Parameter study of framed‐tube structures with outriggers using genetic algorithm

In this paper, the analysis of optimal locations of framed‐tube structures with outriggers is conducted with the uniform and nonuniform core and peripheral columns using genetic algorithm, aiming to minimize the interstory drift. Also, comparison and difference of the results between the uniform and nonuniform structures are carried out and discussed. Besides, several parameters which influence the behavior of the structure are identified and analyzed, such as different objective functions, segments of outriggers, thickness of core wall, stiffness of outriggers, and grade of concrete strength. In addition, a Matlab program is written to perform the parameter analysis of optimal location of outriggers. Take a 260‐m high‐rise building as a target building, the optimal locations of one to two sets of outriggers subjected to three kinds of horizontal loadings (uniform, parabolic, and triangular) are obtained and can be utilized for the structural preliminary design of tall buildings.     

A comparative case study on seismic design of tall RC frame‐core‐tube structures in China and USA

To evaluate the major differences between the Chinese and the United States (US) seismic design codes from a structural system viewpoint, a comparative case study is conducted on a tall frame‐core‐tube building, a typical type of reinforced concrete system widely constructed in both countries. The building, originally designed using the US seismic design code, is firstly redesigned according to the Chinese seismic design code based on the information provided by the Pacific Earthquake Engineering Research Center. Secondly, the member dimensions, the dynamic characteristics, the seismic design forces and the material consumptions of the two designs are compared in some detail. Subsequently, nonlinear finite element models of both designs are established to evaluate their seismic performances under different earthquake intensities. Results indicate that the seismic design forces determined by the Chinese response spectrum are larger than those determined by the US spectrum at the same seismic hazard level. In addition, the upper‐bound restriction for the inter‐story drift ratio is more rigorously specified by the Chinese code. These two aspects have led to a higher level of material consumption for a structure designed by the Chinese code. Despite of the above discussions, the two designs yield roughly similar structural performances under earthquakes. Copyright © 2015 John Wiley & Sons, Ltd.     

Structural design of high‐rise buildings using steel‐framed modules: A case study in Hong Kong

Steel‐framed modular buildings afford certain advantages, such as rapid and high‐quality construction. However, although steel‐framed modules have been adopted in several countries, most of them are limited to low‐to‐medium‐rise structures; modular high‐rise buildings are rare. This study proposes a feasible structural design solution for high‐rise buildings using a steel‐framed modular system. A 31‐story student hostel building in Hong Kong is redesigned as a steel‐framed modular building and used as a case study. The finite element models of the building are formulated, and the structural behaviors under wind and earthquake load scenarios are compared. Moreover, the structural design process used for the 31‐story building is applied to design a hypothetical 40‐story modular building to further examine the proposed design solution. The numerical analysis results indicate that the roof lateral displacements and interstory drift ratios of the redesigned modular building are within the allowable limits of design codes; moreover, the modular connections behave elastically under the most adverse loading scenarios. Accordingly, the proposed solution can be used to design steel‐framed modular buildings of up to 40 stories, while complying with relevant wind and seismic codes.     

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.     

复杂高层建筑抗震与消能减震研究进展

复杂高层建筑的震害在近来的历次地震中都有发生,其抗震分析和设计难度较大,提高其抗震性能是当前建筑抗震的难点之一。通过对近10年来国内在复杂高层建筑抗震方面的研究进行回顾和总结,重点介绍了组合剪力墙及筒体结构、钢管混凝土结构、结构模型振动台试验和三种消能减震方法。提出了采用新型高效的结构体系及高性能抗震部件或消能减震新技术改善复杂高层建筑抗震性能。这些研究工作与工程实践紧密结合,大部分研究成果已在实际工程中成功应用。图18参28     

Performance‐based seismic design of an irregular tall building in Istanbul

Structural design of a 50‐story tall reinforced concrete residential building, which was planned to be constructed in Istanbul and given up afterwards by the investor, has been completed in accordance with the draft version of Seismic Design Code for Tall Buildings in Istanbul that adopts performance‐based seismic design as the basic approach as Tall Buildings Initiative Guidelines do. Seismic design of the building has formed the main part of the structural design process due to high seismicity of the proposed location and extremely irregular floor plan not conforming to usual tall building structures. The building consists of two individual buildings linked through sky floors at the top 12 stories whose design was one of the most challenging works. The building has been designed for design basis earthquake by elastic response spectrum analysis, and its seismic performance has been checked for maximum considered earthquake by nonlinear time‐history analyses carried out using PERFORM‐3D. Copyright © 2015 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.     

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.     

