Proposing the hexagrid system as a new structural system for tall buildings

In order to improve the efficiency of tube‐type structures in tall buildings, a new structural system, called hexagrid, is introduced in this paper. In comparison with diagrid system, it consists of multiple hexagonal grids on the face of the building. In this research, a set of structures using diagrid system having four various diagonal angles and hexagrid system were designed on a strength and stiffness‐based approach for buildings with 30, 50, 70 and 90 stories to withstand wind load. The impact of different geometric configurations of structural members on the maximum lateral displacement and architectural performance in both diagrid and hexagrid systems is compared. The stiffness sensitivity using a similar interior bracing system in both systems is also discussed. In this study, the seismic performance of a 30‐story diagrid structure and a hexagrid structure was evaluated using nonlinear static and dynamic analyses. According to the results, the hexagrid system has a better architectural view and more ductility and stiffness sensitivity, which are about three times than that of the diagrid system. And finally, in comparison with the diagrid system, the hexagrid system has enough potential to push the height limit. The guidelines discussed here are for architectural and structural engineers to improve freehand design. Copyright © 2012 John Wiley & Sons, Ltd.     

Robustness analysis of vertical resistance to progressive collapse of diagrid structures in tall buildings

In order to investigate the vertical resistance to progressive collapse and the evolution of its robustness in the process of loading, a quantitative method of the robustness index of diagrid structure is established based on the mechanical properties of the components and the vertical bearing capacity of the structure. A scale experiment model of diagrid tube structure is established in laboratory which verified the availability of the proposed robustness quantification method. Results demonstrated that, the axial force of inclined column is pressure, and the axial force of ring beam is tension under vertical load. The ring beam is the main restraint to the side bulge of the diagrid structure. The welded strength of the inclined column have great influence on the vertical bearing capacity, so it is necessary to consider the reduction of the strength of welded joint. The influence of the welding line of the joint can lead to the plastic stage of the local components of the structure, which makes the structural robustness worse. In addition, the experimental study and numerical simulation results verify that the proposed method of robustness coefficient quantification for diagrid tube structure can accurately and reasonably evaluate the resistance of vertical progressive collapse performance.     

Design criteria for diagrid tall buildings: Stiffness versus strength

The procedures and formulations suggested in literature for the design of diagrid structures start from the assumption that diagonal sizing process is governed by the stiffness requirements, as usually occurs for other, less efficient, structural types, and that member strength demand is automatically satisfied by the cross section resulting from the stiffness requirements. However, thanks to the high rigidity of the diagonalized façade, strength requirements can be of paramount importance and even be the governing design criterion. In this paper, stiffness and strength design criteria for diagrid structures are examined and translated in simplified formulae for quick member sizing. The application of the two approaches for the design of a 100‐storey building model, carried out for different diagrid geometrical patterns, gives the opportunity of discussing the relative influence of stiffness and strength on the design outcomes, in terms of resulting diagonal cross sections and steel weight, as well as on the structural performance. Copyright © 2013 John Wiley & Sons, Ltd.     

Progressive collapse assessment of new hexagrid structural system for tall buildings

Hexagrid structure is an innovative tube‐type system. It is constructed with hexagonal exterior structural grids. The hexagrid works as an effective lateral and gravitational resisting system. This paper presents the progressive collapse‐resisting capacity of this new system and the common diagrid system based on the local failure of the structural elements in the story above the ground. The collapse behavior is evaluated by two different nonlinear static and dynamic analysis methods. This study was conducted to design two‐type 28‐story and 48‐story building models to withstand wind load for both structural systems. With the analytical results, the hexagrid has enough potential of force redistribution due to its special configuration. It is observed that the new system had high resistance to progressive collapse than diagrids in similar condition. The complementary studies illustrate that resisting progressive collapse capacity, in both hexagrid and diagrid structures, is increased by using the buckling‐restrained elements. The guidelines discussed here can help engineers to understand the mechanism of progressive collapse of the hexagrid structures. Copyright © 2013 John Wiley & Sons, Ltd.     

