件抗震性能试验及数值模拟

为获悉钢管混凝土柱T形件在地震作用下的破坏机理和力学性能,本文进行6个采用单边螺栓的钢管混凝土柱T形件的受拉循环往复加载试验。试验参数包括柱截面类型、钢材型号、端板形状和端板厚度。详细地分析新型T形件的破坏模式、滞回曲线和骨架曲线等。根据欧洲规范EC3的组件法,提出了钢管混凝土柱T形件的力学理论模型和螺栓刚度模型。利用ABAQUS有限元程序对此类新型T形件进行非线性全过程受力分析,考察了试件的破坏形态,试验结果验证计算模型的准确性。研究表明,热轧钢管混凝土柱T形件具有良好的抗震性能、延性和耗能能力;对于冷弯薄壁钢管混凝土柱T形件采用合理的构造措施和钢管厚度,能有效地提高其抗震性能及延性。     

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.     

Experimental and Analytical Behavior of Square CFDST Column Blind Bolted to Steel Beam Connections

In recent years, steel or composite beam-column connections adopting blind fasteners have drawn increasing praise due to the rapid development of assembled steel structures. However, limited researches have paid attention to the experimental and analytical behavior of concrete filled double-skin steel tube (CFDST) column blind bolted joints. For investigating the structural performance and seismic behavior of this type of connection, cyclic tests on blind bolted joints to square CFDST columns were carried out to explore the effects of column hollow ratio and end plate type. Finite element analytical modelling of the semi-rigid joint was performed considering complex contact interactions and material models. Good agreement between the test and analytical results was observed in terms of the failure modes and the hysteretic behavior. Substantial parametric analyses were conducted on typical CFDST column connections to observe the influence of parameters including strength of steel tube, column hollow ratio and bolt pretension force. Furthermore, certain constructional measures commonly employed in engineering practice were also discussed. It was concluded that the CFDST column blind bolted to the steel beam joint has favorable seismic behavior and is feasible for application in high-intensity earthquake regions.

     

侧板加强式梁柱节点抗震性能研究

采用ANSYS软件建立了非线性有限元分析计算模型,对侧板加强式梁柱节点的抗震性能进行了研究,分析了侧板长度对连接性能的影响。结果表明,侧板加强节点滞回性能优于普通无侧板节点,节点承载力也大大提高。侧板加强节点滞回曲线稳定、饱满,这种连接表现出了较好的耗能能力。     

The rigid seismic connection of continuous beams to column

This paper presents a new rigid connection with some specific features for earthquake-resistant steel structures. In common practice, beams are separately placed between two adjacent columns and connected to their flanges. In this new proposed connection, two beams pass next to the column faces without interruption and are connected to the column flanges by vertical plates. Two different details of this connection have been studied experimentally and analytically. In the first detail, two integrated vertical plates which are placed next to the column flanges and welded to the column flanges’ edges and beam flanges were used in order to connect the two channel-section beams to the column. In the second detail, four vertical trapezoidal plates which are welded to the edges of the column flanges and beam flanges were used in order to connect the two I-section beams to the column. Two experimental specimens for each of the two different details were tested under cyclic loading. Experimental results show that all experimented specimens sustained the interstory drift angle greater than 0.08 rad without any significant loss of strength, which is far in excess of the requirements for a beam-to-column connection given by the latest seismic codes. The experimental and analytical results show that moment capacity of these connections is more than bending resistance of connected beams. Therefore, the structural ductility in this structural system is controlled by the flexural behaviour of beam ends; and the total behaviour of connections and also of column might remain reasonably elastic. As a result, the structure might have high ductility and safe seismic behaviour. Parametric studies show that the design relationships of connection plates safely determine the thickness of connection plates for different sizes of beams and columns.     

Bolted large seismic steel beam-to-column connections Part 2: numerical nonlinear analysis

A large bolted steel moment-resisting connection was studied by nonlinear numerical analysis. This connection was a single-sided beam-to-column assembly that is representative of exterior beam-to-column connections. It was composed of a W36 × 150 Grade 50 beam and a W14 × 283 Grade 50 column. The T-stubs were cut from W40 × 264 sections of Grade 50 steel. The T-stub stems were welded and prestressed by high-strength bolts to the beam flanges in a fabricating shop. Final beam-to-column assembly required no additional welding: the T-stub flanges were bolted to the column and the column shear tab was bolted to the beam web. During cyclic testing the beam deformation was minimal due to the active participation of the T-stub flanges. A separation was observed between the T-stub flanges and the column flange. The separation occurred due to plastic bending deformation in the T-stub flanges. This phenomenon allowed energy dissipation and prevented severe buckling in the beam flanges and beam web. The tests revealed the importance of the numerical analysis of the connection to obtain a better understanding of the critical performance parameters. A finite element analysis was conducted on a specimen with rectangular- shaped stems. The analysis consisted of two parts: a solid element analysis of the T-stub under tension load in the stem and a shell element modeling with buckling and instability analysis. The solid element analysis was conducted to study the local behavior of the T-stub, whereas the shell model analysis was performed to study the global behavior of the connection.     

