装配式钢筋混凝土柱-钢梁框架节点抗震性能试验研究

通过4个1/2比例装配式钢筋混凝土柱 钢梁框架节点低周往复荷载作用下的试验研究,分析了节点区加劲腹板厚度及开孔的影响,研究该新型节点连接构造的受力性能及装配式钢筋混凝土柱 钢梁框架单元的抗震性能。基于试验结果对试件的破坏特征、滞回性能及变形组成进行分析。研究结果表明：装配式钢筋混凝土柱 钢梁框架节点滞回曲线呈纺锤形,梁端塑性铰区充分耗散能量,具有良好的抗震性能;装配式螺栓连接钢筋混凝土柱 钢梁混合节点具有良好的连接质量;加劲腹板厚度的增加一定程度上减小了节点的剪切变形,加劲腹板开孔对节点受力性能影响不大;梁弯曲变形引起的层间侧移在强柱弱梁型钢筋混凝土柱-钢梁框架节点总侧移中所占比例最大,节点剪切变形所占比例较小。     

可更换钢连梁抗震性能试验研究

通过拟静力试验,研究由跨中部消能梁段和两端非消能梁段组成的可更换钢连梁的抗震性能和震后可更换能力。试验共包括4个连梁试件,采用4种不同的消能梁段与非消能梁段连接方式,分别为端板-抗剪键连接、拼接板连接、腹板-螺栓连接、腹板-结构胶连接。试验结果表明：采用端板-抗剪键连接时,连梁的塑性变形和损伤集中在消能梁段,连梁的极限塑性转角可达0.06 rad,具有稳定的滞回耗能能力;采用拼接板连接或腹板-螺栓连接时,消能梁段剪切屈服,连接处摩擦型高强螺栓有不同程度的滑移,连梁的极限塑性转角也可达0.06 rad;采用腹板-结构胶连接时,连接处结构胶开裂导致连梁脆性破坏。在连梁转角为0.02 rad加载后对消能梁段进行更换,采用端板-抗剪键连接的试件更换时间最短,而腹板-螺栓连接的试件能在更大的残余转角时更换。此外,消能梁段在较大塑性剪切变形时伴有轴向变形,导致连梁试件承受较大轴力,连梁的轴力影响需要进一步研究。     

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.     

Cyclic behaviour of post-Northridge WUF-B connections

The purpose of this study is to evaluate the cyclic behavior of post-Northridge Welded Unreinforced Flange-Bolted web (WUF-B) connections made using new notch tough welding materials and welding procedures, and a modified access hole. Since no WUF-B connection test results were found which satisfy the minimum design and detail requirements of the 2002 AISC Seismic Provisions for Structural Steel Buildings, this study made three full-scale test specimens of WUF-B connections according to the provisions. The main variable of the specimens was the ratio of the panel zone strength to the connected beam strength (panel zone strength ratio). Quasi-static cyclic testing was conducted. This study found that post-Northridge WUF-B connection specimens having a stronger panel zone experienced more significant slip between the bolted shear tab and the beam web. It was observed that the slip caused stress concentrations in and around the access hole, resulting in connection failure. The WUF-B connection specimen having the weakest panel zone did not, however, experience excessive slip between the bolted shear tab and beam web. Moreover, this WUF-B specimen could not achieve the required beam strength. This study observed that post-Northridge WUF-B connections with a panel zone strength ratio ranging from 0.9 to 1.6 provides a drift ratio exceeding 0.2. This drift ratio is required for satisfactory performance of the connections of Intermediate Moment Frames. Furthermore, this study proposed an analytical model for post Northridge WUF-B connections having different panel zone strength ratios.     

