The Effect of Core Eccentricity on the Structural Behavior of Concrete Tall Buildings

The main purpose of this paper is to investigate the effect of core eccentricity on the structural behavior of concrete tall buildings.Concrete buildings of 55 floors with plan dimensions 48.0×48.0 m2 were investigated.Three cases of main core locations are studied:centric(A),eccentric by one sixth(B)and one third(C)of building width.The three-dimensional finite element method has been used in conducting structural analysis through ETABS software.Gravity and lateral(wind and seismic)loadings are applied to all building cases.It has been concluded that the core location is the prime parameter governing the structural behavior of tall buildings.Although the first two cases(A,B)have acceptable and similar structural behaviors conforming to code limits,in the third case(C),the building behavior came beyond code limits.The author introduced remedial action by adding two secondary cores in the opposite direction of the main core(C-R)to restore the building behavior to the code limits.The results of this action were satisfactory.

Seismic response of tall building considering soil-pile-structure interaction

The seismic behavior of tall buildings can he greatly affected by non-linear soil-pile interaction during strong earthquakes.In this study a 20-storey building is examined as a typical structure supported on a pile foundation for different conditions:(1) rigid base,i.e.no deformation in the foundation:(2) linear soil-pile system;and (3) nonlinear soil-pile system. The effects of pile foundation displacements on the behavior of tall building are investigated,and compared with the behavior of buildings supported on shallow foundation.With a model of non-reflective boundary between the near field and far field, Novak's method of soil-pile interaction is improved.The computation method for vibration of pile foundations and DYNAN computer program are introduced comprehensively.A series of dynamic experiments have been done on full-scale piles, including single pile and group,linear vibration and nonlinear vibration,to verify the validity of boundary zone model.

Influence of soil——structure interaction on seismic collapse resistance of super-tall buildings

Numerous field tests indicate that the soilestructure interaction （SSI） has a significant impact on thedynamic characteristics of super-tall buildings, which may lead to unexpected structural seismic responsesand/or failure. Taking the Shanghai Tower with a total height of 632 m as the research object, thesubstructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower. Therefined finite element （FE） model of the superstructure of Shanghai Tower and the simplified analyticalmodel of the foundation and adjacent soil are established. Subsequently, the collapse process of ShanghaiTower taking into account the SSI is predicted, as well as its final collapse mechanism. The influences ofthe SSI on the collapse resistance capacity and failure sequences are discussed. The results indicate that,when considering the SSI, the fundamental period of Shanghai Tower has been extended significantly,and the collapse margin ratio has been improved, with a corresponding decrease of the seismic demand.In addition, the SSI has some impact on the failure sequences of Shanghai Tower subjected to extremeearthquakes, but a negligible impact on the final failure modes. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Extended consecutive modal pushover procedure for estimating seismic responses of one-way asymmetric plan tall buildings considering soil-structure interaction

Performance based design becomes an effective method for estimating seismic demands of buildings. In asymmetric plan tall building the effects of higher modes and torsion are crucial. The consecutive modal pushover （CMP） procedure is one of the procedures that consider these effects. Also in previous studies the influence of soil-structure interaction （SSI） in pushover analysis is ignored. In this paper the CMP procedure is modified for one-way asymmetric plan mid and high-rise buildings considering $SI. The extended CMP （ECMP） procedure is proposed in order to overcome some limitations of the CMP procedure. In this regard, 10, 15 and 20 story buildings with asymmetric plan are studied considering SSI assuming three different soil conditions. Using nonlinear response history analysis under a set of bidirectional ground motion; the exact responses of these buildings are calculated. Then the ECMP procedure is evaluated by comparing the results of this procedure with nonlinear time history results as an exact solution as well as the modal pushover analysis procedure and FEMA 356 load patterns. The results demonstrate the accuracy of the ECMP procedure.

