连接Maxwell模型的两相邻结构非线性地震反应分析

对连接Maxwell模型的两相邻高层钢筋混凝土结构进行了大震作用下的非线性地震反应分析,相邻结构的本构模型采用三线型刚度退化模型,推导了连接Maxwell型阻尼器的相邻结构的运动方程,研究了Maxwell阻尼器优化参数理论表达式在结构进入非线性阶段的适用性,并研究了碰撞对相邻结构地震响应的影响,提出了不同地震波激励下阻尼器的优化参数值。分析结果表明:相邻结构进入非线性阶段时需要连接具有更强阻尼耗能能力的阻尼器以控制两结构的地震响应;即便在较小的防震缝宽度下,连接了控制装置后的相邻结构在大震作用下发生碰撞的可能性亦较小。     

智能隔震:基于能量响应和可靠度的前景分析

介绍了智能隔震结构能量响应和动力可靠度分析的主要方法和数值规律。以多遇地震的情形为例,显示了线弹性智能隔震体系的瞬时能量传递的解析规律;以罕遇地震的情形为例,列举了滞变智能隔震结构的动力可靠度分析方法。在罕遇地震下,用退化Bouc-Wen模型描述上部结构的恢复力,用非退化Bouc-Wen模型描述隔震层的恢复力。采用虚拟激励法计算结构的随机响应,根据我国抗震规范中“大震不倒”的设防目标,采用各层最大层间位移峰值响应和累积滞变耗能构造双参数的随机疲劳累积损伤指数,作为功能状态指标。以作者承担的一项实际隔震工程作为数值算例,对比了被动隔震、智能隔震与非隔震体系的能量响应和条件失效概率,显示了智能隔震体系的减震优势。     

基于Kriging改进响应面法的桥梁地震动力可靠度研究

鉴于桥梁结构对地震响应的非线性和复杂性等问题,提出了基于Kriging改进响应面法的桥梁结构地震动力可靠度分析方法。首先利用Kriging模型的优越模拟性能,将其作为响应面函数,并采取自适应策略加以改进,而后采取线性过滤器脉冲响应法对地震随机激励荷载进行了离散,并基于首次超越问题的定义建立了动力可靠度极限状态方程,最后对桥梁结构的地震可靠度问题进行了分析。计算分析结果表明:提出的基于Kriging模型的改进响应面法能有效完成桥梁地震动力可靠度的计算分析(包括结构参数随机性对桥梁动力可靠度的影响),且结果具有较高的准确性和高效性。     

基于整体可靠度的隔震结构参数优化分析

为了研究隔震结构关键设计参数对其在地震作用下整体可靠度的影响,将隔震结构简化的两质点计算模型,隔震层采用Bouc-Wen模型来模拟,上部结构采用刚度退化的Bouc-Wen模型来模拟,建立了隔震结构的运动方程,结合虚拟激励法与可靠度理论,分析了隔震结构在不同周期比、屈重比与阻尼比下的平稳随机地震响应与动力可靠度。并以整体可靠度为目标,对隔震结构的设计参数进行优化选取。将上述理论运用于设防烈度为8度的某隔震结构,分析了隔震层与上部结构的层间位移峰值的随机地震响应,并计算了隔震结构的整体可靠度。研究结果表明,隔震结构的周期比、屈重比及阻尼比的适当选取,能使隔震结构的隔震层与上部结构位移响应均较小,从而使隔震结构整体可靠度较高。从整体可靠度的角度对隔震结构的安全性进行评估,对隔震结构的合理设计及性态控制有指导意义。     

地震作用下高耸结构动力响应波动分析方法

针对高耸结构沿高度方向进行空间离散并构造出控制体,基于Timoshenko梁理论,建立控制体的动力学方程。在时间域上交替运用控制体动力学方程和剪力-位移关系式、弯矩-转角关系式,提出一种研究地震作用下高耸结构动力响应的波动分析方法。利用所提出的方法对南京电视塔在地震作用下的动力响应进行分析,计算结果表明:南京电视塔受地震作用时,大塔楼处位移峰值大于有限元方法的计算结果,大塔楼处出现转动惯性力矩峰值,研究高耸结构的地震响应问题时不应忽略转动惯性的影响。所提出的方法为研究地震作用下高耸结构的动力响应问题提供了一种有效的途径。     

