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。     

尺寸偏差对熔透焊缝连接疲劳强度(寿命)的影响

建立了对接熔透焊缝连接在疲劳荷载作用下的断裂力学计算模型 ,计算连接在疲劳荷载作用下不同阶段的裂纹扩展速率 ,分析存在不同尺寸偏差的连接的疲劳强度 (寿命 ) ,得出了尺寸偏差对熔透焊缝连接疲劳强度 (寿命 )的影响 ,可评估已建钢结构熔透焊缝连接在疲劳荷载作用下的疲劳强度 (寿命 ) ,控制新建结构熔透焊缝连接的尺寸偏差。     

Behavior of beam-to-column moment connections under fire load

The welded flange-bolted web type moment connections are commonly used in the construction of modern steel buildings. The behavior of this type of connection under service load and seismic load has been studied extensively; however, the knowledge of its performance under fire load is limited. In this paper, the experimental studies of the welded flange-bolted web moment connections under fire loads are presented. Four full-size steel beam-to-column assemblages, with and without fire-proofing materials, were selected to simulate the moment connection commonly used in steel buildings. The fire load was simulated either by a steady state method to reach a fully-developed fire or by a transient state method following the standard temperature-time curve. Parametric studies were also conducted to examine the strength degradation of steel moment connection at elevated temperature. From these studies, it was found that the beam-to-column connection is able to retain its design strength up to 650 ^°C. However, the stiffness dropped to 25% of the value at ambient temperature. Ductile behaviors were observed on the connections, with necking and tearing at the top flange and local buckling at the bottom flange. It was also found that the stability and integrity of steel connections can be ensured if proper fire-proofing materials were provided.     

On the concept of earthquake resistant hybrid steel frames

The concept of hybrid steel frame system is presented in which mixtures of fully-rigid and semi-rigid steel connections are used in the 9 and 20-story SAC frames. Several different patterns and locations of semi-rigid connection replacements within the frame are examined in order to identify the hybrid frames with most energy dissipation capabilities. Inelastic dynamic analyses are conducted on the proposed selected frames by subjecting them to the Los Angeles earthquake records characterized as those with 10% probabilities of exceedance in 50 years and 2% probabilities of exceedance in 50 years. The maximum story drift for the hybrid frames are determined and compared to the “life safety” and “collapse prevention” limits as recommended by the FEMA 356. The roof-displacement time history, story drift, and member forces for the hybrid frames are reported and compared with those of conventional SAC frames without semi-rigid connections.     

既有钢框架建筑的损伤检测和易损性分析

Northridge地震造成大量钢框架建筑在梁-柱焊接节点发生脆性破坏。对类似框架建筑的抗震性能进行研究,提出了几种旧建筑物修复或升级的课题。首先是可能发生焊接破坏的建筑范围的检测。第二是检测中所识别的连接断裂是否应该在允许长期使用前进行修复。第三是连接修复的费用。选择某既有钢框架中被检测的连接为目标函数,并提出了有效的方法,用于地震脆性评估。     

Cyclic response characteristics of retrofitted moment resisting connections

Experimental studies were conducted in order to investigate the behavior of the weld in steel moment resisting connections. A total of forty seven reduced-scale subassembly model specimens were tested that represent welded moment resisting connections of the beam to box column. These specimens were used to study the following aspects in fabrication and retrofitting of moment resisting connections: Complete joint penetration (CJP) groove weld behavior, transversely loaded fillet weld behavior, grinding and rewelding influence on weld behavior, reinforcing of connection with T-stiffener and rib plates, strain rate effect on weld and material characteristics and electrode toughness effect on weld behavior. Following test result interpretations, five full-scale moment resisting connections of beam to box column were fabricated and tested. These models included one specimen fabricated with details of an outdated connection, two specimens with an improved CJP groove weld detail, and two specimens retrofitted by T-stiffeners. Each specimen was subjected to a standard quasi-static cyclic load pattern. Overall, the improved and retrofitted specimens performed well, achieving total (elastic plus plastic) story drift ratios of at least 4% radians in magnitude before experiencing 20% strength degradation.     

Optimized and decentralized pulse control of seismically excited steel structures

The idea of decomposing a centralized complicated system into several synchronous decentralized subsystems has been resulted into the development of decentralized control methods. In this study, a decentralized pulse control scheme is presented based on the theory of Inclusion Principle for steel systems comprising a multi-overlapping structure. The proposed control algorithm is basically an active control system that generates corrective pulses at each moment when the displacement or acceleration exceeds the predefined threshold. In order to evaluate the performance of proposed control system, a numerical study is conducted. The control system is implemented for two linear structural models of five- and twenty-story steel buildings. An optimization algorithm (PSO) is also used to determine the locations of required control inputs in the 20-story building. The results show that the proposed algorithm can substantially mitigate the structural response under different earthquake records (for 5-story model) and different subsystem configurations (for 20-story model).     

