Local Tensile Strength of Connection Between H-Steel Beam Flange and Concrete-Filled Circular Column Tube with Through Diaphragm

This paper focused on investigating local tensile strength of connection between steel beam flange and concrete-filled circular column tube with through diaphragm. Three specimens were designed and tested to failure, and the structure behavior was studied by experiment and FEM analysis. On the basis of the results obtained, an estimation for local plastic and ultimate strengths of the connections using yield line theory was attempted, which results in a good prediction.

Seismic Behavior of Diaphragm-Through Connections of Concrete-Filled Square Steel Tubular Columns and H-Shaped Steel Beams

Based on the introductions of a type of diaphragm-through connection between concrete-filled square steel tubular columns (CFSSTCs) and H-shaped steel beams,a finite element model of the connection is developed and used to investigate the seismic behavior of the connection.The results of the finite element model are validated by a set of cyclic loading tests.The cyclic loading tests and the finite element analyses indicate that the failure mode of the suggested connections is plastic hinge at the beam with inelastic rotation angle exceeding 0.04 rad.The suggested connections have sufficient strength,plastic deformation and energy dissipation capacity to be used in composite moment frames as beam-to-column rigid connections.

Monotonic and Cyclic Pushover Tests of Wood Beam-Column Connections:Ancient Chinese Tenon Joint vs Typical and Simplified US Connections

Wood beam-column frame is a popular structural system in United States and in ancient China. Chinese wood beam-column frame structures showed better seismic resistance properties than the US ones.The tenon joint is one of the reasons.This study performed monotonic and cyclic pushover tests to understand the behavior of Chinese tenon joints versus the behavior of the commonly used US wood beam-column connections. The test results indicate that the typical US wood beam-column connection is very strong under monotonic loads.The ancient Chinese tenon joint has the best behavior under cyclic loads.

Seismic performance and comparison of three different I beam to box column joints

Despite the inherently advantages of the box column, finding the best option for the I beam to the box column connection is the main challenge in using the box column as a structural member for special moment frames. In this paper, the seismic performance of urtreinforced connection, weakened connection and strengthened connection was evaluated through a comprehensive experimental program. The seismic comparisons were fabricated by assessing the strength, ductility and energy dissipation in each configuration. Three full scale tests with several connections were carried out. All the specimens were subjected to cyclic loading and prior to failure by forming a plastic hinge in the beam, all the connections managed to reach an inelastic rotation of more than 6.0% rad. The experimental and analytical results showed that the seismic performance of the strengthened connection with flange and shear plates turned out to be the most effective in the beam to the box column connection. Moreover, the normalized stress distribution of the continuity plates revealed that the possibility of the weld fracture in unreinforced connection is more than other specimens.

Seismic performance of precast bridge columns connected with grouted corrugated-metal duct through biaxial quasi-static experiment and modeling

In this paper,the seismic behaviors of precast bridge columns connected with grouted corrugated-metal duct(GCMD)were investigated through the biaxial quasi-static experiment and numerical simulation.With a geometric scale ratio of 1:5,five specimens were fabricated,including four precast bridge columns connected with GCMD and one cast-in-place(CIP)bridge column.A finite element analysis model was also established by using OpenSees and was then calibrated by using the experimental results for parameter analysis.The results show the biaxial seismic performance of the precast bridge columns connected with GCMD was similar to the CIP bridge columns regarding ultimate bearing capacity and hysteresis energy,and further,that it could meet the design goal of equivalent performance.The seismic performance of the precast bridge columns connected with GCMD deteriorated more significantly under bi-directional load than under uni-directional load.A proper slenderness ratio(e.g.,7.0-10.0)and longitudinal reinforcement ratio could significantly improve the energy dissipation capacity and deformation capacity of the precast bridge columns,while the axial load ratio and concrete strength had little influence on the above properties.The research results could bring insights to the development of the seismic design of precast bridge columns connected with GCMD.