地震波随机模型对隔震结构地震需求分析的影响

利用谐小波变换对实际强震记录的时变谱进行估计,并统计分析了与抗震规范相容的3类不同场地上地震波的时变谱特征,利用均匀调制非平稳随机模型和时变修正Kanai-Tajimi非平稳随机模型模拟地震波的时变谱,把非线性函数的参数识别问题转化成求解无约束优化问题,利用拟牛顿迭代法求得最优解,得到3类不同场地上这两种模型的参数的具体取值以及参数函数集的具体表达式;研究了以谱强度因子的平方根为强度参数的双向地震动作用下隔震结构概率地震需求分析的步骤,对比了不同的地震动随机模型对隔震结构概率地震需求分析的影响,研究发现在小震作用下,地震动随机模型对隔震结构的地震响应影响不大,但在大震作用下,地震动随机模型对结构响应有较大影响,而且,对于不同场地类别,地震动随机模型对隔震结构概率地震需求分析的影响也不相同.     

基于虚拟激励法的框架-摇摆刚架结构体系的动力可靠度研究

针对框架结构的受力特点,采用增设摇摆刚架的抗震设计方法。以某6层框架结构作为研究对象,建立结构体系的计算模型,并将状态空间与虚拟激励法相结合,求解结构的平稳随机响应;以所得随机响应计算框架-摇摆刚架体系的动力可靠度,探讨了多遇地震作用下不同刚度比的摇摆刚架对结构体系动力可靠度的影响。结果表明：通过增设不同刚度比的摇摆钢框架,可以有效降低结构体系各层及整体结构的条件失效概率,为工程设计和研究提供一些参考。     

非平稳地震作用下随机结构动力可靠度计算

对非平稳地震作用下的含随机参数结构,建议了一类结构体系动力可靠度的数值模拟求解方法.把结构动力方程写成状态方程形式,采用精细积分法对状态方程进行数值求解,将结构响应表达为一系列随机系数和离散时刻处随机激励乘积的和形式.随机系数为结构随机参数的函数,反映结构随机参数对随机响应的影响.在确定性结构非平稳随机响应时域分析方法的基础上,采用不含交叉项的二次多项式对该随机系数进行重构,获得了结构响应关于结构随机参数和离散时刻处随机激励的显式表达式.基于该显式表达式,利用数值模拟技术可以方便地进行首次超越失效准则下结构体系动力可靠度的求解.对一榀非平稳地震作用下的含随机参数框架进行了结构体系动力可靠度分析,并在计算精度和计算效率上与传统蒙特卡罗法进行了比较,结果显示所提出的方法具有理想的精度和相当高的效率.     

小震作用下抗震结构时程可靠度计算方法

采用杆系-层模型,将计算结构静力可靠度的改进虚拟变量法与常规有限元法及时程分析法相结合,建立了小震作用下结构时程可靠度分析方法。本文方法可考虑地震作用及结构参数的随机性以及地震作用与静载的共同影响,可确定小震全过程任一时刻结构各单元承载能力及结构侧向变形能力可靠指标)(tb。采用本文方法及Monte Carlo算法分析了一榀受小震作用的三层框架的时程可靠度。结果表明了本文方法的合理性与有效性。     

组合耗能系统的振动台试验与分析

在一座三层单跨的钢结构模型中安装了金属耗能器及其和油阻尼器并联组合，对这两种耗能体系进行了振动台试验，以研究耗能体系的动力特性，检验其减振效果，试验结果表明：组合耗能体系对位移有良好的减振效果；在小震时，对结构加速度峰值的减振效果不太明显，在大震情况下，基本上都能减小结构加速度峰值；耗能器的刚度与阻尼之间存在匹配关系，最后进行了数值分析，并与试验结果进行了比较，验证了本文提出的计算模型与方法的正确性。     

高层建筑结构嵌固条件影响研究

该文对国内外考虑地下室及周边土体对高层建筑地震作用影响分析方面的研究进展进行了回顾,基于塔楼、地下室结构与周边土体的相互作用机理,建立可以考虑地基基础影响的力学模型。根据场地情况确定地下室周边土体弹簧及相应阻尼的计算参数。考察地下室顶板嵌固、地下室周边嵌固、底板嵌固以及土体-结构相互作用等4类嵌固条件在地震作用下计算结果的合理性,并研究塔楼单侧洞口长度对整体结构与结构构件受力性能的影响。分析结果表明:地下室顶板嵌固模型塔楼侧向刚度偏大,且无法考虑地下室与塔楼之间的相互影响。地下室周边嵌固模型无法反映地下室结构的变形与质量引起的惯性力,在地震作用下水平剪力沿地下室竖向减小过快,计算结果偏于不安全。底板嵌固模型忽略周边土体的作用,导致地下室在地震作用下水平剪力过大,计算结果过于保守。土体-结构相互作用模型可以较为真实地模拟地下室周边土体的刚度与阻尼,与其他计算模型相比,虽然塔楼性能变化较小,但地下室构件内力变化很大。单侧洞口对塔楼整体受力性能影响较小,但对框架柱和楼板的影响值得重视。     