连续性倒塌工况下钢管柱框架节点的破坏模式与鲁棒性

采用双半跨单柱型梁柱子结构,通过静力加载试验考察了圆钢管柱外环板节点与方钢管柱内隔板节点在中柱失效连续性倒塌工况下的破坏模式,并以梁柱子结构竖向抗力来评估梁柱节点的鲁棒性。试验参数包括连接方式、螺栓布置、梁端构造与跨高比。试验结果表明,在柱顶施加竖向位移的过程中,梁柱子结构的破坏均出现在梁柱节点部位,不同的连接构造呈现出不同的损伤演化机制。节点破坏模式可分为梁端连续性破坏、梁端间断性破坏与柱身破坏三类。当节点破坏发生在梁端,采用全焊连接的节点发生梁端连续性破坏,采用栓焊混合连接的节点发生梁端间断性破坏。柱身破坏模式的发生前提为下层内隔板与柱身脱离,与腹板连接方式无直接关系。在梁端间断性破坏或柱身破坏的演化过程中,节点在初始断裂后仍可保持有效的梁柱拉结作用,悬索机制得以开展并为梁柱子结构提供稳定的后期承载力,节点具有较好的鲁棒性。节点若发生梁端连续性破坏,梁端截面面积逐步减小导致梁柱拉结作用削弱,梁柱子结构无法有效开展悬索机制,节点鲁棒性能较差。     

Cyclic seismic testing of steel moment connections reinforced with welded straight haunch

A simplified seismic design procedure as well as force transfer model for seismic steel moment connections using a welded straight haunch was recently proposed. As a follow-up study, cyclic seismic testing was conducted to verify the proposed procedure and to develop strategies that would prevent cracking at the haunch tip. All the specimens based on the proposed procedure effectively pushed the plastic hinging of the beam outside the haunch and developed satisfactory connection ductility with no fracture. A sloped edge combined with a drilled hole near the haunch tip, or a pair of stiffeners that partially or fully extended from the beam web, successfully prevented crack initiation at the haunch tip. The strut action of the haunch web, which had been predicted from the previous analytical study, was also identified through the strain gage readings in this experiment.     

带悬臂梁段拼接的梁柱连接循环荷载试验研究

为了检验带悬臂梁段拼接的梁柱连接抗震性能,对4个试件进行了循环加载试验。试验侧重于对拼接节点的研究,采用10.9级高强螺栓摩擦型连接,翼缘和腹板全部拼接。试验结果表明:螺栓拼接节点的延性远好于梁柱焊缝连接;较弱的拼接节点产生较大的塑性变形;接触面的滑移摩擦、螺栓与孔壁的挤压和翼缘拼接板的屈曲都使连接具有良好的耗能能力;但滑移伴随有剧烈的响声,会使人产生心理恐慌。根据试验结果提出了设计建议:尽量将拼接设计得弱些,可以提高梁柱连接的转动能力,减少地震作用向梁柱连接焊缝的输入,延缓焊缝的脆性破坏。     

外伸端板半刚性节点在循环荷载作用下的研究

介绍了钢框架梁柱采用梁端外伸端板与柱翼缘之间高强螺栓连接的半刚性节点在循环往复荷载作用下的试验过程和结果 .分析了四种不同形式节点的承载能力和延性特征 .依据试验结果 ,对半刚性节点提出了增加节点延性、防止脆性破坏的构造措施 ,为钢框架梁柱半刚性节点的设计提供了试验依据 .     

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.     

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.     

