钢筋混凝土建筑结构的抗地震破坏倒塌能力评估研究

在地震作用下钢筋混凝土建筑结构出现破坏倒塌为地震灾害中的关键,有效评估建筑结构抗地震破坏倒塌能力是建筑结构设计的前提,也是当前建筑结构提高抗震性能与加固的依据。提出变形指标极值、失效判断标准以及钢筋混凝土建筑结构倒塌极限状态判断标准,据此获取倒塌储备系数、倒塌易损性、结构整体超强系数、结构整体延性系数等评估标准。采用Pushover分析法选择相应地震波。依据梁柱线刚比对建筑结构抗倒塌能力的影响,以及柱端弯矩增加系数对建筑结构抗地震破坏倒塌能力的影响,对建筑结构易损性进行分析。结果表明:等跨建筑结构抗地震破坏倒塌能力更强;建筑结构底层是薄弱层,COF值越高,结构越容易倒塌。     

混凝土高层建筑结构地震破坏抗毁能力评估

提出基于构件性能的混凝土高层建筑结构地震破坏抗毁能力评估方法,采用强度与延性法分析混凝土高层建筑构件强度和变形,以对强震作用下混凝土高层建筑结构性能实施准确描述。基于建筑结构性能以及多条地震波情况下高层建筑结构倒塌极限状态的分析规范,采用IDA方法设置建筑结构抗倒塌能力系数,并依据该系数获取基于构件性能的混凝土高层建筑结构地震破坏抗毁能力评估流程,实现建筑结构地震破坏抗毁能力的准确评估。实验结果说明,所提方法实现了混凝土高层建筑结构地震破坏抗毁能力的准确评估。     

不同强度等级混凝土对混凝土框架结构的抗倒塌分析

近几十年来地震频发,给世界各国带来了严重的经济损失和人民生命安全威胁。灾后调查发现,由于建筑物的倒塌带来的灾难影响非常重大。利用PKPM建筑设计软件和SAP2000有限元分析软件,根据美国国防部编制的《结构抗连续倒塌设计》(Do D2005)提出的拆除构件法,对建筑结构常用的一种形式——钢筋混凝土框架结构进行了倒塌过程的分析。通过比较使用不同强度等级的混凝土来分析结构的倒塌,最后得出:混凝土框架结构使用高强度等级的混凝土可以减少结构的层间位移角,从而减少倒塌的范围。     

移除底层关键柱后钢筋混凝土框架结构抗倒塌性能分析

目前国内外学者将地震倒塌和连续倒塌作为两个独立的领域进行研究,实际上框架结构的倒塌破坏系由二种机理耦合作用所致。针对此问题,采用拆除构件设计法,应用有限元程序ANSYS/LS-DYNA完成了钢筋混凝土框架结构拆除底层关键柱后在地震作用下的倒塌仿真分析,重点研究了层高、跨度、层数和关键柱位置对钢筋混凝土框架结构抗倒塌性能的影响。结果表明:对于平面框架模型,由底层柱脚及梁柱节点区柱端失效破坏引起的柱铰破坏机制,是导致结构倒塌的主要原因。底层中柱失效后,底层迅速转化为柱铰机制,结构在重力作用下失稳坍塌,适当增加层高,减小跨度,增加层数对框架结构在底层关键柱失效后的抗地震倒塌性能有益;对于三维空间框架模型,分析表明,空间框架结构在拆除角柱后框架倒塌破坏最为严重,结构的破坏过程可以概括为3个阶段:(1)弹性阶段;(2)重力作用影响占主导地位的塑性阶段;(3)地震作用占主导地位的塑性阶段。     

考虑抗竖向连续倒塌的RC框架结构反应修正系数

震害表明结构反应修正系数的子项冗余度系数取为1,过高地估计了结构通过备用荷载路径进行内力重分布的抗竖向连续倒塌能力。本文拟分别采用静力Pushdown和动力竖向IDA方法对根据《建筑抗震设计规范》GB50011-2010(2016版)设计的RC框架进行分析,采用损伤强度比DSR作为冗余度系数,并根据倒塌临界值,判定结构在设计荷载作用下是否具有足够的抗倒塌能力。分析结果表明,按VII、VIII度设防设计的结构,冗余度系数均大于1,结构在设计荷载作用下不会发生连续倒塌,但是按VI度设防设计的低层结构冗余度系数小于1,在设计荷载作用下结构会发生连续倒塌。针对VI度设防设计的结构,采用实际的冗余度系数最小值0.69,对结构反应修正系数值进行修正,修正后的数值为2.02。实现在结构地震影响系数曲线中考虑抗连续倒塌能力的影响,修正后的地震影响系数为现行抗震规范中相应取值的1.45倍,提高了结构设计地震力,防止结构发生连续倒塌。     