新型全螺栓连接钢框架抗震性能试验研究

针对方钢管柱与H形钢梁难栓接的问题,提出了一种新型全螺栓连接方式。这种连接方式舍去传统螺栓连接的螺帽,由直接在柱壁相应位置的攻丝充当,然后通过高强度螺栓把钢梁和方钢管柱直接连接。为了研究新型全螺栓连接方式运用在钢框架上的抗震性能,按照1:2比例模型,分别制作了采用传统栓焊连接方式(KJ-1)和新型全螺栓连接方式(KJ-2)的单层单跨钢框架。通过低周往复加载试验,对比分析了两者的破坏现象、承载力、滞回曲线、骨架曲线、刚度退化以及延性等抗震性能。结果表明,KJ-2比KJ-1承载力提高了16.1%,延性增加了13.7%,耗能提高了9.5%;二者的刚度退化程度接近。总体而言,采用新型全螺栓连接钢框架的抗震性能稍优于采用传统栓焊连接的钢框架的抗震性能。     

Seismic design of reduced beam section steel moment connections with bolted web attachment

Recent test results on reduced beam section (RBS) steel moment connections showed that specimens with a bolted web connection tend to perform poorly due to premature brittle fracture of the beam flange at the weld access hole. The measured strain data appeared to indicate that a higher incidence of base metal fracture in bolted web specimens is related, at least in part, to the increased demand on the beam flanges due to the web bolt slippage and the actual load transfer mechanism which is significantly different from that usually assumed in connection design. In this paper, the practice of providing web bolts uniformly along the beam depth was brought into question. A new seismic design procedure, which is more consistent with the actual load path identified from analytical and experimental studies, is proposed. A pilot test specimen designed by following the proposed procedure exhibited sufficient cyclic connection rotation capacity without fracture.     

Performance of CFTST column to steel beam joints with blind bolts under cyclic loading

The objective of this research is to investigate the seismic performance of the composite joint consisting of square concrete filled thin-walled steel tubular (CFTST) column and steel beam with end plate and blind bolts. The cold-formed square tube in each CFTST column connection was fabricated by seam welding together four pieces of lipped angle with nominal wall thickness 1.5 mm or 3 mm. Four exterior joint specimens were tested under axially compressive load on the top of the columns and cyclic loads on the beam tip. The experimental parameters in the study were the thickness of the steel tube and the type of end plate. The seismic response of the blind bolted moment joints to CFTST columns was analyzed and evaluated in terms of the hysteretic behavior, failure modes, stiffness and strength degradation, ductility, and energy dissipation capacities of the joints. To improve the tension behavior of the blind bolted moment connections to the thin tube wall, the anchorage action of reinforcing rebar welded to the bolts with concrete-filled steel tubes was also investigated to consider the effect of cyclic loading. The experimental and analytical results indicated that when the end plate thickness is not less than 3 mm, the flush or extended end plate joints to CFTST columns exhibited large hysteretic loops and excellent seismic performance, such as ductility and energy dissipation capacity. The proposed innovative blind bolted joint was verified as a reliable and effective solution applied in mid- and low-rise buildings through properly design and detailing.     

方钢管混凝土柱-钢梁框架耐火性能分析

研究方钢管混凝土柱-钢梁框架结构的耐火性能。基于有限元方法,分析了GB/T 9978（同ISO-834）加热条件下,带有混凝土楼板的方钢管混凝土柱-钢梁单向螺栓连接框架结构的温度分布、耐火时间和破坏模式,并对有限元模拟结果进行了试验验证,在试验结果基础上采用有限元方法分析了方钢管混凝土柱构件与方钢管混凝土框架柱的耐火极限差异。研究结果表明：与方钢管混凝土框架柱的其他区域相比,方钢管混凝土框架柱节点区的温度相对较低;根据本文建议的框架结构判定准则,当单向螺栓节点连接可靠,随着作用在柱和梁上荷载水平的变化,柱破坏模式和梁破坏模式是方钢管混凝土柱-钢梁框架的主要破坏模式;当框架梁上不施加荷载,只对框架柱起到约束作用,其他条件相同时,方钢管混凝土框架柱的耐火极限大于两端铰接柱构件的耐火极限,但小于一端固接一端铰接支撑柱构件的耐火极限。     

A parametric study on ultimate strength of single shear bolted connections with curling

Recommended procedures of finite element modeling for predicting the structural behaviors of single shear bolted connections in cold-formed austenitic stainless steel are presented in this paper. It was shown that predictions by FE analysis method were in a good correspondence with test results for ultimate behaviors such as failure mode, ultimate strength and out-of-plane curling. A parametric study on four-bolted connections with extended variables; plate thickness, end distance and edge distance is performed in order to consider the influence of curling on ultimate strength for practical design and ultimate strengths obtained from FE analysis results are also compared with those calculated by current design standards and recently modified equations by Kuwamura. It is found that Kuwamura's equations, which are specified by SSBA design manual are more valid for predicting ultimate strength of bolted connection without curling compared to other design specifications, while for specimens curled in FE analysis, Kuwamura's equations overestimated the ultimate strength due to strength reduction caused by curling and current other design standards showed a tendency to underestimate the ultimate strength of block shear fracture regardless of curling occurrence. Consequently, revised design formula for considering the effect of curling on bolted connection is proposed in this paper using correlations between strength reduction ratio and plate thickness. Furthermore, the validation of proposed design equations in predicting the ultimate strength is verified through comparisons with existing test results and additional FE analysis results.     

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.     

自复位钢框架节点有限元模拟及参数分析

研究了一种具有自复位能力的钢框架节点的力学性能.该节点在梁柱间通过角钢栓接,并沿梁长布置高强预应力钢绞线.通过对钢绞线施加预应力将梁柱压紧,使节点具备足够的抗弯刚度以满足正常使用情况下的功能性要求,钢绞线同时提供回复力,使节点在地震后具有自复位能力.采用通用有限元分析软件Abaqus 6.9建立节点模型,对9个足尺钢框...