Structural Design of a Tall Building with Underpinning Structure in Guangzhou

This paper introduces the structural design optimization of a tall building with reinforced concrete frame-core shear walls in Guangzhou downtown.To decrease the construction cost,wide flat beam with 400 mm ×650 mm rectangular cross-section are adopted for main beam.Special measures are used to decrease noncoincident centers of mass and stiffness.Because subway tunnels cross the building underground,inclined columns,the second and third floor underground together function as the underpinning structures.Different from traditional transform beam,the proposed underpinning structures show good performance without using large dimensional bending members.Special attentions should be paid to the beams connecting with the inclined column in the underpinning structures,and these beams show large tensile or compressive forces.Settlement observations after completion construction indicate that the building as well as the proposed design measures work well.

Recent progress of seismic research on tall buildings in China Mainland

As a result of rapid economic growth and urbanization in the past two decades,many tall buildings have been constructed in China Mainland,offering researchers and practitioners an excellent opportunity for research and practice in the field of structural engineering. This paper reviews progress by researchers throughout China Mainland on the seismic research of tall buildings,focusing on three major topics that impact the seismic performance of tall buildings. These are:(1) new types of steel-concrete composite structural members such as steel-concrete composite shear walls and columns,(2) earthquake resilient shear wall structures such as shear walls with replaceable structural components,self-centering shear walls and rocking walls,and(3) performance-based seismic design,including seismic performance index,performance level and design method. The paper concludes by presenting future research needs and directions in this field.

Investigation Responses of the Diagrid Structural System of High-rise Buildings Equipped with Tuned Mass Damper Using New Dynamic Method

Due to the shortage of land in cities and population growth,the significance of high rise buildings has risen.Controlling lateral displacement of structures under different loading such as an earthquake is an important issue for designers.One of the best systems is the diagrid method which is built with diagonal elements with no columns for manufacturing tall buildings.In this study,the effect of the distribution of the tuned mass damper(TMD)on the structural responses of diagrid tall buildings was investigated using a new dynamic method.So,a diagrid structural systems with variable height with TMDs was solved as an example of structure.The reason for the selection of the diagrid system was the formation of a stiffness matrix for the diagonal and angular elements.Therefore,the effect of TMDs distribution on the story drift,base shear and structural behaviour were studied.The obtained outcomes showed that the TMDs distribution does not significantly affect on improving the behaviour of the diagrid structural system during an earthquake.Furthermore,the new dynamic scheme represented in this study has good performance for analyzing different systems.Abbreviation:TMD-tuned mass damper;SATMD-semiactive-tuned mass dampers;MDOF-multiple degrees of freedom;m_(i)-mass of ith story of the building;c_(i)-damping coefficient of the ith story of the building;k_(i)-stiffness of ith story of the building;x_(i)-displacement of the ith story of the building;md-mass of damper;c_(d)-damping coefficient of the damper;k_(d)-stiffness of damper;x_(d)-displacement of TMD;M_(i)-generalized mass of the ith normal mode;C_(i)-generalized damping of the ith normal mode;K_(i)-generalized stiffness of the ith normal mode;K_(i)(t)-generalized load of the ith normal mode;Y_(i)(t)-generalized displacement of the ith normal mode;[M]-matrices of mass;[C]-matrices of damping;{P(t)}-consequence external forces;N_(i)(τ)-interpolation functions;[Ai]-mechanical properties of the structure.

A More Precise Computation of Along Wind Dynamic Response Analysis for Tall Buildings Built in Urban Areas

Modern tall buildings are generally built in urban areas, where value of the terrain roughness length is much greater than that of the general terrain areas, therefore wind-induced vibrations become more pronounced. The present formulas of numerical analysis of wind-induced response become less accurate. A more accurate expression of along-wind load spectrum matrix is proposed. On the basis of the expression, structural analysis formula of along-wind displacement and acceleration response are developed and programmed. The rationality of these formulas are illustrated in examples.

