Defining equivalent stationary PSDF to account for nonstationarity of earthquake ground motion   总被引：1，自引：0，他引：1  

I.D. Gupta  M.D. Trifunac 《Soil Dynamics and Earthquake Engineering》1998,17(2):89-99

This paper presents three approaches to defining the stationary power spectrum density function (PSDF) of strong ground acceleration, for prediction of structural response corresponding to the strong-motion stationary part of the input excitation. The first approach defines the PSDF in terms of the Fourier amplitude spectrum and a stationary duration of ground acceleration. The PSDF obtained by this approach predicts accurately the response of structures with low to intermediate natural periods. In the second approach, we introduce the concept of stationary duration of response, which is defined as a function of the natural period and damping ratio of the oscillator. Using this approach, it is possible to get accurate estimates of response amplitudes for the broad range of natural periods. However, it is not convenient in practical applications to deal with several stationary durations for a given input excitation. Further, to evaluate these durations it is necessary to specify both the Fourier and the response spectra of ground accelerations; whereas the common engineering practice is to specify the response spectrum only. Therefore, the third approach suggests the use of the response ‘spectrum compatible’ PSDF. The paper presents several improvements in the general methodology used for this purpose. The improvements mainly relate to using more accurate peak factors and to using the transient nature of response. The spectrum compatible PSDFs, as evaluated in the present study, provide realistic specification of strong ground motion for stochastic seismic response analyses of structures.  相似文献   

Free vibrations of simply supported double plate on two models of elastic soils     

M. A. De Rosa  M. Lippiello 《国际地质力学数值与分析法杂志》2009,33(3):331-353

In this paper the free vibrations of simply supported rectangular plates, resting on two different models of soils, are considered. The first model called Hetényi, by the name of the deviser, assumes a continuous plate, embedded in a Winkler‐type soil to realize the foundation partial continuity. The upper plate rests on a multiple layer characterized by a Winkler‐type soil, a continuous plate and another Winkler‐type soil in sequence. The two Winkler‐type soils have different modules. In the second model, the plate will be embedded in two layers of soils, whose behavior is similar to that of the Pasternak–Kerr‐type soil. The two models have been already used for the study of the double beam system. The free motions, in both cases, are described by a homogeneous set of partial differential equations, based on Kirchhoff–Love theory. Next, the homogeneous equations of motion are solved by using the classical Navier method. The free frequencies and associated vibration mode shapes of double plate system are found and numerical examples are illustrated to compare the two models. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Modal analysis of a fast patrol boat made of composite material     

F.M. Santos  C. Guedes Soares 《Ocean Engineering》2009,36(2):179-192

The structural dynamic behaviour of a fast patrol boat is studied with two- and three-dimensional idealizations for dry-hull analysis. A preliminary two-dimensional beam analysis is conducted by means of the Prohl-Myklestad method to derive a first estimate of the first four symmetric mode shapes. A more complex three-dimensional finite element model is developed in order to evaluate the modal characteristics for both symmetric and coupled anti-symmetric distortions, with the emphasis placed on the former.  相似文献   

Characterization of ground motions using recurrence plots     

Silvia R. García  Miguel P. Romo  Jesús Figueroa-Nazuno 《Geofísica Internacional》2013,52(3):209-227

The current analysis of earthquakes is typically based on linear mathematical models that may fail to describe and forecast particular behaviors, because in many cases the data complexity may induce a highly non linear behavior. In this paper the implementation of an alternative method for seismic time series analysis is presented. The RPs (Recurrence Plots) enables recognition and treatment of measured accelerations. An RP obtained from seismic data allows a more efficient interpretation of the ground motions and this explanation contributes to characterize materials and responses. The nonlinear attributes from RPs analysis can be used as filters to reveal patterns or be combined to predict a seismic property. Automated seismic data characterization, based on nonlinear seismic attributes, could rewrite the rules of earthquake phenomena interpretation. The objective of this work is to establish a new methodology for practical application of nonlinear dynamics in seismic pattern/attributes recognition, an evolving and challenging engineering field.  相似文献   

基于薄层法的饱和土桩纵向振动研究     

刘林超  杨骁 《岩土力学》2010,31(1):92-98

在饱和多孔介质理论的基础上,将桩周土体看作液固饱和两相介质,借助于Novak薄层理论得到了饱和土层的竖向动力阻抗,研究了饱和土中桩的纵向耦合振动,并对比分析了采用三维模型和薄层法的结果,验证了结果的正确性。分析讨论了桩土主要力学参数对饱和土-桩耦合体系动力行为的影响。研究结果表明,桩的长径比、桩土模量比等对饱和土桩耦合体系纵向振动的影响相对较大,而土的黏滞阻尼系数和液固耦合系数的影响相对较小。  相似文献   

LNG储罐高低承台桩基础抗震性能对比分析     

李云鹏  王芝银 《岩土力学》2010,31(Z2):265-269

目前全容式LNG储罐基础常采用低承台和高承台桩基2种形式。采用弹性振动理论,并考虑壳液耦联振动效应,对全容式储罐高、低承台桩基的抗震性能进行对比分析,给出了2种桩基础形式下全容式LNG储罐结构与基础的震动特性,包括自振周期、单桩水平地震力、抗倾覆性能、罐底周边单位长度上的提离力、储液晃动周期以及晃动波高等。分析表明,高承台桩基的水平地震响应大于低承台8.69%、垂直地震响应大于6.34%;低承台桩基的抗倾覆能力比高承台高12.11%,抗提离能力高于高承台储罐11.42%;高承台的自振周期高于低承台;低承台基础结构的抗震能力要优于高承台基础结构。其结论对桩基础全容式LNG储罐的设计与施工具有一定的参考价值。  相似文献   

