Energy dissipation and performance assessment of double damped outriggers in tall buildings under strong earthquakes

The use of a single set of outriggers equipped with oil viscous dampers increases the damping ratio of tall buildings in about 6–10%, depending on the loading conditions. However, could this ratio be further increased by the addition of another set of outriggers? Should this additional set include dampers too? To answer these questions, several double damped outrigger configurations for tall buildings are investigated and compared with an optimally designed single damped outrigger, located at elevation 0.7 of the total building's height (h). Using free vibration, double outrigger configurations increasing damping up to a ratio equal to the single‐based optimal are identified. Next, selected configurations are subjected to several levels of eight ground motions to compare their capability for avoiding damage under critical excitations. Last, a simplified economic analysis highlights the advantages of each optimal configuration in terms of cost savings. The results show that, within the boundaries of this study, combining a damped outrigger at 0.5h with a conventional outrigger at 0.7h is more effective in reducing hysteretic energy ratios and economically viable if compared with a single damped outrigger solution. Moreover, double damped outrigger configurations for tall buildings exhibit broader display of optimal combinations, which offer flexibility of design to the high‐rise architecture.     

Distribution of strong earthquake input energy in tall buildings equipped with damped outriggers

The seismic design of optimal damped outrigger structures relies on the assumption that most of the input energy will be absorbed by the dampers, whilst the rest of the structure remains elastic. When subjected to strong earthquakes, nevertheless, the building structure may exhibit plastic hinges before the dampers begin to work. In order to determine to which extent the use of viscously damped outriggers would avoid damage, both the host structure's hysteretic behaviour and the dampers' performance need to be evaluated in parallel. This article provides a parametric study on the factors that influence the distribution of seismic energy in tall buildings equipped with damped outriggers: First, the influence of outrigger's location, damping coefficients, and rigidity ratios core‐to‐outrigger and core‐to‐column in the seismic performance of a 60‐story building with conventional and with damped outriggers is studied. In parallel, nonlinear behaviour of the outrigger with and without viscous dampers is examined under small, moderate, strong, and severe long‐period earthquakes to assess the hysteretic energy distribution through the core and outriggers. The results show that, as the ground motion becomes stronger, viscous dampers effectively reduce the potential of damage in the structure if compared to conventional outriggers. However, the use of dampers cannot entirely prevent damage under critical excitations.     

Analysis of a high‐rise steel structure with viscous damped outriggers

Damped outriggers for tall buildings draw increasingly attentions to engineers. With a shaking table test, two models of a high‐rise steel column‐tube structure are established, one with outriggers fixed to the core and hinged at the columns, whereas the other's cantilevering outriggers are connected to columns by viscous dampers. According to their dynamic properties, five earthquake waves are selected from the Ground Motion Database of Pacific Earthquake Engineering Research Center (PEER), and two artificial waves are generated by software SIMQKE_GR. Under various peak ground accelerations (PGAs), nonlinear time‐history analysis is applied to compare structural elastic seismic responses, including accelerations, inter‐story drifts, base shear force, damper's response and additional damping ratios. It is concluded that under minor earthquakes, accelerations, inter‐story drifts and base shear force of structure with damped outriggers are larger than or nearly equal to those of the one with fixed outriggers, and the viscous dampers hardly work. But as PGA increases, the contrary situation happens, and the effect of viscous dampers is enhanced as well. The additional damping ratio reaches around 4% under mega earthquakes. Copyright © 2013 John Wiley & Sons, Ltd.     

