Optimal lateral stiffness design of tall buildings of mixed steel and concrete construction

This paper presents an optimal sizing technique for the lateral stiffness design of tall steel and concrete buildings. The minimum structure cost design problem subject to lateral drift constraints is first mathematically formulated and then solved by a rigorously derived Optimality Criteria (OC) method. The emphasis is particularly placed on the practical applicability of the optimization technique in engineering practice. Once the structural form of the lateral load resisting system of a building is defined, the optimal steel and concrete element sizes are then sought while satisfying all serviceability lateral stiffness and practical sizing requirements. The effectiveness and practicality of the optimization technique is illustrated through an actual application to the preliminary design of an 88‐storey building in Hong Kong. When complete, the building will be 420 m tall and will become the tallest building in Hong Kong. Copyright © 2001 John Wiley & Sons, Ltd.     

Lateral stiffness characteristics of tall reinforced concrete buildings under service loads

This paper presents an analytical method for quantitatively predicting the effects of cracking on the lateral deflection and stiffness characteristics of tall reinforced concrete buildings under service loads. The effects of cracking in tall reinforced concrete buildings can be considered using an element stiffness reduction model. This model determines the probability of cracking occurrence by dividing the area of the moment diagram, S_cr, where the working moment exceeds the cracking moment by the total area of the moment diagram, S. A practical cracking analysis method can be established by integrating the proposed stiffness reduction model with an iterative algorithm and commercial linear finite element analysis package. The proposed method has been validated by good agreement of results between the numerical computation and experimental testing of large‐scale rigid‐frame and wall‐frame structural sub‐assemblages. The effectiveness of the numerical analysis method is also illustrated through a practical 40‐storey reinforced concrete building example. The cracking effects on the lateral deflection and stiffness characteristics of this building were analysed both explicitly and quantitatively. Copyright © 2000 John Wiley & Sons, Ltd.     

Integrated aerodynamic load determination and stiffness design optimization of tall buildings

Modern tall steel buildings are wind sensitive and are prone to dynamic serviceability problems. Although wind tunnel techniques have emerged as valuable tools in providing reliable prediction of the wind‐induced loads and effects on tall buildings, current design practice normally considers the wind tunnel‐derived loads as constant static design loads. Such practice does not take into account the change in wind‐induced structural loads while the dynamic properties of a building are modified during the design synthesis process. This paper presents a computer‐based technique that couples together an aerodynamic wind tunnel load analysis routine and an element stiffness optimization method to minimize the cost of tall steel buildings subject to the lateral drift design criteria, while allowing for instantaneous prediction and updating of wind loads during the design synthesis process. Results of a full‐scale steel building framework with the same geometric shape of the Commonwealth Advisory Aeronautical Research Council (CAARC) standard building indicate that not only is the proposed technique able to produce the cost‐effective element stiffness distribution of the structure satisfying the serviceability wind drift design criteria, but a potential benefit of reducing the design wind loads can also be achieved by the stiffness optimization method. Copyright © 2007 John Wiley & Sons, Ltd.     

A review of the diagrid structural system for tall buildings

Unlike vertical columns of traditional structure, diagrid structural systems for tall buildings have special inclined columns. Due to the inclined columns, a diagrid structural system for tall buildings produces axial force along the column direction under horizontal load, which has the advantage of resisting horizontal wind load and seismic load and gives more freedom to architectural design, so a diagrid structural system for tall buildings becomes an effective new structure style for tall and super‐tall buildings. Theories and tests regarding the diagrid structural system for tall buildings have been intensely researched since the exterior tube of diagrid structural system for tall buildings was first proposed by Torroja in his seminal book. At present, studies for mechanical characteristics, joint form, theories, and tests have been systematized. This paper systematically summarizes existing research achievements of the diagrid structural system for tall buildings and confirms that the structure has larger lateral stiffness and good seismic performance. Based on the favourable performance of concrete‐filled steel tubes, this paper advises the use of concrete‐filled steel tube columns as the columns in diagrid structural systems for tall buildings.     