Aseismic behaviors of steel moment resisting frames with opening in beam web

Opening in beam web short away clear of beam-to-column connection is an effective method to improve the aseismic behaviors of steel moment resisting frames (MRFs). The pseudo-dynamic (PSD) test and the quasi-static test on the aseismic behaviors of full-size steel MRFs with opening in beam web are carried out. The PSD test shows that the tested frame can satisfy the design requirement and its stiffness isn’t weakened by the web opening. It can be judged from the strain distribution around the beam-to-column connection that the seismic energy is dissipated by local deformation in the weakened area of the beam due to the opening in the case of severe earthquake action, and the expected failure mode of a ductile frame (‘strong column but weak beam’ and ‘strong connection but weak component’) is reached. In the quasi-static test, the failure mode of the tested frame is in conformity with the judgement, i.e., Vierendeel mechanism is formed in weakened areas due to web opening and brittle weld fracture is avoided, which results in an improvement of the aseismic behaviors of steel MRF. Based on numerical analysis, the non-linear analysis model of steel MRF with opening in beam web is provided. Some experimental tests are numerically re-analyzed by applying the proposed model and the numerical results are in conformity with the test results, which verify the validity of the model. A 17-story steel MRF building, damaged during the Northridge earthquake and measured in detail after the earthquake, is selected as the studied case. Push-over analysis shows that the ultimate displacement of the modified building with web openings increases a lot due to the opening and the building’s ductility is improved greatly. Plastic hinge distribution in time-history analysis indicates that brittle weld fracture can be avoided in the frame including connection with opening and the maximum plastic zone moves to the weakened areas. It can be concluded that the aseismic behaviors of steel MRF are improved due to the opening in beam web.     

钢框架梁柱半刚性节点在循环荷载作用下的试验研究

介绍了钢框架梁柱采用梁端外伸端板与柱翼缘之间高强螺栓连接的半刚性节点在循环往复荷载作用下的试验过程和结果。分析了 4种不同形式节点的承载能力和延性特征。依据试验结果 ,对半刚性节点提出了增加节点延性、防止脆性破坏的构造措施 ,为钢框架梁柱半刚性节点的设计提供了试验依据。     

高温下单剪螺栓连接薄钢板的试验研究(Ⅱ):瞬态试验

采用瞬态试验方法,对62根单剪螺栓连接试件进行试验研究。制作了3种不同厚度的单剪螺栓连接薄钢板。常温下,对25%,50%和75%三种荷载级别的极限荷载进行试验。采用瞬态试验方法得到的强度折减类似于恒温下的试验结果。结果显示:相对恒温试验结果,瞬态试验的结果比较保守。在瞬态试验中,研究了支座破坏、撕裂和净截面拉伸3种主要的破坏模式。在常温下,25%的破坏荷载下瞬态试验中试件的失效模式,与恒温条件下试件的失效模式一致。     

腹板双角钢梁柱连接循环荷载试验研究

为了研究腹板双角钢梁柱连接的抗震性能,对四个连接试件进行了梁端循环位移加载试验。试验中考察了角钢高度、角钢与柱翼缘连接高强螺栓的直径和排列布置对连接的承载能力、滞回性能和破坏机理的影响,分析了这种连接的破坏模式和变形能力。试验结果表明:连接在循环荷载作用下表现出良好的延性,转角均超过0.04rad,连接的最终破坏均为角钢的塑性撕裂破坏;连接具有相当的抗弯能力,在结构分析中,须考虑节点抗弯强度对框架性能的影响,不能简单作为铰接处理;增大角钢的高度,能提高连接的强度;增大螺栓间距,减小螺栓直径,能提高连接的延性。最后,根据试验结果提出设计施工建议。     

Tests of single shear bolted connections of thin sheet steels at elevated temperatures—Part II: Transient state tests

A total of 62 single shear bolted connection specimens were tested using transient state test method. The specimens of single shear bolted connections were fabricated by three different thicknesses of thin sheet steels. The tests were conducted at three different load levels of 25%, 50% and 75% of the failure load at ambient temperature. The tendency of the test strength reduction of the single shear bolted connections conducted using the transient state test method is generally similar to that for the steady state test method. However, it is shown that the transient state test results are always conservative compared with the steady state test results. Three main failure modes, namely the bearing, tear out and net section tension, were observed in the transient state tests. The failure modes of the specimens in transient state tests for the load level of 0.25 of the failure load at ambient temperature are generally consistent with those specimens in the steady state tests.     

