狗骨式钢结构梁柱节点的冲击荷载试验研究和有限元分析

设计采用FEMA标准过焊孔构造的2个削弱型狗骨式全焊连接的钢结构梁柱节点试件,对试件施加落锤冲击荷载来模拟结构的动态倒塌效应,考察狗骨式节点削弱程度对钢框架梁柱节点抗冲击性能的影响。通过试验获得节点试件的破坏形态及其冲击荷载和位移时程曲线,分析试件冲击过程动态响应规律以及节点动态转角和耗能能力。试验结果表明:节点试件的主要破坏形态是钢梁塑性铰截面上翼缘屈服的面外变形和腹板扭曲变形;2个节点试件均具有良好的抗冲击转动能力,其最大转角均远远超过FEMA350标准抗震设计的转角限值(θ=0.077 rad)要求;削弱型狗骨式全焊连接节点相对普通全焊接节点的耗能能力和延性均明显提高。采用ABAQUS软件建立了狗骨式梁柱节点子结构的有限元分析模型,通过分析狗骨式梁柱节点在冲击作用下内力发展规律可知,狗骨式节点设计有助于构件向悬链线效应转换。     

预应力型钢混凝土梁-钢管混凝土叠合柱框架中节点受剪性能分析

基于ABAQUS平台,建立了预应力型钢混凝土梁-钢管混凝土叠合柱框架中节点精细化数值有限元模型,计算得到了柱顶水平荷载-位移滞回和单调加载曲线。在对比计算单调加载和实测滞回曲线基础上,研究了节点在柱顶水平荷载下的破坏全过程,细致考察了框架中节点的混凝土、型钢骨架、钢筋骨架以及预应力筋的应力状态,探讨了此类框架节点的破坏机理;基于参数分析结果,研究了轴压比、预应力度、核心区钢管配钢率和配箍率对节点柱顶水平荷载-位移曲线和核心区剪力-剪切变形的影响,提出了节点核心区受剪承载力计算公式。研究结果表明,当节点试件水平荷载达到峰值点时,核心区钢管、箍筋及预应力筋均达到屈服,核心区混凝土被压碎,此时可作为节点核心区抗剪承载力计算的标志;提出的节点核心区的抗剪承载力计算公式,可供工程设计参考。     

Q460高强钢管柱-H形梁焊接节点循环拉伸性能试验研究

为研究Q460高强钢管柱-H形梁焊接节点在地震作用下的力学行为,对11个梁翼缘板与柱段焊接组成的节点进行了低周循环拉伸性能试验,研究了梁翼缘板与钢管宽度比α、厚度比β以及钢管宽厚比λ等参数对节点破坏模式、承载力、延性和耗能能力的影响规律。结果表明：在循环拉伸荷载作用下,Q460高强钢管柱-H形梁焊接节点的失效模式主要分为连接处焊缝断裂、连接处钢管面板断裂或梁翼缘板被拉断三种;高强钢梁翼缘板与钢管宽度比、钢管柱宽厚比对焊接节点的受力行为影响较大,当宽厚比α由25.0减小到18.75时,节点的应变能减小了134%;当节点破坏时,具有新型焊接通过孔构造的焊接节点极限位移超过传统构造节点近2倍,前者延性性能较好。研究成果可为高强钢管柱与梁焊接节点的抗震设计以及进一步的理论研究提供依据。     

