A study on the seismic performance of steel‐reinforced concrete frame‐concrete core wall high‐rise mixed structure by large‐scale shaking table tests and numerical simulations

This paper reports a study for the seismic performance of one large‐scaled (1/15) model of 30‐story steel‐reinforced concrete frame‐concrete core wall mixed structure. The study was implemented by both shaking table tests, in which the similarity ratio for lateral and gravitational accelerations was kept to 1:1, and numerical nonlinear dynamic analysis. The test observations presented herein include story displacement, interstory drift, natural vibration periods, and final failure mode. The numerical analysis was performed to simulate the shaking table test procedure, and the numerically obtained responses were verified by the test results. On the basis of the numerical results, the progressions of structural stiffness, base shear, and overturning moment were investigated, and the distributions of base shear and overturning moment between frame and core wall were also discussed. The test demonstrates the seismic performance of the steel‐reinforced concrete frame‐core wall mixed structure and reveals the potential overturning failure mode for high rise structures. The nonlinear analysis results indicate that the peripheral frames could take more shear forces after core wall damaged under severe earthquakes. Copyright © 2013 John Wiley & Sons, Ltd.     

多塔高层结构隔震设计与分析

结合某多塔高层隔震结构,采用弹性时程分析方法,分析了隔震结构在多遇地震和罕遇地震作用下的响应。主要包括自振周期、层间剪力、倾覆力矩和楼层位移等内容。结果表明,与非隔震情形相比,结构的自振周期明显增大,地震作用得到了较大的衰减。结构在地震作用下的隔震效果明显,楼层剪力及倾覆力矩均得到折减,在罕遇地震作用下隔震效果尤为显著。层间位移主要集中在隔震层,上部结构的层间位移几乎为零。     

最小剪力系数及其调整方法对超高层建筑地震响应的影响

超高层结构地震剪力响应由振型分解反应谱法得到的结果经常不能满足规定的最小剪力系数要求。为此,文章简述剪力系数的概念和调整方法,以具有不同剪力系数的两个模型对比分析结构弹性、弹塑性地震响应差异,探讨剪力系数对超高层结构地震响应的影响。以通过强度和刚度调整使最小剪力系数满足规范要求的两个模型,分析不同调整方法引起的结构响应的合理性。结果表明:满足最小剪力系数的结构的弹性基底剪力大、层间位移角较小,结构的弹塑性位移响应也较小,受力状态优于不满足最小剪力系数的结构,安全性得到了提高。结构弹性倾覆力矩需求和弹塑性基底剪力按刚度调整大于按强度调整;结构弹塑性最大顶点位移和层间位移角响应相差不大,但出现刚度大\,层间位移角也大的与抗震理论相悖的情况;在满足抗震要求的情况下,构件的受力状态则是按强度调整更优,构件截面更加经济合理。     

增设节点阻尼器的外附钢框架结构抗震性能试验研究

提出一种组合型减震结构,由钢框架、节点阻尼器和原结构连接组成,外附钢框架将节点阻尼器连接在原混凝土框架结构上形成的增设节点阻尼器的外附钢框架结构,节点阻尼器的剪切滞回变形可以减小结构自身需要消耗的能量,从而提高原结构抗震性能。对原混凝土结构和增设节点阻尼器的组合型结构进行了的振动台试验。通过分析结构在不同地震波激励下的加速度和位移响应,得出楼层加速度和层位移的减震效果。研究结果表明:该结构体系在小震作用下通过提高结构刚度来增强其抗震性能;在大震作用下则可借助节点阻尼器的变形耗能来提升结构耗能能力,结构加速度减震系数达到53%,层间位移减震系数高达72%,验证了增设节点阻尼器的外附钢框架结构的减震效果。     