采用纤维模型的钢管混凝土框架-中心支撑结构抗连续倒塌非线性分析

为研究不同形式的中心支撑对钢管混凝土结构抗连续倒塌性能的影响,基于纤维梁模型建立5种钢管混凝土框架-中心支撑结构数值模型,在合理选取钢材和混凝土材料本构模型的基础上,计算不同失效工况下结构的抗连续倒塌非线性动力响应,通过非线性静力加载获得结构的整体刚度和极限承载力。研究结果表明：设置中心支撑均可以提高结构的整体刚度和抗倒塌承载能力,其中对边柱失效工况的提升效果好于中柱失效工况;设置中心支撑提供了新的荷载传递路径,可以有效减小失效柱相邻构件的分配内力;X型支撑在不同失效工况下都能显著提升框架刚度和承载能力,降低失效节点的竖向位移,反斜支撑框架表现出更好的延性和极限承载能力,研究结果可为建筑结构抗连续倒塌设计提供参考。     

公共建筑结构的抗地震倒塌能力优化评估分析

以往基于模态增量动力方法对公共建筑进行抗地震倒塌能力评估时是单纯地从总体角度进行考察的,其得到的结果较为粗糙,无法准确反映出公共建筑的抗地震倒塌能力,导致其经济效益较差。提出新的公共建筑结构抗地震倒塌能力优化评估方法以分析公共建筑整体的抗地震倒塌能力,总结出其与子结构以及构件三者间的关系,进而研究构件的损毁情况,以实现对建筑抗地震倒塌能力的整体评估。基于公共建筑的倒塌破坏区间,采用其结构抗震倒塌能力评估方法,对公共建筑结构的抗地震倒塌能力实施优化评估分析,得到其具体破坏指数,实现对其进行准确评估。实验结果说明,所提方法可准确描述公共建筑结构的抗地震倒塌能力,提高建筑结构抗地震倒塌能力和经济效益。     

设置粘滞阻尼器的钢框架防连续性倒塌分析

为了研究设置有粘滞阻尼器的减震钢框架结构的防连续倒塌性能,对设置阻尼器的减震钢框架和未设置阻尼器的原钢框架分别进行了地震弹塑性时程分析,比较了两种情况下的层间位移角.分析结果表明,地震作用下,与原结构相比减震结构的层间位移角最大降低了64.3％.接着采用瞬时加载法对底层各柱失效时的减震钢框架和不设置阻尼器的原钢框架分别进行了动力倒塌分析,比较了减震结构和原结构防连续倒塌的能力,分析结果表明,底层柱失效时,减震结构各柱端点处位移均比原结构降低,最大处降低了63.5％.因此减震结构的阻尼器对结构防连续倒塌能起到较大的作用.     

钢筋混凝土框架结构强震连续倒塌破坏分析

为研究结构在强震作用下的连续倒塌机制,提高建筑抗震性能,对10层钢筋混凝土框架结构进行了倒塌模拟,得到其破坏起始点和传递路径并与实际震灾进行对比。研究发现:框架结构设计时应重点加强潜在破坏起始点和传递路径上的抗震能力。强柱弱梁结构真正起到增加结构延性的常是底部几层梁,当其达到耗能极限,底柱便开始破坏,易导致结构整体倒塌。研究结构对钢筋混凝土框架结构抗连续倒塌设计具有参考价值。     

基于OpenSees的强震下混凝土结构梁-梁碰撞行为数值实现

绝大多数针对极端作用下的结构连续倒塌分析,在分析过程中不能实时地根据构件的损伤状态对分析模型进行修改,也不能考虑连续倒塌过程中的各种碰撞问题。连续倒塌过程中发生的碰撞对结构响应预测有重大影响。本文依据钢筋混凝土框架结构发生梁-梁碰撞的机理,基于OpenSees平台建模,结合Matlab的混合编程计算碰撞力,通过添加碰撞时程力并对结构进行模型更新,合理地实现钢筋混凝土框架结构在强震作用下的连续倒塌过程中发生梁-梁碰撞的具体过程。将得到的结果和传统时程分析法的结果进行的对比表明,结合Matlab和OpenSees命令可以实时地计算碰撞力序列和对结构进行更新,梁-梁碰撞和构件的逐步失效使结构的水平位移和转角有一定的增大,竖向位移有一定减小。     