矩形钢管混凝土柱-混凝土梁穿筋节点力学性能试验研究EI北大核心CSCD

针对矩形钢管混凝土柱-混凝土梁连接节点在高层建筑工程中存在传力不直接,施工难度大,施工质量难以保证的问题,结合北京CBD核心区Z13地块超高层项目,提出了矩形钢管混凝土柱-混凝土梁穿筋节点,对不同配筋率的矩形钢管混凝土柱-混凝土梁穿筋节点试件进行低周往复加载试验,研究节点的滞回性能、破坏形态、耗能能力和延性等力学性能。并与传统的矩形钢管混凝土柱-混凝土梁焊接牛腿式连接节点和矩形钢管混凝土柱-混凝土梁套筒牛腿式连接节点进行性能对比。在试验基础上,对矩形钢管混凝土柱-混凝土梁穿筋节点受力性能进行理论分析并推导适用的设计公式。结果表明:矩形钢管混凝土柱-混凝土梁穿筋节点与另外两种类型节点相比有较强的承载能力,能够满足“强节点,弱构件”及传递竖向荷载的结构设计要求,并且便于施工、质量可靠。在此基础上进行理论分析,提出节点受弯承载力设计公式并推荐型钢牛腿截面按照承担梁端剪力80%进行截面设计,为矩形钢管混凝土柱-混凝土梁穿筋节点设计提供技术支撑。     

矩形钢管混凝土框架节点抗震性能试验研究

通过三个矩形钢管混凝土框架节点(外加强环)模型的拟静力试验,以轴压比和梁柱线刚度比为参数,研究了该类框架节点的滞回曲线、延性、强度与刚度退化、耗能能力及其破坏特征。结论表明:矩形钢管混凝土框架节点滞回曲线呈饱满的"梭形",耗能能力强;强度与刚度退化缓慢;在达到极限荷载后具有良好的延性和后期变形能力,位移延性系数在3.5~4.48之间,满足延性节点的要求。经与钢筋混凝土框架、组合结构框架及钢框架节点抗震性能比较,可知:全钢管混凝土框架节点具有较好的受力性能和抗震能力,该文的研究成果可用于指导钢管混凝土结构的工程实践。     

预应力钢带加固钢筋混凝土框架抗震性能试验研究

预应力钢带加固技术是一种新型加固技术,采用预应力钢带加固技术对钢筋混凝土框架梁端、柱端和节点核心区进行约束加固,可以有效提高钢筋混凝土框架结构抗震性能。对一榀采用预应力钢带加固的1/2比例的单跨三层钢筋混凝土框架试件进行低周反复加载拟静力试验,结合试验研究结果,对预应力钢带加固钢筋混凝土框架试件的破坏形态、荷载-位移滞回曲线、骨架曲线、层间位移角、位移延性系数、耗能性能和刚度退化等抗震性能进行了深入分析。研究结果表明,试件最大层间弹塑性位移角可以达到1/28.8,预应力钢带加固钢筋混凝土结构具有良好的延性和耗能性能,是一种切实可行、效果良好的抗震加固技术。     

方钢管混凝土柱-钢梁节点抗震性能试验研究与有限元分析

根据《矩形钢管混凝土结构技术规程》推荐的节点形式,制作5个隔板贯穿式节点试件,通过低周反复加载试验,探讨此类节点的抗震性能,分析梁端翼缘两侧的侧板、钢管柱的宽厚比以及隔板的外伸长度等因素对节点抗震性能的影响。试验结果表明:各试件实测滞回曲线均比较饱满,没有明显的刚度退化现象,具有较好的耗能性能;梁端翼缘两侧增加侧板不仅可以缓解隔板与梁相交的角隅处应力集中现象,而且提高了节点的延性。运用ANSYS 8.0对各节点试件在低周反复荷载作用下的滞回性能进行非线性模拟计算,分析轴压比、核心区混凝土强度、隔板外伸长度等因素对节点受力性能的影响。结果表明:轴压比和隔板外伸长度对节点受力性能的影响较大;有限元计算所得的骨架曲线与实测骨架曲线吻合较好。     

钢-混凝土组合框架子结构动态倒塌性能试验研究

为了研究中柱失效后钢-混凝土组合框架结构的动态倒塌性能,对2个1/3缩尺的组合框架子结构试件进行了抽柱试验研究。研究结果表明:当在组合框架梁上分别悬挂30 kN和60 kN的配重时,2个试件在中柱处的最大动态位移至少为振动停止后静态位移的1.34倍;在中柱抽除后,剩余结构仍处于弹性受力阶段且阻尼比较小;采用栓钉抗剪连接件的组合框架梁具有较大的加速度响应和动态位移响应;组合梁中采用开孔板连接件的框架子结构具有较好的整体刚度,其受倒塌荷载动力冲击作用的影响相对较小;随着中柱竖向位移的增加,组合框架倒塌荷载动力增大系数(DIF)呈现两阶段的变化规律。基于试验研究,建立了组合框架倒塌荷载DIF的数学计算模型。该研究成果可为钢-混凝土组合框架结构的倒塌性能分析提供参考。     

