Approximate analysis of tall buildings using sandwich beam models with variable cross‐section

In this paper an approximate method is carried out for determining the natural periods of multistory buildings subjected to earthquake. The building resists lateral forces through a combination of lateral resisting systems. These systems could be replaced by a cantilever Timoshenko or a sandwich beam with varying cross‐section that characterizes three kinds of stiffnesses: the global bending stiffness, the local bending stiffness and the shear stiffness. Using appropriate transformations, the differential equations for flexural and shear free vibration of a cantilever beam with variably distributed mass and stiffness are reduced to Bessel's equations and ordinary differential equations. The frequency equations can be solved by selecting suitable expressions such as exponential and power functions for stiffness and mass distribution along the height of the building. The calculated frequencies are combined appropriately by using approximate methods. Based on the fact that shear and bending deformations are all considered, the free vibration frequency of the structure could be calculated. The capability and accuracy of the proposed method are demonstrated by a numerical example in which finite element results are compared with the proposed methodology and other approximate methods. Copyright © 2007 John Wiley & Sons, Ltd.     

A new approach for free vibration analysis of nonuniform tall building structures with axial force effects

Dynamic analysis of beam‐like structures is significantly important in modeling actual cases such as tall buildings and several other related applications as well. This article studies free vibration analysis of tall buildings with nonuniform cross‐section structures. A novel and simple approach is presented to solve natural frequencies of free vibration of cantilevered tall structures with variable flexural rigidity and mass densities. These systems could be replaced by a cantilever Timoshenko beam with varying cross‐sections. The governing partial differential equation for vibration of a nonuniform Timoshenko beam under variable axial loads is transformed with varying coefficients to its weak form of integral equations. Natural frequencies can be determined by requiring the resulting integral equation, which has a nontrivial solution. The presented method in this study has fast convergence. Including high accuracy for the obtained numerical results as well. Numerical examples including framed tube as well as tube‐in‐tube structures are carried out in the study and compared with available results in the literature, and also with the results obtained from finite element analysis in order to show the accuracy of the proposed method in the study. Obtained results indicate that the presented method in this study is powerful enough for the free vibration analysis of tall buildings.     

多阶变截面杆弯曲自由振动的计算

本文通过引入一组用矩阵形式表示的基本函数,分解了单阶杆的精确解,导出了相应于多阶变截面杆的频率方程和振型函数的通式,并通过计算机处理得到了精确数字解。最后还给出了数值解与理论解的比较。     

Second-order and second-approximation theory in the statics and dynamics of thin-walled straight bars

This paper concerns the analysis of lightweight structures and especially the single bars from which they are composed. It is a further development of the general thoery derived previously by the author and allows one to analyse the single thin-walled bar exactly by the second-approximation approach in the areas of statics, dynamics, stability, dynamical stability, as well as natural or forced vibrations. The theory is valid for bars with arbitrary cross-section and any boundary conditions. It can be applied to thin-walled bars of large dimensions, such as is used in bridges, viaducts, etc., and even to high buildings stiffened by shafts treated either as single units or as groups of thin-walled bars.     

Coupled flexural and torsional vibrations of ship-like girders

The paper is related to investigation of coupled horizontal flexural and torsional vibrations of container vessels. Differential equations of coupled vibrations of a prismatic beam with open cross-section are derived. The equations are solved analytically by direct integration and by variational method. In the former case, the frequency equation is reduced to a polynomial of the fourth order. In the latter case, beam deflection and twist angle are assumed in the form of series of natural modes of uncoupled vibrations of free beam with suspended warping. The variational method manifests very fast convergence and high accuracy. Application of the developed methods is illustrated in the case of a prismatic pontoon with cross-section of a container vessel. The same numerical example is used for checking 1D FEM mathematical model and code developed for analyses of real structures of container vessels with variable cross-sections. In addition, correlation analysis of 1D and 3D FEM results is done to validate the accuracy of the former.     

液体黏滞阻尼器在超高层结构上的抗震抗风效果和经济分析

为了保护地震及大风环境下的高层和超高层建筑,加设液体黏滞阻尼器是目前被工程界广泛认同、发展最为迅速、最为有效的结构振动保护方案。综合介绍国内外安装液体黏滞阻尼器的7座高层建筑,对阻尼器的安置方式、减振结构的抗震(振)效果、相关规范以及经济性进行评述。其中墨西哥Mayor大楼、美国波士顿大楼是世界工程界成功应用耗能减震装置的经典案例,银泰中心、盘古大观是我国首批使用阻尼器进行减振控制的超高层建筑,对这些工程采用的计算分析方法,结构抗震设计进行汇总,并提供相关建议和意见,供设计者参考。近期美国几位学者在一座42层钢筋混凝土结构的概念设计中,提出采用阻尼器替代剪力墙体系进行抗震设计的理念,对这一高层建筑工程的抗震新方向进行介绍,引为参考。     

