Y形高强钢组合偏心支撑框架结构抗震性能简化分析方法研究

通过对1∶2缩尺三层Y形高强钢组合偏心支撑框架结构(Y-HSS-EBF)模型试件的振动台试验,考察了结构的抗震性能。基于结构的恢复力模型与等代拉杆简化模型,采用SAP2000程序中的多线段塑性Kinematic连接单元代替拉杆,进行Y-HSS-EBF结构的地震反应简化分析,并将简化分析计算结果与试验结果、有限元计算结果进行了对比。研究结果表明:Y-HSS-EBF结构具有良好的抗震性能;由简化计算方法得到的Y-HSS-EBF结构滞回曲线与试验结果基本一致,简化分析模型能较好地模拟结构的非线性性能;振动台模型的简化计算结果具有一定的精度,简化分析模型能够较好的用于Y-HSS-EBF结构的弹性与弹塑性地震反应分析。在初步设计时,可采用简化分析模型对结构地震作用进行计算。     

Y形高强钢组合偏心支撑框架结构抗震性能简化分析方法研究EI北大核心CSCD

通过对1∶2缩尺三层Y形高强钢组合偏心支撑框架结构(Y-HSS-EBF)模型试件的振动台试验,考察了结构的抗震性能。基于结构的恢复力模型与等代拉杆简化模型,采用SAP2000程序中的多线段塑性Kinematic连接单元代替拉杆,进行Y-HSS-EBF结构的地震反应简化分析,并将简化分析计算结果与试验结果、有限元计算结果进行了对比。研究结果表明:Y-HSS-EBF结构具有良好的抗震性能;由简化计算方法得到的Y-HSS-EBF结构滞回曲线与试验结果基本一致,简化分析模型能较好地模拟结构的非线性性能;振动台模型的简化计算结果具有一定的精度,简化分析模型能够较好的用于Y-HSS-EBF结构的弹性与弹塑性地震反应分析。在初步设计时,可采用简化分析模型对结构地震作用进行计算。     

梁柱四角钢连接钢框架内填RC墙结构滞回性能试验研究

该文通过6榀1/3缩尺的两层单跨梁柱四角钢连接钢框架内填钢筋混凝土剪力墙结构(简称PSRCW)试件模型的低周反复荷载试验,研究了PSRCW结构的传力机理及破坏模式,分析了PSRCW结构的滞回性能、刚度退化、变形及延性性能、耗能能力以及内力分配关系等。研究结果表明:PSRCW结构具有较高的承载力和较大的抗侧移刚度,耗能能力一般。设计荷载水平,与钢梁相连抗剪连接件分担约80%的水平剪力,钢框架分担约70%倾覆力矩。抗剪连接件在拉剪耦合受力状态下易发生低周疲劳破坏,改善抗剪连接件的性能是提高PSRCW结构延性的关键。     

考虑强度和刚度退化及捏拢效应的钢筋混凝土桥墩滞回模型及其参数识别

为了有效地模拟强震作用下桥梁结构的非线性地震反应,需要确定钢筋混凝土（RC）桥墩非线性力-位移滞回关系。基于Bouc-Wen模型,给出了一种考虑RC桥墩强度和刚度退化以及捏拢效应的改进非线性滞回模型,确定了影响该滞回模型的控制参数,并在Matlab/Simulink里实现对RC桥墩各种破坏模式非线性滞回性能预测。同时,通过对1/3比尺的RC桥墩分别在压弯、扭转和弯剪作用下的往复荷载试验研究,试验得到的力-位移关系滞回曲线与本文提出的改进滞回模型预测结果吻合较好,验证了本文提出改进模型的正确性和有效性。并采用汶川地震波对绵州市回澜立交桥匝道桥的RC桥墩的滞后性能进行了数值模拟,分析结果和桥墩的震害一致,证实了采用本文提出的改进滞回模型可以较准确的预测RC桥墩在强震作用下的非线性滞后性能。在此基础上,运用无迹卡尔曼（UKF）方法对Bouc-Wen模型进行参数估计,模拟结果和误差分析表明,该方法能够精确的估计出改进的Bouc-Wen模型的参数。     

基于拟力法的钢支撑非线性滞回行为模拟

钢支撑在轴力作用下会同时发生材料非线性和几何非线性,复杂的力与变形关系是数值模拟过程中的重点与难点。该文基于拟力法的基本理论,提出了支撑非线性滞回行为的计算模型,通过塑性转动铰来模拟由屈曲行为引起的塑性弯曲变形;通过滑动铰来模拟由拉伸屈服和增长效应产生的轴向塑性伸长行为,模型中计及了弹性弯曲变形本身的几何非线性行为。该模型物理意义简单、力学行为明确,在模拟支撑非线性滞回行为的过程中保持初始刚度不变,塑性铰的变形可直观地衡量支撑的屈曲程度。数值模拟与试验结果对比验证了该方法的精确性与适用性。将该模型应用于某钢框架-支撑结构地震反应分析中,计算结果表明:该方法可以模拟支撑在复杂荷载作用下的非线性行为,具备拟力法所特有的精确、高效及稳定等优点。     