钢框架梁端翼缘板式加强型节点力学性能试验研究

钢框架梁端翼缘板式加强型节点是梁柱改良抗震节点的一种形式,这种节点包括翼缘板加强型及盖板加强型节点两种类型.为了研究这两种连接形式的延性及抗震性能,设计制作了4个缩尺比例为1/2的梁柱T型试件,研究了节点试件在循环荷载作用下的破坏形态、滞回曲线、骨架曲线、极限荷载、最大塑性转角、延性性能等,作为比较,还进行了1个传统栓...     

全再生方钢管混凝土柱-钢筋混凝土梁框架的抗震性能试验研究

通过1榀全再生方钢管再生混凝土柱-钢筋再生混凝土梁框架试件的低周反复加载试验,揭示了由再生粗骨料取代率为100%的全再生混凝土组成的方钢管混凝土柱-钢筋混凝土梁框架的受力机理和破坏形态,获取了其荷载-位移滞回曲线、骨架线、位移延性、能量耗散等抗震性能指标,并对其进行了详细分析。研究结果表明:即便是再生粗骨料取代率为100%的全再生混凝土组成的方钢管混凝土柱-钢筋混凝土梁框架,经过合理设计依然能够满足现行国家抗震设计标准要求;其滞回曲线饱满、位移延性系数接近3、层间位移转角达到1/30;破坏时的等效粘滞阻尼系数达到0.216,耗能能力强。     

采用螺栓连接的工字形全装配式RC剪力墙试验研究

采用连接钢框、高强度螺栓将带有内嵌边框的纵横向预制钢筋混凝土（RC）剪力墙连接起来,形成工字形剪力墙。为研究该全装配式剪力墙的受力性能和抗震性能,进行了3榀墙体的单调加载试验和1榀墙体的低周反复荷载试验,分析了该全装配式工字形剪力墙的承载能力、刚度、延性性能、耗能能力、连接件的应变分布以及连接件间的相对滑移等,最后探讨了试件的极限抗剪抵抗机制。研究结果表明:该全装配式剪力墙具有较高的承载能力、较好的延性性能以及耗能能力,位移延性系数约为3~6;高强度螺栓的直径、连接钢框钢板的厚度对装配式剪力墙的抗侧刚度及峰值荷载有一定的影响;内嵌边框既传递了分布钢筋的应力,也起到了约束混凝土、增加RC剪力墙延性性能的作用。     

Exploratory investigation on mechanical anchors for connecting SMA bars to steel or FRP bars

Using superelastic shape memory alloys (SMAs) as reinforcing bars in concrete structures proved to have a great potential in seismic areas because of its recentering capability. However, using them in an entire structure is generally not economically feasible due to their high cost. Therefore, it is more practical to limit their use to the plastic hinge zones, while regular steel can be used in the other regions of the structure. Connections between SMA and steel are critical, and need to be strong enough to transfer the full force from SMA bars to steel bars. Various mechanical couplers are available in the market to splice bars in reinforced concrete (RC) structures, each of which has several advantages and disadvantages. The efficiency of these couplers for connecting steel bars is tested and reported in this paper. Since these couplers are intended for connecting steel bars only, another experimental investigation has been performed to determine the suitability of these couplers for connecting SMA with steel bars. Commercially available screw-lock couplers are found to be unsuitable for connecting SMA to steel bars. An existing coupler has been modified for SMA–steel splicing to allow SMA bars to achieve their full superelastic strain. Additional tests have also been performed for connecting FRP bars to SMA bars. A new generation mechanical-adhesive type coupler has been developed for splicing FRP to SMA bars.     