Influence of Axial Load Ratio on Shear Behavior of Through-Diaphragm Connections of Concrete-Filled Square Steel Tubular Columns

Nonlinear finite element analysis and parametric studies were carried out to study the influence of axial load ratio on the shear behavior of the through-diaphragm connections of concrete-filled square steel tubular columns. The analysis reveals that smaller axial load ratio can improve the shear bearing capacity and ductility while larger axial load ratio will decrease the shear behavior of the through-diaphragm connections. The parametric studies indicate that the axial load ratio should be limited to less than 0.4 and its influence should be considered in the analysis and design of such connections.

Seismic performance of interior precast concrete beam-column connections with T-section steel inserts under cyclic loading

An experimental investigation was conducted to study the performance of precast beam-column concrete connections using T-section steel inserts into the concrete beam and joint core,under reversed cyclic loading.Six 2/3-scale interior beam-column subassemblies,one monolithic concrete specimen and five precast concrete specimens were tested.One precast specimen was a simple connection for a gravity load resistant design.Other precast specimens were developed with different attributes to improve their seismic performance.The test results showed that the performance of the monolithic specimen M1 represented ductile seismic behavior.Failure of columns and joints could be prevented,and the failure of the frame occurred at the flexural plastic hinge formation at the beam ends,close to the column faces.For the precast specimens,the splitting crack along the longitudinal lapped splice was a major failure.The precast P5 specimen with double steel T-section inserts showed better seismic performance compared to the other precast models.However,the dowel bars connected to the steel inserts were too short to develop a bond.The design of the precast concrete beams with lap splice is needed for longer lap lengths and should be done at the beam mid span or at the low flexural stress region.

Numerical stress analysis of crack at welded beam-to-column connection

In the past, brittle fracture of steel structure was reported rarely under earthquake. However, recent earthquakes, especially Northridge Earthquake (USA) and Hyogoken Nanbu earthquake (Japan), astonished engineers in the field of construction. The experience from recent earthquakes of USA and Japan shows that brittle fracture of welded steel structure always starts from high stress zone with welded crack [1～5] . As backing bar for grooved weld on beam flange exists, artificial crack is formed because of lack of fusion at the root of flange weld. In this paper stress distribution of connection is computed with FEM, and stress concentration at the root of flange weld is also analyzed. Stress intensity factors (SIFs), K I, at the root of flange weld are computed in the method of fracture mechanics. The computation shows that stress intensity factor on bottom flange weld is obviously higher than that on top flange weld. It is proved by the fact that brittle fracture is liable to start at the root of bottom flange weld on actual earthquake [1,4] . Finally measures are brought forward to avoid fracture of weld structure against earthquake.

Punching Shear Behavior of RC Slab-Column Connections with Nonrectangular Columns

This paper present an experimental study on the RC slab-column connections with nonrectangular columns, namely cross-shaped column, T-shaped column and L-shaped column. The punching shear deformation and strength characteristics of slab-column connections with nonrectangular columns under punching shear load are investigated. Nine specimens with the three kinds of nonrectangular columns and two reference specimens with square columns are tested. The tested ultimate loads, deformations, and failure modes of specimens are presented and discussed. Test results reveal that the punching shear strength and ductility of the connections with nonrectangular columns are higher than those of the corresponding connections with square columns, and also prove that the application of nonrectangular columns to flat-plate structure was feasible. Based on the test results, one method of calculating punching shear strength of connections with nonrectangular columns is proposed, which conforms with the current design practice of China. The test results on the punching shear strength are compared with the predictions of the formulas proposed by codes of several different countrie; and the predictions given by ACI code and China code are found to be conservative as the reinforcement ratio is increased.

