Lap shear tests of bolted and screwed ferritic stainless steel connections

The development of design guidance for stainless steel structures requires more tests on ferritic grade connections. This paper deals with a series of lap shear tests which have been carried out on various configurations of bolted and screwed connections. The tests demonstrate net section failure, bearing failure and block tearing failure. The material is a ferritic stainless steel of grade 1.4509 (AISI 441) with a thickness of 0.5–4.5 mm. The results are utilized in developing design guidance in accordance with Eurocodes.     

An investigation of the block shear strength of coped beams with a welded clip angle connection — Part I: Experimental study

The ends of a coped beam are commonly connected to the web of a girder by double clip angles. The clip angles may either be bolted or welded to the web of the beam. One of the potential modes for the failure of the clip angle connection is the block shear of the beam web material. To investigate the strength and the behavior of the block shear of coped beams with welded end connections, ten full-scale coped beam tests were conducted. The test parameters included the aspect ratio of the clip angles, the web shear and tension area around the clip angles, the web thickness, beam section depth, cope length, and connection position. The test results indicated that the specimens failed, developing either tension fractures of the web near the bottom of the clip angles or local web buckling near the end of the cope. Although the final failure mode of the six specimens was local web buckling, it was observed during the tests that these specimens exhibited a significant deformation of the block shear type prior to reaching their final failure mode. No shear fracture was observed in all of the tests. A comparison between the ultimate loads in the test and the predictions using the current design equations indicates that the current design standards such as the AISC-LRFD, CSA-S16-01, Eurocode 3, BS5950-1:2000, AIJ and GB50017, are inconsistent in predicting the block shear strength of coped beams with welded end connections. The analytical study of the strength of the test specimens using the finite element method, a parametric study, and a proposed design model for designing block shears for coped beams with welded clip angles are included in a companion paper.     

Parametric Study on Ultimate Strength of Four-bolted Connections with Cold-formed Carbon Steel

The curling(out-of-plane deformation in the plate thickness direction) influence on the ultimate strength of cold-formed stainless steel bolted connection has been investigated and modified equations for predicting the ultimate strength considering strength reduction caused by curling through finite element analysis have been suggested by previous researchers. In this paper, single shear four-bolted connections fabricated with thin-walled carbon steel commonly utilized in the light-weight structural members of building were tested under static shear in order to investigate block shear fracture behavior and curling influence on the ultimate strength and fracture mode. Main variables of specimens are plate thickness and end distance parallel to the direction of loading. Curling in the perpendicular direction of applied force also occurred for bolted connections with a relatively long end distance and thin plate. The curling occurrence caused a sudden strength drop and reduced the ultimate strength of bolted connections. Current design specifications such as AISC, AIJ and AISI for block shear strength were summarized and it is known that design equations did not provide the accurate prediction of ultimate strength and fracture mode for thin-walled carbon steel bolted connections. Strength reduction by curling and the condition of curling occurrence were investigated through an additional parametric finite element analysis. As a result, revised strength equations for block shear fracture and bearing fracture were suggested considering fracture path and curling effect and their validity was also verified.     

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.     

Numerical investigation of the effects of connection rotational stiffness on block shear capacity of coped beams with a welded end connection

In order to investigate the effects of connection rotational stiffness on the block shear capacity of coped beams with welded end connections, a numerical investigation was conducted. Parametric study is conducted based on the validated finite element model. Based on the mechanical model of double angle connection, the pitch and the beam element length-to-angle thickness (L/t) ratio of the outstanding leg are selected as two important parameters to consider the effects of the connection rotational stiffness. The results of parametric study show that the connection rotational stiffness has a great influence on the block shear capacity of coped beams with double welded clip angle connection. The results of parametric study also show the pitch has no significant effect on the block shear capacity. Based on the results of finite element analysis, the design equation proposed by Yam et al. (2007) was modified to account for the effects of the connection rotational stiffness.     