Dynamic analysis of combined system of framed tube and shear walls by Galerkin method using B‐spline functions

In this article, dynamic parameters (natural frequencies and mode shapes) of tall buildings that consist of framed tube and shear walls are obtained using a simple approximate method. The three‐dimensional structure is replaced by an equivalent cantilever beam, considering both bending and shear deformations. On the basis of dynamic equilibrium, the governing differential equation of motion is obtained and converted to its corresponding weak form. B‐spline functions are then utilized to approximate the weak form and to obtain the final matrix form of the problem. Finally, by applying essential boundary conditions, the natural frequencies and corresponding mode shapes are calculated. To demonstrate the accuracy of the proposed method, numerical examples are solved, and the results are compared with those obtained from SAP2000 computer analysis. The results show that the proposed method is efficient and accurate enough to be used in preliminary design. Copyright © 2014 John Wiley & Sons, Ltd.     

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。     

Prediction of shear‐lag effects in framed‐tube structures with internal tube(s)

The shear‐lag phenomenon is a critical consideration in high‐rise building analysis and design. The shear‐lag behaviour of framed‐tube (including tube, tube‐in‐tube and tubes‐in‐tube constructions) is investigated for the behavioural characteristics of the structures and their performance in relation to the various structural parameters. The stiffness factor in terms of the axial stiffness of the columns and the bending stiffness of columns and beams is chosen as a main parameter to explain the shear‐lag phenomenon and the global behaviour of the structures. A simple numerical technique is also proposed for estimating the shear‐lag behaviour of framed‐tube systems with and without multiple internal tubes. Further work is carried out to demonstrate the simplicity and accuracy of the proposed method through the analysis of three framed‐tube structures (of different heights) without internal tubes and three other framed‐tube structures with single, two and three internal tubes. The shear‐lag phenomenon of such structures is studied taking into account the additional bending stresses in the tubes. Copyright © 2002 John Wiley & Sons, Ltd.     

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.     

Application of earthquake‐induced collapse analysis in design optimization of a supertall building

In recent years, a combination of rapid construction of supertall buildings and frequent occurrence of strong earthquakes worldwide demands a rational seismic design method for structures of this kind. Although earthquake‐induced collapse analysis is one of the most efficient methods to quantify the collapse resistance of buildings, little research has been reported on using the collapse analysis to evaluate the seismic safety of supertall buildings during the design stage. To optimize the design taking into account earthquake‐induced collapses, a real‐world supertall building with a height greater than 500 m is investigated in this work. Throughout its design procedure, earthquake‐induced collapse analyses are performed to optimize the design at three different levels (i.e. the structural system level, design parameter level and component level). At the structural system level, the influence of different lateral force‐resisting systems on the collapse resistance is discussed; at the design parameter level, the influence of minimum base shear force is discussed; and at the component level, the influence of high‐performance shear wall on the collapse resistance is studied. Based on these discussions, the optimal design scheme of the building is established to improve the seismic safety while maintaining the cost of construction. Given more and more supertall buildings will be constructed with new structural system and components, this work will provide important references for the seismic design of supertall buildings and the corresponding collapse resistance research in the future. Copyright © 2016 John Wiley & Sons, Ltd.     

Integrated wind‐induced response analysis and design optimization of tall steel buildings using Micro‐GA

This paper presents an integrated procedure for wind‐induced response analysis and design optimization for rectangular steel tall buildings based on the random vibration theory and automatic least cost design optimization technique using Micro‐Genetic Algorithm (GA). The developed approach can predict wind‐induced drift and acceleration responses for serviceability design of a tall building; the technique can also provide an optimal resizing design of the building under wind loads to achieve cost‐efficient design. The empirical formulas of wind force spectra obtained from simultaneous measurements of surface pressures on various rectangular tall building models in wind tunnel tests are verified testified using a published example. Upon the known wind force spectra, the equivalent static wind loads for every storey, such as along‐wind, across‐wind and torsional loads, are then determined and applied for structural analysis including estimation of wind‐induced responses. An improved form of GAs, a Micro‐GA, is adopted to minimize the structural cost/weight of steel buildings subject to top acceleration and lateral drifts constraints with respect to the discrete design variables of steel section sizes. The application and effectiveness of the developed integrated wind‐induced response analysis and design optimization procedure is illustrated through a 30‐storey rectangular steel building example. Copyright © 2009 John Wiley & Sons, Ltd.     

