Prediction of design wave loads of the ocean structure by equivalent irregular wave approach     

Ming-Chung Fang  Chih-Chung Fang  Chun-Hsien Wu 《Ocean Engineering》2007,34(10):1422-1430

The present study is employing the equivalent irregular wave approach to predict the wave loads for a ship encountering the worst sea state with respect to the critical dynamic loading parameter. Two different hydrodynamic numerical models, i.e. 3D pulsating source technique and 3D translating pulsating source technique, are applied to calculate the corresponding RAO of the ship moving in waves. Incorporating the RAO of the related physical properties, we can calculate the extreme value for the corresponding ship loading factor, which can be regarded as the worst sea state in the service lifetime of the ship. With the time and period of the occurrence of the corresponding extreme value, we can simulate the time history of the wave load in this period, which is so-called equivalent irregular wave approach. Comparing with the results calculated by the traditional equivalent regular wave approach, we find that the equivalent irregular wave approach can simulate the corresponding wave load more realistic, especially for dynamic pressure. Using the equivalent irregular wave approach can offer the effective and practical base for the ship structural analysis.  相似文献   

Analysis of equivalent-dose distributions for single grains of quartz from modern deposits   总被引：1，自引：0，他引：1  

M. Ballarini  J. Wallinga  A.G. Wintle  A.J.J. Bos 《Quaternary Geochronology》2007,2(1-4):77-82

Two modern coastal sands are studied through single-grain optical dating techniques. The first sample is estimated to be less than 10 y old by means of independent age control and is known to be well-bleached on the basis of preliminary single-aliquot studies. The second sample is less than 1 y old, but an age of 73±24 years had been determined through single-aliquot analysis. For both samples we compare equivalent doses obtained from single-grain analysis to those obtained by means of similar single-aliquot methods. We found that results are comparable although equivalent doses determined through single-aliquot methods are more precise. The reason for this may be ascribed to the limited number of grains on which single-grain measurements were carried out. The presence of poorly bleached grains within a sample could be identified by dose distribution analysis of individual grains.  相似文献   

Study of the effect of a thermal treatment on the D_E determination in ESR dating of speleothems     

F. Pirouelle  J.J. Bahain  C. Falgures  J.M. Dolo 《Quaternary Geochronology》2007,2(1-4):386-391

The choice of the ESR signal in the dating of speleothems is still debated. Among the peaks observed in speleothem ESR spectra, the most frequently signals used for the determination of the palaeodoses are the peaks at g=2.0007 (h3 line), g=2.0040 (Broad Line) and g=2.0057 (h1 line).

In order to determine the better analytical way to obtain reproducible D_E values from these three ESR signals, successive additional annealing treatments ranging from 60–300 °C were performed on several samples of a stalagmitic floor from the Mousterian site of the Caverna delle Fate (Liguria, Italy), also dated by U-series between 90 and130 ka. The results confirm that D_E values can be obtained from h3 and BL signals without annealing, while the h1 signal requires a thermal pre-treatment, to obtain the maximum intensity of this line. Then, on our samples, the D_Evalues derived for the three lines are equivalent. It gives, hence, the opportunity to obtain data when the g=2.0007 line cannot be used.  相似文献   

内核超速旋转及其对重力场的影响          下载免费PDF全文

申文斌  刘琳  宁津生 《地球物理学报》2007,50(2):430-436

本文研究由内核超速旋转引起的地球重力场的变化.论述了内核具有三个主要特征：椭球形状,各向异性对称轴与内核自转轴重合,内核自转轴与地球自转轴之间存在夹角并绕地球自转轴进动.内核超速旋转引起地球体系物质的重新分布,导致重力场变化.通过研究内核超速旋转的运动规律,建立了内核超速旋转导致重力场变化的模型,给出了由于内核超速旋转而引起的整个地球表面的重力变化,其中,在假定了内核超速旋转速率为1°/a的前提下,历经一年的最大重力变化量级约为037 μGal.  相似文献   