西昌市某高层剪力墙结构隔震设计与分析

针对西昌市某高层钢筋混凝土剪力墙结构进行了橡胶支座隔震设计和抗震性能分析。西昌市抗震设防烈度为9度,历史上曾发生过7.5级地震。该工程场址地质构造较复杂,东侧区域有一条隐伏断层,属则木河断裂带次生断层。则木河断裂带是川西主要发震断裂带之一,至今仍是一条活动较强烈的大断裂。按照《建筑抗震设计规范》(2016版)要求,取近场影响系数1.5,以提高结构的安全度;选取Ⅱ类场地5条天然地震波和2条人工模拟地震波,共计七条符合规范要求的地震波;基于SAP2000软件对结构进行了隔震设计,中震作用下结构层间剪力和倾覆弯矩减震系数最大值为0.24,比非隔震结构地震响应减小显著,罕遇地震下隔震支座的面压、水平位移能够满足规范要求。采用ABAQUS对结构进行了罕遇地震动力弹塑性时程分析,结果表明结构能够满足"大震不倒"的抗震设防目标。     

非一致地震波动输入下大型钢筋混凝土框架结构-地基体系地震响应规律

为探索非一致地震波动输入对大型钢筋混凝土框架结构地震响应的影响,基于OpenSees软件平台建立二维钢筋混凝土框架结构\|地基动力相互作用有限元模型。将El-Centro地震波按P波波形分别以0°、15°、30°和35°角入射该有限元模型进行计算,对比分析框架柱内力和楼层层间位移的地震响应。研究发现非一致地震波输入方法对于大型钢筋混凝土框架结构建筑动力响应影响明显,随着地震波入射角的增大,钢筋混凝土框架结构底层柱的轴力幅值减小,剪力幅值增大,而弯矩幅值变化较小,楼层层间位移幅值也随之增大。研究结果对于大型钢筋混凝土框架结构抗震设计具有参考意义。     

Shake-table testing of a self-centering precast reinforced concrete frame with shear walls

The seismic performance of a self-centering precast reinforced concrete (RC) frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls (SPCW), which utilize a combination of unbonded prestressed post-tensioned (PT) tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.     

考虑SSI效应的设圈梁构造柱农村民居振动台试验研究

将参数化建模的方法引入减震结构的分析与设计中,通过预设目标和迭代优化计算,以天水市某高层住宅消能减震结构为例,寻找最优的阻尼器布置方案。为评估和验证该消能减震结构的抗震性能,分别采用Perform 3D和ETABS等软件分析结构在多遇和罕遇地震作用下的结构响应,分析结果表明：小震作用下,消能减震结构的楼层位移、层间位移角、楼层弯矩及楼层剪力均减小6.5%以上,达到了设计要求;大震作用下,结构框架柱、框架梁、剪力墙和阻尼器能够满足既定的性能要求,层间位移角满足规范限值,能够达到“大震不倒”的设计目标,研究结果为实际工程预设减震目标和阻尼器优化布置提供参考。     

地震作用后钢筋混凝土框架结构恢复性模拟研究

钢筋混凝土框架结构在地震冲击后,其刚体退化特性复杂,存在模拟时结果失真明显的问题。为此,在考虑刚度退化规律的基础上进行分析模拟,研究地震冲击下钢筋混凝土框架结构的恢复性。提取地震作用下钢筋混凝土框架结构滞回曲线,通过有限元分析获取不同的特征点,形成恢复力模型的骨架曲线;依据恢复力模型骨架曲线和刚度退化规律,构建滞回曲线,模拟地震作用后钢筋混凝土框架结构恢复过程。在模拟的钢筋混凝土框架结构恢复实验中,层间位移结果低于5 mm、层间绝对加速度和柱底抬升结果的误差均低于0.1 mm;模拟得到结构的弯矩缝隙都能够实现闭合,钢筋混凝土结构未出现屈服现象,说明模拟的结果较好。     

