框架-防屈曲开缝钢板墙体系设计方法的比较研究

防屈曲开缝钢板墙是一种新型的抗侧力构件,除具有一般钢板墙的特点外,还具有塑性性能好、滞回特性稳定以及可以独立地变化墙板承载力和刚度等优点。目前,有学者针对该结构体系提出基于性能设计的能力设计法和能力准则法,采用上述理论以及日本被动减震结构的设计方法(性能需求法),对1榀6层3跨的防屈曲开缝钢板墙结构算例进行了分析,比较研究了3种方法对结构性能的影响。计算结果表明:对于能力设计法,适当提高墙板的设计屈服位移,可以有效地增大结构的延性;能力准则法需要多次试算,结构性能指标不易控制,通过承载力控制设计墙板屈服位移,耗能效率较高;性能需求法得到的结构延性最好,但用钢量较大,应用于防屈曲开缝钢板墙设计,尚需解决框架梁设计、墙板屈服位移取值等问题。     

中小跨径板式橡胶支座梁桥横向抗震设计研究

为提高中小跨径板式橡胶支座梁桥在强震作用下的横向抗震性能,在总结汶川震区该类梁桥震害特点和国内外桥梁抗震设计规范中相关抗震设计策略规定的基础上,归纳当前我国板式橡胶支座梁桥横向抗震体系存在的问题,提出适合我国中小跨径板式橡胶支座梁桥的横向抗震设计方法,即允许上、下部结构连接构件牺牲的准隔震设计方法,介绍该抗震设计方法设计思想,给出在两设防水准下结构各部件的性能目标要求。选择一座典型板式橡胶支座简支梁桥为研究对象,基于文中抗震设计方法的设计思想,提出采用新型隔震系统对计算桥例进行准隔震设计。结果表明：通过对横向限位装置力学性能参数的合理设计,通过桥梁结构在强震作用下板式橡胶支座的滑移、横向限位装置的损伤或牺牲,控制上、下部结构间传递的梁体惯性力,保护墩柱和基础等下部结构免遭严重损害,同时能有效控制墩梁相对位移,防止过大的梁体移位导致的交通阻断、甚至落梁。     

考虑位移协调的上埋式圆管涵设计方法

埋入式圆形涵管上的填土不但是荷载,也是涵管与土发生作用的介质,这种特性决定了圆管涵的工作性质。本文考虑了涵管结构与土的位移协调,提出了相应的涵管设计方法。结合现有规范方法和试验结果的比较分析,证实了本文方法的合理性。     

Fuzzy‐Valued Intensity Measures for Near‐Fault Pulse‐Like Ground Motions

Two fuzzy‐valued (FV) structure‐specific intensity measures (IMs), one based on squared spectral velocity and the other on inelastic spectral displacement, are presented to characterize near‐fault pulse‐like ground motions for performance‐based seismic design and assessment of concrete frame structures. The first IM is designed through fuzzying structural fundamental period to account for the period shift effect due to stiffness degradation, whereas the second IM is developed to take into account higher mode contribution in high‐rise buildings by employing a fuzzy combination of the first two or three modes for the lateral loading pattern in pushover analysis. A benchmark study of three example reinforced concrete frame structures shows that for moderate‐ to medium‐period structures, both of the proposed IMs improve prediction accuracy in comparison with the existing IMs. For short‐period structures, the FV inelastic spectral displacement is the best.     

Mitigation of vortex-induced vibrations in bridges under conflicting objectives

Aerodynamic performance of long-span bridges can be improved by retrofitting cross-sectional shapes or by adding tuned mass dampers. When both the approaches are used simultaneously, the design problem may become too complicated to solve by engineering judgment. The complexity becomes even greater in a real world problem in which both the performance and the cost have to be considered. We propose a multi-objective based approach to obtain optimal solution of the design problem. The approach effectively deals with highly nonlinear design space and the conflicting objectives between the performance and the cost. Due to the conflict of the two objectives, multiple optimal solutions are obtained, which are called Pareto-optimal solutions. The final design is obtained considering the cost and the performance criteria. The proposed method is applied to the mitigation of vortex-induced vibrations, but its general framework is applicable to any other aerodynamic problems.     