Midas Building在高层建筑结构中的应用

介绍了一款适用于高层和多层钢筋混凝土框架、框架—剪力墙、剪力墙及筒体结构,以及高层钢结构及钢—混凝土混合结构的三维结构分析与设计软件Midas Building.利用该软件分析了某综合办公楼框架—剪力墙结构体系的基本振型、风荷载作用下结构的变形云图、反力图等结构响应,并同常用的PKPM软件进行比较,结果表明:Midas Building软件能较直观地反映结构的受力与变形情况,而且能得到较高的精度,完全可以满足工程需求.

Wind-resistant studies on tall buildings and structures

This paper introduces some aspects of wind-resistant studies of our research team on tall buildings and structures. Wind tunnel tests were carried out on 27 typical tall building models by using wind pressure scanning and HFFB techniques. The characteristics of wind pressures and forces acting on these buildings were analyzed. Some results have been adopted in a Shanghai code for structural design of steel tall buildings. Interference effects on wind forces and wind pressures among two and three tall buildings were experimentally investigated with about 10000 testing conditions. Regression analyses of the interference factors under different parameter conditions were made and the main regression formulas are presented. Theoretical study on equivalent static wind loads of tall buildings and structures are then introduced. Especially,a new concept of "mode coupling factor" and a modified SRSS method for wind response and equivalent static wind load of complicated tall buildings and structures with consideration of multi mode contributions and their coupling effects are presented. Finally,practical applications of wind-resistant studies on tall building and structures,taking the Guangzhou New TV Tower as an example,are presented.

Across-wind loads and effects of super-tall buildings and structures

Across-wind loads and effects have become increasingly important factors in the structural design of super-tall buildings and structures with increasing height. Across-wind loads and effects of tall buildings and structures are believed to be excited by inflow turbulence, wake, and inflow-structure interaction, which are very complicated. Although researchers have been focusing on the problem for over 30 years, the database of across-wind loads and effects and the computation methods of equivalent static wind loads have not yet been developed, most countries having no related rules in the load codes. Research results on the across-wind effects of tall buildings and structures mainly involve the determination of across-wind aerodynamic forces and across-wind aerodynamic damping, development of their databases, theoretical methods of equivalent static wind loads, and so on. In this paper we first review the current research on across-wind loads and effects of super-tall buildings and structures both at home and abroad. Then we present the results of our study. Finally, we illustrate a case study in which our research results are applied to a typical super-tall structure.

超高层内倾外斜式大直径分叉圆管柱施工技术

在西安曲江文创中心项目中,塔楼外框主体结构3根角部钢柱为内倾外斜式分叉大直径圆管柱,分叉处柱体直径大,分叉相交贯口长、轴向受力大,对钢构件加工和现场安装精度要求高,不宜应用常规贯口切割技术。为解决相交大贯口加工难度大、制作精度与现场安装要求高、分叉节点整体运输难度大、焊接要求高的难题,从节点优化、贯口放样切割、工厂预拼装、现场安装等过程进行控制,顺利实现项目分叉圆管柱安装,且精度控制满足设计要求。

落地与悬挑组合式支模体系在高位逐层外悬挑结构施工中的应用

高位逐层外悬挑混凝土结构造型奇特、受力复杂,在建造过程中普遍存在技术难度大、安全风险高、措施费用高、施工工期长等突出问题。以光谷人民医院项目塔楼单侧高位逐层外悬挑混凝土结构支模体系实施为例,从安全性、经济性、可实施性等多方面进行方案综合比选,采用落地与悬挑组合式支模体系。分析结构荷载传递路径和多种施工工况,对支模体系进行精细设计和验算。严格按设计方案指导现场支模体系搭设和拆除。实践表明,提出的落地与悬挑组合式支模体系可安全、便捷、高效地完成高位逐层外悬挑混凝土结构施工。