Collapse simulation of reinforced concrete high‐rise building induced by extreme earthquakes

Collapse resistance of high‐rise buildings has become a research focus because of the frequent occurrence of strong earthquakes and terrorist attacks in recent years. Research development has demonstrated that numerical simulation is becoming one of the most powerful tools for collapse analysis in addition to the conventional laboratory model tests and post‐earthquake investigations. In this paper, a finite element method based numerical model encompassing fiber‐beam element model, multilayer shell model, and elemental deactivation technique is proposed to predict the collapse process of high‐rise buildings subjected to extreme earthquake. The potential collapse processes are simulated for a simple 10‐story RC frame and two existing RC high‐rise buildings of 18‐story and 20‐story frame–core tube systems. The influences of different failure criteria used are discussed in some detail. The analysis results indicate that the proposed numerical model is capable of simulating the collapse process of existing high‐rise buildings by identifying potentially weak components of the structure that may induce collapse. The study outcome will be beneficial to aid further development of optimal design philosophy. Copyright © 2012 John Wiley & Sons, Ltd.     

填充墙RC框架结构加固方法的研究现状及展望

综述了用于提高填充墙钢筋混凝土(RC)框架结构抗震性能和改善结构损伤模式的几类加固措施,从工艺、加固效果和破坏形式3个角度进行了分析。在建筑结构设计过程中,填充墙通常被视为一种典型的脆性非均质非结构构件,忽视了填充墙与RC框架之间的相互作用。地震调查报告表明,在结构遭受地震作用时,填充墙通常先于钢筋混凝土框架发生破坏,未经合理设计的填充墙RC框架结构将在地震作用下产生严重不良后果。试验结果和数值模拟分析结果证明,砌块的强度越低、砂浆的强度越高,结构的承载能力和刚度退化越慢、耗能能力越好。文中根据目前已有的建筑材料改性试验结果,从改性机理出发,分析了一系列有利于提高结构抗震性能的新型材料,并对结构的设计方案进行了探讨。     

强震作用下混凝土框架结构倒塌过程的数值分析

本文引入机械铰概念解释了钢筋混凝土杆件在地震作用下的失效过程，继而建立了以楼层为基本单位的强梁弱柱型框架结构的倒塌分析模型。并将离散单元法的中心算法一动态松弛法运用到结构倒塌分析模型中，成功地模拟了钢筋混凝土框架结构在地震作用下的倒塌全过程反应。     

Seismic collapse simulation of existing masonry buildings with different retrofitting techniques

Masonry buildings are primarily constructed out of bricks and mortar which become discrete pieces and cannot sustain horizontal forces created by a strong earthquake.The collapse of masonry walls may cause significant human casualties and economic losses.To maintain their integrity,several methods have been developed to retrofit existing masonry buildings,such as the constructional RC frame which has been extensively used in China.In this study,a new method using precast steel reinforced concrete(PSRC)panels is developed.To demonstrate its effectiveness,numerical studies are conducted to investigate and compare the collapse behavior of a structure without retrofitting,retrofitted with a constructional RC frame,and retrofitted with external PSRC walls(PSRCW).Sophisticated finite element models(FEM)were developed and nonlinear time history analyses were carried out.The results show that the existing masonry building is severely damaged under occasional earthquakes,and totally collapsed under rare earthquakes.Both retrofitting techniques improve the seismic performance of existing masonry buildings.However,it is found that several occasional earthquakes caused collapse or partial collapse of the building retrofitted with the constructional RC frame,while the one retrofitted by the proposed PSRC wall system survives even under rare earthquakes.The effectiveness of the proposed retrofitting method on existing masonry buildings is thus fully demonstrated.     

A novel structural detailing for the improvement of seismic and progressive collapse performances of RC frames

Earthquake-induced building collapse and progressive collapse due to accidental local failure of vertical components are the two most common failure modes of reinforced concrete (RC) frame structures. Conventional design methods usually focus on the design requirements of a specific hazard but neglect the interactions between different designs. For example, the progressive collapse design of an RC frame often yields increased reinforcement and flexural strength of the beams. As a result, the seismic design principle of “strong-column-weak-beam” may be violated, which may lead to unfavorable failure modes and weaken the seismic performance. To avoid these adverse effects of the progressive collapse design on the seismic resistance of RC frames, a novel structural detailing is proposed in this study. The proposed detailing technique intends to concurrently improve the seismic and progressive collapse performances of an RC frame by changing the layout of the newly added longitudinal reinforcement against progressive collapse without introducing any additional reinforcement. A six-story RC frame is used as the prototype building for this investigation. Both cyclic and progressive collapse tests are conducted to validate the performance of the proposed structural detailing. Based on the experimental results, detailed finite element (FE) models of the RC frame with different reinforcement layouts are established. The seismic and progressive collapse resistances of different models are compared based on the incremental dynamic analysis (IDA) and nonlinear dynamic alternate path (AP) methods, respectively. The results indicate that the proposed structural detailing can effectively resolve the conflict between the seismic and progressive collapse designs.     