再生混凝土的低温抗震性变化对比分析

再生混凝土作为建筑材料在被使用前,需要对其低温抗震性能做出分析。但目前我国是全球新建筑数量最多的国家,再生混凝土成本低、需求量大,建筑方根据对普通混凝土的印象,直接将再生混凝土应用到建筑工程建设中,其中存在低温抗震性能不明确的问题。针对这个问题,提出再生混凝土的低温抗震性变化对比分析,通过再生混凝土的材料配比及实验搭建设计再生混凝土低温抗震结构模型。根据其指标对其低温抗冻性能、加速度变化、损伤指标、刚度稳定性、层位移变化等几个方面进行变化对比分析。对比实验结果表明:再生混凝土当含气量在逐渐降低时,其保温效果降低,强度在降低,抗冻性也在降低,耐久性和稳定性较差,并且在地震后楼层间的位移和加速度变化较大,不能保证楼层的稳定性;位移角无法降低到最小;随着位移和负载地震力不断增加,再生混凝土逐渐产生开裂变化,刚度减小速度较快,刚度退化程度较大,低温抗震性能较差。     

基于等损伤的主余震序列型地震动PGA放大系数谱研究

大地震发生后往往会伴随强余震发生,强烈余震会加重结构的破坏程度,在抗震设计及结构损伤评估中考虑余震的影响是一重要课题。采用NGA-West2数据库建立主余震序列型地震动记录数据集,基于损伤等效思想定义主余震作用下PGA放大系数α,针对单自由度体系结构,通过动力时程分析建立不同相对强度、不同场地条件下平均PGA放大系数谱,进一步通过回归分析构建PGA放大系数谱的预测方程,分析统计结果的离散性。结果表明：PGA放大系数谱受场地条件影响较小,受主余震相对强度影响显著;放大系数谱值随周期增大而减小。谱预测方程能够提供目标损伤下结构的主震PGA放大需求,并可以作为设计谱调整系数使用,以实现在结构抗震设计及结构损伤评估中考虑余震的影响。     

浮放储罐三维地震反应有限元分析

针对立式储罐,考虑液固耦合效应、地基与储罐结构的相互作用,采用有限元分析方法,对储罐在三维地震荷载作用下动反应进行了数值分析。分析结果表明：储罐三维地震加速度反应较一维地震加速度反应增加、提离高度明显放大、储罐轴向应力增加、基底剪力与弯矩增大。     

屈曲约束支撑钢框架结构影响因素的静力弹塑性分析

为检验抗侧刚度比和支撑布置方式等因素对具有不同总层数的屈曲约束支撑钢框架的抗震性能影响,借助SAP2000软件,探讨6层、12层、18层屈曲约束支撑钢框架结构在抗侧刚度比分别为1、2、3、4、5共五种工况及倒V型和单斜向两种支撑布置方式下的抗震性能。结果表明,屈曲约束支撑钢框架结构基底剪力-顶点位移曲线呈典型的双线性特征;随抗侧刚度比的增大,结构的层间位移角总体上呈降低趋势,基底剪力及支撑轴力增大,顶点水平位移变小,框架所分担的剪力降低;倒V型布置支撑较单斜向布置具有略大的基底剪力、谱加速度,较小的顶点位移、层位移、层间剪力和框架剪力分担率。分析表明,总体上来看,倒V型布置较单斜向布置时支撑框架结构具有略优的抗震性能;抗侧刚度比较支撑布置方式对支撑框架结构抗震性能的影响更为显著。     

Mechanisms to limit higher mode effects in a controlled rocking steel frame. 2: Large‐amplitude shake table testing