带有复合摩擦阻尼系统的基础隔震结构分析     

张延庆  杨庆丽  高向宇 《吉林大学学报(地球科学版)》2013,43(3):908-913

针对常规摩擦阻尼器的起滑力难以确定的问题,提出了复合摩擦阻尼系统（CFDS）,它由非线性硬弹簧和摩擦阻尼器串联而成。当地震较小时,摩擦阻尼器处于附着状态,非线性硬弹簧发挥作用,防止隔震层位移过大;当地震较大时,非线性硬弹簧的变形则保持不变,摩擦阻尼器处于滑动状态,通过摩擦阻尼耗散能量。建立了带有复合摩擦阻尼系统的基础隔震结构的运动方程,指出摩擦阻尼器处于附着和滑移2种状态下边界条件。据此研究了常规强震和近断层脉冲型地震动作用下复合摩擦阻尼装置对橡胶隔震结构的减震效果。仿真分析表明：安装复合摩擦阻尼系统,在显著降低隔震层位移的同时,对上部结构的层间位移和加速度均有一定的减震效果;并且,在整个运动过程中,摩擦阻尼器会在附着和滑移2种状态之间来回切换。详细研究了复合摩擦阻尼系统的３个参数对隔震结构的减震效果。结果表明：在不同地震波作用下,由于摩擦阻尼系统参数的变化导致隔震结构地震响应的变化趋势是不同的,因此最优参数的取值与输入地震波类型和地面加速度峰值有关,并且不存在使隔震层位移和上部结构加速度同时达到最小的最优参数,因此需要设定合适的控制目标以确定适当的阻尼系统参数。  相似文献   

Experimental and numerical evaluation of the effectiveness of a stiff wave barrier in the soil     

《Soil Dynamics and Earthquake Engineering》2015

This paper discusses the design, the installation, and the experimental and numerical evaluation of the effectiveness of a stiff wave barrier in the soil as a mitigation measure for railway induced vibrations. A full scale in situ experiment has been conducted at a site in El Realengo (Spain), where a barrier consisting of overlapping jet grout columns has been installed along a railway track. This barrier is stiff compared to the soil and has a depth of 7.5 m, a width of 1 m, and a length of 55 m. Geophysical tests have been performed prior to the installation of the barrier for the determination of the dynamic soil characteristics. Extensive measurements have been carried out before and after installation of the barrier, including free field vibrations during train passages, transfer functions between the track and the free field, and the track receptance. Measurements have also been performed at a reference section adjacent to the test section in order to verify the effect of changing train, track, and soil conditions over time. The in situ measurements show that the barrier is very effective: during train passages, a reduction of vibration levels by 5 dB is already obtained from 8 Hz upwards, while a peak reduction of about 12 dB is observed near 30 Hz immediately behind the barrier. The performance decreases further away from the jet grouting wall, but remains significant. The experimental results are also compared to numerical simulations based on a coupled finite element–boundary element methodology. A reasonable agreement between experiments and predictions is found, largely confirming the initially predicted reduction. This in situ test hence serves as a ‘proof of concept׳, demonstrating that stiff wave barriers are capable of significantly reducing vibration levels, provided that they are properly designed.  相似文献   

Three-dimensional dynamic response of multilayered poroelastic media     

Teerapong Senjuntichai  Suraparb Keawsawasvong  Rawiphas Plangmal 《Marine Georesources & Geotechnology》2013,31(4):424-437

ABSTRACT

The dynamic response of a multilayered poroelastic medium under 3D time-harmonic loading is studied using an exact stiffness method. The poroelastic medium under consideration consists of N layers of different thicknesses and properties and an underlying poroelastic half-space. The exact stiffness matrices for each layer and the underlying half-space are derived explicitly using Biot’s poroelastodynamic theory and double-dimensional Fourier transforms. Selected numerical results are presented to demonstrate the influence of various parameters on dynamic response of multilayered poroelastic media under traction and fluid loading. The application of proposed solution scheme to soil–structure interaction problems is also presented.  相似文献   

Live load induced vibrations in Ullevi Stadium - dynamic dynamic soil analysis   总被引：1，自引：0，他引：1  

Sigurdur Erlingsson  Anders Bodare 《Soil Dynamics and Earthquake Engineering》1996,15(3):171-188

The paper describes a case history where during two rock music concerts the audience at the large outdoor stadium Nya Ullevi, Gothenburg, Sweden, started to jump in time to the music. Violent vibration levels occurred in the ground and a part of the audience observed considerable motion in the structure. Based on finite element analysis, it is concluded that the underlying soft clay of the structure was excited with the same frequency as the beat of the music. The whole clay deposit under the stadium started, therefore, to vibrate with great variations in amplitudes over the field due to the complex geometry. Through interaction with the basement of the structure as well as its deep foundation the waves were transmitted to the superstructure. Parts of the structure framework have natural frequencies close to those of the beat. Consequently they started to vibrate violently.  相似文献