Structural performance of multi‐outrigger‐braced tall buildings

The optimum designs of multi‐outriggers in tall building structures are presented and discussed in this paper, through the analysis of structural performance of outrigger‐braced frame‐core structures. The influences of the locations of outriggers and the variations of structural element stiffness on the base moment in core, top drift and fundamental vibration period of such tall building structures are analysed in detail. A non‐linear optimum design procedure for reducing the base moment in the core is presented based on the penalty function method. The computer programs are developed on the basis of the proposed methods for analysing the behaviour and optimum design of multi‐outrigger structures. A series of figures presented in this paper can be used for the design purposes of outrigger‐braced tall building structures. Copyright © 2003 John Wiley & Sons, Ltd.     

Optimal lateral stiffness design of composite steel and concrete tall frameworks

This paper presents the optimal lateral stiffness design of composite steel and concrete tall frameworks subject to overall and interstorey drift constraints as well as member sizing limits using an efficient numerical approach developed based on the Optimality Criteria (OC) method. Taking into account the composite interaction between the structural steel and concrete materials, the stiffness-based optimal design problem is first formulated according to the European Code 4 (EC4). The necessary optimality criteria are then derived for the design followed by the construction of an iterative scheme to satisfy these optimality conditions while indirectly optimizing the design problem with multiple constraints. The recursive OC process is then carried out with the initial member sizes obtained from a closed-form solution developed for the similar problem with a single drift constraint. The effectiveness and practicality of the developed optimization approach is further illustrated through a series of framework examples.     

Seismic evaluation of a 56‐storey residential reinforced concrete high‐rise building based on nonlinear dynamic time‐history analyses

In recent decades, shear walls and tube structures have been the most appropriate structural forms for the construction of high‐rise concrete buildings. Thus, recent Reinforced Concrete (RC) tall buildings have more complicated structural behaviour than before. Therefore, studying the structural systems and associated behaviour of these types of structures is very important. The main objective of this paper is to study the linear and nonlinear behaviour of one of the tallest RC buildings, a 56‐storey structure, located in a high seismic zone in Iran. In this tower, shear wall systems with irregular openings are utilized under both gravity and lateral loads and may result in some especial issues in the behaviour of structural elements such as shear walls and coupling beams. The analytical methodologies and the results obtained in the evaluation of life‐safety and collapse prevention of the building are also discussed. The weak zones of the structure based on the results are introduced, and a detailed discussion of some important structural aspects of the high‐rise shear wall system with consideration of the concrete time dependency and constructional sequence effects is also included. Copyright © 2010 John Wiley & Sons, Ltd.     

Drift design of steel‐frame shear‐wall systems for tall buildings

Drift design methods based on resizing algorithms are presented to control lateral displacements of steel‐frame shear‐wall systems for tall buildings. Three algorithms for resizing of structural members of the steel‐frame shear‐wall systems are derived by formulating the drift design process into an optimization problem that minimizes lateral displacement of the system without changing the weight of a structure. During the drift design process, cost‐effective displacement participation factors obtained by the energy method are used to determine the amount of material to be modified instead of calculating sensitivity coefficients. The overall structural design model with the drift design method for the steel‐frame shear‐wall systems is proposed and applied to the structural design of three examples. As demonstrated in the examples, the lateral displacement and interstorey drift of a frame shear‐wall system can be effectively designed by the drift design method without the time‐consuming trial‐and‐error process. Copyright © 2002 John Wiley & Sons, Ltd.     