框架-剪力墙结构在水平荷载作用下的内力和位移计算

高层建筑结构中,较规则的框架-剪力墙体系的计算,是根据墙、梁、柱变形协调建立的一个四阶微分方程式,并考虑四个边界条件后所得出的内力和位移的计算式,皆为双曲线函数。本文将其四阶微分方程式转化为二阶微分方程式,求解时采用了新的齐次解的表达式,所得的内力与位移的计算式为一般常用的指数函数,从而计算较为方便。经过对比,结果完全一致。本文还可推广应用到部分变层高、变刚度的建筑。     

矩形隧道中变截面杆件的内力分析

本文推导了变截面杆的单元刚度矩阵和荷载结点化的计算公式，可用于编制变截面框架结构的电算程序。并通过隧道衬砌结构算例，比较了按实际变截面计算和简化等截面直杆计算两种方法的差异，说明隧道结构按变截面实际情况计算的必要性。     

复杂连体高层结构整体稳定研究

针对JGJ 3—2010《高层建筑混凝土结构技术规程》中关于高层结构整体稳定判断及刚重比限值的适用条件,明确了相关规定应用到复杂连体高层结构时存在的缺陷。在此基础上,基于欧拉临界失稳的基本原理,推导了适用于塔式刚性连体高层结构的刚重比限值,该限值主要受连接体与塔楼相对刚度的影响,并通过4个工程案例计算,表明采用规范方法将偏于保守,会放大二阶效应的不利影响。对于连接关系更加复杂的异形连体结构,通过刚重比判断结构的稳定性不再适用,应直接进行考虑二阶效应的非线性稳定分析,并建议借鉴空间结构稳定判断的方法,通过特征值屈曲分析、考虑几何非线性的直接静力稳定分析、考虑材料非线性的极限稳定破坏分析等,对结构的整体稳定进行评估。以某复杂三塔连体高层结构为例,采用所建议的方法进行稳定分析和评价。结果表明,该结构在弹性假定下稳定荷载因子大于10,考虑材料非线性时稳定承载力的安全系数超过2.0,满足安全要求。     

Vibration analysis of tall buildings with narrow rectangular plane configuration

In this paper, tall buildings of narrow rectangular plane configuration are treated as one-step or multi-step cantilever flexural-shear plates for the analysis of their free vibrations. The governing differential equations for the vibration of flexural-shear plates considering the effects of both flexural and shear deformation are established. The general solutions for one-step flexural-shear plates are derived and used to obtain the eigenvalue equation for multi-step cantilever flexural-shear plates. A new exact approach is presented which combines the transfer matrix method and a closed-form solution for a uniform flexural-shear plate. A numerical example demonstrates that the calculated natural frequencies and mode shapes of a tall building are in good agreement with the experimentally measured data. It is also shown that the effect of shear deformation on the fundamental natural frequency can be ignored, but its effect on the higher natural frequencies should be considered. Copyright © 1998 John Wiley & Sons, Ltd.     

调频减振系统和黏滞阻尼系统在超高层结构中风振控制性能的对比研究

超高层建筑中常用的风振控制措施主要包括调频减振系统和黏滞阻尼系统。系统地阐述了两种方案的基本原理、工程适用性以及参数取值,并结合实际项目较为全面地对比了其抗风性能。虽然调频减振系统在建筑功能的适应度上和施工可实施性上都存在一定的不足,但作为结构风振控制措施仍不失为一种可取方案。黏滞阻尼系统不但可以提升结构在风荷载下的舒适度,还能提升结构在风荷载和地震作用下的刚度和强度,适应了结构应对不同抗风设防水准的性能需求。结合高效的连接形式,黏滞阻尼系统是一种适用于高层、超高层建筑抗风的高性能且经济的减振控制措施。     

基于高层建筑短肢剪力墙结构肢高比设计

短肢剪力墙结构是一种新型抗侧力结构体系,被广泛用于高层及超高层民用建筑中。针对《高层建筑混凝土结构技术规程》(JGJ3—2002)短肢剪力墙定义叙述的不足之处,通过有限元法对154片肢墙系数α及整体性系数ζ各不相同的8层、10层、12层对称双肢剪力墙按1/7缩尺比例进行了弹性分析,按只在少数楼层出现反弯点的要求,对三种楼层分别施加水平均布荷载和水平倒三角形分布荷载进行低周反复试验。规范了高层建筑短肢剪力墙结构的定义,明确了剪力墙结构肢高比设计的选取范围。     

高层民用建筑火灾自动报警系统的设计

由于目前的城市增长过于迅速,而适合人们使用的土地资源非常有限,从而使城市建筑当中,高层建筑趋于主流.但是,高层建筑能够容纳较多的人流,对于纵向交通的容量十分的有限.因此,当火灾发生的时候,无论是群众的避难,还是消防都会面临很大的困难,从而导致人身与财产遭受巨大的损失.因此,在目前的高层民用建筑设计当中,提出了建筑火灾自动报警系统的设计.     

