Finite element analysis of concrete-filled circular steel tubular columns subjected to post-earthquake fire

为研究圆钢管混凝土柱经历地震损伤后的耐火性能,选取了合理的地震损伤指数及材料本构模型,采用有限元分析软件ABAQUS,对钢管混凝土柱在往复荷载和火灾等不同工况下的试验进行了数值模拟验证。在验证模型可靠性的基础上,利用ABAQUS中的数据传递功能,建立了震损后圆钢管混凝土柱耐火极限有限元计算模型。以圆钢管混凝土典型轴心受压柱为分析对象,对其先后经历地震和火灾作用下的破坏形态、损伤机理进行了分析,研究了损伤指数对圆钢管混凝土柱震后耐火极限的影响。结果表明：震损后圆钢管混凝土柱在高温下的破坏形态是在前期地震损伤基础上的发展和蔓延;地震损伤指数是影响圆钢管混凝土柱震后耐火极限的重要参数,随着地震损伤指数增大,圆钢管混凝土柱的耐火极限有所减小。     

震损钢筋混凝土平面框架结构抗火性能研究

为明确混凝土框架结构受地震破坏造成的几何损伤对其遭受地震次生火灾后耐火性能退化规律的影响,分析总结震害资料以及抗震实验记录,将混凝土保护层剥落、残余变形作为混凝土结构的震损形式,通过数据统计与回归分析的方法确定损伤尺寸,从而建立了两层两跨震损钢筋混凝土平面框架有限元模型,得到了框架结构变形特点和受火位置、轴压比、层间位移角对平面框架结构耐火极限的影响规律。     

A method for examining the seismic performance of steel arch deck bridges

To examine the seismic resistance performance of a steel arch bridge during a strong earthquake, an approach is proposed in this paper to determine the ultimate strain of an arch rib using the static elasto-plastic large deformation theory. A steel fixed-end deck arch bridge with a span length of 200 m was used as an example in this study. The ultimate strain of the arch rib was calculated using the elasto-plastic finite element model. The seismic responses of the arch bridge exposed to strong earthquakes in two and three directions were also simulated. Moreover, the effect of earthquake motion in the lateral direction on the elasto-plastic earthquake response was discussed, and the seismic resistance of the structure was analyzed. The results show that steel arch bridges have preferable seismic resistance under strong earthquake conditions. While lateral earthquake motion has some influence on the damage to an arch bridge, it has little effect on the displacement, axial force, and bending moment responses of the arch rib. It is feasible to examine the seismic performance of the arch bridge by ascertaining the out-of-plane and in-plane earthquake responses of the bridge.     

Structural fire performance of earthquake-resistant composite steel–concrete frames

Seismic and fire design of a building structure may be two very demanding tasks, especially if included in a performance based design philosophy. For the time being, the necessary harmonization on the regulations concerning these two design fields is almost missing, thus preventing the effective possibility of an integrated design. Besides, while many countries have already moved towards the use of performance-based codes for seismic design, the application of such methodologies for the fire design of structures is still limited in scope. Within this framework, the development of suitable procedures introducing structural fire performance issues for a comprehensive design methodology is needed.In this paper, a numerical investigation for the assessment of the structural fire performance of earthquake resistant composite steel–concrete frames is presented. With reference to a case study defined in the framework of a European Research Project, a great effort was devoted to the identification of the key structural parameters allowing for a possible correlation between the predictable performances under seismic and fire loadings, when these two are considered as independent actions.At the conceptual design level, the most suitable structural solution with respect to both design actions was chosen, including composite beams and circular steel concrete-filled columns. The frame was designed in order to resist severe seismic action according to the ductile design approach provided by Eurocode 8; the parameters affecting members’ sizing were outlined in this phase. Afterwards, the seismic performance of the designed frame was investigated by means of non-linear static analyses; once the seismic performance objectives were met, in order to evaluate the structural fire performance of the whole frame a set of criteria was defined. To this purpose, thermo-mechanical analyses under different boundary conditions were developed and in order to identify the possible mechanisms leading to structural failure, the state of stress at the critical cross-sections at different times of fire exposure was investigated. Another point of main concern was represented by the assessment of the influence of different restraining conditions on the achieved fire resistance rating and kind of structural failure.Moreover, the proposed methodology allowed making an estimate of the amount of axial restraint provided to the heated beams by the surrounding structure; in this view, the importance of choosing column elements in function of their flexural stiffness was revealed, in order to correlate it with the predictable performances under both seismic and fire loadings.     

