结构弹塑性等效线性化方法的研究

等效线性化方法是估算结构最大弹塑性反应的实用化方法.等效线性化方法中,体系等效周期和等效阻尼比被视为位移延性系数的函数,把弹塑性体系等效为弹性体系来进行时程分析并求出结构最大反应.通过列举7种等效线性化方法--割线刚度法、平均刚度和能量法、平均刚度和阻尼法、Iwan方法、Hwang方法、Kowalsky方法、Iwan和Guyader方法,选取59个结构周期控制点、32条地震波,共进行了26432次弹塑性和等效线弹性时程分析.对每种等效方法的精度以及适用范围进行了对比和讨论,提出了选取等效线性化方法的建议.     

全局等效线性化土层地震反应分析方法

强非线性下土层地震反应数值模拟方法是国际难题,等效线性化是该类问题最佳求解方式之一.提出了全局等效剪应变的概念和算法,编制了新的等效线性化土层地震反应计算程序.研究表明,以0.65倍最大剪应变为等效剪应变的传统方法不适于土层强非线性应变模拟,采用全局优化,以可参与性和完整性为原则构建全局等效剪应变.可参与性由有效剪应变...     

Optimal control of structures under earthquake excitation based on the colonial competitive algorithm

The active control of engineering structures is one of the best methods to reduce structural responses under seismic excitation for the best performance of structures. This study presents an effective approach for the optimal control of structures under strong ground motion using the colonial competitive algorithm. The colonial competitive algorithm was developed over the last few years in an attempt to overcome the inherent limitations of traditional optimize method. The colonial competitive algorithm has been applied due to its ideal performance in optimal control problem. The effectiveness and performance of the proposed method have been investigated through two numerical examples for the response control of earthquake‐excited structures. The obtained results have been compared with the Linear Quadratic Regulator (LQR) control algorithm, and the performance of the proposed control approach has been found to be better than the LQR controller. Copyright © 2012 John Wiley & Sons, Ltd.     

Feedback-feedforward control of structures under seismic excitation

While the base acceleration resulting from a seismic activity on a civil engineering structure is not known a priori, it can be measured in real time. In this paper, it is shown that this extra information can be used for achieving a better control of the structure with little additional effort. The approach taken is to augment the equations of motion for the structural system with an appropriate model of the earthquake excitation based on filtering a Gaussian white noise process. The augmented equations of motion are used to determine a control which utilizes both feedback and feedforward compensation. The feedback loop incorporates measurements of the response of the structure into the control law. The information from both the structure and the earthquake excitation model is utilized in the feedforward control law with an observer designed to estimate the states of the eartquake model based upon the base acceleration measurements. A quadratic performance index is used as a measure of optimality of the control algorithms. Results are given which indicate that the proposed method offers advantages in performance over the control method employing only state feedback and that it is also able to improve upon results of the recently develped instntaneous control algorithms. It is also shown that the nostationarity in the earthquake excitation can often be neglected in practical design of linear systems. Finally, a discussion is given of how the method might be coupled with equivalent linearization techniques and extended for use with nonlinear structures.     

Neuro-control of fixed offshore structures under earthquake

An intelligent control technique using a neural network is proposed for seismic protection of offshore structures. Fluid-structure interaction was considered in developing controller and a training algorithm for the neuron-controller is presented. In the numerical example, the performance of the proposed neuron-controller was evaluated. Moreover, a neuron-controller is tested even when it is trained by using a linearized equation of motion for fluid structure interaction (FSI). Based on the examples, it can be concluded that the proposed neuro-control scheme can be used for offshore structures which have intrinsic nonlinearity due to FSI.     

A novel approach to evaluate the equivalent dynamic stiffness of guy clusters in telecommunication masts under ground excitation

Telecommunication structures are essential components of communication and post-disaster networks and critically important facilities require reliable earthquake-resistant design procedures in seismically active regions. Calculation of the nonlinear seismic response of tall guyed masts using detailed time-step finite element methods is far more complex than linear response spectrum analysis that is routinely used in structural engineering practice. It is recognized that detailed computational procedures are not always necessary, in particular when the goal of the analysis is to provide a global earthquake-resistant design check on a regular structure with predictable response: this is when rational simplified methods are called upon to calculate the seismic demand. However, up until now, no such method exists for tall guyed masts that can account for the dynamic cable-mast interactions which dominate seismic effects in these structures. In the study reported here, the writers explore the dynamic behavior of guy cables under harmonic and seismic support ground motion through detailed computational modeling and propose a novel frequency-dependent method to evaluate the equivalent dynamic stiffness of guy clusters. This development will contribute efficiently towards a new robust rational model of general applicability for simplified seismic analysis of tall guyed telecommunication masts.Detailed numerical simulations involving 57 guy cables from eight existing towers with varying heights of 150-607 m were used in the study. A mathematical procedure was developed to replace the nonlinear time-variant cable stiffness with an equivalent linear frequency-dependent spring/mass system, based on the response spectrum of individual guy cables and the frequency content of the seismic excitation. Comparison of the main response indicators of these equivalent models and the detailed nonlinear finite element analysis results confirmed the reasonable and consistent engineering accuracy of the proposed simplified method with considerable savings in analysis effort.     