Collapse resistance of unreinforced steel moment connections

Experimental and analytical studies of steel moment connections in gravity load resisting systems were conducted to understand the connection behaviour under progressive collapse. An exterior beam–column assemblage was selected from the gravity load resisting system in a steel building. Two identical, full‐scale, unreinforced welded steel beam‐to‐column moment connection specimens were tested under monotonic and cyclic loading to investigate the effects of applied loading conditions on the connection rotation capacity. The beam web was connected to the column flange by bolting and the beam flanges were complete joint penetration welded to the column flange. The specimens failed by fracture in the beam flange CJP weld at story drifts of 9.2 % (specimen SP1 under monotonic loading) and 3.4% (specimen SP2 under cyclic loading). The maximum drift angle achieved in the monotonic test exceeded the General Service Administration criterion for welded unreinforced flange connections, and the amount of dissipated energy of SP1 turned out to be smaller than that of SP2. The finite element analysis of the test specimen was also conducted to validate the test results, and the analysis results matched well with those obtained from experiments. Copyright © 2010 John Wiley & Sons, Ltd.     

Tests on block shear of coped beams with a welded end connection

An experimental study of block shear of coped beams with a welded clip angle connection is presented in this paper. Twelve full-scale coped steel I-beam tests were conducted. The test parameters included the web block aspect ratio (height to width ratio of the web block connected to the clip angle) and the connection rotational stiffness. Out of the 12 test specimens, eight test specimens failed in block shear of the connection, namely, tensile fracture of the block width (the web underneath the clip angle) and shear yielding of the block height (the web along the vertical side of the clip angle). Two test specimens failed by local web buckling at the cope, one test specimen failed in the welds and the remaining one did not fail due to the limited capacity of the loading jack.The test results showed that in general the block shear capacity of the test specimens increased with increasing web block aspect ratio and increasing connection rotational stiffness. The current design specifications (AISC-LRFD, CAN/CSA-S16-09, CAN/CSA-S16-01, BS EN 1993-1-8-2005, BS5950-1:2000, and AIJ-1990) provide conservative estimates of the block shear capacity of the test specimens except for the specimen that had the smallest connection rotational stiffness. It should be noted that none of the design equations evaluated in this programme consider the influence of the web block aspect ratio and the connection rotational stiffness.     

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...     

Tests of single shear bolted connections of thin sheet steels at elevated temperatures—Part I: Steady state tests

The current design rules on bolted connections of thin sheet steels for cold-formed steel structures are applicable for ambient temperature condition only. Investigation of single shear bolted connections at elevated temperatures is limited. In this study, 120 single shear bolted connection specimens involving three different thicknesses of thin sheet steels and 30 coupon specimens were conducted by using steady state test method in the temperature range from 22 to 900 °C. There are three main failure modes observed in the single shear bolted connection tests, namely the net section tension, bearing, and tear out. The test results were compared with the predicted values calculated from the American, Australian/New Zealand and European specifications for cold-formed steel structures. In calculating the nominal strengths of the connections, the reduced material properties were used due to the deterioration of material at elevated temperatures. It is shown that the strengths of the single shear bolted connections predicted by the specifications are generally conservative at elevated temperatures. The comparison between the deterioration of the tested connection strengths and that of the material properties at elevated temperatures showed a similar tendency of reduction.     

Development and performance evaluation of weak-axis column bending connections for advanced constructability

This paper reports a new beam-to-column connection that is suitable for use in the weak axis of a column. The proposed system mainly uses bolts, and it minimizes the use of welding, which is generally difficult to perform onsite. In this system, an H-shaped steel beam is joined to an H-shaped steel column by bolted splices at the top flange and without a scallop at the web. Eight specimens were tested to verify the structural performance of the developed connection; in doing so, the effects of geometry and arrangement of the plate were also considered. The connection materials required and CO₂ emissions were estimated to evaluate the cost-effectiveness of the proposed system. The obtained results showed that this system was suitable had better structural performance than standard weak-axis connections and excellent constructability, making it suitable for replacing existing bracket-type weak-axis connections.