【作者】 何晓宇；

【导师】 李宏男；

【作者基本信息】 大连理工大学 ， 防灾减灾工程及防护工程， 2009， 博士

【摘要】 理论研究和震害经验都表明,地震时地面运动对结构物的作用是多分量的,包括三个平动和三个转动分量。国内外学者致力于地震作用下海洋平台结构动力响应及震动控制的研究,取得了一些成果,但主要是基于单向水平地震作用时平台结构的动力分析,另外,海洋环境有别于陆地环境,海洋环境中平台结构地震反应的特殊性问题还有待于进一步研究。因此,对于海洋平台,研究其多维地震反应与控制具有重要的现实意义。在此背景下,本论文在以下几方面进行了系统的理论分析和试验研究:（1）针对海洋环境的特殊性,研究了地震波浪的联合作用对平台动力响应的影响。以桩柱、对称平台、偏心平台为研究对象,对环境荷载强度（地震、波浪）、场地土条件、平台周期特点以及偏心平台的偏心率不同时,地震波浪联合作用对平台响应的影响进行了大量的参数分析。分析结果表明:当进行地震波浪联合作用分析时,有必要考虑流体附加质量效应和流固耦合效应对结构响应的影响;地震烈度水平较低,中等及较大风浪条件下有必要考虑地震波浪的联合作用;四类场地土条件下的长周期平台均有必要考虑这种联合作用,短周期平台则可以不考虑,对于中等周期平台这种联合作用与场地土条件及平台偏心情况有关。（2）研究了地震动单向输入、双向输入以及地震动不同输入方向对平台结构响应的影响,并提出了一种基于小波能量原理的用于确定海洋平台多维地震响应分析中地震动最不利输入方向的方法。通过小波变换可以获取地震动有效能量输入和有效能量输入速率两个重要参数,从而预测地震动的最不利输入方向。以某一实际平台和一组单层平台系统为算例进行了数值分析。分析结果表明:该方法可以快捷方便地预测地震动的最不利输入方向,且预测精度较高,可以满足工程应用的需要,小波能量原理在多维地震反应分析中具有很好的应用前景。（3）对地震作用和地震波浪联合作用下偏心平台结构扭转耦联地震响应进行了参数研究,推导出多维地震动输入下可以考虑不同偏心形式的偏心平台运动方程及其无量纲化形式。分析了偏心形式、地震动转动分量、偶然偏心、波浪入射方向、场地土条件和平台周期特点对偏心平台扭转耦联响应的影响。分析结果表明:结构的偏心形式对结构扭转耦联响应影响较大,不可忽视,同时地震动转动分量对结构平扭耦联响应也存在一定的影响;偶然偏心的存在可能增大结构的扭转耦联效应,且其对双向偏心结构的影响程度要远大于对单向偏心结构的影响程度;波浪入射方向对平台位移响应的影响随着结构扭转平动频率比Ω_θx的减小而增大,且对双向偏心平台影响稍大;另外偏心平台的扭转耦联效应与平台的周期特点有一定的对应关系而与地震动场地条件间的关系比较复杂,没有明显的规律性。（4）利用随机振动理论研究了地震、波浪作用下调谐液柱阻尼器（Tuned LiquidColumn Damper,简称TLCD）对平台的振动控制效果,重点分析了外荷载模型（高斯平稳白噪声模型、波浪谱模型和地震动谱模型）选取对TLCD阻尼器参数优化及结构振动控制效果的影响。分析中为了更好地反映实际波浪特点,在采用波面谱的同时引入波浪的方向谱,比较了考虑波浪方向分布对结构响应控制的影响。分析结果表明:按波浪谱模型对TLCD阻尼器参数模型进行优化所获得的减振效果要好于按高斯平稳白噪声模型进行优化的结果,不考虑波浪方向分布特性可能会高估TLCD的减振效果,建议实际工程中应选择波浪谱模型,并考虑波浪方向分布函数进行TLCD阻尼器的参数优化设计。此外,从TLCD最优振动控制效果来看,地震荷载作用时的控制效果要好于波浪荷载作用时的情况。（5）在普通粘弹性阻尼器的基础上通过构造上简单的改变设计了一种能同时对结构两水平方向振动和绕竖轴扭转振动进行控制的新型粘弹性阻尼器,并对阻尼器的恢复力模型及其对结构震动控制参数进行了理论分析。针对传统恢复力模型中关于阻尼器温频特性描述所存在的问题提出了两种改进模型,解决了模拟精度的问题。利用时程分析方法对新型粘弹性阻尼器在海洋平台多维震动控制效果进行了参数分析,研究了粘弹性材料尺寸形状、环境温度、响应频率对振动控制效果的影响规律,并对阻尼器数量的选取、位置的布设进行了初步的探讨。在此基础上利用反应谱法对阻尼器震动控制效果进行了理论分析,并给出合理的解释。（6）对新型粘弹性阻尼器的力学性能及其对结构震动控制效果进行了试验研究。通过力学性能试验,测定了粘弹性材料的剪切模量、损耗因子随激励频率、应变幅值和环境温度的变化规律,在此基础上通过对一组单层平台框架（对称平台、不同偏心形式的偏心平台）的振动台试验,验证了新型粘弹性阻尼器的多维震动控制效果。试验结果表明:不同频率下阻尼器剪切变形时恢复力理论模型的模拟精度很高,且扭转变形和扭剪组合变形试验时,恢复力模型也具有满意的模拟精度;另外震动台试验结果验证了阻尼器多维震动控制效果,阻尼器的增加除了为主体结构附加了一定的初始刚度,还在结构震动过程中消耗了大量的震动能量;对对称框架结构,粘弹性阻尼器能同时对结构双向加速度响应有明显的控制作用,对于位移响应而言,虽能同时对双方向响应起到控制作用,然而当两主轴响应相差很大时,对于响应较小的结构主轴方向,控制作用不明显;对偏心框架结构,粘弹性阻尼器对结构双向加速度和位移响应都具有明显的控制效果;当考虑水下环境震动时,粘弹性阻尼器对平台位移和加速度响应的振动控制效果要比陆上相应情况略有降低。更多还原