高强度钢材疲劳性能研究进展

疲劳破坏是钢结构失效的主要形式,也是工程界与学术界关注的重点。在总结了国内外高强钢母材、焊缝连接和螺栓连接的疲劳性能研究现状基础上,介绍了疲劳寿命理论计算方法,结合大量试验数据分析统计了高强度钢材疲劳寿命发展规律,并基于国内外不同的疲劳设计规范对高强钢母材及连接接头的抗疲劳能力进行了评估。结果表明：随着钢材强度等级的提高,高强钢母材表现出较好的疲劳性能,规范设计曲线偏于保守,明显低估了高强钢母材的抗疲劳性能;受焊接工艺和焊接质量影响,高强钢焊缝连接的疲劳强度提高幅度较小,ANSI/AISC 360-10和EN 1993-1-9规范曲线能够较好地评估Q460D与Q690D焊缝连接的疲劳特性,并具有足够的安全储备;螺栓连接的疲劳强度受预紧力、摩擦面处理、成孔方式等众多因素影响,已有研究表明随着钢材强度的提高,疲劳强度亦有改善,ANSI/AISC 360-10和BS 7608-2014设计曲线适用于Q460螺栓连接疲劳寿命计算,具有足够安全保障,对于Q690钢螺栓连接疲劳性能评估,规范方法偏于保守。随着高强度钢材在实际工程中的应用增多,需开展大量不同等级高强钢母材和连接形式的疲劳试验,补充Q460及以上强度钢材的疲劳设计方法和细部连接构造。     

高强度钢框架梁柱节点低周疲劳断裂性能试验研究

高强度钢结构节点的低周疲劳断裂性能是影响其抗震性能的关键因素,对于高强度钢结构的抗震设计及其在抗震区的推广应用至关重要。为研究受强震作用高强度钢结构节点的低周疲劳断裂性能,完成了4个高强钢框架栓-焊混接梁柱节点足尺试件的低周疲劳往复加载试验,包括2种不同的焊接孔形式和4种焊接工艺,测得各试件的断裂失效模态及承载性能。基于试验结果,分析了焊接工艺细节及焊接孔形式、钢材强度对高强钢框架梁柱节点断裂性能的影响,研究了这类节点的断裂失效机制。结果表明：当采用有效的构造改进措施,且翼缘焊缝质量得以保证时,高强度钢框架梁柱节点破坏前能承受较大的塑性变形,断裂性能良好。     

Reducing seismic vibrations of typical steel buildings using new multi-level yielding pipe damper

Multi-level Pipe Damper (MPD) recently proposed by the authors is a passive control device to reduce the seismic vibration. In this research, seismic response of steel structures equipped with MPD is studied. To evaluate the effects of the proposed damper, typical 5, 10 and 15-story steel buildings are modeled and their seismic responses under seven earthquake excitations are investigated using dynamic nonlinear time-history analyses by SAP2000 program. Results show the effectiveness of MPD to altering the seismic response of the structures such that maximum displacement reduced by average of 54, 52, and 19% and maximum roof acceleration decreased by average of 16, 14, and 11% compared to those of the bare frames for the 5, 10 and 15-story buildings respectively. Moreover, using MPD decreases the structural and nonstructural damages noticeably by limiting the inter story drifts because of the secondary hardening branch of force-displacement by average of 53, 54, and 11% for the 5, 10 and 15-story buildings respectively proving the effectiveness of the proposed damper as a retrofitting technique for structures at high seismic risk areas.     

Fatigue of girth butt weld for cast steel node connection in tower structure under wave loadings

The application of cast steel node shows a popular tendency in long‐span space structures. The girth butt welds in the joint are the critical parts under fatigue loading. This study presents a fatigue life evaluation of the girth butt welds for the cast steel node connections, which are in a steel tower structure on an offshore platform under heavy wave fatigue loadings. The refined node FEM model is built including the welds. The random waves are treated as ergodic stationary stochastic process; the node structure is considered as a linear dynamic amplification system to decide its output of the stress amplitude response while the random wave is inputted into the system. The welds are designed as different details of bilateral weld, single‐sided weld with a sleeve, single‐sided weld with a backing plate or without a backing plate. The fatigue life of every weld detail is studied by hot‐spot stress method, and the design of weld detail combination is analyzed. Copyright © 2013 John Wiley & Sons, Ltd.     