Large‐scale shaking table test on pile‐soil‐structure interaction on soft soils

The two large‐scale shaking table tests of tall buildings on soft soils in pile group foundations are performed to capture the effect of the seismic pile‐soil‐structure interaction (PSSI) on the dynamic responses of the pile, soil, and structure. The two different model conditions are observed, including a fixed‐base structure and a structure supported by 3‐by‐3 pile group foundation in soft soil, representing the situations excluding the soil‐structure interaction (SSI) and considering the SSI, respectively. In the tests, the superstructure is a tall building with 12‐story reinforced concrete frame. The pile‐soil‐structure system rests in a shear laminar soil container, which is designed to minimize the boundary effects during shaking table tests. The two models are subjected to various intensity seismic excitations of Shanghai bedrock waves, 1995 Kobe earthquake, and 1999 Chi‐Chi earthquake events. According to the experimental and analytical results, SSI systems have longer natural periods than the fixed‐base structure. In addition, soft soil has amplification effect under smaller seismic excitations and isolation effects under larger earthquake intensities. The strain amplitude at the top of pile is large, and the strain at the middle and tip is relatively small. Whereas the contact pressure is small at the top of pile and large at the middle and tip. From the dynamic responses of the superstructure, it is found that the PSSI amplifies the peak displacements and interstory drifts of the structures supported by pile group foundations by comparing with the fixed‐base structure. Whereas the peak acceleration and interstory shear force of the structure are reduced considering seismic PSSI. The results show that the seismic SSI is not always favorable, however, it may increase certain dynamic responses of the structure. Consequently, the seismic SSI should be considered reasonably, providing insight towards the rational seismic design of buildings rested on soft soils.     

Seismic fragility analysis of concrete encased frame‐reinforced concrete core tube hybrid structure based on quasi‐static cyclic test

Concrete‐encased frame‐core tube hybrid structural system has been widely employed in high‐rise buildings. This paper intends to analyze the seismic fragility of this structural system under ground motion excitation. The quasistatic cyclic test on a 1/5‐scaled, 10‐story three‐bay specimen is introduced. Fiber‐based finite element model is developed and integrated with numerical techniques that would be able to simulate the nonlinear response based on the OpenSees program. As the model is verified by the experimental data, a series of incremental dynamic analyses (IDAs) considering different frame‐tube stiffness ratios are carried out. IDA curves are drawn to describe each structural performance state. Fragility curves and probabilistic demand models are proposed for quantifying failure probability. The collapse margin ratio is employed to evaluate the collapse probability. The result shows that the collapse probability under rare earthquake still meets the requirement of Applied Technology Committee‐63 Report. The hybrid structure is proved to perform superior collapse resistance ability. The proper increase in the stiffness of core tube can reduce the collapse probability and enhance the collapse resistance capacity.     

Dynamic characteristics and seismic response of frame–core tube structures,considering soil–structure interactions

In order to study the dynamic characteristics and seismic response of high‐rise buildings with a frame–core tube structure, while considering the effect of soil–structure interactions (SSIs), a series of shaking table tests were conducted on test models with two foundation types: fixed‐base (FB), in which the superstructure was directly affixed to the shaking table, and SSI, consisting of a superstructure, pile foundation, and soil. To increase the applicability of the model to the dynamic characteristics of real‐world tall buildings, the superstructure of test models was built at a scale of 1/50. This simulated a 41‐floor high‐rise building with a frame–core tube structure. The mode shape, natural frequency, damping ratio, acceleration and displacement response, story shear, and dynamic strain were determined in each of the test models under the excitation of simulated minor, moderate, and large earthquakes. The SSI effect on frame–core tubes was analyzed by comparing the results of the two test models. The results show that the dynamic characteristics and seismic response of the two systems were significantly different. Finally, these results were verified by performing a numerical analysis on the differences in the seismic responses of the FB and SSI numerical models under various simulated seismic conditions.     

用高阶有限单元法分析高层建筑筒体结构

横向水平荷载作用下高层建筑筒体结构的内力分析是建筑设计中确定柱子截面的关键.本文提出了一种14节点56自由度的高效高阶平面应力单元列式,并用FORTRAN语言编制了个相应的结构分析程序,分析了高层建筑墙体和筒体结构在横向水平荷载作用下的内力,获得了满意的高精度结果,表明本文提出的高效高阶单元列式正确,程序可靠,可十分方便地应用于高层建筑筒体结构的高精度工程分析问题.     

上海嘉定凯悦酒店超高层结构设计

介绍了上海嘉定凯悦酒店超高层结构的抗震设计与分析.主楼地下2层、地上40层、高184 m,设计采用钢骨混凝土混合框架—钢筋混凝土核心筒结构,使用了三种程序进行整体结构在多遇地震作用下的弹性计算,同时进行了小震作用下的弹性动力时程分析、中震作用下的结构性能分析和罕遇地震作用下弹塑性动力时程分析.各项计算指标均达到了设计的要求,结构设计和分析方法可供今后类似超限高层筑和其他复杂结构设计参考.     

关于超限高层建筑抗震设防审查的若干讨论

超限高层建筑的抗震设防审查,是提高高层建筑工程抗震设计的可靠性、避免抗震安全隐患,同时又促进高层建筑技术发展的有力手段,本文就抗震设防审查的必要性、主要内容和实现超限高层建筑设计的重要概念及关键技术措施提出若干参考意见。