高层建筑钢结构基于风振响应和动力特性的优化设计

高层建筑的风致响应和等效静力荷载虽然可以通过风洞试验和动力分析有效的加以确定,在结构设计的整个过程中这些等效风力却往往被当作常数来应用。本文提出了一个结合气动风力分析和结构刚度优化的自动化技术。在结构设计中利用这个技术,可以在优化结构刚度和最小化结构造价的同时,实时检查和更新作用在建筑结构上的等效风荷载。一个几何尺度与航空研究共同顾问理事会(CAARC)建议的建筑模型一致的钢框架结构被用来进行风力分析和结构优化的例子。结果表明这个技术不但能在满足位移设计要求的情况下优化结构刚度降低造价,而且也降低了作用在结构上的等效风力。     

Dynamic characteristics and viscous dampers design for pile‐soil‐structure system

A series of large‐scale shaking table tests are conducted on tall buildings with and without energy dissipation devices on soft soils in pile group foundations, representing pile‐soil‐structure interaction (PSSI) system and the corresponding fixed‐base situations. The superstructure is a 12‐story reinforced concrete (RC) frame. The dynamic characteristics of the test models show that the frequencies decrease and the damping ratio increase in PSSI system by comparison with the fixed‐base structures. The mode shapes of PSSI system are different from that under fixed‐base condition, and the mode shapes of structure without dampers change greater than that with energy dissipation devices under various white noises. An improved method for structural dynamic characteristics, considering the impedance function of piles, is developed to address the issue of modal parameters with PSSI effect. In addition, the structural dynamic parameters of the large‐scale shaking table tests are identified using the modification method and other regulation methods, demonstrating that the improved approach is highly accurate and effective. Subsequently, a design procedure for viscous dampers of structures with PSSI effect is presented based on the dynamic characteristics of the system. Finally, the dynamic responses of the structure with viscous dampers in the practical engineering are decreased effectively, indicating the good performance of designed viscous dampers. The numerical results also show that the damping efficiency of interstory drift is larger than the acceleration and interstory shear force. Therefore, the improved modal parameters method, validated through a series large‐scale shaking table tests, is applicable for identifying dynamic characteristics of pile‐soil‐structure with energy dissipation devices system. The design procedure of viscous dampers, proved by a reinforced concrete frame structure located on a practical Shanghai soft site, can be employed to design the viscous dampers considering seismic PSSI effect.     

Evaluation of deformation capacity including yield deformation in displacement‐based design of special RC shear wall

A displacement‐based design scheme can be applied to the seismic designs of special reinforce concrete (RC) shear walls. However, the displacement‐based design in the current seismic design codes does not consider the contribution of yield deformation of RC shear walls. In this study, the evaluation method of the deformation capacity for seismic designs of RC shear walls was analyzed and applied to a parametric study for the lateral deformations of RC shear walls. From the results of analyses with various design conditions, the contribution of yield deformation to the deformation capacity of an RC shear wall was analyzed. It was demonstrated that, for RC shear walls in tall buildings, the yield deformation increased as the ratio of wall height to length increased and reached more than 50% of total deformation. Therefore, for the reasonable design of special RC shear walls in tall buildings, the design equation including the yield deformation in the displacement‐based design process is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

An inter‐story drift‐based parameter analysis of the optimal location of outriggers in tall buildings

Outriggers are usually added in structural systems of tall buildings to collaborate central shear walls with peripheral columns. With outriggers, the structural overturning moment can be balanced, and the inter‐story drift can be controlled under horizontal loads. Therefore, the optimal location of outriggers plays a very important role in controlling the behavior of the whole building. Existing research has focused on the optimal position of outriggers on the base of the structural roof deflection. In the engineering practice, however, inter‐story drift is the most important target to control the design of tall building structures. This paper investigates the theoretical method of inter‐story drift‐based optimal location of outriggers. A Matlab program is written to perform the parameter analysis of optimal location of outriggers. Take a 240‐m tall building for a target building, the optimal location of one to three sets of outriggers under wind and earthquakes is obtained and can be utilized for the structural preliminary design of tall buildings. Copyright © 2015 John Wiley & Sons, Ltd.     