Numerical Modeling on Seismic Performance of Castellated Composite Beam⁃Reinforced Concrete Column Connection

The hybrid structure consisting of castellated composite beam and compound spiral hoop reinforced concrete column take full advantages of steel and concrete material.To popularize the structural form in real conditions,a beam⁃through⁃type beam⁃column connection is proposed.Two 1/2⁃scaled connection specimens were tested and three⁃dimensional finite element models of the beam⁃column connection were set up.The longitudinal reinforcements,concrete beam,and column were simulated by link and solid elements,respectively.The influences of the parameters such as expansion ratio,location of web opening,and original height of steel beam were studied.The results show that connections possessed high initial rigidity.The expansion ratio of steel beam showed more important influence on the connection’s ultimate bearing capacity.For the connection models with steel beam expansion ratio of 1.4,the maximum increment of the ultimate bearing capacity of the connection could reach 28%.In order to prevent the local buckling failure of steel beam from occurring near web opening,the expansion ratio of steel beam should not be greater than 1.3.

Experimental study on full-scale steel beam-to-column moment connections

Ten full-scale steel beam-to-column moment connections used in moment-resisting frames （MRFs） were tested to study the failure process, failure mode, strength and plastic rotation capacity. The specimens include one traditional welded flange-bolted web connection, one traditional fully welded connection, four beam flange strengthened connections, three beam flange weakened connections, and one through-diaphragm connection. The test results show that the connections with flange cover plates or with partly cut beam flanges satisfy the beam plastic rotation demand for ductile MRFs. From the measured stress profiles along the beam flange and beam web depth, the mechanics of brittle fracture at the end of the beam is discussed. Design recommendations for steel beam-to-column moment connections are proposed.

部分包覆钢-混凝土组合梁柱节点抗震性能试验研究

为研究不同连接构造的部分包覆钢-混凝土组合梁柱节点(PEC梁柱节点)的抗震性能,对2个PEC梁柱节点试件进行了拟静力加载试验,研究了低周往复荷载作用下PEC梁柱节点试件的破坏现象、滞回曲线、骨架曲线、延性、耗能能力和刚度退化等抗震性能。结果表明:强轴连接PEC梁柱节点的滞回曲线呈梭形和弓形,在达到极限承载力后仍能保持一定的延性和耗能能力;弱轴连接PEC梁柱节点牛腿与梁间的焊缝处发生破坏,未展现出预期的耗能能力,PEC梁仍在弹塑性状态,没有达到极限状态;PEC梁柱节点核心区混凝土替换为加劲肋板后,试件仍具有较好的承载力、延性和耗能能力,刚度退化规律无明显变化,且强轴连接节点与弱轴连接节点刚度变化规律基本一致;PEC柱牛腿设计过短会导致焊缝连接处断裂,试件延性和耗能能力得不到发挥,剩余刚度较大。

模块化钢结构梁柱子结构抗连续倒塌性能研究

模块化钢结构作为一种高度预制的装配式建筑,具有工业化程度高、绿色节能环保等优点。但是,由于模块化钢结构体系超静定次数较低,其在极端荷载工况下的抗连续倒塌性能应予以特别关注。模块化钢结构梁柱子结构作为主要的传力路径,具有多梁多柱等有别于传统框架梁柱子结构的特点,需对其抗连续倒塌性能开展研究工作。该文针对采用螺栓-角件连接节点的模块化钢结构梁柱子结构进行Pushdown试验及数值模拟,分析了在双柱失效、单柱失效工况下试件的破坏模式和抗连续倒塌机理。结果表明,梁柱子结构在两种工况下的受力机理不同:在双柱失效工况下,梁柱子结构抗力主要由梁机制提供,加载后期抗力提供方式体现出一定的悬链线机制,并随水平连接板厚度的增加而增强;在单柱失效工况下,子结构抗力主要由模块间水平连接抗剪能力提供,由梁机制及悬链线机制提供的抗力较小。

