高层建筑主动变刚度多模态抗震分析

提出了一种基于动能为性能控制指标的AVS系统的控制算法——多模态法,通过数值仿真分析研究了该方法应用于高层建筑抗震设计的控制效果,结果表明:多模态法具有计算精度高和计算速度快的优点,解决了主动变刚度控制中的在线控制问题。     

Effect of strength deterioration on inelastic seismic torsional behaviour of asymmetric RC buildings

The paper presents a limited study on the inelastic torsional behaviour of reinforced concrete (RC) asymmetric buildings using idealized one-storey models. The strength deterioration characteristics of reinforced concrete members is included in the hysteresis rules of the load-resisting elements in this study. It is observed that these characteristics may largely magnify the displacement and ductility demand in structural elements due to successive localized unsymmetric yielding and progressive strength deterioration; resulting in continuous shifting of the centre of strength and thereby increasing strength eccentricity. This magnification effect is generally found to be increasing with the rate of strength deterioration. This effect is not recognized in numerous studies on inelastic behaviour of asymmetric buildings as these studies considered a bilinear hysteresis behaviour devoid of strength deterioration characteristics for lateral load-resisting elements; and as a consequence comparatively lower displacement and ductility demand in load-resisting elements were observed. While using the results of existing literature on inelastic seismic torsional behaviour of asymmetric buildings to predict the behaviour of RC asymmetric buildings, this limitation should seriously be considered.     

Optimum strength distribution for seismic design of tall buildings

This paper examines the effects of strength distribution pattern on seismic response of tall buildings. It is shown that in general for an MDOF structure there exists a specific pattern for height‐wise distribution of strength and stiffness that results in a better seismic performance in comparison with all other feasible patterns. This paper presents a new optimization technique for optimum seismic design of structures. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. This process is continued until a state of uniform deformation is achieved. It is shown that the seismic performance of such a structure is optimal, and behaves generally better than those designed by conventional methods. The optimization algorithm is then conducted on shear building models with various dynamic characteristics subjected to a group of severe earthquakes. Based on the results, a new load pattern is proposed for seismic design of tall buildings that is a function of fundamental period of the structure and the target ductility demand. The optimization method presented in this paper could be useful in the conceptual design phase and in improving basic understanding of seismic behavior of tall buildings. Copyright © 2007 John Wiley & Sons, Ltd.     

Selection of earthquake records for seismic design of tall buildings

One of the most difficult questions that the designer of tall earthquake resistant buildings must address is the determination of the critical earthquake. This is the earthquake ground motion that will drive the structure being designed to its critical response. This paper seeks to help the seismic design engineer address this difficult problem by identification of the severity and damage potential of critical components obtained from a database of more than 5000 records of strong earthquake ground motion. These records virtually represent all the available North American and Hawaiian records written by ground-level instruments for the period of 1933–1992. Elastic and inelastic response and energy spectra are studied. Spectral data are sorted in terms of the mean value of the response parameter in bracketed bands of the fundamental period.     

Analysis of torsional moments on tall buildings

Spectra of fluctuating wind forces on tall buildings can be determined experimentally from wind-tunnel-model tests either by measuring base torques using a force balance or by integrating the pressures measured on the sides of the model. The force balance technique is less costly, but may substantially overestimate the actual generalized forces. This study examines the relation between the spectra of base torques and generalized torques experienced by tall buildings.     

高层建筑抗震设计AVS构件的优化布置

研究了主动变刚度系统中AVS构件(即钢性斜支撑)的优化布置问题,结合部分状态反馈的次最优控制理论中选择所采用的部分状态反馈的思想,提出了确定AVS系统中AVS构件的优化布置方法,并通过数值模拟对其有效性进行了验证。     

A new method for the design of tall buildings: The mit design method

A new method for the design of tall and super-tall buildings is presented in this paper. The method is based on transforming the stiffness properties of the building to equivalent beam properties. The equivalent beam is allowed to deform both in bending and shear to capture the true behavior of the building. The method is a stiffness based approach that later requires checks for strength. This is quite appropriate since the design of tall and super-tall buildings is governed by stiffness and not by strength. Knowing the load and assuming a desired shape of the beam, the required shear and bending rigidities of the beam can be calculated. The method is robust and easy to apply, and is particularly suited for space truss systems. The simplicity and efficiency of the method are illustrated with an example.     