Study on seismic performance of a super‐tall steel–concrete hybrid structure

Many steel–concrete hybrid buildings have been built in China. The seismic performance of such hybrid system is much more complicated than that of steel structure or reinforced concrete (RC) structure. A steel–concrete hybrid frame‐tube super‐tall building structure with new type of shear walls to be built in a district of seismic intensity 8 in China was studied for its structural complexity and irregularity. Both model test and numerical simulation were applied to obtain the detailed knowledge of seismic performance for this structure. First, a 1/30 scaled model structure was tested on the shaking table under different levels of earthquakes. The failure process and mechanism of the model structure are presented here. Nonlinear time‐history analysis of the prototype structure was then conducted by using the software PERFORM‐3D. The dynamic characteristics, inter‐story drift ratios and energy dissipation conditions are introduced. On the basis of the comparison between the deformation demand and capacity of main structural components at individual performance level under different earthquake level, the seismic performance at the member level was also evaluated. Despite the structural complexity and code‐exceeding height, both experimental and analytical results indicate that the overall seismic performance of the structure meet the requirements of the Chinese design code. Copyright © 2012 John Wiley & Sons, Ltd.     

SATWE软件如何计算刚度比

总结了地震剪力与地震层间位移比、剪切刚度比、剪弯刚度比在《建筑抗震设计规范》和《高层建筑混凝土结构技术规程》中的定义和计算方法。为了帮助SATWE软件用户正确地选择刚度比的设置,结合一个框支剪力墙结构算例,探讨这三种刚度比在SATWE软件里的适用范围及实现过程,并提出在运用SATWE软件进行结构计算时应注意的问题。     

RC框架-核心筒高层隔震结构支座拉应力控制方法研究

合理控制隔震支座拉应力是RC框架-核心筒高层隔震结构设计的关键难点问题。采用4种拉应力控制方法对一抗震设防烈度为8度(0.3g)、高度为98.1m的基本案例进行了拉应力控制,综合考虑控制效果和上部结构材料用量对比分析了各方法的优劣。结果表明:增大结构整体刚度可较好控制拉应力,但会显著提升材料用量和工程造价;调整支座方案可一定程度降低拉应力,基本不会改变隔震设计关键指标;优化外框架与内核心筒尺寸也可较好控制拉应力且基本不会改变材料用量和工程造价;优化外框架与内核心筒尺寸,结合支座优化可获得与增大结构整体刚度相近的控制效果。在此基础上,提出了适用于该类结构的拉应力优化控制流程体系,相比于传统方法,可采用较少的额外经济投入获得更好的拉应力控制效果。相关研究成果可为RC框架-核心筒高层隔震结构的设计提供参考。     

多层多跨钢筋混凝土平面框架拟静力倒塌试验研究#br#

建筑结构的破坏具有离散性和系统性的特点,该特性决定结构抗地震倒塌的研究需多参数、多层次考虑问题。文章结合结构地震倒塌破坏模式的研究,完成了三榀钢筋混凝土平面框架的低周反复荷载试验,通过对模型框架破坏过程、破坏形态、滞回耗能及刚度退化的分析,探讨轴压比和梁柱线刚度比对RC框架结构抗震性能的影响,以期为后续结构地震倒塌破坏机理的研究提供参考。分析结果表明：降低结构的竖向荷载和梁柱线刚度比,有利于梁端塑性铰的充分发育,从而更易实现理想的“梁铰”破坏机制;试验框架的最终破坏是由底层柱下端塑性铰充分发育后、混凝土突然压溃所致,底层构件的耗能能力得到充分发挥,而中间层构件和顶层构件所耗散的能量较少;KJ-2的峰值荷载及极限荷载比KJ-1的峰值荷载及极限荷载分别大约9.9%和8.7%、等效黏滞阻尼系数比KJ-1大约16.5%,但位移延性系数比KJ-1小约57.1%,说明增大结构的竖向荷载可以提高其承载能力及耗能能力,但会降低延性及变形能力,同时,一定程度地增大竖向荷载,有利于强化结构的初始抗侧刚度,延缓刚度退化趋势,但在层间位移角较大情况下P-Δ效应的影响凸显;结构梁柱线刚度比的增大可以提高其耗能能力,但会降低结构的承载能力、延性及初始抗侧刚度;对于轴压比及梁柱线刚度比较小的“梁铰”结构,临近倒塌时的层间位移角可达1/25,此时结构仍具有一定的竖向承载能力。     