Optimal Design of Scissor-Link Foldable Structures Using Ant Colony Optimization Algorithm

Abstract:   In this article, the Ant Colony Optimization (ACO) algorithm is employed to size optimization of scissor-link foldable structures. The advantage of using ACO lies in the fact that the discrete spaces can be optimized with no complexity. The algorithm selects the optimum cross-sections from the available sections list. Elastic behavior is assumed for the formulation of the problem. In addition to strength constraints, the displacement constraints are considered for design. Here, the displacement method is used for analysis employing a special 3-node beam known as a uniplet. Two design examples are presented to demonstrate the performance of the algorithm.     

基于SAP2000的钢管拱桁架非线性静力推覆分析

采用SAP2000有限元软件对钢管拱桁架进行非线性静力推覆分析,得出结构性能点水平位移小于结构刚进入塑性时对应的水平位移,说明可以根据提前定义容许准则并分析结构性能点的行为,判断设计目标是否满足抗震性能要求。     

Experimental investigation of heat transfer during night-time ventilation

Night-time ventilation is seen as a promising approach for energy efficient cooling of buildings. However, uncertainties in the prediction of thermal comfort restrain architects and engineers from applying this technique. One parameter essentially affecting the performance of night-time ventilation is the heat transfer at the internal room surfaces. Increased convection is expected due to high air flow rates and the possibility of a cold air jet flowing along the ceiling, but the magnitude of these effects is hard to predict. In order to improve the predictability, heat transfer during night-time ventilation in case of mixing and displacement ventilation has been investigated in a full scale test room. The results show that for low air flow rates displacement ventilation is more efficient than mixing ventilation. For higher air flow rates the air jet flowing along the ceiling has a significant effect, and mixing ventilation becomes more efficient. A design chart to estimate the performance of night-time cooling during an early stage of building design is proposed.     

Prediction of nonlinear seismic demands of high‐rise rocking wall structures using a simplified modal pushover analysis procedure

This study presents a simplified analysis procedure for the convenient estimation of nonlinear seismic demands of high‐rise rocking wall structures. For this purpose, the displacement modification approach used in the nonlinear static procedure of ASCE/SEI 41‐13 is adopted. However, in the current study, this approach is extended to every significant vibration mode of the structure whereas the displacement modifying coefficients for different modes are calculated using the typical flag‐shaped hysteresis behavior of rocking walls. The parameters of this hysteresis behavior are selected to represent rocking walls with a practical range of energy dissipation capacity and postgap‐opening stiffness. The computed peak inelastic‐to‐elastic displacement ratios are presented as mean spectra, which can be used for the convenient estimation of pushover target displacement for every significant vibration mode. The accuracy of proposed procedure is examined using the seismic demands obtained from the nonlinear response history analysis of a 20‐story case study rocking wall structure. Furthermore, a modal decomposition technique is used to determine the individual modal seismic demands. The proposed procedure is found to predict both the combined and the individual modal demands with a reasonable accuracy and can serve as a convenient analysis option for the design and performance evaluation of high‐rise rocking wall systems.     

Analysis and Design of Elliptical Concrete-Filled Thin-Walled Steel Stub Columns Under Axial Compression

To analyze the axial compressive performance of elliptical concrete-filled thin-walled steel tube (ECFTST) columns, finite element (FE) modeling was built up by ABAQUS software in this paper. The material nonlinearity and the complex interaction between steel tube wall and core concrete in an elliptical section were considered in this numerical analysis. Failure modes and interaction mechanism of ECFTST stub columns were also studied. Moreover, a modified equivalent circular diameter approach for ellipse feature was proposed to substitute for the constitutive relation of ECFTST columns. The prediction accuracy of this method was verified by the comparison of the FE and test results in terms of failure modes, axial compressive capacities and axial force-axial displacement relation curves. Further, the influence of diameter-to-thickness ratio, cross-section slenderness and scale effect etc. on the performance of ECFTST stub columns were estimated under axial compressive loading. The results of numerical analysis showed that the axial force-axial displacement curves of the ECFTST stub columns were obviously affected by the confinement factor. Lastly, based on the simple superposition approach and the unified theory approach, two simplified design methods were proposed to predict the axial compressive capacities of ECFTST columns.     