四塔高位连体钢桁架结构施工关键技术

以江门市档案中心高层建筑工程为例,该工程为四塔高位连体结构,在高层塔楼结构顶部采用带悬挑的大跨度钢桁架作为连接体,将4栋塔楼连为一体,其结构形式较复杂、施工难度大。为此,根据结构特点、工期、场地及垂直运输等因素,提出高位连体桁架采用“胎架拼装、低位滑移后整体提升”的一体化施工工艺,局部悬挑桁架采用“高空散装+临时支撑”的常规施工方法。在此基础上,制定了钢结构施工总体流程和具体实施要点。

上盖预留超高层办公建筑设计研究与应用

探讨了“上盖预留”开发模式,即预留建筑物下方空间,以建造上层建筑或设施。此模式满足轨道交通建设、管理和运营需求,降低未来扩建和改造成本及影响,提高城市土地利用效率和发展潜力。并以广州市棠溪项目为案例,深入探讨了如何规避现有不利影响,将上盖预留与超高层写字楼设计结合,为上盖超高层设计提供参考。

基于FAHP的高层既有结构可靠性评定研究

为准确评估烂尾楼的整体可靠性,提出采用三角模糊层次分析法(FAHP)对高层烂尾楼工程进行安全评估,可全面考虑地基基础、上部承重结构、围护系统等因素对结构可靠性的影响,且三角模糊数的引入使专家决策具有更大的余度和容错性,从而有效减少判断的主观性。首先建立高层烂尾住宅楼的递阶层次结构模型,构造各层次元素的模糊判断矩阵,从而计算得到各构件的可靠性等级,根据模糊判断矩阵加权计算得到各层次元素的可靠性等级,最终得出结构的可靠性等级。采用所提出的方法,分析深圳某改造项目的可靠性等级,并建议随楼层数的增加,楼层权重系数的取值线性减小,以突出底层构件对整体结构的控制作用。

某既有结构续建施工全过程仿真分析

在烂尾楼停工阶段,混凝土收缩徐变持续发展,影响续建阶段结构的竖向变形分布。为研究烂尾楼建设-停工-续建全过程的施工力学特性,在某续建烂尾楼项目中,对考虑混凝土收缩徐变效应的施工进行仿真分析,并对比实测结果。研究结果表明,续建烂尾楼的竖向变形沿楼层的变化曲线与连续建设结构不同,在已建部分的最高层达到最大值,续建部分呈两端小、中间大的规律。已建部分长时间停工对续建部分收缩徐变变形有明显的减小作用。停工时间越长,已建部分在续建阶段的徐变变形越小。随着结构组内划分的层数越多,计算结果误差越大,且结构组内楼层越高误差越大。考虑收缩徐变和施工全过程的烂尾楼续建施工仿真计算结果与实测结果吻合较好,收缩徐变和施工过程对计算结果的影响大,应予以重视。

软土地基上桩-土-高层结构体系动力特性的振动台试验

为了研究软土地基上桩-土相互作用对高层结构动力特性的影响机理,设计了1:6比例的高层结构-桩-土动力相互作用体系,进行了软土地基上框架结构的模型振动台试验。试验采用层状剪切盒模拟土体的边界,锯末和砂土的混合物作为地基土、以12层钢筋混凝土框架结构模拟上部结构,基础采用3×3群桩基础。通过对比考虑土-结构相互作用(SSI)框架模型和刚性地基框架模型的结构动力特性,总结出本试验中SSI效应对高层框架结构的动力特性影响规律:土体对地震动存在显著的过滤作用,放大土体基频附近的振动,且放大幅度随地震动的加强而减小;小震时土体对加速度峰值起放大作用,而在大震时起减小峰值的作用;考虑SSI效应后,结构的频率降低,阻尼比提高,结构的损伤出现得更晚,发展也更慢。在土体频率处,SSI体系的振型受土体影响显著;在远离土体频率处,SSI体系振型与刚性地基一致。