A method for examining the seismic performance of steel arch deck bridges

To examine the seismic resistance performance of a steel arch bridge during a strong earthquake, an approach is proposed in this paper to determine the ultimate strain of an arch rib using the static elasto-plastic large deformation theory. A steel fixed-end deck arch bridge with a span length of 200 m was used as an example in this study. The ultimate strain of the arch rib was calculated using the elasto-plastic finite element model. The seismic responses of the arch bridge exposed to strong earthquakes in two and three directions were also simulated. Moreover, the effect of earthquake motion in the lateral direction on the elasto-plastic earthquake response was discussed, and the seismic resistance of the structure was analyzed. The results show that steel arch bridges have preferable seismic resistance under strong earthquake conditions. While lateral earthquake motion has some influence on the damage to an arch bridge, it has little effect on the displacement, axial force, and bending moment responses of the arch rib. It is feasible to examine the seismic performance of the arch bridge by ascertaining the out-of-plane and in-plane earthquake responses of the bridge.     

土结相互作用对质量不规则钢框架抗地震倒塌性能的影响

对4种钢结构体系进行振动台实时动态子结构试验研究,包括规则钢框架(R-SMRF)、不规则钢框架(Ir-SMRF)、 土结规则钢框架(R-SMRF-SSI)和土结不规则钢框架(Ir-SMRF-SSI)。研究发现,附加的设备质量和地基土会对低层钢框架结构抗地震倒塌性能产生影响,结构的倒塌模式为侧移性倒塌。在小震作用下,设备鞭梢效应导致结构顶层的加速度响应增大;在中震作用下,结构中损伤发展,因此设备质量甚至会降低结构的加速度响应;相比之下,地基土增大的自振周期总是降低结构的加速度响应。随着震级增加,结构的位移响应增强,结构的损伤和残余变形增大,最终大震结构发生底层侧移性倒塌。地基土减小上部结构的位移响应,具有减震作用;而设备质量增大结构的位移反应,对结构抗地震倒塌不利。     

广东科学中心土建工程灾害防护新技术研究与应用

针对广东科学中心土木建筑工程遇到的岩土工程地质灾害、地震灾害、环境风致灾害、火灾等难题,利用微观结构研究与宏观结构研究相结合、振动台试验研究与有限元分析相结合、风洞试验与有限元分析结合、计算机模拟分析等技术手段,开展了广东科学中心饱和软土地基预处理、工程抗震、工程防风和性能化防火设计等工程灾害防护新技术的研究。研究提出了地基分区处理技术路线和动静结合排水固结法,完成了广东科学中心复杂超限结构抗震性能化优化设计,解决了广东科学中心工程在极端风荷载作用下主体结构和围护结构的安全性问题,探讨了火灾危险性与火灾荷载分析等火灾场景及疏散状况。研究成果为广东科学中心工程优化设计提供了必要的参数。     

火灾作用后圆钢管混凝土柱荷载-位移滞回性能研究

火灾作用后,钢管混凝土柱的强度和刚度均会遭受损失,需进一步考察其抗震能力。本文介绍了7个火灾后圆钢管混凝土试件滞回性能试验研究,采用数值方法对荷载位移滞回关系曲线进行全过程分析,计算分析了轴压比、长细比、含钢率、钢材屈服极限、混凝土抗压强度、受火时间等参数对荷载位移关系骨架线的影响。研究结果表明,火灾作用后圆钢管混凝土柱滞回关系曲线形状饱满,无明显的捏缩现象,但试件的极限承载力和弹性刚度会有所降低。本文的研究成果可为火灾后该类结构的抗震修复加固提供参考。     

屈曲约束支撑钢框架的地震反应分析

应用ANSYS软件对屈曲约束支撑钢框架（BRBFs）和普通支撑钢框架的抗震性能进行有限元数值模拟,对比分析了这两种体系大、小震的时程响应,结果表明,在小震作用下两种结构抗震性能均表现良好,但在罕遇地震作用下普通支撑钢框架刚度退化,而屈曲约束支撑钢框架则能降低结构的地震响应。     