C F RP加固震损钢筋混凝土框架结构的抗整体性倒塌能力分析

首先介绍了CFRP加固受损钢筋混凝土柱的数值模拟方法,通过OpenSees软件进行了建模分析,数值模拟结果与试验结果的对比验证了该数值模型的有效性;其次,对一6层钢筋混凝土框架以受极罕遇地震影响进行预损,采用损伤指数和折减系数的方法建立震损钢筋混凝土框架的分析模型,并选择5种不同的CFRP加固方案对其进行加固;最后,对CFRP加固的震损RC框架进行增量动力分析。定量的评价了CFRP加固震损RC框架的抗整体性倒塌能力和抗倒塌安全储备。结果表明:CFRP加固能有效提高震损钢筋混凝土框架结构的抗震性能。加固部位的选择对加固效果的影响很大,在所选用的5种CFRP加固方案中,对底层及第2层的梁柱进行加固的方案对提高震损钢筋混凝土框架的抗整体性倒塌能力效果最佳。     

Mesoscopic investigation on seismic performance of corroded reinforced concrete columns

In addition to the normal service loadings, engineering structures may be subjected to occasional loadings such as earthquakes, which may cause severe destruction. When the steel rebar is corroded, the damage could be more serious. To investigate the seismic performance of corroded RC columns, a three-dimensional mesoscale finite element model was established. In this approach, concrete was considered as a three-phase composite composed of aggregate, mortar matrix and interfacial transition zone (ITZ). The nonlinear spring were used to describe the bond slip between steel and concrete. The degradation of the material properties of the steel rebar and cover concrete as well as the bonding performance due to corrosion were taken into account. The rationality of the developed numerical analysis model was verified by the good agreement between the numerical results and the available experimental observation. On this basis, the effect of corrosion level, axial force ratio and shear-span ratio on the seismic performance of corroded RC columns, including lateral bearing capacity, ductility, and energy consumption, were explored and discussed. The simulation results indicate that the mesoscopic method can consider the heterogeneity of concrete, to more realistically and reasonably reflect the destruction process of structures.

     

带有可更换连梁的钢筋混凝土结构设计方法

钢筋混凝土剪力墙结构通过设置可更换连梁,在地震作用下集中损伤,保护主体结构不受或只受微小破坏,震后更换损伤构件即可恢复结构功能。参照现行规范和已有试验分析结果,在普通钢筋混凝土结构设计基础上,提出带有可更换连梁的钢筋混凝土结构实用设计方法,设定性能目标,总结设计流程。采用提出的设计方法对1个50层钢筋混凝土结构进行设计,并采用大型有限元分析软件ABAQUS建立数值模型,验证结构性能目标和提出的设计方法。结果表明:按该方法设计的带有可更换连梁的钢筋混凝土结构能满足所设定的性能目标,设计方法合理实用,为该新型结构的工程应用提供了参考。     

考虑悬链线效应的RC框架结构鲁棒性分析

为了充分反映结构的抗连续倒塌能力,文中基于能量原理,将结构倒塌时消耗能量与屈服时消耗能量之比定义为考虑悬链线效应的结构鲁棒性指标。首先进行一榀1/2缩尺的RC平面框架的连续倒塌试验,得到了具有双峰值点的荷载-位移曲线。基于试验数据对有限元模型进行验证与校准。进一步建立了18个RC平面框架结构数值分析模型,研究了中柱失效、边柱失效及不同梁底部纵向钢筋配筋率、顶部纵向钢筋配筋率等对考虑悬链线效应的结构鲁棒性影响规律。分析结果表明,由于边柱失效的结构无法发挥悬链线效应,鲁棒性较差;而中柱失效后的结构,由于其存在悬链线效应,结构表现出了更好的鲁棒性。结构鲁棒性系数随着梁底部钢筋配筋率的增加而降低,随着梁上部钢筋配筋率的增加而提高,梁上部钢筋配筋率显著影响结构的鲁棒性。本文提出的基于能量的考虑悬链线效应的结构鲁棒性计算方法,为RC框架结构抗连续倒塌设计提供了理论支持。