设置屈曲约束支撑的斜交网筒结构延性有限元分析

斜交网筒结构具有较大的抗侧刚度,但其延性较差,通过设置屈曲约束支撑可改善斜交网筒结构延性。以30层的斜交网筒结构模型为研究对象,分别对普通斜交网筒结构和设置屈曲约束支撑斜交网筒结构进行静力弹塑性推覆（Pushover）分析。结果表明：屈曲约束支撑可有效改善斜交网筒结构延性。此外,对立面中部、立面角部、底部楼层、上部楼层共4种局部区域布置屈曲约束支撑的方案进行了结构延性分析。局部设置屈曲约束支撑斜交网筒结构的设计应确保斜柱处于弹性工作状态,屈曲约束支撑率先进入塑性耗能状态。建议采用立面中部布置屈曲约束支撑的方案,可实现在保证结构受剪承载力的前提下,较好地改善斜交网筒结构的延性,避免结构发生脆性破坏。     

Seismic performance factors for low‐ to mid‐rise steel diagrid structural systems

Diagrids are known as an esthetically pleasing and structurally efficient system. The current design codes and provisions, however, provide no specific guidelines for their design under extreme events such as earthquakes. This paper presents a comprehensive investigation of the performance of steel diagrid structures to evaluate their key seismic performance factors. Nonlinear static, time‐history dynamic, and incremental dynamic analyses are used to assess diagrid performance and collapse mechanisms in a high seismic region. Seismic performance factors including response modification factor, ductility factor, overstrength factor, and deflection amplification factor are quantified using 4 different methodologies. Four archetype groups of diagrid buildings ranging in height from 4 to 30 stories have been investigated. An R factor in the range of 4 to 5 is recommended for steel diagrid frames in the range of 8 to 30 stories unless supplementary analyses are conducted to find the optimal diagonal angle. For low‐rise steel diagrids (under 8 stories), an R factor in the range of 3.5 to 4 is recommended. Further, an overstrength and ductility of 2.5 and 2 are recommended. This paper lays the groundwork for including steel diagrids in design provisions.     

Diagrid structural systems for tall buildings: Changing pattern configuration through topological assessments

Diagrid structural systems have been widely adopted for high‐rise buildings in the last decades, due to their structural efficiency and architectural potentials. The paper gives a comprehensive outline of the peculiarities of diagrids, providing a complete framework of their mechanical behaviour and investigates the accuracy of the assumptions used in common practice. The study explores, firstly, the effectiveness of the stiffness‐based methodology for optimal (69°) and nonoptimal (82°) diagonal inclinations, evaluating if the common approach leads to the definition of optimized cross sections in terms of reducing drifts and steel utilization. Subsequently, the paper analyses and compares diagrid models with non‐uniform pattern configuration generated from topological assessments. The authors test the contribution of a hybrid structure combining diagrid and outrigger systems to appraise whether a local increase in the pattern might be advantageous and preferable to a gradual stiffening from the top of the building toward the base.     

斜交网格筒-核心筒结构地震非线性性能研究

斜交网格筒新型结构体系具有较大的侧向刚度,为建造高层、超高层结构提供了有利条件。然而目前该类型结构的地震非线性性能尚未被明确掌握,导致在结构设计中面临体系构件屈服顺序不明确、外网筒斜柱受力和屈服机制不清楚、外网筒地震失效路径不清晰等关键性抗震问题。通过对典型高层斜交网格筒-核心筒结构地震非线性有限元分析和典型模块子结构的拟静力试验研究,针对该类型体系构件的屈服顺序、斜柱受力和屈服机制以及外网筒的地震失效路径等进行系统研究,明确了该类型体系的上述地震非线性性能。     

A proposal for the classification of structural systems of tall buildings

In the early structures at the beginning of the 20th century, structural members were assumed to carry primarily the gravity loads. Today, however, by the advances in structural design/systems and high-strength materials, building weight is reduced, and slenderness is increased, which necessitates taking into consideration mainly the lateral loads such as wind and earthquake. Understandably, especially for the tall buildings, as the slenderness, and so the flexibility increases, buildings suffer from the lateral loads resulting from wind and earthquake more and more. As a general rule, when other things being equal, the taller the building, the more necessary it is to identify the proper structural system for resisting the lateral loads. Currently, there are many structural systems that can be used for the lateral resistance of tall buildings. In this context, authors classify these systems based on the basic reaction mechanism/structural behavior for resisting the lateral loads.     

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.     

Studies on various structural system design options for twisted tall buildings and their performances

Employing twisted forms for tall buildings is a recent architectural phenomenon. This paper studies various structural system design options for twisted tall buildings and their performances based on lateral stiffness. Twisted tall buildings of various heights and rates of twist are designed with different types of contemporary tall building structural systems, such as diagrids, braced tubes and outrigger systems. The heights of the studied buildings range from 60 to 100 stories, and the rates of twist range from 0° to 3° per floor. As the rate of twist increases, the lateral stiffness of the tower decreases. The stiffness reduction rate caused by twisting is very much dependent upon the structural systems employed for twisted tall buildings. While an emphasis is placed on the structural performance of twisted tall buildings, other aspects, such as architectural and constructional issues, are also discussed holistically. Copyright © 2012 John Wiley & Sons, Ltd.     

Finite element analysis of optimized brace angle for the diagrid structural system

International Journal of Steel Structures - The Diagrid structural system is considered to be the best structural system for constructing free form structures, but it is also a very effective...     