RC框架-剪力墙结构的框架地震层剪力分配

我国《建筑抗震设计规范》与《高层建筑混凝土结构技术规程》关于框架-剪力墙结构地震层剪力分配的规定是依据设计经验提出来的,并没有考虑框架与剪力墙各自抗侧刚度比值的影响,因而较为笼统,明显欠缺合理性。连续化分析方法中框架-剪力墙结构的刚度特征值是表征框架-剪力墙受力和变形的重要指标。本文采用静力弹塑性分析（Pushover）方法和动力弹塑性时程分析方法对刚度特征值为1.0～4.5的8栋框架-剪力墙结构进行了全过程研究,得到了多遇、基本和罕遇地震作用下不同刚度特征值的框剪结构楼层剪力分配,以及罕遇地震下剪力墙刚度退化对楼层剪力分配的影响,并给出了框架层剪力分配公式供设计参考。     

DBJ/T 15-92—2021《高层建筑混凝土结构技术规程》的修订依据及相关问题说明

介绍了广东省标准DBJ/T 15-92—2021《高层建筑混凝土结构技术规程》的修订背景、原则和依据,并对相关概念予以说明。采用“二阶段、二水准”的性能设计方法,承载力计算式按抗力大于设防烈度地震效应组合表达,以可计算验证的方式保证“中震可修”目标的实现;采用改进后的抗震设计谱,避免了原《规程》抗震设计谱长周期段的缺陷;论证了结构最大层间位移角与混凝土构件是否开裂无关,指出控制层间位移角的主要目的在于避免非结构构件因主体结构过大的变形而损坏,合理放宽层间位移角限值;轴压比不应作为柱安全度的指标,将轴压比作为竖向荷载作用下的混凝土允许压应力比,可避免长期荷载作用下框架边柱的压应力小、中柱的压应力大而引起的徐变变形差,也可避免某些柱截面偏大成为短柱而又需构造配筋,延性反而变差;规定全框支剪力墙结构设计原则及构造要求,要求上部剪力墙先于下部框架屈服,不控制上下层刚度比;规定重力柱-核心筒结构的设计原则,要求核心筒有能力承担全部地震剪力、确保楼盖面内的弯、剪承载力;解释了美国规范UBC中区分规则和不规则结构的主要目的,指出扭转位移比不是衡量结构扭转效应大小的指标;有必要总结经验,清理不正确、过时的抗震设计概念,避免或减少不必要的超限审查,为结构设计及其创新营造更好的环境。     

Experimental study and design of a new hybrid RC frame system with stiffened masonry wall subjected to cyclic loading

This paper experimentally investigates the hysteresis behavior of a hybrid reinforced concrete (RC) frame system with stiffened masonry wall to enhance the seismic performance of existing RC buildings subjected to cyclic loading. The influences of the depth of the columns section, the length of masonry walls, and the grouting ratio of reinforced masonry were evaluated by designing a series of orthogonal quasi‐static tests on a half‐scale specimen. Test results indicated that the grouting ratio played the most significant role on the maximum strength, energy dissipation capacity, and the relative stiffness degradation rate of the hybrid structural system, whereas the length of masonry walls tends to dominate the deformation capacity. A trilinear analytical model and design recommendations are proposed to estimate the cyclic behavior based on force‐displacement hysteresis law that takes account of the effects of the post‐peak strength and unloading stiffness degradation.