基于转动摩擦铰阻尼器的干式装配梁-柱节点抗震性能试验

基于转动摩擦铰阻尼器(RFHD),提出了转动摩擦耗能干式装配梁-柱节点(DRFDBJ)。为了验证DRFDBJ结构对于实现预期力学性能的可行性和合理性,以施加在摩擦片表面的螺栓预紧力(P_(c))为变量,开展了2个工况下的DRFDBJ试件低周往复拟静力试验研究。结果表明:DRFDBJ结构的力学性能主要由RFHD提供并控制,试验中节点呈现了稳定的承载力和理想的变形、耗能能力,并实现了预期的损伤集中;2个不同P_(c)水准下节点承载力的试验值与理论值误差不超过5%,通过调整P_(c)可实现节点承载力的调控,为DRFDBJ结构承载力的可调控提供了支撑。

钢管混凝土柱-钢梁外加强环螺栓连接节点抗震性能有限元分析

为深入研究钢管混凝土柱-钢梁外加强环螺栓连接节点的抗震性能,建立了螺栓连接节点的精细化三维实体有限元模型。在对已有试验成果进行验证分析的基础上,研究加劲肋、螺栓连接数量对节点塑性耗能分配机制的影响。结果表明:当钢材本构后期考虑韧性损伤后,有限元计算结果与已有拟静力试验结果更吻合;CFST-1节点(梁高300 mm,有螺栓垫板)耗能能力最优,但仅达到相应焊接节点的一半;与CFST-1节点相比,CFST-3节点(梁高300 mm,无螺栓垫板)及CFST-2节点(梁高250 mm,有螺栓垫板)的总耗能更低;各螺栓节点的塑性耗能分配机制主要依靠梁耗能,而相应的加强环焊接节点主要依靠梁与加强环耗能;当螺栓节点采用环板加劲肋、4排螺栓以及腹板加劲肋构造优化后,刚度、承载力、延性与相应焊接节点一致,总塑性耗能达到刚接节点的79.1%,基本达到刚接节点的抗震水平。

柱脚不同连接形式钢框架-摇摆墙结构抗震性能对比分析

增设摇摆墙后框架结构地震下柱脚仍会发生一定程度的塑性损伤,将柱脚设置为铰接或提离后有望减轻上述缺陷。以三层、六层和九层钢框架为基准模型,分别建立柱脚固接、铰接及提离三种框架-摇摆墙结构模型并进行动力弹塑性时程分析,对比各结构最大侧向位移、层间位移角、峰值加速度、层间剪力、墙体剪力和弯矩等;进一步建立耗能连梁固接和铰接的对比模型,研究连梁连接方式对结构抗震性能的影响。结果表明:三层模型中柱脚固接时侧向位移、层间位移角、加速度、层间剪力及摇摆墙墙体剪力的控制效果最优,六层、九层模型中分别对应柱脚提离和柱脚铰接效果最好;摇摆墙墙体剪力图和弯矩图分别呈现“C形”和“反C形”,柱脚固接时墙体弯矩均为最小,与层数无关。柱脚固接耗能连梁两端采用固接最优,柱脚铰接和柱脚提离时耗能连梁两端采用铰接形式效果更优。此分析可为框架-摇摆墙结构进一步推广应用提供参考。

功能可恢复RCS混合框架结构研究进展

钢筋混凝土柱-钢梁(RCS)混合框架结构以其结合了混凝土优异的抗压性能及钢材优异的抗弯性能而受到广泛关注,而可恢复功能结构以其震后快速恢复使用功能的能力,也成为地震工程界研究的新热点。功能可恢复RCS混合框架结构可以在弯矩较大的梁端和柱脚部位设置可更换构件,实现结构的功能可恢复能力。文中简述了近年来功能可恢复RCS混合框架结构研究进展,重点关注各类型功能可恢复钢梁、功能可恢复摇摆柱脚的构造研究,介绍了功能可恢复RCS混合框架结构性能分析研究进展。最后,对功能可恢复RCS混合框架结构仍需深入研究的问题进行了展望。