An investigation of the block shear strength of coped beams with a welded clip angle connection — Part II: Numerical study

An experimental study of the block shear capacity of ten full-scale coped beams with a welded clip angle connection was presented in Part I. The test results were compared with predictions using block shear design equations in several current design standards. In general, the results showed that the existing design standards did not provide consistent predictions of the block shear capacity of coped beams with welded clip angles. In addition, the equations provided by the standards cannot accurately reflect the failure mode of the specimens observed in the tests. In order to gain a better understanding of the connection behavior, such as the stress distribution in the web near the periphery of the clip angles and the failure mechanism of the connection, an analytical study of the block shear capacity of coped beams with welded clip angles was carried out using the finite element method. Based on the limited test data and the results of the finite element analysis (FEA), a strength model was established and a design equation was proposed to evaluate the block shear strength of coped beams with welded clip angles. It was shown that the proposed design equation gave better predictions of the block shear capacity of the specimens.     

Microcomputer-Aided Design and Drafting of Moment-Resisting Connections in Steel Buildings

A microcomputer-aided system has been developed for interactive design and drafting of connections in steel buildings made of standard. rolled-I sections, called STEELCON. The basis of design is AISC specification. In addition to interactive design, STEELCON can displaylplot any isometric view of the connection plus three orthographic views, i.e., front, side, and top face views. The orthographic views show all the necessary details for fabrication and construction of the connections. Interactive design and drafting of two different moment resisting connections are presented. They are the shop welded and field bolted framed flange plate connection and the shop and field welded flange plate connection.     

Analytical prediction on deformation characteristics of lapped connections between cold-formed steel Z sections

This paper presents an analytical method to predict the deformation characteristics of lapped connections between cold-formed steel Z sections. Based on the test results of typical lap shear tests on bolted fastenings between cold-formed steel strips of various strengths and thicknesses, a normalized bearing deformation curve was established. The curve was then adopted to predict the deformation characteristics of lapped connections between cold-formed steel sections where deformations due to global bending and shear actions as well as local bearing were significantly. The predicted deformation characteristics of a total of 26 lapped Z sections with different section sizes and connection configurations up to failure were then compared with the measured results, and comparison is found to be highly satisfactory. Moreover, an empirical formula was also proposed for the moment rotation relationship of lapped connections at large deformations after failure under combined bending and shear.The proposed method is considered to be very important in assessing the structural behaviour of multi-span purlin systems with lapped Z sections, in particular, in determining the effective flexural rigidities of lapped connections over internal supports. Such design data is essential for the establishment of internal force distribution along the entire lengths of the purlin members. Hence, the co-existing shear forces and moments at the ends of lap of the lapped connections are obtained accurately to check against section failure under combined bending and shear.     

矩形钢管混凝土柱-混凝土梁搭接式节点抗震性能研究

在现有钢管混凝土柱与混凝土梁连接形式基础上,提出一种新型搭接式钢管混凝土柱-混凝土梁节点,通过低周反复荷载试验和数值模拟分析,研究了节点的破坏形态、承载能力、刚度退化、延性及耗能能力等,分析了梁端纵筋和搭接牛腿翼缘的应变发展规律。结果表明:钢管混凝土柱-混凝土梁搭接式节点表现出典型的混凝土梁端塑性铰破坏模式,符合“强节点、弱构件”的抗震设防理念; 节点的滞回曲线饱满,捏缩现象较轻,刚度退化明显,强度退化较小,具有较好的延性及耗能能力; 梁纵筋及牛腿各测点中搭接牛腿端部截面应变最大,通过搭接连接方式可实现梁端弯矩和剪力的有效传递,但搭接牛腿长度不足会使节点发生锚固破坏; 在节点设计时,应保证足够的搭接长度,以实现钢筋混凝土梁纵筋在弯剪复合受力状态下锚固性能的可靠性,充分发挥节点的抗震耗能能力; 有限元计算结果与试验结果吻合良好,该模型能够准确反映节点在实际受力情况下的力学特性,所得结论可为此类新型搭接式节点工程应用提供技术支撑。     