含端板螺栓连接耗能梁段的高强钢框筒结构基于性能的塑性设计方法研究

含端板螺栓连接耗能梁段的高强钢框筒结构(SFTSs)可以有效改善传统钢框筒结构的抗震性能,且可实现震后功能可快速恢复,是一种新型的高层可恢复功能结构。由于现行规范的抗震设计方法无法准确预测和控制结构的弹塑性性能,可能会使结构损伤集中于个别楼层出现薄弱层。为了设计具有理想失效模式的SFTSs,建立该结构体系“小震不坏,中震及大震可修,巨震不倒”的四水准抗震设防性能指标。考虑不同地震水准作用下的性能目标,采用三线型的能力曲线对传统的基于能量平衡的塑性设计方法进行改进,且考虑结构高阶振型和屈服后刚度的影响,提出了SFTSs基于性能的塑性设计方法。采用建议的设计方法设计了一个30层的结构算例,并基于OpenSees对结构算例进行弹塑性时程分析。结果表明:采用提出的设计方法设计的结构算例能够实现结构预期的失效模式以及不同地震水准作用下的性能目标,结构具有良好的抗震性能,验证了所提出的基于性能的塑性设计方法的有效性,可以为SFTSs的工程设计提供参考。     

地震作用下大型升船机结构的响应特征分析

从振动力学的角度,以某大型升船机建筑结构为背景,对升船机结构的动力特性及在地震作用下升船机结构的确定性和随机反应特征进行了较系统的分析。首先建立了升船机建筑结构的三维分析模型,对升船机结构进行了动力特性及时程响应特征分析。然后,在总结与分析有关地震动随机模型研究成果的基础上,通过比较,选择了具有较全面描述输入地震动随机特性的数学模型,并对升船机结构的功率谱响应特征进行了分析。最后,基于上述结构反应特征分析,给出了升船机建筑结构抗震可靠度计算模型的适用性建议。     

地震动信号小波谱分析与结构损伤评估

地震动是一个复杂的非平稳随机过程，基于傅立叶变换的传统谱分析方法已经难以发挥作用，小波变换因其在时一频两域都具有表征信号局部特征的能力而成为非平稳信号分析的有力工具。通过采用小波能量理论对一个三层钢筋混凝土框架一剪力墙模型地震模拟振动台试验实测数据进行了不同小波中心频率下的小波谱分析，探索了在同一地震中信号能量累积和能量累积变化率与结构动力特性变化的关系；提出了小波传递函数的方法并将其用于不同加载条件后结构模态参数的求解，清晰地得到了结构在不同地震后力学性能的退化趋势。     

INFLUENCE OF DAMPING MODELS ON DYNAMIC ANALYSES OF A BASE-ISOLATED COMPOSITE STRUCTURE UNDER EARTHQUAKES AND ENVIRONMENTAL VIBRATIONS

Structural design simultaneously governed by earthquakes and environmental vibrations has received a lot of attention in recent years.Base-isolated composite structures are typically used in the above-mentioned structural design.The corresponding analysis involves validating structural safety under earthquakes and human comfort under environmental vibrations through a time-history analysis.Thus,a reasonable damping model is essential.In this work,the representatives of viscous damping model and rate-independent damping model,namely the Rayleigh damping model and uniform damping model,were adopted to investigate the influence of damping models on the time-history analysis of such structural designs.The energy dissipation characteristics of the above-mentioned damping models were illustrated via a dynamic test of recycled aggregate concrete specimens.A case study was performed on a base-isolated steelconcrete composite structure.The dynamic responses under the excitation of earthquakes and environmental vibrations were compared using different damping models.The uniform damping model was found to be more flexible than the Rayleigh damping model in dealing with excitations with different frequency components.The uniform damping model is both theoretically advantageous and easy to use,demonstrating its potential in dynamic analysis of structures designed simultaneously governed by earthquakes and environmental vibrations.     