This paper presents the results of 56 large‐amplitude shake table tests of a 30% scale eight‐storey controlled rocking steel frame. No significant damage or residual deformations were observed after any of the tests. The frame had four possible configurations on the basis of combinations of two higher mode mitigation mechanisms. The first mitigation mechanism was formed by allowing the upper section of the frame to rock, so as to better control the mid‐height overturning moment. The second mitigation mechanism was formed by replacing the conventional first‐storey brace with a self‐centering energy dissipative (SCED) brace, so as to better control the base shear. The mechanisms had little effect during records where higher mode effects were not apparent, but they substantially reduced the shear and overturning moment envelopes, as well as the peak floor accelerations, during more demanding records. The reduction in storey shears led to similarly reduced brace force demands. Although the peak force demands in the columns were not reduced by as much as the frame overturning moments, using an upper rocking joint allowed the column demands to be estimated without the need to assume a lateral force distribution. The tests demonstrated that multiple force‐limiting mechanisms can be used to provide better control of peak seismic forces without excessive increases in drift demands, thus enabling more reliable capacity design. These results are expected to be widely applicable to structures where the peak seismic forces are significantly influenced by higher mode effects. Copyright © 2012 John Wiley & Sons, Ltd.     

近断层地震动作用下风机塔地震反应分析

为了研究近断层地震动速度脉冲及强竖向地震动对风机塔地震响应的影响,以某陆上风电场1.5 MW风机塔为研究对象开展了结构在水平向脉冲型地震动、水平向非脉冲型地震动、水平与竖向地震动组合3种地震输入工况的时程分析。通过3种工况下塔顶位移时程、加速度时程、塔底剪力、弯矩及轴力的对比分析发现:近断层速度脉冲对结构塔顶水平位移、塔顶水平加速度、塔底剪力与弯矩均影响显著;竖向地震动会加大结构的塔顶竖向加速度响应及塔底轴力响应;随着竖向与水平加速度峰值比增大,塔顶竖向加速度响应增大,最大轴力随着峰值比增大而增大,最小轴力随着峰值比增大而减小。此外,增量动力分析表明,采用自接触的有限元模型可以更真实地预测风机塔的失稳破坏机制。     

考虑周期折减的结构弹性时程分析调整方法

针对结构弹性时程分析时无法考虑周期折减的问题展开研究,通过对比结构时程分析的过程中,地震波的选取是否考虑周期折减的差异,提出采用增大系数放大时程分析法输入地震波有效峰值加速度以及地震响应;考虑弹性时程分析过程中,周期折减对结构地震作用的增大效应。理论分析增大系数取值的影响因素,并基于单自由度体系对比两种调整方法的效果及差异,采用实际算例以验证所提出弹性时程分析中考虑周期折减调整方法的有效性。结果表明:增大系数的取值与周期折减系数、结构自振周期及场地特征周期等因素有关;对于单自由度体系,两种调整方法具有完全相同的调整效果;按文章提出方法考虑周期折减的算例结构,弹性时程分析所得各楼层地震剪力及层间位移角与考虑周期折减的反应谱(CQC)计算结果均较为接近。     

A cantilever beam analogy for quantifying higher mode effects in multistorey buildings

This paper examines higher mode effects in systems where the ductile mechanism for seismic design is the base moment‐rotation response. The modal properties of flexural and shear beams with uniform mass and elasticity and with a variable amount of base rotational restraint are derived. As the base fixity is released, the first mode becomes the rigid body rotation of the beam about the base, but the higher modes change much less, particularly for the shear beam model. Most response quantities that are of interest in the seismic design of typical mid‐rise buildings are controlled by the first two lateral modes, except at locations along the height where the second mode contributes little. However, the third and higher lateral modes are more significant for high‐rise buildings. Based on the theory of uniform cantilever shear beams, expressions are developed to avoid the need for a modal analysis to estimate the overturning moment, storey shear, and floor acceleration envelopes. Considering the measured response from the shake table testing of a large‐scale eight‐storey controlled rocking steel braced frame, the proposed expressions are shown to be of similar or better accuracy to a modified modal superposition technique, which combines the higher mode response from an elastic modal analysis with the response associated with achieving the maximum base overturning moment according to an inverted triangular load distribution. Because the proposed method uses only parameters that are available at the initial design stage, avoiding the analysis of a structural model, it is likely to be especially useful for preliminary design. Copyright © 2015 John Wiley & Sons, Ltd.     