山地小城市地震次生火灾风险等级评估

选取昆明市东川区为研究对象,以结构性危险概率、 功能性危险概率评估地震次生火灾的危险性,引入重大危险源修 正系数后,建立单体建筑震后次生火灾起火概率模型,通过Arc- GIS 平台进行图像、数据分析,评估东川城区建筑地震次生火灾 风险等级。研究表明以框架、砖混结构建筑为主的新城区、中心城 区,建筑密度低、抗震等级高,次生火灾风险低,而以砖砌、土木结 构建筑为主的老城区、边缘行政村,建筑密度大、抗震等级低,次生 火灾风险普遍较高。     

住宅建筑中推广钢管混凝土柱的优点

住宅钢结构是我国十五期间推广的重点。为此 ,介绍了住宅钢结构中采用钢管混凝土柱的优点 :节约钢材 ,降低造价 ,其造价可低于一般钢混结构 ,且抗震性能优越。并提出采用耐火耐候钢材和高流态混凝土等建议。     

Experimental study on seismic performance of steel frame- K-shaped brace structure system

为实现钢结构住宅中不凸梁凸柱的建筑效果，采用小截面钢构件组成的钢框架-K形支撑结构体系，通过K形钢支撑的设置，有效减小了构件截面尺寸。为研究钢框架-K形支撑结构体系的抗震性能，选取其中典型的抗侧力单元，制作足尺模型进行拟静力试验，并采用ABAQUS软件对其抗震性能进行有限元分析。研究结果表明：该结构体系可实现多遇地震弹性、罕遇地震不倒的设计目标，当结构位移角达1/30时仍可保持承载能力，表现出良好的抗震性能；按照斜向支撑、竖杆、框架梁柱的顺序依次屈服，斜向支撑可有效保护主体框架；位移延性系数为10.0，滞回曲线饱满；当位移角为1/50时，等效阻尼比为18.9%，耗能能力优异。     

钢框架-K形支撑结构体系抗震性能试验研究

为实现钢结构住宅中不凸梁凸柱的建筑效果,采用小截面钢构件组成的钢框架-K形支撑结构体系,通过K形钢支撑的设置,有效减小了构件截面尺寸。为研究钢框架-K形支撑结构体系的抗震性能,选取其中典型的抗侧力单元,制作足尺模型进行拟静力试验,并采用ABAQUS软件对其抗震性能进行有限元分析。研究结果表明：该结构体系可实现多遇地震弹性、罕遇地震不倒的设计目标,当结构位移角达1/30时仍可保持承载能力,表现出良好的抗震性能;按照斜向支撑、竖杆、框架梁柱的顺序依次屈服,斜向支撑可有效保护主体框架;位移延性系数为10.0,滞回曲线饱满;当位移角为1/50时,等效阻尼比为18.9%,耗能能力优异。     

Study on influence of different buried depth of steel cylindrical breakwater on seismic stability of structure

以位于高地震烈度区的某实际港口防护用的大直径薄壁钢圆筒-筒内改良土防波堤结构为研究对象,基于有限元数值模拟与室内振动台试验,探讨钢圆筒不同入土深度对该结构抗震稳定性的影响规律,得到在不同峰值加速度的地震波作用下,不同钢圆筒埋深比结构的位移与加速度时程反应曲线、地震作用前后地基土体的剪应力分布曲线。研究结果表明：钢圆筒埋深比、地震动峰值加速度、地基土压力是显著影响防波堤结构动力稳定性的重要参数,并且三者具有紧密的关联性。随着钢圆筒埋深比的增大,其地震位移响应与加速度响应呈现相反的变化趋势,并且地震前后的地基土压力变化幅度也相差较远。基于实际钢圆筒防波堤工程的场地条件与抗震等级,为保证钢圆筒防波堤结构的正常使用状态,提出了钢圆筒埋深比的合理取值范围。     