钢框架梁柱连接节点转动刚度试验研究

为了探讨钢框架梁柱连接节点的转动刚度和破坏模式,针对常见梁柱节点类型,包括全焊接连接、外伸式端板螺栓连接、T型钢螺栓连接、上下翼缘及腹板角钢螺栓连接等,进行了单向加载试验研究。试验结果表明,各类节点的总转角均超过了0.05 rad,塑性转角均超过了0.04 rad;节点域剪切变形较大,特别是全焊接节点,使节点转动刚度显著降低;当连接较强时,框架梁可以在连接破坏之前形成塑性铰;当连接较弱时,连接件容易因过度变形而破坏。通过对试验数据的分类整理分析,梁柱节点总转角可以分成节点域转角和连接转角两大部分,给出了常见节点类型在弹性阶段的转角及转动刚度简化计算方法,并与试验结果进行了对比,计算结果与试验结果吻合较好。     

Thin steel plate shear walls behavior and analysis

Steel plate shear walls have been used in buildings in North America and Japan. Until recently, the design practice has been to limit the strength of the wall to the buckling strength of the plate. The post-buckling strength of thin plates subjected to shear has been recognized for more than 60 years, since it was outlined by Wagner in the early 1930s. Tests of a quarter and one third scale specimens of thin steel plate shear walls under cyclic loading were performed; the tests are described and the results are summarized. An analytical model to determine the behavior of thin steel plate shear walls was developed and is given. The model is capable of depicting the behavior of walls with plates welded or bolted to the surrounding beams and columns of the building frame. Comparisons between the analytical and experimental results are made.     

铝合金板件环槽铆钉搭接连接受剪性能试验研究

针对工程中常用的铝合金板件环槽铆钉搭接连接,进行了受剪性能的静力试验。通过拉伸试验测得铝板用6061-T6铝材和铆钉用304HC不锈钢材的物理参数,测定了环槽铆钉的预紧力。试验中获得了12个单铆钉搭接连接试件的荷载-位移曲线和极限荷载,分析了其破坏模式及铆钉孔径、端距、边距等参数的影响。结果表明：试件的破坏形式有环槽铆钉剪切破坏、板件顶端纵向撕裂破坏与侧边横向撕裂破坏3种,控制铆钉孔端、边距尺寸能避免后两种破坏;环槽铆钉预紧力在板件间产生的摩擦力有限,因此该搭接连接应属于承压型连接;铆钉与孔壁间的间隙最终会因板件间的相对滑移而致密,故过大的铆钉孔径将造成大的残余变形,但对承载力的影响有限;剪力作用下节点的荷载-位移曲线早期有较明显弹性段,可取其弹性段的末端荷载值作为受剪承载力设计值,极限荷载和该承载力设计值的比值约为2.3。     

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.     

木梁柱螺栓钢填板节点转动性能理论计算方法

文章首先通过单调加载试验研究胶合木梁柱螺栓钢填板节点在弯剪复合作用下的转动性能,随后基于Johanson屈服模型提出胶合木梁柱钢填板螺栓节点在弯剪复合作用下的极限承载力和节点刚度的计算方法;同时提出节点弯矩转角曲线的理论预测模型.理论计算与试验结果相比具有较高的准确性.最后,基于节点承载力的理论计算方法分析节点抗剪承载...     

钢板攻丝高强螺栓连接钢框架节点力学性能试验研究

对采用钢板攻丝高强螺栓连接的钢框架节点分别进行了高强螺栓拉伸及剪切试验、钢柱法兰连接节点静力及拟静力试验、梁柱半刚性连接静力试验.基于试验数据对节点连接的承载能力、失效模式以及刚度特征等关键问题进行了分析.研究结果表明:由自攻螺纹钢板及高强螺栓构成的连接形式具有良好的抗拉、抗剪性能,以螺杆断裂为最终破坏模式;钢柱法兰连...     