圆弧扩大头狗骨隔板贯通方钢管混凝土柱-H形钢梁节点抗震性能分析

对圆弧扩大头狗骨隔板贯通方钢管混凝土中柱-H形钢梁节点和常规节点进行了循环加载试验,对比研究了圆弧扩大头狗骨隔板对方钢管混凝土柱-H形钢梁节点抗震性能的影响,对节点试验试件进行了基于结构钢椭球面断裂模型和屈服模型的强震灾变分析。结果表明,隔板贯通方钢管混凝土中柱-H形钢梁节点起裂于梁腹板工艺孔处,节点域核心区混凝土形成"斜压短柱"效应,直至节点破坏时,核心混凝土未发生压碎或拉裂破坏。常规节点脆断于几何变化剧烈、应力高度集中的梁翼缘对接焊缝边缘,节点塑性转角约为0.016 rad。圆弧扩大头狗骨隔板构造消除了梁翼缘对接焊缝处的几何突变,促使塑性铰形成于远离节点区的梁削弱截面。圆弧扩大头狗骨节点的塑性转角可达到0.033 rad~0.041 rad,耗能性能和承载力较常规节点分别提高72%~86%和下降9.6%~12.6%。     

NES减震RC框架结构节点动力性能分析

为研究NES减震装置对钢筋混凝土框架结构节点抗震性能的影响,设计加工出一种NES新型减震器,进行了一个缩尺比为1∶4的五层钢筋混凝土框架结构模型振动台试验,对NES减震框架结构的1层和2层节点处钢筋应变、节点破坏模式、结构位移及结构自振频率在震害后的变化情况进行分析研究。试验结果表明:NES减震器可以有效降低钢筋混凝土梁柱纵筋箍筋应变以及减少结构的相对位移,减缓柱底和柱顶塑性铰的产生;节点处出现了梁端破坏和节点内剪切破坏,基本实现了框架“强柱弱梁”机制;NES减震器能够有效减少节点处混凝土的剪应力从而缓解节点混凝土的剪切破坏,整体结构最终破坏是由于柱底钢筋屈服,柱脚混凝土被压碎,与底板连接松动导致;设置NES减震器后结构自振频率下降速率降低,NES非线性减震器在降低结构地震响应,提高结构抗震能力、减轻结构震害损伤方面具有良好的控制效果。     

600MPa级钢筋混凝土柱抗震性能试验研究

为研究配置600 MPa级钢筋混凝土柱的抗震性能,对5个配置600 MPa级钢筋混凝土柱和1个对比普通钢筋混凝土柱进行低周往复荷载试验;分析了钢筋强度、箍筋间距和轴压比对试件破坏形态、滞回性能、承载力及延性、耗能性能以及刚度与强度退化的影响。研究结果表明:试件仍主要发生弯曲破坏,但600 MPa级纵筋与混凝土间出现了明显的粘结失效,且纵筋容易断裂;提高钢筋强度,试件的承载力和能量耗散均显著增加,但延性和耗能能力有所降低;而增大箍筋间距会明显降低试件延性和耗能能力,加快试件后期的强度衰减,但基本不影响承载力。总体上看,600 MPa级钢筋混凝土柱具有较好的抗震性能,能通过合理的设计将其应用于抗震结构中。     

Shear strength of concrete beams reinforced with steel bars milled from scrap metals

The paper reports a study on the shear resistance of concrete beams reinforced with mild steel bars that are milled from scrap metal such as old vehicle parts and obsolete machinery. It has been previously reported that because the chemical compositions of carbon, sulphur and phosphorus in these reinforcing steel bars exceed the maximum allowable limits, the characteristic tensile strengths are too high and ductility too low for standard mild steel. Concrete beams reinforced with such bars to resist flexural tensile and shear stresses were tested under a two-point loading system to provide a central constant moment region and outer shear spans. Tested beams exhibited little deflection and very low ductility prior to collapse. Experimental failure loads for the beams averaged 123% of the theoretical failure load, which was generally governed by either shear or yielding of the tension steel. Shear failure was mostly initiated by diagonal tension cracks, followed by either crushing of the concrete, or splitting of the concrete over the longitudinal tensile bars near the supports. Failure of the beams was brittle and the post-cracking strain energy absorption averaged 357.9 Nm. At failure the maximum crack width in the beams ranged from 1.12 to 5.0 mm, the largest sizes forming in the diagonal shear cracks.     