A simplified model for analysis of high‐rise buildings equipped with hysteresis damped outriggers

A simplified model is developed to estimate the seismic response of high‐rise buildings equipped with hysteresis damped outriggers. In the simplified model, the core tube is considered as a cantilever beam, and the effects of outriggers on the core tube are considered as concentrated moments. Modal decomposition method is adopted to obtain the seismic response of the simplified model. To investigate the accuracy and effectiveness of the simplified model, a high‐rise building with a height of 160 m was adopted as the example structure, and its response subjected to a ground motion was analyzed using the simplified model. A corresponding finite element model was built and analyzed by a finite element program called SAP2000 (Computers and Structures, Inc. Berkeley, California, United States). The analysis results obtained from the two models were compared. To consider the randomness of the ground motion, comparisons between the two models were further conducted using another 22 ground motions. It is found that the analysis results obtained from the simplified model agree well with those obtained from the finite element model, and the computation time used for the simplified model is almost negligible compared to that used for the finite element model. Such observations demonstrate that the simplified model is accurate and effective. Copyright © 2013 John Wiley & Sons, Ltd.     

Stiffness optimization technique for 3D tall steel building frameworks under multiple lateral loadings

Although today's engineering computer technology allows for precise analysis of the structural response of a building, it does not readily provide insight for economical design. Due to the complex nature of a modern tall building consisting of thousands of structural members, the traditional design method is generally highly iterative and time consuming. This paper describes an efficient computer-based technique for least-weight design of three-dimensional (3D) tall steel building frameworks under multiple lateral loading conditions. Stiffness constraints in terms of interstorey drifts are considered and optimum discrete member sizes are automatically selected from databases of commercial standard steel sections. The technique is remarkably efficient and the optimum design generally converges in a few cycles. The designs of two 3D lateral-load resisting building frameworks are presented as illustrations. The effectiveness and suitability of the technique for the design of large-scale tall steel building frameworks are discussed.     

带伸臂超高层结构最优伸臂道数及位置确定的灵敏度向量法

以最大层间位移角为优化目标,提出一种简单有效的向量积算法,可以快速确定最优的伸臂桁架设置数目及位置。以上海中心大厦为例,给出了该算法的应用方法及过程,并结合分析结果对带伸臂超高层结构的最优伸臂道数及位置的设置规律进行了分析。对于典型的100层以上的超高层建筑,向量积算法的效率比常规的穷举法提高约28倍。分析表明,最优的伸臂桁架设置方案与桁架设置的数目和位置均有关系,且伸臂桁架设置方案的最优性并非随着伸臂桁架数目的增加而增加。     

基于振动台试验的超高层结构伸臂消能体系抗倾覆性能研究

本研究通过对某超高层结构模型进行模拟地震振动台试验,考察核心筒、外围框架与伸臂结构组成的抗侧力体系在地震作用下的整体抗倾覆性能,重点分析在伸臂结构设置黏滞阻尼器的消能减震策略对结构底部弯矩的控制效果,为该类超高层结构体系减震研究提供参考。     

受扰高层建筑的风致响应分析

受扰状态下高层建筑的静动力响应明显不同于单体建筑。以一实际姊妹塔楼为研究对象,根据风洞试验中获得的风压分布结果,计算塔楼结构的风致响应。风洞试验及结构响应计算不仅考虑了两栋塔楼同时存在的情况,还考虑一栋塔楼先期建成,另一塔楼尚未建造的情况。细致分析了不同风向下结构的平均及脉动位移响应、静动力干扰因子的特点。结果表明,施扰建筑位于受扰建筑正前方时具有最大的干扰效应,此时受扰塔楼的总位移峰值最小;而当受扰建筑处于施扰建筑下游时,在风向偏斜时,受扰塔楼的总位移峰值最大。     