相邻结构碰撞研究进展

地震引起的相邻结构碰撞会导致结构局部破坏或倒塌,造成人员伤亡和财产损失。文章将相邻结构碰撞模型分为经典碰撞模型、接触单元法碰撞力模型和有限元碰撞模型,并对研究现状分别进行介绍,梳理相邻结构设计参数对结构碰撞响应的影响,归纳最小防震缝宽度对相邻结构的影响及缝宽的计算方法,总结相邻结构防止碰撞的研究,分析相邻结构碰撞研究中存在的问题,提出今后应研究的方向。     

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.     

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。     

Active pipe-embedded structures in buildings for utilizing low-grade energy sources: A review

Low-grade energy sources such as geothermal energy, favorable ambient air and industrial waste heat etc. exist widely. Sufficient utilization of these low-grade energy sources may reduce our daily dependence on high-grade energy sources such as electricity resulting in reduced emission of green house gas for environmental conservation. Active pipe-embedded structure as floor/ceiling usually with water as the medium to carry heat or coolth may utilize these low-grade energy sources for providing space air-conditioning. Compact arrangement of pipes in the structure may significantly enlarge heat transfer surface between the slab mass and water in the pipe allowing substantial heat flows even for relatively small temperature differences. Application of the heat or coolth storage capacity of this structure for preheating or pre-cooling is also one among the advantages of this structure for shifting load and exploiting the nighttime cheap electricity tariff in some regions. This paper presents the technology of the active pipe-embedded structure for utilizing widely existing low-grade energy sources following by a comprehensive review on the heat transfer calculation models of this structure and its practical applications in real building systems for space air-conditioning. This review shows that more works on the active structure, especially simple and transient models for dynamic and accurate performance prediction and easy integration with existing building energy simulation packages, are worthwhile for further promoting the practical application wherever the low-grade energy sources are favorable.     

中高层住宅结构体系的优选

中高层住宅结构体系的优选是一个综合性的多目标决策问题。通过简要介绍中高层住宅常用的钢筋混凝土结构体系及其优缺点 ,提出了影响中高层住宅结构体系优越性的因素     

空间结构理念在高层建筑中的应用与发展

简要介绍空间结构理念在若干重要高层超高层建筑结构中的应用.天津卫津南路超高层住宅,应用剪力墙束筒理念,满足和改善了建筑使用功能和结构抗震性能目标.深圳福建兴业银行大厦,应用楼盖刚度和承载力的空间结构理念实现创新的搭接柱转换,取代高位大梁转换,改善了立面外凸内收的高层办公建筑使用功能和结构抗震性能.卡塔尔多哈外交部大楼,采用精细化施工模拟和适度部分预应力,针对性地纠偏和钢板凳节点加强,纠正了法国工程师标书设计重大失误,成功实现世界首创清水混凝土交叉柱外网筒超高层结构设计施工.     

Calculation model of the lateral stiffness of high‐rise diagrid tube structures based on the modular method

High‐rise diagrid tube structures are widely used in high‐rise buildings because of their strong lateral stiffness and flexible arrangement of plane layout. The lateral stiffness of rectangular diagrid tube structures is studied by many researchers, but it seldom attracts attention for arbitrary polygonal ones. Therefore, it is necessary to propose a calculation model for lateral stiffness of arbitrary polygonal diagrid tube structures. First, the basic concept of modular method is defined. Assuming that diagonals are only subjected to axial force, a calculation model of lateral stiffness of arbitrary polygonal diagrid tube structures is presented. The lateral displacements of structures are calculated by modular method. Then the accuracy of modular method and calculation model of lateral stiffness are verified by finite element method. Intersection law of structural lateral displacement curves is achieved. Taking the top displacement of structures as the reference index and based on the principle of equivalent material, diagonal angle optimization method is proposed, whose rationality is validated by finite element method. Based on the design method of top displacement control, preliminary design method of cross section of diagonals is suggested. Results in this paper are expected to provide a theoretical reference for preliminary engineering design.     

超高层建筑结构优化过程中的环境成本计算

近年来中国大陆掀起了超高层建筑的兴建热潮。超高层建筑体量巨大,其碳排放和能源消耗对环境有显著影响。在评估和优化超高层建筑的全生命周期环境成本时,提出了一个全新的全生命周期模型。新模型有两大特征：首先,同时考虑了建筑材料的空间分布与时间特征;其次,把单尺度生命周期概念拓展到多尺度生命周期概念,以从更多角度来研究碳排放情况。建立了一个基准超高层建筑模型来阐释对新模型的应用。根据初步研究结果,应用新方法可以选择出更优化的结构设计方法,以最大程度减少碳排放量。