马鞍山长江公铁大桥Z3号桥塔施工关键技术

巢马城际铁路马鞍山长江公铁大桥主航道桥为(112+392+2×1120+392+112)m三塔钢桁梁斜拉桥,Z3号桥塔为超高多肢钢-混组合塔,高308 m。上塔柱钢结构高87.5 m,分13个吊装节段,最重505 t;中、下塔柱混凝土结构高217.5 m,分38个节段液压爬模施工;钢-混结合段高3 m,内部采用PBL键+剪力钉+高强度钢锚杆+高强度混凝土结构形式。在中塔柱设置钢管临时横撑控制塔柱线形及应力;下横梁采用落地支架法分层施工,与对应塔柱同步浇筑;钢-混结合段混凝土采用C60细石补偿收缩混凝土+高强度灌浆料,保证了混凝土施工质量;采用工厂“2+1”立体匹配制造、“提升站+运输栈桥”钢塔节段转运等技术,并研制15000 t•m超大型塔吊,实现了钢塔柱大节段的制造、整体滩地运输和吊装;钢塔节段间采用栓焊组合连接形式,通过设置工艺隔板、双面坡口等措施控制了钢塔焊接变形;利用定位桁架临时锁定钢塔合龙段实现了钢塔的精确合龙,定位桁架受力及变形均满足要求。

装配式双槽钢拼合PEC柱受压性能试验研究

为发挥钢-混组合结构优良性能及装配式结构施工节能、质量可控的优势,满足建筑模块化、工业化发展需求,提出螺栓连接装配式双槽钢拼合部分包裹混凝土(PEC)组合柱,开展1个纯钢拼合柱、5个组合拼合柱轴心受压及偏心压弯性能试验,结合数值模拟对组合柱破坏形态、应变发展规律、变形性能和承载能力进行分析研究,揭示了螺栓间距、混凝土外伸宽度、相对偏心距大小等因素对双槽钢拼合柱受压力学性能的影响规律.研究结果表明:轴心受压双槽钢拼合柱破坏模式均为整体失稳破坏,偏心受压双槽钢拼合柱均为压弯破坏,使用钢板及螺栓能可靠连接构件,加载过程双肢未发生分离;加密螺栓间距能有效增强组合柱峰后延性,在一定间距范围内构件具较高刚度,由1000mm加至500 mm极限承载力提高4.43%;开孔钢板连接件能约束且保证混凝土与型钢协同工作,破坏阶段前混凝土与型钢未出现明显黏结分离;混凝土外伸宽度增加能提高构件稳定性能.提出考虑单肢影响的轴压承载力计算方法与基于Eurocode 4规范双槽钢拼合柱轴力-弯矩(N-M)相关曲线,理论结果与试验吻合较好,可为装配式拼合柱设计应用提供理论支撑.

蜂窝梁H型柱绕弱轴向端板连接节点抗震性能研究

目的 提出一种蜂窝梁H型柱绕弱轴向端板连接节点,探究节点抗震性能及不同因素对其影响规律,为相关设计提供借鉴。方法 理论分析蜂窝梁H型柱绕弱轴向端板连接节点传力机制,建立并验证蜂窝梁H型柱绕弱轴向端板连接节点ABAQUS模型,研究端板厚度、开孔率对节点初始转动刚度、承载能力、耗能能力、延性、刚度退化及破坏形式影响规律。结果 蜂窝梁H型柱绕弱轴向端板连接节点弯矩最终由柱腹板与正向端板抗弯、柱翼缘与侧向端板抗剪承担;剪力最终由高强摩擦型螺栓连接面间摩擦力承担;端板厚度及开孔率越大,节点耗能进入蜂窝梁耗能阶段越早,连接刚度足够时节点抗震性能主要取决于蜂窝梁。结论 提出了蜂窝梁H型柱绕弱轴向端板连接节点弯矩路径传递分配系数计算方法,建议节点端板厚度应大于1倍柱翼缘厚度,开孔率取值为60%~65%。