高层混凝土框架核心筒-木盒混合结构抗震性能研究

提出了一种以混凝土框架-核心筒结构为“主结构”,每层主结构间内嵌3层装配式轻型木结构为“子结构”的装配式高层建筑结构体系。该混合结构体系实现了建筑使用功能多样化,结构体系集成化,建筑材料绿色化,建造施工装配化的特点。着重研究了体系中主结构与子结构间的连接,根据连接的特点和强弱,提出了3种不同的结构模型：1）重力模型,其特点是主结构与子结构在侧向不连接或弱连接,不考虑子结构对整体结构抗侧刚度的贡献;2）刚度模型,主子结构间采用螺栓有效连接;3）隔震模型,其子结构底面与主结构采用隔震支座连接。采用有限元软件SAP2000对3种具有不同受力特点的模型结构进行抗震性能分析研究。结果表明：重力模型主结构受力安全合理;刚度模型中子结构对整体结构抗侧刚度的贡献可达6%~35%;隔震模型中隔震子结构可明显降低整体结构的地震反应。与建筑功能相同的混凝土框架核心筒结构相比,混凝土框架核心筒-木盒结构自重可减轻25%,地震作用可减小30%,有利于在地震设防区应用。     

某高层剪力墙住宅结构减震分析与设计

将铅剪切阻尼器应用于某高层剪力墙住宅结构的减震分析与设计中,经过多次试算分析得到了阻尼器的优化布置方案。小震下的弹性时程分析和大震下的静力弹塑性分析结果表明,铅剪切阻尼器的减震率达到了40%,可以使该结构的抗震能力约提高1度。对布置阻尼器后的结构竖向承载力进行了验算,并对有关部位、附加剪力墙配筋和预埋件进行了设计。     

高层建筑需要控制的参数及调整方法

本文介绍了轴压比、周期比、位移比、刚度比、刚重比、剪重比、层间受剪承载力之比、框架柱及短肢墙地震倾覆力矩及0．2V。剪力调整这几个高层设计中常见的指标。分别从指标的概念,控制意义,规范限值,SATWE软件的结果判断,调整方法几个方面进行说明。     

Optimal parameters for tall buildings with a single viscously damped outrigger considering earthquake and wind loads

Tall buildings suffer from low inherent damping and high flexibility. Therefore, a core-outrigger system is often used to stiffen such buildings. A modified form, known as the damped outrigger system, wherein vertically oriented dampers are installed between outriggers and perimeter columns, has been recently developed to supplement the damping. This paper studies the efficacy of a viscously damped outrigger system through dynamic analysis of a 60-story tall building subjected to nonconcurrent earthquake and wind excitations. Two ground motion sets (100 accelerograms) are used for the former and wind tunnel test data for the latter. Effects of three building parameters, namely, (i) the core-to-column stiffness ratio, (ii) the outrigger location, and (iii) the damper size, on the dynamic characteristics and seismic and wind responses are evaluated. Effects of damper nonlinearity on seismic and wind responses are also investigated considering energy-equivalent nonlinear viscous dampers. Finally, the optimum values of these parameters are determined. For example, the optimum outrigger location is found to be between $0.6H$ to $0.9H$, where $H$ is the height of the building. The results also show that the damped outrigger system significantly outperforms the conventional one for seismic excitation, and it is very effective in reducing the wind-induced floor accelerations, provided the parameters are chosen appropriately.     

不规则复杂平面高层结构抗震计算和设计探讨

对一平面不规则的工程实例采用SATWE程序进行了小震作用下的空间结构振型分解法和弹性时程分析法的计算,采用PUSH程序进行了静力弹塑性分析,并采用EPDA程序进行了中震、大震作用下的弹塑性时程分析。结果表明,对于不规则复杂平面结构,在空间结构振型分解法、弹性时程分析法及静力弹塑性分析计算符合要求的情况下,在中震、大震作用下弹塑性时程分析的弹塑性层间位移角也超出了限值,因此,建议对该类结构补充弹塑性时程分析,并宜采用有害层间位移角来控制结构的层间位移,判断结构的薄弱层。     

基于SMA拉索的高层建筑结构振动控制研究

介绍了形状记忆合金（SMA）的基本特性和本构模型,并通过建立被动控制高层建筑结构地震响应的运动方程,探讨其控制原理和方法,通过与无控方案和设置了传统钢拉索的方案进行比较,结果表明形状记忆合金具有明显的阻尼特性,可以显著地抑制结构的地震反应。     