A new proxy for ground motion selection in seismic collapse assessment of tall buildings

Tall buildings are long‐period structures that are sensitive to the long‐period content of ground motions. Selection of appropriate ground motions is an important step in seismic collapse assessment of tall buildings using nonlinear dynamic analyses. Epsilon (ε_Sa) and eta (η) are two spectral shape indicators, which have been recently proposed for ground motion selection in the technical literature. In this study, a new parameter gamma (γ) is proposed, which has considerable correlation with the collapse capacity of long‐period structures having a fundamental period greater than 1 s. This parameter is a linear combination of ε_Sa and the displacement spectrum intensity epsilon (ε_DSI). The parameter γ is obtained and optimized by applying the particle swarm optimization algorithm. Since γ has significant correlation with the collapse capacity of long‐period structures, it can be used as an efficient proxy for ground motion selection in seismic collapse assessment of tall buildings. The results of this study show that ground motion selection considering the new proxy γ causes reduction in the dispersion of structural response and also decrease in the mean annual frequency of collapse, when compared with ground motion selection based on ε_Sa and η. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of vertical structural irregularity on seismic design of tall buildings

Many tall buildings are practically irregular as an entirely regular high‐rise building rarely exists. This study is thus devoted to assessing the approach and coefficients used in the seismic design of real‐life tall buildings with different vertical irregularity features. Five 50‐story buildings are selected and designed using finite element models and international building codes to represent the most common vertical irregularities of reinforced concrete tall buildings in regions of medium seismicity. Detailed fiber‐based simulation models are developed to assess the seismic response of the five benchmark buildings under the effect of 40 earthquake records representing far‐field and near‐source seismic scenarios. The results obtained from a large number of inelastic pushover and incremental dynamic analyses provide insights into the local and global seismic response of the reference structures and confirm the inferior local response of tall buildings with severe vertical irregularities. Due to the significant impacts of the severe irregularity types on the seismic response of tall buildings, the conservative code approach and coefficients are recommended for design. It is also concluded that although the design coefficients of buildings with moderate irregularities are adequately conservative, they can be revised to arrive at more consistent safety margins and cost‐effective designs.     

大底盘不对称双塔楼高层建筑的抗震设计

以某高层建筑抗震设计为例,介绍了大底盘不对称双塔楼高层建筑的抗震设计,具体就结构设计、计算以及结构构造措施作了探讨,旨在提高建筑的抗震能力,解决其超限问题。     

Improved multimode pushover procedure for asymmetric in plan buildings under biaxial seismic excitation—application to tall buildings

An improved version of a recently developed multimode pushover procedure for asymmetric in plan buildings under biaxial seismic excitation is presented and evaluated. The proposed methodology is quite similar to the well‐known modal pushover analysis. However, the establishment of the equivalent single‐degree‐of‐freedom systems is based on a new concept, which takes into account multidirectional seismic effects. The proposed methodology does not require independent analysis in the two orthogonal directions, and therefore, the application of simplified directional combination rules is avoided. The improvement presented here consists in definition of correction factors to be applied to the response values at the stiff side of buildings. An extensive evaluation study comprising applications to tall buildings is presented. The response parameters obtained from the proposed methodology in most cases envelope the values resulting from nonlinear dynamic analysis (NDA). Furthermore, the mean errors with regard to the NDA results are smaller than those obtained from a multimode pushover procedure comprising independent analysis along two horizontal axes and directional combination of the results. In general, the proposed methodology provides a reasonable estimation of the seismic performance of asymmetric buildings.     

A new modelling technique using a subsystem for structural schematic design of tall buildings

In the schematic design of a tall building structure, a structural designer builds structural analysis models for many schemes. However, conventional modelling techniques force the designer to view the scheme as an assembly of many members related in a complicated manner. Therefore, the modelling scheme is laborious, prone to error and time‐consuming. In this study, we present a new modelling technique that uses a subsystem—that is, the assembly of the members participated in a specific type of load transfer—as the primary modelling unit. We expect this modelling technique to allow simple modelling of a scheme. Copyright © 2004 John Wiley & Sons, Ltd.     

Propagation of seismic waves in tall buildings

A discrete-time wave propagation formulation of the seismic response of tall buildings is introduced. The building is modeled as a layered medium, similar to a layered soil medium, and is subjected to vertically propagating seismic shear waves. Soil layers and the bedrock under the foundation are incorporated in the formulation as additional layers. Seismic response is expressed in terms of the wave travel times between the layers, and the wave reflection and transmission coefficients at the layer interfaces. The equations account for the frequency-dependent filtering effects of the foundation and floor masses. The calculation of seismic response is reduced to a pair of simple finite-difference equations for each layer, which can be solved recursively starting from the bedrock. Compared to the commonly used vibration formulation, the wave propagation formulation provides several advantages, including simplified calculations, better representation of damping, ability to account for the effects of the soil layers under the foundation, and better tools for identification and damage detection from seismic records. Examples presented show the versatility of the method. Copyright © 1998 John Wiley & Sons, Ltd.     

