共查询到20条相似文献,搜索用时 15 毫秒
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Maharaj K. Kaul 《Engineering Structures》1978,1(1):17-23
The analysis techniques for offshore floating structures have, until recently, been borrowed from the study of ship motions. These structures, however, differ in many ways from surface ships and simplified procedures developed for the latter are, therefore, not applicable. In this paper these dissimilarities are discussed and an overview of the techniques suited to the analysis of these structures is presented. 相似文献
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以国内首例采用钢管混凝土的750kV超高压变电构架工程为背景,设计了3个1:2缩尺、主管灌注混凝土的Y型相贯节点试件,其中包括2个采用不同加强方式(即瓦形板、外套筒加强)和1个作为对比的无加强节点试件,并对其进行了平面内受弯性能试验。试验结果表明:相比无加强节点,采用的2种加强节点的最终破坏形态均为支管失效破坏,均符合“强柱弱梁”的设计原则;节点的转动刚度和受弯承载力均显著提高,平面内转动刚度均可达到欧洲规范规定的刚性节点要求,且平面内受弯承载力基本可以达到支管全截面塑性时的弯矩值。此外,对节点的有限元分析表明:主管轴压比、瓦形板长度和宽度对节点刚度和承载力影响较小,而瓦形板厚度对此影响较为显著。 相似文献
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This study presents a risk-based decision support framework for seismic retrofit of building structures where the decision
criterion is to minimize the sum of the cost required for the rehabilitation and the expected seismic loss over a specified
time period. Probabilistic seismic hazard model (PSHM) and probabilistic seismic demand model (PSDM) are utilized for manipulation
of the uncertainty propagation from the seismic hazard to the structural damage. A mathematical formula is then developed
for probabilistic estimation of the seismic damage and losses over a specified time period. The analysis procedure is developed
such that the effect of the different configurations of the decision inputs can be promptly observed. The proposed procedure
is demonstrated by performing a decision analysis for a hypothetical RC building structure for determination of the optimal
level of seismic rehabilitation using steel bracings. 相似文献
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Eun‐Taik Lee Heon‐Soo Chung Hee‐Chang Eun 《The Structural Design of Tall and Special Buildings》2008,17(1):67-78
This study presents a dynamic equation of constrained motion and illustrates its validity through a dynamic analysis on the structural control by a constraint. Minimizing a function of the variation in kinetic energy at constrained and unconstrained states with respect to the velocity variation, the dynamic equation is derived and it is shown that the result compares with the generalized inverse method proposed by Udwadia and Kalaba. It is investigated that the responses of a 10‐story building are controlled by a constraint due to the installation of a two‐bar structure. The structural responses are affected by various factors like the length of each bar, damping, stiffness of the bar structure, and the boundary positions between two structures. Under an assumption that the bars have the same mass density, this study determines the optimal boundary positions to minimize the total responses of the structure, and compares the responses and control forces by optimal feedback control with the results. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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通过对结构工程分析,采用大跨度高支撑木模板体系进行施工,分析、计算了这一技术的可行性和可操作性并组织施工,并得到了良好的效果。 相似文献
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A mixed-mode method is investigated for the dynamic analysis of partially prismatic structures, such as box girders with intermediate diaphragms and supports, or with variable-depth webs. Thus the prismatic ‘main structure’ is discretised by finite strips, and the non-prismatic ‘sub-structure’ by finite elements. After dynamic reduction of the finite element degrees of freedom, advantage may be taken of the finite strip harmonic expansions in determining mode shapes. The method is tested by a variety of examples. Thus for structures with transverse substructures (e.g. diaphragms), the method is shown to be successful, being up to an order of magnitude faster than finite elements. However, for structures with longitudinal substructures (e.g. variable-depth webs) the method is shown to be unreliable. This is because for such structures, approximations in the dynamic reduction procedure are found to be significant. 相似文献
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The wind-excited vibrations of structures induce fluctuating stresses around mean deformation states that lead to fatigue damage accumulation and can determine structural failure without exceeding design wind actions. This paper proposes a mathematical model aimed at deriving a histogram of the stress cycles, the accumulated damage and the fatigue life of slender vertical structures (e.g. towers, chimneys, poles and masts) in alongwind vibrations. The formulation, integrally in closed form, is based on a probabilistic counting cycle method inspired by narrow-band processes. An example illustrates the proposed procedure and shows, through the comparison with Monte Carlo simulations, the entity of the approximations involved by treating the response as narrow-banded instead of broad-banded. 相似文献