钢筋拼接GFRP管混凝土组合构件的轴压性能试验研究

钢筋拼接GFRP管混凝土组合构件是利用在2个独立的GFRP管连接处的内部设置一定长度钢筋笼,再在内部浇注混凝土,而形成的一种新的连续GFRP管混凝土组合构件。近年来,不少国内外研究人员对连续GFRP管混凝土构件的力学性能做了一些研究,而对拼接GFRP管混凝土构件的力学性能研究较少,所以,有必要借助试验,研究其力学性能。该文主要对钢筋拼接GFRP管混凝土组合构件的轴压性能进行了一定的试验研究,试验结果表明,在荷载达到60%Pu(Pu-极限荷载)左右时,GFRP管开始发挥“套箍”作用,拼接试件破坏位置不同于连续试件发生在一定范围内,而是发生在距连接处一定距离,并且,钢筋连接件的箍筋对混凝土起到约束作用。此外,试件破坏时纵筋均屈服,且纵筋对连接处的变形基本没有影响,拼接试件连接处均未破坏,说明采用低含钢率1.96%即可保证拼接GFRP管轴心受压组合构件正常工作。     

Repairing corroded RC beam with near-surface mounted CFRP rods

This experimental program investigates the possibility of using Carbon-Fiber-Reinforced Polymer (CFRP) rods to repair RC beams damaged by steel corrosion. The 6-mm-diameter carbon-epoxy pultruded FRP rods were implemented in undamaged areas of the concrete cover by using the Near Surface Mounted reinforcement (NSM) technique. The corroded beam tested was stored in a chloride environment under service loading for 23 years, which was representative of real structural conditions. The corroded beam showed longitudinal corrosion cracks more than 3 mm in width along the tension reinforcing bars. The repaired corroded beam was tested in three-point flexure up to failure. Then, concrete was removed around the reinforcing bars in order to measure the real local steel cross-section distribution. The maximum reduction in steel cross-section measured in the tension area was about 36% and was located at mid-span. In spite of this heavy corrosion, the bearing capacity measured on the repaired beam was equal to that of the uncorroded control beam. In our experimental conditions, the NSM technique was applicable for repairing corroded concrete structural members.     

Nonlinear static cyclic pushover analysis for flexural failure of reinforced concrete bridge columns with combined damage mechanisms

In a fixed connection of a reinforced concrete bridge column, experiments have shown that the longitudinal reinforcing bars slip at the interface of the connection under cyclic seismic loading. The bond-slip (or strain penetration) of the longitudinal reinforcing bars causes a pinching effect in the column’s hysteresis curve. The bond-slip (or strain penetration) reduces the column’s stiffness and increases its deformations during an earthquake event, significantly affecting the performance of the column. Significant strength degradation has also been observed after the column reaches its ultimate strength. This study is to model a reinforced concrete column’s performance under cyclic pushover analysis with combined damage mechanisms including concrete cracking, concrete strength degradation due to concrete spalling, longitudinal reinforcing bars buckling, and bond-slip between longitudinal reinforcing bars and concrete. Two multi-scale nonlinear finite element models with and without the bond-slip (or strain penetration) of a reinforced concrete bridge column are proposed. The simulated column’s hysteresis curves under nonlinear cyclic pushover are compared with available experimental data. The results show that the proposed models with bond-slip together with combined damage mechanisms can effectively predict the seismically induced flexural failure behavior of the reinforced concrete bridge columns.