预压弹簧自恢复耗能支撑恢复力模型与滞回特性研究

为研究新型预压弹簧自恢复耗能支撑结构的自恢复性能和耗能性能,对预压弹簧自恢复耗能支撑在低周往复荷载作用下的滞回特性进行了模拟研究,分析了自恢复耗能支撑旗形滞回曲线的特点,给出了支撑恢复力的计算方法,建立了基于Bouc-Wen模型的预压弹簧自恢复耗能支撑恢复力模型,并与ANSYS数值模拟结果进行了对比,结果表明建立的恢复力模型可准确模拟支撑在动力荷载作用下的力学性能。恢复力-位移曲线整体吻合程度较高,该恢复力模型对自恢复耗能支撑结构的设计及抗震性能研究具有较好的参考价值。     

ABAQUS中混凝土本构模型用于模拟结构静力行为的比较研究

对大型通用有限元程序ABAQUS中的混凝土弥散开裂模型和塑性损伤模型进行了详细的介绍,包括单轴应力-应变关系、裂缝模型、屈服准则、流动法则和滞回规则等。然后对混凝土本构模型中影响结构构件静力行为的关键因素进行了详细的对比分析,并结合采用不同混凝土模型对钢筋混凝土构件和钢-混凝土组合结构构件的受力行为的模拟结果,指出了分析实际结构构件时不同混凝土材料本构模型的适用情况,可供研究设计参考。     

剪切型金属阻尼器恢复力模型研究

剪切型金属阻尼器在新建工程及结构抗震加固工程中已得到了较广泛的应用,其恢复力模型是进行整体结构非线性地震反应分析的基础。为了更准确地描述剪切型金属阻尼器的剪力-变形滞回关系,提出了一种考虑性能退化的新型恢复力模型。通过独立参数控制恢复力模型,以考虑剪切型金属阻尼器在大变形下的强度退化、刚度退化、耗能能力退化等特征。根据所提模型,采用C++语言开发了能够用于剪切型金属阻尼器抗震分析的计算程序,并将其嵌入到结构通用分析软件OpenSees中。使用该模型对现有钢连梁和钢板剪力墙两类剪切型金属阻尼器进行了模拟。结果表明:该文建立的恢复力模型能较准确地模拟试验结果,能够反映剪切型金属阻尼器包括大变形阶段在内的整个变形阶段的滞回性能。该模型可用于安装了剪切型金属阻尼器的整体结构非线性地震反应分析。     

板式剪切型铅阻尼器的试验研究及有限元分析

提出一种新型的剪切型铅阻尼器,该装置中铅块直接嵌于滑动钢板与固定钢板的凹槽之间,构造简单。基于性能试验和有限元分析对该装置的滞回性能及关键参数进行了研究,研究结果表明:该阻尼器的滞回性能可以采用双线性模型加以模拟;阻尼器屈服阻尼力由铅块的剪切面积决定;加载曲线中弹性阶段与完全塑性阶段之间的过渡弧段的曲率半径与剪切铅块的长厚比成反比。     

圆钢管混凝土柱的受扭性能研究

对四个圆形截面钢管混凝土柱在纯扭和压扭荷载作用下的滞回性能进行了试验研究, 将试验所测得的扭矩-扭转角滞回曲线与采用分层筒模型计算的理论结果进行了对比, 结果表明分层筒模型在分析圆钢管混凝土柱在纯扭和压扭往复荷载作用下的受力性能时具有较高的精度。基于分层筒模型, 对钢管混凝土柱在纯扭和压扭荷载作用下的轴力和扭矩分配, 应变变化规律和主要影响参数进行了较为详细的分析和讨论。最后采用回归方法, 基于大量理论计算结果提出了钢管混凝土柱的抗扭承载力和轴力-抗扭承载力相关关系简化计算公式, 可适用于实际工程设计。     

Stress-strain relations in elastoplastic solids with Dugdale-type cracks

Mechanical behavior of a two-dimensional elastoplastic solid with rectilinear cracks is investigated. Plastic strip model is used to reduce plasticity problem to the equivalent linear elasticity formulation. Two realizations of the mixed mode plastic strip model are considered: in-line plastic strips as proposed by Becker and Gross [Int. J. Fract. 37 (1988) 163], and inclined plastic strips of Panasyuk and Savruk [Appl. Mech. Rev. 47 (1994) 151]. The effective mechanical response predictions are based on the procedure presented in Kachanov et al., [Appl. Mech. Rev. 47 (1994) 151]. Stress-strain relations are obtained for parallel and randomly oriented non-interacting cracks. Results are compared with known elastic solutions.     