WPT模态控制算法在空间结构振动控制上的应用

针对复杂结构自由度庞大、频率密集的特点,引入了小波包分解对传统的模态半主动控制算法进行改进,提出了WPT模态半主动控制算法。通过在一体育场挑篷结构上进行的数值仿真结果表明:WPT控制算法在竖向地震激励下可以有效减小结构的地震响应,其对峰值反应的控制效果比传统模态控制算法有所改进。由于WPT模态控制算法中控制方程的维数较少,因而具有更好的实用性和工程应用前景。     

基于等效峰值能量的建筑物爆破振动安全评价探讨

爆破地震效应研究的中心话题就是如何对爆破地震的危害作出准确而又科学的评价。结合建筑物能量破坏机理,考虑爆破地震能量分布及建筑物动力响应特性,构造了基于“等效峰值能量”(EPE)的爆破地震安全评价方法。在相关研究的基础上,提出了EPE的爆破地震安全评价指标,并研究了EPE及等效速度的计算过程,探讨了不同爆源形式下的EPE简化计算方法,认为采用以等效速度表示的EPE指标来衡量爆破地震的危害程度是可行的,它较振速-频率相关的安全判据更能全面反映爆破地震危害的本质,并且具有很强的可操作性。     

Optimum design of active/passive control devices for tall buildings under earthquake excitation

To economically enhance the performance of active/passive control devices for seismic response reduction of tall buildings, this paper investigates the optimal placement and optimal parameter of control devices using the linear quadratic performance index as an objective function. The linear relation between the increment of performance index and the change of the position matrix of control devices is first established based on the assumption that the control gain remains unchanged. The optimal placement of control devices is then determined in terms of the sequence of the calculated performance index increments and the number of control devices to be used. With the control devices at their optimal places, the seismic response of the building is finally computed using the suboptimal control gain derived using the minimum error principle, from which the equivalent optimal parameters of passive devices can be also determined. The applicability of the proposed approach and its limitation are carefully examined through numerical examples. The results from the numerical examples show that the suggested approach is quite accurate and effective in determining the optimal placement and optimal parameter of control devices if the number of removed control devices is limited to a certain range. Copyright © 2002 John Wiley & Sons, Ltd.     

Critical building separation distance in reducing pounding risk under earthquake excitation

A separation distance between adjacent buildings is provided to reduce the risk of pounding of adjacent buildings under seismic excitations. It should be recognized that the evaluation of the critical separation distance is a one-sided barrier crossing problem while the problem of structural design under seismic excitations is a two-sided crossing problem. A procedure for assessing the required separation distance with or without considering possible uncertainty in structural properties was presented based on the reliability methods and random vibration theory. The procedure was used to carry out parametric analyses. It is shown that use of the complete quadratic combination (CQC) rule with the modal responses employed for designing structures may over- or underestimate the critical separation distance, depending on the damping ratios and the closeness of the natural vibration periods of adjacent buildings. This is due to not only one-sided versus two-sided crossing problem but also the approximation in the CQC rule. Further, the effect of the uncertainty in structural properties on the estimated separation is investigated. The results indicate that this uncertainty tends to increase the required critical separation distance.     

日本钢筋混凝土结构大震抗震验算的保有耐力计算方法

介绍基于弹塑性理论的日本现行钢筋混凝土结构大震抗震验算的保有耐力计算法,包括：保有耐力计算法的基本原理、确定方法和使用准则;结构楼层偏心率和刚性率对保有耐力的影响;结构各层的保有水平耐力计算;反映结构抗震特性的结构特征系数计算;结构保有耐力计算法的步骤和公式。并给出一个简单示例。以上有助于我国结构设计人员详细了解日本钢筋混凝土结构大震抗震验算的体系和具体方法,为发展我国的建筑结构大震定量计算方法提供借鉴。     

Anisotropic failure criterion for soils based on equivalent stress tensor

Experimental evidence shows that both the inherent anisotropy and the loading direction have a considerable influence on the failure of geomaterials. Based on a micro-macro analysis of soil skeletons, the equivalent stress tensor is extracted from the equilibrium equation to measure the joint effect of the fabric tensor and the stress tensor. Using the equivalent stress tensor, an anisotropic failure criterion is proposed which combines the magnitude and the direction of the effective stress together with the microscopic characteristics of anisotropy. With the parameters determined by conventional laboratory tests, the predicted results are compared with the experimental results using various stress paths obtained from the literature. The results show that the anisotropic failure criterion is reliable and accurate for both true triaxial tests and torsional shear tests. Finally, the possible applications of the equivalent stress and the improvements necessary for the anisotropic failure criterion are discussed.     