抗震结构粘钢加固动力计算、试验与实践

本文作者结合国内一大型工厂工业厂房的抗震加固，对框架结构厂房进行了动力有限元计算，在振动台上，模拟地震波形，对模型粘钢加固和不粘钢原始结构抗震效果进行了比较试验。得出了：该厂房抗震中构架的薄弱部位（首坏位置）；在地震波作用下结构破坏的规律和特征；粘钢加固后抗震达到的等级。     

框架结构轻钢加层的地震反应分析

利用ANSYS有限元软件,结合具体工程实例,对框架结构直接采用轻钢结构加层建立了三维有限元模型,对原框架结构与加层后整体结构的抗震性能进行了模态分析和时程分析,通过分析比较获得了原框架结构、加层结构和整体结构的动力特性和地震作用效应的变化规律,为相似加层结构的抗震设许提供了一些理论参考．     

低延性中心支撑钢框架结构振动台试验

中心支撑钢框架结构是一种典型的双重抗侧力体系，强震作用下支撑失效会引起结构承载力和刚度的折减，支撑失效后，结构剩余部分作为储备体系能够继续承担地震作用。为深入了解低延性中心支撑钢框架结构在地震作用下的非线性反应，研究在支撑失效后结构储备体系的抗震性能，开展了3层中心支撑钢框架结构模型的振动台试验。模型结构为3榀2跨结构，中间榀布置一跨低延性人字形中心支撑(截面宽厚比超出我国规范限值)，模型长度缩尺比为1∶6.5，分别采用硬土、软土场地的地震波单向激励，峰值加速度逐级增加。结构在7度罕遇地震作用下发生底层支撑失效，储备体系避开了硬土场地地震波的卓越周期，加载至超过9度罕遇地震后依然未出现明显损伤。储备体系对软土场地地震波(宁河波)更为敏感，在8度罕遇地震作用下濒临倒塌。结构2、3层支撑始终未发生屈曲和破坏。研究结果表明，当储备体系设计合理时，低延性中心支撑钢框架结构具有良好的抗震性能和抗倒塌能力。     

砖混结构顶部钢结构加层的抗震性能分析

钢结构加层技术是目前逐步被推广的一种房屋改造形式,但目前设计方法还不够完善.利用ANSYS有限元软件,结合具体工程实例,对砖混结构顶部直接采用轻钢结构加层建立三维有限元模型,对原砖混结构与加层后整体结构的抗震性能进行模态分析、谱分析以及时程分析,通过分析比较获得结构的动力特性和地震作用效应的变化规律,为相似加层结构的抗震设计提供了一些理论参考.     

Performance assessment of innovative seismic resilient steel knee braced frame

Buckling restrained knee braced truss moment frame (BRKBTMF) is a novel and innovative steel structural system that utilizes the advantages of long-span trusses and dedicated structural fuses for seismic applications. Steel trusses are very economical and effective in spanning large distance. However, conventional steel trusses are typically not suitable for seismic application, due to its lack of ductility and poor energy dissipation capacity. BRKBTMF utilizes buckling restrained braces (BRBs) as the designated structural fuses to dissipate the sudden surge of earthquake energy. This allows the BRKBTMF to economically and efficiently create large span structural systems for seismic applications. In this paper, a prototype BRKBTMF office building located in Berkeley, California, USA, was designed using performance-based plastic design procedure. The seismic performance of the prototype building was assessed using the state-of-the-art finite element software, OpenSees. Detailed BRB hysteresis and advanced element removal technique was implemented. The modeling approach allows the simulation for the force-deformation response of the BRB and the force redistribution within the system after the BRBs fracture. The developed finite element model was analyzed using incremental dynamic analysis approach to quantify the seismic performance of BRKBTMF. The results show BRKBTMF has excellent seismic performance with well controlled structural responses and resistance against collapse. In addition, life cycle repair cost of BRKBTMF was assessed using the next-generation performance-based earthquake engineering framework. The results confirm that BRKBTMF can effectively control the structural and non-structural component damages and minimize the repair costs of the structure under different ranges of earthquake shaking intensities. This studies conclude that BRKBTMF is a viable and effective seismic force resisting system.     

钢结构的抗震优越性

针对钢结构的自重、强度、塑性与耗能等方面的特点,并且结合实例,分析对比了钢结构与混凝土结构在地震过程中对建筑物的破坏性,得出钢结构在抗震作用上有明显的优越性的结论。