Analysis of the behaviour of stainless steel bolted connections

This study is focused on two types of bolted connections that are common in steel structures. They concern cover plate connections and T-stubs, where the bolts are loaded in shear or in tension. The Eurocode 3 requirements for stainless steel connection design are essentially the same as for carbon steel. The study considers the case of austenitic stainless steel for which the conventional elastic limit is relatively low compared to the ultimate strength. In bearing, criteria on deformation limits have to be considered for cover plate connections. In T-stubs, strain hardening of stainless steel exhibits a continuous increase of the applied load and can influence the failure mode. A finite element model is developed and validated for the two types of connections. A more extensive parametric study should be carried out to develop a better understanding of the behaviour of stainless steel connections.     

焊接及螺栓连接钢框架的循环加载试验研究

为了探讨、比较焊接和螺栓连接钢框架的极限承载能力、滞回性能及动力特性,本文进行了6榀1∶2比例的单跨双层钢框架循环加载试验和动力特性测试,其中焊接、端板螺栓连接、角钢螺栓连接钢框架各两榀。试验过程中每层框架都铺设了混凝土楼板和配重,水平循环荷载按三角形分布施加。循环加载试验表明:当焊接连接框架的焊缝质量较高时,钢框架具有良好的承载能力和滞回性能,其最终破坏模式是构件形成塑性铰而发生强度破坏,属于典型的延性破坏,框架侧向层间塑性变形可以达到层高的1/25,塑性变形主要来自梁柱连接节点域的剪切变形和柱、梁的弯曲变形;端板螺栓连接框架的承载能力和滞回性能也较好,耗能能力略低于焊接框架,框架侧向层间塑性变形可以达到层高的1/30,但端板焊缝容易发生断裂;角钢螺栓连接框架的承载能力和耗能能力相对较低,塑性变形主要发生在连接角钢和柱脚部位,且翼缘连接角钢容易发生低周疲劳破坏。动力特性测试结果表明:随着节点转动刚度的减小,框架自振     

Comparison of bolted end plate and T-stub connections sensitivity to bolt diameter on cyclic behavior

Considering the construction limitations, proper and correct design of connections is vital and of great importance. At the construction stage, it is probable to use a connection bolt with a diameter less than the design assumptions. It can occur due to an imperfection in construction or even to changes in the function of the building. The unforeseen changes can increase the structural load, and consequently the moment and shear force demand values. Therefore, the present paper is aimed to examine the sensitivity of the bolted connections to the diameter of bolts using a numerical method. The results show that bolted T-stub connections are more sensitive to bolt diameter than end plate connections. Hence, the bolted end plate connections are recommended where the imperfection in construction or changes in function of the building is probable. Moreover, in construction of bolted connections, if changing the number of bolts regarding the constant total cross sectional area is considered, it is recommended to use the symmetric arrangement of bolts on each beam flange. In design of connections for a particular frame according to AISC, the moment capacity of T-stub connection is higher than that of end plate connection. However, the total energy absorptions of these connection types are approximately equal.     

复式钢管混凝土柱与H形钢梁连接节点抗震性能试验研究

借鉴方钢管混凝土柱-钢梁外肋环板节点形式,将非梁柱连接面的柱两侧外肋环板改为竖贴于柱侧的竖向肋板并伸出与梁翼缘焊接,同时设置锚固腹板,形成复式钢管混凝土柱与H形钢梁连接节点。通过7个梁柱组合体试件的低周反复荷载试验,分析各试件的破坏过程及特征,并对试件的滞回性能、承载力、延性、耗能能力和承载力及刚度退化等抗震性能进行研究。研究结果表明：节点的破坏形态基本相同,梁端先屈曲,形成塑性铰;锚固腹板可有效提高节点的承载力和变形能力;竖向肋板外伸长度可提高试件的初始刚度,使梁端塑性铰外移,有效保护节点核心区;试件的滞回曲线呈明显的梭形,具有良好的承载力、延性及耗能能力;试件在整个加载过程中刚度退化现象明显,承载力退化很小,可应用于抗震设防地区。