奥氏体型S30408不锈钢角焊缝连接拉伸试验研究

为研究奥氏体型S30408不锈钢角焊缝连接接头的承载性能,对6个正面角焊缝连接试件和5个侧面角焊缝连接试件进行了拉伸试验,测得焊缝连接试件在拉伸作用下的极限荷载,以及焊缝强度、焊缝随荷载的变形情况,并对焊缝的破坏状态进行了观察。试验结果表明：正面角焊缝连接接头焊缝断裂面呈底部垂直于芯板表面而上部接近30°斜截面的不规则撕裂状,其抗拉强度平均值742 MPa,焊缝平均变形量为2 875 mm。侧面角焊缝连接接头焊缝断裂面较为平整,接近45°理论值,其剪切强度平均为506 MPa,焊缝平均变形量为4 387 mm。正面角焊缝连接试件焊缝抗拉强度为侧面角焊缝连接试件剪切强度的1.47倍。正面角焊缝和侧面角焊缝连接试件承载力试验值均高于CECS 410:2015《不锈钢结构技术规程》和欧洲规范Eurocode 3的设计值,CECS 410:2015规程中对于正面角焊缝和侧面角焊缝连接试件承载力设计值的规定过于保守;欧洲规范Eurocode 3对正面角焊缝连接试件承载力设计值的规定也较为保守,而对侧面角焊缝连接试件承载力设计值的规定较为合理。     

Seismic Performance Evaluation of Steel Box-Column Connections with ESW Stiffeners

The purpose of this study is to evaluate the seismic performance of steel box-column connections with electro-slag welding (ESW) stiffeners. Steel box columns have been widely adopted in seismically active areas, such as Japan and Taiwan. It is a common practice to weld diaphragm plates to the inner walls of steel box columns using the ESW process. However, there is still a lack of study evaluating the seismic performance of these steel box-column connections. In the first part of this paper, a literature review examines ESW stiffeners and their impacts on steel box-column connections. In the second part, finite element analysis is conducted on ESW misalignment and eccentricity. The result shows a correlation between connection failures and ESW stiffeners. In addition, ESW fusion diameters can affect the connections more significantly than ESW eccentricities and the thickness of diaphragm plates.

     

浅谈建筑工程的质量和房屋的寿命

从基础处理，地梁、圈梁、角柱的设置，砌体锚固筋的放置，钢筋的搭接长度和焊接要求等方面，就工程的质量与房屋寿命的关系进行了探讨，以提高建筑工程的质量，延长建筑物的使用寿命。     

Experimental investigation of beam-to-column connection with SHN490 steel under cyclic loading

Seismic performance of beam-to-column connections used in the middle-low rise buildings was investigated through the cyclic loading test. Four joint specimens were prepared in accordance with the variables of material and connection type. In two cases of welded connection, the brittle fracture in weld did not occur but cracked at heat-affected zone (HAZ) and/or near weld access hole. In the connections with extended end-plate, punching failure followed by end-plate failure occurred at the flange of column around bolt head. The moment capacities based on failure modes were calculated and compared with the test results. The connections were classified as rigid, semi-rigid, flexible in terms of bending stiffness and strength.

     

Ductility reduction factor and collapse mechanism evaluation of a new steel knee braced frame

In this study, the suitability of a new structural system called the knee braced frames (KBFs) is investigated for seismic resistant steel structures. In these structural systems, ends of beams are connected to columns by hinges (simple connection) instead of rigid connections, and ends of knee braced elements are connected to columns and beams by hinges as well. In the present paper, in addition to a comparison between elastic behaviour and elastic fundamental natural period, the ductility reduction factor and the type of collapse mechanism in steel KBFs and steel moment resisting frames (MRFs) are compared. The study revealed that the stiffness of steel buildings can be increased considerably by applying knee braced elements and the effects of knee braced elements are highly dependent on knee braced configuration. By applying the pushover analysis, it was observed that the type of collapse mechanism of KBFs is very similar to the mechanism of MRFs. Furthermore in most cases, the ductility reduction factor, R_μ, obtained from steel KBFs is greater than the ductility reduction factor obtained for steel MRFs. Based on the similarity between type of collapse mechanism and the proximity of ductility reduction coefficients of the KBFs and MRFs systems, it can be concluded that the new steel knee braced frame systems can be categorised as steel MRFs with rigid connections.     