Hysteretic behavior of RC shear walls strengthened with CFRP strips

The purpose of this study was to investigate the hysteretic behavior of shear deficient reinforced concrete (RC) walls that were strengthened with carbon fiber reinforced polymer (CFRP) strips. Totally, ½ scale five specimens with 1.5 aspect ratio walls were constructed. One of them was tested without any retrofitting as a reference specimen and four of them were retrofitted specimens with CFRP strips. All of the specimens were tested under cyclic lateral loading. CFRP strips with different configurations were tested like X-shaped, horizontal and parallel strips or combinations of them. All of the CFRP configurations were symmetrically bonded to both sides of the shear wall and were anchoraged to the wall. The research focuses on the effect of using CFRP strips for enhancing strength and increasing ductility of the non-seismic detailed shear walls. Test results shows that all of the CFRP strip configurations significantly improves the lateral strength, energy dissipation and deformation capacity of the shear deficient RC walls. The specimen that was strengthened with X-shaped CFRP strips was failed with premature shear failure. The specimen that was strengthened with horizontal strips was showed flexural hysteretic behavior and plastic hinge was developed at the wall base. CFRP strips were controlled shear crack propagation and resulted in improvement of displacement capacity.     

Axial compressive behavior of concrete actively confined by metal strips; part A: experimental study

This paper presents the results of an experimental study on the application of strapping technique for retrofit of concrete compressive specimens. In this technique, standard strapping devices, which are used in the packaging industry, are applied to post-tension high strength metal strips around the concrete columns. Experimental program included axial compressive tests on 72 cylindrical and prismatic compressive specimens, which were actively confined by pre-stressed metal strips. The effects of various parameters on strength and ductility of confined concrete were studied including compressive strength of concrete, mechanical volumetric ratio of confining strips, post-tensioning force in the strip, number of strip layers wrapped around the specimens and details of strip joint. The effects of strength and ductility of confining strips on the behavior of confined specimens were also studied. Longitudinal and lateral strains of concrete and strain of the strips were monitored. Test results showed significant increase in the strength and ductility of specimens due to active confinement by metal strips. It was observed that ductility of confining material plays the most important role in enhancement of concrete ductility. The gain in strength is strongly dependent to the effective mechanical volumetric ratio of confining strips. It was also observed that the active confinement of concrete by post-tensioning the confining element results in stiffer pre-peak response of concrete specimens than the usual passive confinement.     

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。     

设置自复位支撑的钢筋混凝土框架结构抗震性能研究

提出了一种能准确描述预压弹簧自复位耗能（PS-SCED）支撑滞回性能的力学模型,引入状态变量区分支撑不同工作阶段从而确定其力学响应。基于ABAQUS平台对该力学模型进行二次开发,将开发的PS-SCED支撑单元模拟结果与支撑力学性能试验结果进行对比,并对设置PS-SCED支撑的3层钢筋混凝土框架结构进行抗震性能分析。结果表明:该支撑单元模拟得到的滞回曲线与试验结果吻合较好,可准确描述支撑在动力荷载作用下的力学性能;强震作用下,PS-SCED支撑能够充分耗散地震能量,有效控制结构的塑性变形;此外,PS-SCED支撑框架结构相比于原框架结构残余变形减小了72.1%~92.1%。PS-SCED支撑具备良好的耗能能力和自复位特性,能够显著提高钢筋混凝土框架结构的抗震性能。     

A computational model for reinforced concrete members confined with fiber reinforced polymer lamina: Implementation and experimental validation

This study presents a computational model to simulate the behavior of confined concrete in column plastic hinge zones. The model describes the distribution of confining stresses within a circular column cross-section and the hysteretic behavior of concrete under passive confinement. Of particular interest is the ability of the model to predict the maximum circumferential strains and thus estimate the limit state of the confining medium rather than relying on empirical limits such as concrete compressive strain or drift ratio. This is performed with fiber-discretized beam column analysis without the computational expenses of a continuum finite element (FE) model. The confined section and material model are implemented in an object-oriented computational platform for structural analysis. New classes are developed and presented for a confined fiber section, a confined concrete material, and associated hysteretic behavior rules. Finally, the results from two experimental programs on columns strengthened using fiber reinforced polymer (FRP) lamina are reproduced using the developed computational model. Comparison of simulation and experiment shows that the computational model can closely match the observed response characteristics and can adequately predict the deformation level leading to FRP rupture.     