Strength demand of dual‐purpose outrigger system for reducing lateral displacement and differential axial shortening in a tall building

Certain maximum lateral displacement (LAT) and differential axial shortening (DAS) values can lead to the deterioration of the serviceability of a structure. Previous studies indicated that an outrigger system can be used to control both the DAS and the LAT in a tall building. In order to enhance the applicability of the dual‐purpose outrigger system, the amount of stress developed on the outrigger due to the reductions of the LAT and DAS should be determined. Therefore, in this study, the stresses due to the LAT and DAS were analyzed in terms of the reduction ratio of the LAT and DAS, and the absolute sum of stresses, which was the strength demand of the outrigger, was evaluated as well. To identify the parameters affecting the additional stress of the outrigger, analytic equations were proposed to predict the additional shear force acting on the outrigger due to DAS reduction. A finite‐element analysis was performed to quantitatively identify the reduction ratio of the LAT and DAS as well as the resulting stress by changing four parameters: the stiffness, location, number, and connection time of outriggers. The results demonstrated that the stress of the dual‐purpose outrigger can be minimized by adjusting the design parameters.     

成都某大厦大底盘双塔连体结构抗震设计

通过对连体结构的工程实例进行在地震作用下反应谱分析和弹性时程分析,探讨连体结构的动力反应特性;用EPDA弹塑性时程分析软件进行在罕遇地震作用下的弹塑性时程分析,对该工程的结构抗震性能进行评估,找出连体结构的薄弱部位和受力特性,并针对这些薄弱部位和受力特性提出抗震设计时的加强措施和方法。     

高层建筑与裙房基础整体设计的若干问题

通过带裙房高层建筑与地基基础共同作用的理论研究以及实测调查，就高层建筑与裙房基础整体设计的一些问题提出看法与建议。其中包括整体设计裙房基础悬臂长度的建议值和相对弯曲参考值。推荐在软土地基合适的桩箱（筏）基础沉降计算方法以及上海各类桩持力层基床系数的建议值，以供设计者参考。     

高层建筑加压送风系统试验研究

介绍了哈尔滨市一座高层建筑楼梯间及其前室、合用前室的加压送风系统的试验情况。分析了几种不同试验工况下，楼梯间与前室、合用前宣的正压值、门洞风速、加压送风量等问题，并对机械加压送风的若干问题作了探讨。试验结果表明，目前国内在加压送风系统设计、验收、防排烟产品质量方面存在不少问题，必须认真对待。《高规》中有关加压送风的某些条文有待进一步充实和完善。     

Detail design,building and commissioning of tall building structural models for experimental shaking table tests

In the areas of seismic engineering, shaking table tests are powerful methods for assessing the seismic capacity of buildings. Since the size and capacity of existing shaking tables are limited, using scale structural models seems to be necessary. In recent years, many experimental studies have been performed using shaking table tests to determine seismic response of structural models subjected to various earthquake records. However, none of the past research works discussed practical procedure for creating the physical model. Therefore, in this study, a comprehensive procedure for design, building and commissioning of scale tall building structural models has been developed and presented for practical applications in shaking table test programmes. To validate the structural model, shaking table tests and numerical time history dynamic analyses were performed under the influence of different scaled earthquake acceleration records. Comparing the numerical predictions and experimental values of maximum lateral displacements, it became apparent that the numerical predictions and laboratory measurements are in a good agreement. As a result, the scale structural model can replicate the behaviour of real tall buildings with acceptable accuracy. It is concluded that the physical model is a valid and qualified model that can be employed for experimental shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd.     

非刚性楼板对高层建筑结构内力和位移的影响分析

考虑高层建筑结构楼板的非刚性，将框架-剪力墙结构连续化，建立结构的平衡微分方程，采用通用的常微分方程求解器求解，得到了高层建筑结构考虑非刚性楼板与刚性楼板的内力和位移。