Schweißen unter Betriebsbeanspruchung – Werkstoffkennwerte für einen S 355 J2G3 unter Temperaturen bis 1200 °C

Welding under service conditions – Material properties of S 355 J2G3 at temperatures of up to 1200 °C. Measures for rehabilitation, revitalisation of buildings are important future tasks to reduce costs. If reinforcements or changes of the system are necessary, welding is often the simplest way. If the structure, e.g. a bridge, a mast, an offshore platform, is exposed to varying load conditions, the question arises if it is possible to weld even under these service load conditions, which cause harmonic or repeated displacements of the weld seam. Systematic tests of welding under different load conditions as well as numerical simulations are described. An important task in this field is the determination of the material parameters under temperatures which approach the smelting point. Results showing the mechanical behaviour of construction steel S 355 J2G3 are presented in the paper.     

Effects of weld profile and undercut on fatigue crack propagation life of thin-walled cruciform joint

Fatigue may occur in undercarriages and support systems of trailers, haymakers, graders and swing-ploughs made up of thin-walled tubular sections with wall thicknesses less than 4 mm. Little research has been done on the fatigue of thin-walled tubular sections below 4 mm thickness. The weld profile and weld undercut may affect the fatigue crack propagation life of welded joints especially for thin-walled sections. Numerical analysis of 2-dimensional non-load carrying thin-walled cruciform joints was performed to determine the effect of weld profile and weld undercut on fatigue crack propagation life under cyclic tensile loading. The cruciform joints analysed are made up of 3 mm thick plates, joined by fillet welds. The Boundary Element Analysis System Software (BEASY) is used, which uses fracture mechanics theory to carry out crack propagation analysis. The weld profiles and weld undercuts were measured from welded connections in thin-walled fillet welded sections. The measured weld profiles and undercut were used in the analysis. The results are compared with those of a similar study to determine the comparative reduction in fatigue crack propagation life between thin-walled cruciform joints (T=3 mm) and thicker walled cruciform joints (T=20 mm). This paper provides an understanding of the impact which weld toe undercut has on the fatigue crack propagation life of thin-walled cruciform joints. The presence of undercuts may reduce the benefits of the thickness effect in thin-walled joints of thicknesses less than 4 mm.     

同跨受火时两层两跨组合钢框架抗火性能的试验研究

利用自行研制的火灾试验炉,对两榀两层两跨组合钢框架在同跨火灾作用下的性能进行了试验研究,火灾工况包括:梁、板、柱同时受火、节点不受火,梁、板受火而柱、节点不受火两种。试验中量测了各种工况的炉温,框架梁、柱及混凝土楼板中的温度分布及框架水平和竖向位移。结果表明:钢柱四面受火时,钢柱翼缘、腹板的温度相差很小;对于钢梁,除了与混凝土接触的上翼缘外,其余H型钢梁的裸露部分温度分布基本均匀;混凝土内部的温升一般滞后于钢梁,钢筋混凝土板对钢梁有约束作用,升温时混凝土限制钢梁的膨胀、降温时则限制钢梁的收缩,致使钢筋混凝土板中出现很多裂缝;组合梁的抗火性能明显优于钢柱,工程中应对钢柱和节点实施保护;钢框架未受火部分对受火部分约束很大,导致受火跨边柱与中柱的变形不对称,同样也产生了内力重分布。     

新型装配式钢管混凝土柱-钢筋混凝土梁框撑体系振动台试验研究

结合装配式建筑和钢管混凝土柱-钢筋混凝土梁组合框架结构的优点,提出新型装配式方钢管混凝土柱-钢筋混凝土梁组合框撑体系。为研究该类新型体系的整体抗震性能,设计制作了缩尺比为1/3的6层整体模型,对该模型输入了《建筑抗震设计规范》(GB 50011—2010)所建议的多种烈度下的地震激励,获得了其在相应地震激励作用下的结构响应及破坏形态,分析研究了其整体抗震性能、结构失效路径以及连接节点的可靠性。研究表明：①该类结构体系具有“强钢管混凝土柱-弱钢筋混凝土梁”及“强节点-弱构件”的理想失效路径;②梁的破坏点位于工字型钢接头梁段与钢筋混凝土梁段交界位置,距梁柱节点核心区域有一定距离,从而保证了节点核心区域的完整性;③结构部分楼层在强震下会因斜撑失效而形成薄弱层,造成结构响应的放大。