Implications of the 1994 northridge earthquake ground motions for the seismic design of tall buildings

Design characteristics of selected 1994 Northridge strong motion records are evaluated. Instrumental, spectral, and energy content attributes of the records are examined. Seismic design implications of these data for tall buildings are discussed. The weaknesses of the current seismic design philosophy in dealing with near-field strong ground motions, representing significant acceleration pulses, are demonstrated and recommendations for improving both the demand side and the capacity side of current seismic design formulations are provided.     

高层建筑色彩设计浅析

高层建筑色彩有自身的规律性,对城市色彩有举足轻重的作用,但设计方面存在不少问题,学界亦鲜有研究成果。本文从对高层建筑色彩的基本认识出发,指出高层建筑色彩设计的要点和难点,同时初步探讨了高层建筑基调色、装饰色和点缀色的设计方法和手法。     

A multi-objective structural optimization method for serviceability design of tall buildings

Structural optimization design aims to identify optimal design variables corresponding to a minimum objective function with constraints on performance requirements. To this end, many optimization frameworks have been proposed to determine optimal structural systems that are subjected to seismic and wind hazards in isolation. However, some modern tall buildings are sensitive to seismic and wind excitation owing to their complex structural systems and geographic regions. Therefore, a proper structural optimization method for such buildings is required to ensure that the expected performance is achieved in a multi-hazard scenario. This study proposes a multi-objective serviceability design optimization methodology for buildings in multi-hazard seismic and wind environments by combining optimality criteria and the nondominated sorting genetic algorithm II (NSGA-II). Seismic and wind effects can be instantaneously updated due to changes in the structural dynamic properties during the optimal design process. A neural-network-based surrogate model with self-updating is proposed to predict the structural natural frequency so that the overall computation time of the optimization process can be reduced. The proposed method was used to optimize a 50-story frame-tube building and was compared against the general genetic algorithm and general NSGA-II to verify the feasibility and effectiveness.     

A consecutive modal pushover procedure for estimating the seismic demands of tall buildings

The nonlinear static procedure (NSP), based on pushover analysis, has become a favourite tool for use in practical applications for building evaluation and design verification. The NSP is, however, restricted to single-mode response. It is therefore valid for low-rise buildings where the behaviour is dominated by the fundamental vibration mode. It is well recognized that the seismic demands derived from the conventional NSP are greatly underestimated in the upper storeys of tall buildings, in which higher-mode contributions to the response are important. This paper presents a new pushover procedure which can take into account higher-mode effects. The procedure, which has been named the consecutive modal pushover (CMP) procedure, utilizes multi-stage and single-stage pushover analyses. The final structural responses are determined by enveloping the results of multi-stage and single-stage pushover analyses. The procedure is applied to four special steel moment-resisting frames with different heights. A comparison between estimates from the CMP procedure and the exact values obtained by nonlinear response history analysis (NL-RHA), as well as predictions from modal pushover analysis (MPA), has been carried out. It is demonstrated that the CMP procedure is able to effectively overcome the limitations of traditional pushover analysis, and to accurately predict the seismic demands of tall buildings.     

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.     

高层建筑地震作用计算的时域显式随机模拟法

目前我国GB 50011—2010《建筑抗震设计规范》中所推荐的振型分解反应谱法和时程分析法尚无法完全反映地震动随机性对建筑结构的影响,采用真正意义的随机振动方法计算复杂高层建筑地震响应的需求越来越迫切。结合新修订的广东省标准DBJ 15-92—2013《高层建筑混凝土结构技术规程》,全面介绍了结构地震作用计算时域显式随机模拟法的计算原理和实现方法,内容包括:1)通过迭代计算直接获得与现行规范反应谱完全等效的地震动加速度功率谱;2)给出基于精细积分和Newmark-β积分格式的结构地震响应显式表达式的构建方法;3)结合地震动随机过程的数值模拟,统计分析得到结构平均峰值响应。以广州西塔等4栋超高层和高层建筑为工程应用实例,显示了时域显式随机模拟法在高层结构抗震分析中的高效性和实用性。计算结果表明,时域显式随机模拟法和传统振型分解反应谱法的计算结果存在一定差异,最大差异可超过25%,反应谱法的内力计算结果普遍偏小。     

高层钢-混凝土混合结构弹塑性地震位移的工程实用计算

本文针对目前高层建筑中常用的外钢框架-内混凝土核心筒混合结构体系的弹塑性地震位移的实用计算开展研究。在合理选取一定数量的地震记录及典型的结构形式的基础上,采用经实验检验的分析模型与计算程序,得到了钢-混凝土混合结构的弹塑性层间相对位移与主要结构参数之间的大致规律,并通过统计分析,得到了混合结构的弹塑性层间相对位移与各参数的定量关系,以此提出了进行罕遇地震下高层钢-混凝土混合结构弹塑性位移验算时的计算数表。