Calibration of the equivalent linearization gaussian approach applied to simple hysteretic systems subjected to narrow band seismic motions

A calibration of the equivalent linearization approach (EL) applied to simple hysteretic systems subjected to narrow band seismic motions is reported. The results obtained through this method are compared with those derived using the Monte Carlo simulation technique. An evaluation is presented of the influence of the ductility demand of the system, as well as of the degradation parameters, hardening ratio and smoothness of the hysteretic behavior on the accuracy of the EL approach. The computational efficiency of the approach is estimated for the cases analyzed.     

多点输入下大跨空间结构动力稳定性分析

大跨空间结构属于缺陷敏感性结构形式,在进行地震动输入时需要考虑时空相干性对结构动力响应的影响。为分析这类结构的动力稳定性,将随机振动方法和时程分析方法结合,将包含了场地统计规律的功率谱函数转化为时程分析方法的荷载输入,人工合成具有概率意义且考虑空间相干性的地震波,对实际工程中的大跨空间结构进行多点输入。结果表明:多点输入下的地震相干效应使结构失稳峰值加速度明显小于一致输入对应的失稳峰值,该方法适用于大跨度空间结构的动力稳定分析。     

Biaxial and torsional response of inelastic structures under random excitation

Structures under strong motion earthquake excitation often go into the inelastic range, and the restoring force becomes nonlinear and hysteretic. Since only very rarely the excitation direction perfectly aligns with the structural orientation, the response is generally biaxial and torsional motion often becomes important for structures which have geometric of a random vibration method to predict the inelastic response including the biaxial interaction and torsional motion. A previously developed differential equation model for the restoring force and the equivalent linearization solution procedure are generalized for this purpose. The methods are tested using a single-story space-frame and a three-story space-frame with setbacks. Comparisons with Monte Carlo simulations are made and methods for improvement of the accuracy are suggested.     

竖向地震作用下钢-钢筋混凝土塔式#br# 组合结构抗震性能研究

为研究钢-钢筋混凝土塔式太阳能发电组合结构在竖向地震作用下的抗震性能,对一实际工程的1/18缩尺模型结构进行模拟地震振动台试验。通过观察试验现象和分析试验结果,得出结论为：模型结构竖向前三阶频率分别为18.55Hz、20.12Hz和22.14Hz;结构质心处加速度反应最大,紫铜结构的加速度反应小于混凝土筒体的加速度反应;结构质心处位移反应最大,最大值为4.79mm;强震作用下竖向地震影响对结构起控制作用,同等水准地震作用下水平向地震加速度反应最大值出现时间晚于竖向地震加速度反应最大值;结构塔顶竖向伸缩效应不明显。     

双向地震下高铁客站抗震性能的振动台试验研究

“房桥合一”新型混合结构体系作为高速铁路大型客站典型结构形式,其结构特征复杂,抗震性能并不明确,理论和数值分析之外尚缺少试验论证。以天津西站典型结构为例,进行缩尺比为1/35的振动台模型试验,研究其在多级双向典型地震波激励下的抗震性能,通过试验分析并与有限元计算结果比较,获得了客站典型结构在不同水准双向地震下的动力响应特性和结构损伤情况,指出当前所设计客站结构的抗震性能良好、设计偏于保守、薄弱环节主要集中于上部屋盖结构。     

Ductility failure criterion for infilled-wall frame structures

填充墙框架结构与纯框架结构抗震性能差异显著，建立填充墙框架结构的破坏准则，有助于揭示填充墙破坏对结构整体性能的影响规律，阐明其性能退化机理。为此，对14组共59榀不开洞填充墙框架模型的变形能力和承载力对结构性能退化的影响规律进行研究，得到破坏过程中框架柱、填充墙及整体性能退化之间的量化关系，进而提出不开洞填充墙框架的延性破坏准则和性能评价标准。研究结果表明：填充墙框架模型对应延性准则的破坏指数平均值在0.724~0.928之间，延性准则能够实现填充墙框架结构倒塌破坏的量化表征；综合6组19榀填充墙框架的试验现象、性能退化特点和破坏指数统计结果，建议中等破坏和严重破坏临界点破坏指数分别取0.1和0.4，延性准则可用于填充墙框架结构的抗震性能研究和倒塌破坏评估。     

填充墙框架结构延性破坏准则

填充墙框架结构与纯框架结构抗震性能差异显著,建立填充墙框架结构的破坏准则,有助于揭示填充墙破坏对结构整体性能的影响规律,阐明其性能退化机理。为此,对14组共59榀不开洞填充墙框架模型的变形能力和承载力对结构性能退化的影响规律进行研究,得到破坏过程中框架柱、填充墙及整体性能退化之间的量化关系,进而提出不开洞填充墙框架的延性破坏准则和性能评价标准。研究结果表明：填充墙框架模型对应延性准则的破坏指数平均值在0.724～0.928之间,延性准则能够实现填充墙框架结构倒塌破坏的量化表征;综合6组19榀填充墙框架的试验现象、性能退化特点和破坏指数统计结果,建议中等破坏和严重破坏临界点破坏指数分别取0.1和0.4,延性准则可用于填充墙框架结构的抗震性能研究和倒塌破坏评估。