A criterion for optimal damping design

The design of elements for maximum damping of vibrations in a linear elastic system is described. Single and multiple damping elements of purely viscous, visco-elastic, rigid-plastic, or Coulomb type are treated.A general theorem is developed which equates the optimal impedance (dynamic stiffness) of the damping element to the impedance (elastic plus inertial stiffness) of the linear system at the point at which the element is applied. This theorem provides a criterion which may be used directly to design the elements: Formulae are derived from there to specify the elements and to evaluate their effectiveness and thus indirectly indicate where to locate them.Applications include damping of sway vibrations of tall buildings, and of vibrations in floor systems, vehicles and machines. Noise producing vibrations may be included. In each case, the optimal impedance characteristics of the damping element may be expressed in terms of the impedance characteristics of linear system, e.g. the elastic stiffness of the structure or the mass of the machine, and the frequency of the loading force.     

A combined tuned damper and an optimal design method for wind‐induced vibration control for super tall buildings

The wind‐induced vibrations of super tall buildings become excessive due to strong wind loads, super building height and high flexibility. Tuned mass dampers (TMDs) and tuned liquid column dampers (TLCDs) have been widely used to control vibrations for actual super tall buildings for decades. To fully use both the economic advantage of the TLCD system and the high efficiency of the TMD system, an innovative supplemental damping system including both TLCD and TMD and called combined tuned damper (CTD), which can substantially decrease the cost of the damper, was proposed to control the wind‐induced vibrations of tall buildings. The governing equations are generated for the motion of both the primary structure and the CTD and solved to anticipate the dynamic response of the CTD‐structure system. Moreover, an optimal design method of human comfort performance is proposed, in which the life cycle cost of the damper‐structure system is considered as the quantitative index of the performance. The life cycle cost includes the initial cost, the maintenance cost and the failure cost. The failure cost can be calculated using the vibration‐sensation rate model, which is based on the Japanese code AIJES‐V001‐2004. Copyright © 2016 John Wiley & Sons, Ltd.     

竖井自然排烟在高层民用居住建筑中的应用

概要地介绍了自然排烟竖井在高层民用居住建筑中应用的可行性及竖井断面的确定原则，并通过所做的某一实例，对该做法的优点进行了总结，以推广该排烟方案，从而达到有效、方便、经济的目的。     

带加强层的高层建筑结构性能水准的量化

基于性能的抗震设计方法在一些超限高层和复杂高层建筑中已经开始应用,但是目前对于各种类型结构体系缺乏量化的性能水准定义。通过对已有资料的分析,建立了带加强层的高层建筑结构的层间侧移计算方法,结合带加强层框架-核心筒结构的受力特点,采用剪力墙构件的性能水准来量化带加强层的高层建筑结构的性能水准,为该类高层建筑基于性能的抗震设计提供结构性能水准的参考依据。     

Simplified formulas for evaluation of wind-induced interference effects among three tall buildings

The base-bending moment (BBM) response and the mean BBM of grouped high-rise buildings are studied by a series of wind tunnel tests on typical tall building models using the high-frequency force balance technique. Interference excitations of two upwind buildings with various heights in different upwind terrains are considered. An effective method is proposed to represent the distribution of the envelope interference factor (EIF) among three tall buildings. The results show that two upstream buildings cause more adverse dynamic effects on the downstream building than a single upstream building does. Significant correlations are found in the distributions of the interference factors of different configurations and upwind terrains. Relevant regression equations are proposed to simplify the complexity of the multi-parameter wind-induced mean and dynamic interference effects among three tall buildings. Finally, an example of how to use the data provided in this paper and the proposed methodology is presented.     

Practical calculation of the torsional stiffness radius of multistorey tall buildings

The present paper refers to the definition of the torsional stiffness radii of multistorey tall buildings using both the continuous and the discrete model of the structure. The magnitude of the torsional stiffness radius of a building is the most important structural characteristic in order to explain the torsional behaviour of a building during an earthquake as it directly affects the building's torsional flexibility. The importance of the torsional flexibility of buildings is recognized by contemporary Seismic Codes that propose a grid of torsional provisions in order to avoid soft‐storey operation due to floor torsional vibrations around a vertical axis. However, contrary to single‐storey buildings, the torsional stiffness radius of multistorey buildings is not defined directly because both the translational and torsional stiffness of these buildings are expressed in matrix form. In the present paper, this weakness has been overcome using the continuous model of the structure, from which the torsional stiffness radius of a general monosymmetric multistorey tall system arises via a closed mathematical equation. The discrete model of the structure has numerically verified this closed mathematical equation. Copyright © 2007 John Wiley & Sons, Ltd.     

Coupled vibrations of rectangular buildings subjected to normally-incident random wind loads

A method for analyzing the three-directional coupled dynamic response of wind-excited buildings is presented. The method is based on a random vibration concept and is parallel to those currently used for analyzing alongwind response. Only the buildings with rectangular cross-section and normally-incident wind are considered. The alongwind pressures and their correlations are represented by the well-known expressions that are available in the literature. The acrosswind forces are assumed to be mainly due to vortex shedding. The torque acting on the building is taken as the sum of the torque due to random alongwind forces plus the torque due to asymmetric acrosswind forces.The study shows the following: (1) amplitude of acrosswind vibrations can be several times greater than that of alongwind vibrations; (2) torsional vibrations are significant if the building has large frontal width, and/or it is asymmetric, and/or its torsional natural frequency is low; (3) even a perfectly symmetric structure with normally incident wind can experience significant torsional vibrations due to the randomness of wind pressures.