Determination of optimal target reliabilities for design and upgrading of structures

A systematic approach is proposed for formulating risk-based cost-effective criteria for the design and upgrading of structures with special reference to earthquake protection. Target reliabilities (or acceptable risks) for damage control and life safety are determined on the basis of minimum expected life-cycle cost and from which risk-consistent criteria for design or upgrading are developed. The approach is illustrated for a specific class of reinforced concrete buildings in Mexico City.     

基于位移的框剪结构抗震性能分析及设计

框架-剪力墙结构为高层建筑常用的一种结构体系,其地震中的震害也比比皆是,为细化其抗震的可靠性,对其受力变形特点进行论述,对其抗震设计的总体要求进行阐述,结合其特点并根据规范确定其抗震性能水平及量化标准,根据其初始侧移模式推导其目标侧移曲线并依据规范的加速度反应谱推出其位移反应谱,最后提出框剪结构性能设计的一般步骤,可用于结构设计的初步论证阶段并为抗震性能设计在结构软件中的实现提供途径参考。     

体系能力设计法与基于性态/位移抗震设计

首先论述了基于性态 /位移抗震设计方法的发展及其需解决的问题 ,综合了结构抗震耗能原理、破坏机制控制概念、抗震体系和能力设计法等结构抗震原理 ,提出了体系能力设计法思想。体系能力设计法要求结构具有多重抗侧力抗震体系 ,并对不同子抗侧力结构采用不同的抗震能力 ,通过对抗侧力体系间能力差的控制 ,以实现主体抗侧力结构对整体结构在地震作用下的位移模式和破坏机制控制 ,进而使得整体结构的弹塑性地震响应和耗能分布的规律便于把握和确定 ,从而解决了基于性态 /位移抗震设计方法中的一些难以确定和计算的关键问题。最后通过一实例介绍了体系能力设计法的应用 ,并讨论了实现体系能力设计法基本概念和需进一步研究的问题     

New criteria for assessing local wind environment at pedestrian level based on exceedance probability analysis

In this present study, the wind environment was evaluated for local void domain at pedestrian level in the aspect of ventilation performance and thermal comfort. Exceedance probability analysis was applied as the main approach in order to estimate the uncertainties associated with the influence of climate on wind environment. Two criteria were proposed based on local air change rate and local kinetic energy respectively, which are domain-based indices allowing comprehensive estimation of local wind environment. Calculating output of these criteria in the form of cumulative distribution function forms a ground for reliability analysis of inadequate ventilation or thermal discomfort. A simple street canyon situated in Tokyo, defined as void model, was applied as an illustration of the new criteria in evaluating the local wind environment at ground level. The influences of two configuration factors: orientation and aspect ratio of the void model were investigated by CFD simulation. The results demonstrated that both factors show great influences on local ventilation performance, which also indicated the practicability and effectiveness of the proposed criteria to help achieving good wind environmental design.     

Decision‐making in a model‐based design process

Decisions early in the design process have a big impact on the life cycle performance of a building. The outcome of a construction project can be improved if different design options can rapidly be analysed to assist the client and design team in making informed decisions in the design process. A model‐based design approach can facilitate the decision‐making process if the design alternatives' performances can be evaluated and compared. A decision‐making framework using a performance‐based design process in the early design phase is proposed. It is developed to support decision‐makers to take informed decisions regarding the life cycle performance of a building. A scenario is developed in order to demonstrate the proposed framework of evaluating the different design alternatives' energy performance. The framework is applicable to decision‐making in a structured design process, where design alternatives consisting of both objective and subjective evaluation criteria can be evaluated.     