【Abstract】 Both theoretical research and earthquake damage analysis indicate that earthquake excitations are complex multi-component movements including three translational motion components and three rotational motion components.Most researchers have been devoted to the dynamic response analysis and response control for offshore platform only considering one directional earthquake acceleration acting along one axis of the platform.Moreover, different from land environmental conditions,the particularity issues in ocean ambient environment are needed to consider in seismic analysis for offshore platform.Therefore,it is necessary to implement research on multi-dimensional seismic response analysis and vibration control of offshore platform under ambient excitation.The six aspects of work in this thesis are listed as follows.(1) The influence of combined actions for earthquake and wave on the dynamic response of platform has been studied.The small dimension piles,symmetric platforms and asymmetric platforms are selected as research objects.The parameters which will affect the platform response are analyzed,such as seismic intensity,wind wave state,the site conditions, period characteristic of platform and the eccentricity of asymmetric platform.Results show that the effects of added mass of sea water and fluid-structure coupling on the pile responses are necessary to consider for the combined action analysis.When the seismic intensity is low and wind wave state is moderate or rough,or for the long-period platform in different ground conditions,considering the combination of seismic action and wave action is necessary for the seismic analysis of offshore platforms,while for the short-period platform,such combined action effect could be neglected.(2) The influence of single direction input,bi-direction input and different incidence of earthquake action on the dynamic response of platforms is studied.Then a wavelet energy method is presented to search the critical incidence of earthquake excitation in multi-dimensional seismic response of offshore platforms.The total effective energy and the instantaneous effective energy input rate of an earthquake can be obtained by wavelet transformation to predict the critical incidence of the earthquake and then the maximum dynamic response of the platform can be calculated.The critical incidence is determined using this method for an actual platform and a group of one-storey platform systems. Numerical results show that the application of wavelet transform in multi-dimensional seismic response of structures is convenient and reliable.(3) The torsion coupling seismic response of asymmetric platforms considering the combined action effect of earthquake and wave is studied and the vibration equations and its dimensionless form considering earthquake rotational component are derived for different eccentricity forms.The influence factors on torsion coupling response,such as eccentricity forms,earthquake rotational component,occasional eccentricity,incidence of wave action, the ground site conditions and the period characteristic of platform are analyzed through numerical studies.The results indicate that the influence caused by different eccentricity forms is nonnegligible and the torsion component of earthquake motion has some influences on the seismic response of the asymmetric structure.Accidental eccentricity may increase platform’s rotation response and it will be more severe for bi-directional eccentricity case. Such rotation coupling effects do have relation with the period characteristic of platforms. However there is not obvious rule for the ground types.(4) The effectiveness under optimal design of a Tuned Liquid Column Damper(TLCD) in suppressing environmental excitation-induced vibrations of offshore platform is studied in this paper.The problem is analyzed in the frequency domain with white noise excitation, wave spectrum excitation and earthquake spectrum excitation as three kinds of action models in this study.Optimum parameters of the TLCD for maximum reduction of peak structural response to the three models are calculated and compared.The numerical analysis results show that for the wave-induced vibration better control performance can be obtained when wave spectrum model is chosen instead of white noise excitation.Directional wave spectrum which can describe the full nature of wind-induced wave is first addressed in the analysis so that the directional distribution can be considered.In addition,from the view of optimum control effect,it is better for earthquake-induced vibration than for wave-induced vibration.(5) Based on the classical viscoelastic damper,a brand-new damper is designed by the change of simple construction to implement vibration control for both translational vibration and rotational vibration simultaneously.Theoretic analysis has been carried out on the restoring force model and the control parameters.Two improved models are presented to obtain high simulation precision.The influence of the size,shape of the viscoelastic material, the ambient temperature,the response frequency and the optimal number and its arrangement of damper on the vibration control effect is analyzed.Then reasonable explanation on the control effects is made by the response spectrum method.(6) Experiments on the mechanical behaviors of the new viscoelastic dampers and its vibration control for steel frame structure are performed.Excitation frequency,strain amplitude and ambient temperature are considered to investigate their effects on the mechanical parameters of the damper.Then,shaking table tests on a group of one-storey platform systems(symmetric platform,asymmetric platform with different eccentricity forms) are performed to investigate the multi-dimensional control effect.The experimental results show that the restoring force model has a high precision for the pure shear test and has a satisfied precision for the rotation and the complex deformation.The dampers installed in the steel frame absorbing much vibration energy as well as increase the structural initial rigidity. The damper has a significant control effect for both directional vibration of the symmetric and asymmetric structure.However,such control effect is not obvious for the structure direction in which its vibration is very weak while the vibration in the other direction is very strong. When the shaking table is filled with water,the control effect is relatively lower than the corresponding case in air.更多还原