地裂缝场地结构抗震设防避让距离研究

以西安地铁二号线沿线地质勘查资料为基础,借助ABAQUS有限元软件建立地裂缝场地与结构共同作用模型,将结构分别置于距地裂缝不同距离的位置,并施加El-Centro地震波,通过比较不同位置结构的层间位移角、框架柱剪力的变化情况,研究近地裂缝结构在地震作用下的工作特性,找出不同避让距离下的结构动力响应变化规律,并与地表峰值加速度的变化规律进行对比分析,为地裂缝场地结构的避让距离选取提供参考。结果表明:上盘结构层间位移角放大幅度为30%~41%,而下盘结构层间位移角放大幅度为18%~22%,上盘结构的破坏程度远大于下盘结构。随避让距离的增大,地表加速度峰值逐渐减小,结构破坏情况相应减弱,但地表峰值加速度表现出现较为平缓的线性下降,而其上部结构的峰值位移曲线则出现大幅度的下降,甚至在近地裂缝处产生突变,其最大层间位移角放大幅度由41%降为21%,地表加速度峰值的变化并不能完全反映出近地裂缝结构的动力响应规律。位于地裂缝场地的结构动力时程响应规律明显区别于普通场地上的结构,对位于地裂缝场地的结构进行抗震设计时应对水平地震影响系数最大值αmax进行调整。     

Shaking table tests and numerical analyses of an RC coupled wall structure with replaceable coupling beams

The replaceable coupling beam (RCB) is an innovative structural component developed to increase the seismic resilience of reinforced concrete (RC) shear wall structures. In this study, two 1/5‐scale 5‐story 3‐dimensional RC shear wall structures—one with conventional RC coupling beams and the other with RCBs—were designed, constructed, and tested on a shaking table. The failure pattern, dynamic properties, and structural responses, including the acceleration, displacement, story force, and strain responses, of the 2 structures are compared under earthquake excitations. The test results demonstrate that the seismic performance of the structure with RCBs was improved when RCBs were working compared with the structure with conventional RC coupling beams. In addition, the replaceable devices suffering the severe damage during an earthquake can be conveniently replaced after the earthquake. However, after the sudden failure of RCBs during the severe earthquakes, the inter‐story drift and floor acceleration of the structure with RCBs became larger. The design and manufacture quality of RCBs should be improved to avoid the sudden failure. Then, numerical models for the test structures were established using the commercial software PERFORM‐3D. Numerical simulations of the tests were conducted. The simulation results correspond well with the experimental results, thus verifying the accuracy of the numerical models. The RC shear wall structure installed with RCBs can be applied as a new type of earthquake‐resilient structure in engineering practice.     

Evaluation of the seismic performance of a three‐story ordinary moment‐resisting concrete frame

This study focuses on the seismic performance of Ordinary Moment‐Resisting Concrete Frames (OMRCF) designed only for gravity loads. For this purpose, a 3‐story OMRCF was designed in compliance with the minimum design requirements in the American Concrete Institute Building Code ACI 318 (1999). This model frame was a regular structure with flexure‐dominated response. A 1/3‐scale 3‐story model was constructed and tested under quasi‐static reversed cyclic lateral loading. The overall behavior of the OMRCF was quite stable without abrupt strength degradation. The measured base shear strength was larger than the design base shear force for seismic zones 1, 2A and 2B calculated using UBC 1997. Moreover, this study used the capacity spectrum method to evaluate the seismic performance of the frame. The capacity curve was obtained from the experimental results for the specimen and the demand curve was established using the earthquake ground motions recorded at various stations with different soil conditions. Evaluation of the test results shows that the 3‐story OMRCF can resist design seismic loads of zones 1, 2A, 2B, 3 and 4 with soil types S_A and S_B . For soil type S_C , the specimen was satisfactory in seismic zones 1, 2A, 2B and 3. For soil type S_D , the OMRCF was only satisfactory for seismic zones 1 and 2A. Copyright © 2004 John Wiley & Sons, Ltd.