Reliability analysis of laterally loaded piles using response surface methods

Response surface methods have been applied to the reliability analysis of laterally loaded piles. Beam elements and a series of discrete springs are used to model the pile–soil system. The pile head displacement and the maximum bending moment in the piles are used as the performance criteria in this study. It is shown in the illustrative example that the CDF and PDF curves of the pile head displacement and the maximum bending moment in the pile obtained from the proposed methods are in good agreement with Monte Carlo simulation. The failure probabilities of the pile under specified performance criteria, the probabilistic responses of the pile-soil system, and the effect of pile-soil parameters to the failure probability of the pile are also studied.     

A performance based methodology for fire design of restrained steel beams

A performance based approach is developed for assessing the fire resistance of restrained beams. The proposed approach, based on equilibrium and compatibility principles, takes into consideration the influence of many factors including fire scenario, end restraints, connection configuration (location of axial restraint force), thermal gradient, load level, beam geometry, and failure criteria in evaluating fire resistance. The validity of the approach is established by comparing the predictions from the proposed approach with results obtained from rigorous finite element analysis. The applicability and rationality of the proposed approach to practical design situations is illustrated through a numerical example.     

Efficient estimation of tuned liquid column damper inerter (TLCDI) parameters for seismic control of base-isolated structures

This paper presents an enhanced base-isolation (BI) system equipped with a novel passive control device composed of a tuned liquid damper and an inerter (TLCDI). With the aim of reducing the seismic response of BI systems, this contribution focuses on the design of the TLCDI providing analytical solutions for the optimal TLCDI parameters, easily implementable in the design phase. The effectiveness of the proposed approach in terms of seismic response reduction and computational gain is validated by comparison with classical numerical optimization techniques. The control performance of two different base-isolated TLCDI-controlled structures is assessed by employing real-ground motion records, and relevant comparisons with both uncontrolled base-isolated structures and equipped with a conventional TLCD are presented.     

Engineering Integration: Real-Time Approaches to Performative Computational Design

Parametric techniques herald an age of predictive design. Results from simulations, analytical data and design performance criteria directly influence or drive architecture. However, this is still a relatively passive design approach: parameters go in, design comes out. Al Fisher explains the work of Buro Happold's SMART Solutions team on developing real-time simulations where the analysis is persistent within the model. Lightweight, mobile versions of tools traditionally reserved for detailed analysis can form the early conceptual stages of design. Interactive models can be tweaked and manipulated, with the live feedback of results providing a link to the materiality of the design. Through a responsive approach, hybrid design can be achieved that blends performance with design intent. Copyright © 2012 John Wiley & Sons, Ltd.     

Robust optimum design of tuned liquid column damper in seismic vibration control of structures under uncertain bounded system parameters

The optimum design of a tuned liquid column damper (TLCD) considering system parameter uncertainty is usually performed by minimising the performance measure obtained by the total probability theory without any consideration to the variation of its performance due to parameter uncertainty. However, such a design method does not necessarily correspond to an optimum design in terms of maximum response reduction as well as its minimum dispersion. Furthermore, such approach cannot be applied in many real situations when the required detailed information about the uncertain parameters is limited. The robust design optimisation (RDO) of a TLCD system to mitigate seismic vibration effect in which the bounds on the magnitude of the uncertain properties of the structural and ground motion model parameters are only required is attempted in this study. The RDO is formulated as a two-criterion optimisation problem where the weighted sum of the maximum root mean square displacement of the structure and its dispersion is minimised. The conventional interval analysis-based bounded optimum solution is also obtained to demonstrate the effectiveness of the proposed RDO approach. A numerical study elucidates the effect of parameter uncertainty on the RDO of TLCD parameters by comparing the RDO results with the bounded optimum results.