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The nonlinear response and failure mechanism of reinforced concrete frame-wall systems is investigated through the employment of a mathematical model. The mathematical model is composed of two mechanical models: a concentrated spring model used for the flexural behaviour of beam and column type members and a multiple spring model used for the response of the wall system. Both account for inelastic behaviour of reinforced concrete.The mathematical model is applied to a ten-storey frame-wall system. The constituent members are replaced by one of the mechanical models whose stiffness characteristics reflect the inelastic properties and hysteresis tendencies of the member. The resulting equations are solved by a step by step time integration procedure. Computed results are compared with experimental results obtained from a structure tested on the Illinois earthquake simulator. The correlated results are then used to define the significant response characteristics. 相似文献
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An approximate method is proposed for the dynamic analysis of torsionally coupled tall building structures by utilizing the properties of their uncoupled counterparts. An exact solution is first given for the particular case in which the lateral and torsional stiffness matrices are uncoupled by same transformation. The method is then applied to a wider class of structures where this condition is only approximately satisfied by reducing the dynamic coupling problem to an approximate two-degrees-of-freedom system. Simple formulae and graphical representations of dynamic magnification of static eccentricity are given. Two numerical examples illustrate the use of the proposed method, checking on its accuracy and comparing its results with seismic code provisions. 相似文献
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基于波动力学理论,考虑土–结构动力相互作用、土介质特性及地震波的传播特性,提出了地震作用下地下结构的动土压力简化抗震设计方法。首先,将土–地下结构体系简化为单自由度的质量–弹簧–阻尼体系。其次,通过建立该体系的波动方程,并进行求解,将自由场响应换算为作用在结构上一点的动土压力,并结合结构周围土体的自由场响应分布特征,可得整个结构上的动土压力分布。最后,以振动台试验结果为基础进行了简化方法的验证,得出本文提出方法能够与试验结果吻合很好。该方法具有概念明确、计算简便、计算效率和精度高等特点,能够求解各类地下结构的地震反应,为地下结构的抗震设计提供了一种简单、实用的工具。 相似文献
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Hiroyuki Fuyama Helmut Krawinkler Kincho H. Law 《The Structural Design of Tall and Special Buildings》1994,3(3):183-200
This paper describes the development and utilization of a computer-based support system for the conceptual design of moment resisting steel frame structures. This design support system, ‘Building Engineering and Reasoning Tool’ (BERT), incorporates a behavior-based methodology for designing structural members that satisfy strength and interstory drift requirements due to gravity and lateral (earthquake) loads. Given the loading conditions and building configuration, BERT has the capability of selecting efficient member sizes through reasoning about the behavior of the structure. Different configurations can be evaluated by means of a cost estimating scheme that incorporates steel material, fabrication, and erection costs. This paper focuses on a discussion of the design methodology implemented in BERT. Illustrative examples are presented to demonstrate the range of applications of this design support system. 相似文献
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A new kind of metamaterial based on hierarchically organized mirror channels with partially reflecting walls, metamirror structures (MMS), is proposed. Properties of MMS are close to those exhibited by left-handed materials, despite the difference in underlying physical mechanisms. Transmission and reflection of rays are considered for different MMS geometries and types. It is shown that a one-step reflective 2D MMS based on rectangular elementary unit cells, being properly curved, possess the properties of a lens, and a generalized law describing MMS-based lenses is presented. If the MMS have relatively small sizes of unit cells (from one to tens of micrometers), then they may be treated as solid materials with anomalous optical properties in a wide range from visible and near-infrared up to UV wavelengths. It is concluded that MMS features may be observed in metamaterials of other kinds. 相似文献
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建立了冲击地压巷道围岩支护作用动力学模型,模型将上覆岩层简化为由多个质量块组成的块系,岩块简化为刚体,岩块间的连接简化为Kelvin-Voigt模型,把支护系统简化为弹簧和耗能阻尼器,初始岩块受冲击载荷作用。支护系统中阻尼为零时,为常规支护系统;支护系统中阻尼大于零时,为吸能防冲支护系统。分析得出:加强支护,提高支护强度,可以大幅度减少巷道冲击载荷作用下围岩加速度和位移幅值;支护系统中加入阻尼构件有利于快速平息围岩震动,增强支护抗冲击载荷能力,提高巷道围岩稳定性。提出了高强度吸能支护防治巷道冲击地压,为冲击地压巷道安全防冲支护设计提供理论依据。 相似文献