PVC-CFRP管混凝土柱-钢筋混凝土环梁T型节点拟静力试验与弯矩-曲率恢复力模型研究

开展11根PVC-CFRP管钢筋混凝土柱-钢筋混凝土环梁T型节点低周反复加载试验,分析环梁尺寸、环筋配筋率、CFRP条带间距、梁纵筋配筋率、轴压比等因素对其破坏形态、滞回性能、骨架曲线等影响。结果表明：节点破坏经历初裂、通裂、极限和破坏四个阶段,节点的弯矩-曲率滞回曲线包括弹性段、弹塑性段和平稳段,节点滞回环饱满,显示出良好的抗震性能。基于软化混凝土本构关系模型,考虑各因素对骨架曲线特征点的影响,提出骨架曲线特征点简化计算公式。基于退化三线型恢复力模型,给出卸载刚度计算公式,提出节点滞回规则,建立预测精度较高的环梁节点弯矩-曲率恢复力模型。     

Behavior of RC T-section beams strengthened with CFRP strips,subjected to cyclic load

This paper presents results of an experimental investigation on T-section reinforced concrete (RC) beams strengthened with externally bonded carbon fiber-reinforced polymer (CFRP) strips. Specimens, one of which was the control specimen and the remaining six were the shear deficient test specimens, were tested under cyclic load to investigate the effect of CFRP strips on behavior and strength. Five shear deficient specimens were strengthened with side bonded and U-jacketed CFRP strips, and remaining one tested with its virgin condition without strengthening. The type and arrangement of CFRP strips and the anchorage used to fasten the strips to the concrete are the variables of this experimental work. The main objective was to analyze the behavior and failure modes of T-section RC beams strengthened in shear with externally bonded CFRP strips. According to test results premature debonding was the dominant failure mode of externally strengthened RC beams so the effect of anchorage usage on behavior and strength was also investigated. To verify the reliability of shear design equations and guidelines, experimental results were compared with all common guidelines and published design equations. This comparison and validation of guidelines is one of the main objectives of this work. The test results confirmed that all CFRP arrangements differ from CFRP strip width and arrangement, improved the strength and behavior of the specimens in different level significantly.     

小跨高比钢筋混凝土连梁非线性剪切滞回和分析模型研究

基于修正力插值的纤维单元（MFBFE）的力插值函数中加入剪力插值函数,从单元层次上考虑了弯矩和剪力的耦合作用,适合以剪切变形为控制因素的小跨高比连梁（跨高比小于2.5）的非线性数值模拟。本文从截面层次上建议了一种针对小跨高比连梁的剪切滞回模型,该模型抛弃了屈服剪力与峰值剪力相等的假设条件,其骨架曲线为四折线型,包括开裂点、屈服点、峰值点以及破坏点,卸载、再加载路径的变化以及捏缩效应由所建议的滞回规则体现。在OpenSees中单轴材料类开发这一剪切滞回模型（CBHShear）,给出了OpenSees框架下MFBFE单元调用CBHShear材料的实现方式。最后基于MFBFE单元和CBHShear模型,对不同小跨高比、配筋率、配箍率、钢筋强度、混凝土强度的4个连梁试件进行低周反复加载数值分析,所得结果与试验结果进行对比,验证了CBHShear能够很好地体现连梁的非线性行为,具有较高地预测精度,适用范围更为广泛。     

Experimental study on RC beams with FRP strips bonded with rubber modified resins

This paper presents the effects of adhesive properties on structural performance of reinforced concrete (RC) beams strengthened with carbon fiber reinforced plastic (CFRP) strips. The epoxy adhesives modified with liquid rubber of different content were used to bond the CFRP strips, and four point bending experiments were carried out on RC beams. The experimental results show that different CFRP strip thickness of 0.22 and 0.44 mm resulted in a transition of failure mechanism from interfacial debonding along the CFRP-concrete interface to concrete cover separation starting from the end of CFRP strips in the concrete. Moreover, it is suggested that no matter interfacial debonding or concrete cover separation, the rubber modifier enhanced the structural performance by increasing the maximum load-carrying capacity and the corresponding ductility, compared with the beams bonded with a neat epoxy resin. The improvement of structural performance due to modified adhesive was associated with the modification of stress profiles along the CFRP-concrete interface especially the stress concentration at the end of FRP, and the enhanced interlaminar fracture toughness. Rubber modified epoxy therefore is worth further studying in practical repair applications.