Reliability models for existing structures based on dynamic state estimation and data based asymptotic extreme value analysis

The problem of time variant reliability analysis of existing structures subjected to stationary random dynamic excitations is considered. The study assumes that samples of dynamic response of the structure, under the action of external excitations, have been measured at a set of sparse points on the structure. The utilization of these measurements in updating reliability models, postulated prior to making any measurements, is considered. This is achieved by using dynamic state estimation methods which combine results from Markov process theory and Bayes’ theorem. The uncertainties present in measurements as well as in the postulated model for the structural behaviour are accounted for. The samples of external excitations are taken to emanate from known stochastic models and allowance is made for ability (or lack of it) to measure the applied excitations. The future reliability of the structure is modeled using expected structural response conditioned on all the measurements made. This expected response is shown to have a time varying mean and a random component that can be treated as being weakly stationary. For linear systems, an approximate analytical solution for the problem of reliability model updating is obtained by combining theories of discrete Kalman filter and level crossing statistics. For the case of nonlinear systems, the problem is tackled by combining particle filtering strategies with data based extreme value analysis. In all these studies, the governing stochastic differential equations are discretized using the strong forms of Ito–Taylor’s discretization schemes. The possibility of using conditional simulation strategies, when applied external actions are measured, is also considered. The proposed procedures are exemplified by considering the reliability analysis of a few low-dimensional dynamical systems based on synthetically generated measurement data. The performance of the procedures developed is also assessed based on a limited amount of pertinent Monte Carlo simulations.     

Probability density evolution analysis of stochastic seismic response of structures with dependent random parameters

Performance evaluation and reliability assessment of real-world structures under earthquakes is of paramount importance. Generally, different mechanical property parameters of a structure are usually not independent, nor completely dependent, but partly dependent or correlated. Therefore, how to reasonably characterize such partial dependency and whether such partial dependency real matters in the stochastic response and reliability of structures under earthquakes are crucial issues. For this purpose, in the present paper, a novel physically-guided data-driven methodology of capturing the correlation configuration of basic random variables and the probability density evolution method are synthesized. The physically-guided data-driven methodology is firstly outlined. In this methodology, the underlying physical mechanism between dependent random variables is firstly involved to establish a random function model, and then the available observed data are adopted to identify the parameters in this model. What is more, physical constraints are also revealed for the initial modulus of elasticity and compressive strength of concrete. The probability density evolution method is then adopted, and the point selection by minimizing the GF-discrepancy is adjusted according to the correlation configuration and physical constraints. A reinforced concrete frame structure subjected to earthquake input is studied. It is found that when the structure is in the strongly nonlinear stage, the correlation configuration has considerable effects on the standard deviation of the stochastic responses, by a factor of nearly 2. In addition, whether the mechanical parameters in different floors are independent or not has great effects on the stochastic responses as well. Problems to be further studied are also outlined.     

Energy-based collapse assessment of concrete structures subjected to random damage evolutions

The assessment of structural capacity against collapse is conducive to the optimal design of new structures as well as checking the safety of existing structures. However, the evaluation cannot be typically carried out by means of destructive tests on prototype or reduced scale structures. In this regard, the numerical models that adequately represent the prototype structures can be alternatively used. Specifically, both the nonlinearities and randomness as well as their coupling effect of materials need to be represented in a unified manner in structural analysis. The present paper aims at providing an effective approach to incorporate the stochastic nature of damage constitutive relationships in collapse analysis and assessment of concrete structures subjected to earthquake ground motions. Within the framework of stochastic damage mechanics, the spatial variability of concrete is represented by a two-scale stationary random fields. The concept of covariance constraint is introduced to bridge the two-scale random fields such that the scale-of-fluctuation of the random material property is satisfied at both scales. Random damage evolution induced structural collapse analysis is achieved via the nonlinear stochastic finite element method. To address the randomness propagation across scales, the probability density evolution method is employed. By exerting the absorbing boundary condition associated with an energy-based collapse criterion on the generalized probability density evolution equation, the anti-collapse reliability of concrete structures can be evaluated with fair accuracy and efficiency. Numerical investigation regarding an actual high-rise reinforced concrete frame-shear wall structure indicates that the random damage evolution of concrete dramatically affects the structural nonlinear behaviors and even leads to entirely different collapse modes. The proposed method provides a systematic treatment of both uncertainties and nonlinearities in collapse assessment of complex concrete structures.     

水平任意向地震输入下双塔楼连体结构的动力分析

双塔结构在塔间设置连接可以组成减震控制体系，本文建立了体系的设计模型和运动方程，并在频域内对体系进行随机地震响应分析，同时比较了水平任意向地震输入时，无连接，有连接情况下的双塔结构的随机动力响应。表明有连接时结构的扭转变形不可忽略，最后就连接装置各参数对扭转反应效果的影响进行了分析。