反演磁性地层界面的逐步剥离磁场法   总被引：5，自引：0，他引：5       下载免费PDF全文

赵百民  郝天珧  徐亚  周立宏  高嘉瑞  袁淑琴 《地球物理学报》2007,50(2):611-618

在对前人研究方法总结对比的基础上，本文提出了一种逐步剥离位场反演磁性地层界面的方法，该方法假定位场是由一个等效单位厚度层的等效磁化强度变化引起，通过逐步剥离位场，得到等效单位厚度层的等效磁化强度，进而求取磁性地层的起伏.本文进行了理论模型计算和野外实例处理，取得了良好效果.  相似文献   

地震危险性分析发展与工程应用   总被引：5，自引：0，他引：5  

周克森 《华南地震》1998,18(1):27-34

系统阐述了地震危险性分析方法发展中三种典型概率模型的特点和实质,它们被分别称之谓：简单概率模型、分段泊松模型以及复合概率模型。在此基础上,提出了一种基于复合概率模型的地震影响场等效地震的计算方法,并给出了它们在一个重大工程场地地震安全性评价中的应用。  相似文献   

Robust estimator for correlated observations based on bifactor equivalent weights   总被引：26，自引：1，他引：26  

Y. Yang  L. Song  T. Xu 《Journal of Geodesy》2002,76(6-7):353-358

 A new robust parameter estimator for the adjustment of correlated observations is developed based on a `bifactor reduction' model of weight elements. A shrinking factor for weight elements is proposed. The new equivalent weight matrix composed by the bifactor weight elements preserves the symmetry and keeps the original correlation coefficients unchanged. The new parameter estimator with its error influence function is derived. The robustness and efficiency of the new robust estimator is demonstrated with a simulated example and some conclusions are drawn. Received: 5 March 2001 / Accepted: 17 January 2002  相似文献   

The near-field method for dynamic analysis of structures on soft soils including inelastic soil–structure interaction     

《Soil Dynamics and Earthquake Engineering》2015

The problem of soil–structure interaction analysis with the direct method is studied. The direct method consists of explicitly modeling the surrounding soil to bedrock and the structure resting on the soil. For the soil medium, usually the traditional equivalent linear method with a reduced shear modulus and an increased damping ratio for the soil is used. However, this method does not work in the vicinity of foundation where the soil behavior is highly nonlinear because of presence of large strains. This research proposes a modified equivalent linear method with a further reduction of the soil shear modulus in the near-field of foundation that results in validity of using the equivalent linear method throughout. For regular short, intermediate and tall structures resting on such soft soils, a series of dynamic time-history analysis is implemented using earthquake records scaled to a sample design spectrum and the nonlinear structural responses are compared for different assumptions of soil behavior including the elasto-plastic Mohr–Coulomb, the traditional equivalent linear, and the proposed modified equivalent linear method. This analysis validates the proposed method.  相似文献   

基于DEEPSOIL的软土场地地震反应研究     

张海  王震  周泽辉  尤红兵 《震灾防御技术》2015,10(2):291-304

软土场地地震反应分析是目前工程场地地震安全性评价中的重要组成部分,对场地设计地震动参数的确定具有重要意义。利用一维场地地震反应分析软件DEEPSOIL,可进行场地线性、等效线性化和时域非线性等多种分析,并可考虑孔隙水压的影响。笔者根据土层计算参数,编制了DEEPSOIL软件场地模型输入文件的自动生成程序,可高效、快速地完成对场地的建模。通过数值算例验证了DEEPSOIL软件的精度。同时通过对某典型Ⅲ类软土场地的地震反应分析,研究了拟合参数的敏感性以及等效线性化方法和时域非线性方法对峰值加速度和地表加速度反应谱的影响,并指出了等效线性化方法在分析软土场地地震反应中的不足。对于软土场地建议采用DEEPSOIL软件进行时域非线性分析,因为其参数简单并容易确定,适合建模快速和使用方便的要求。  相似文献   

Numerical validation of analytical solutions and their use for equivalent-linear seismic analysis of circular tunnels     

《Soil Dynamics and Earthquake Engineering》2014

The first part of this paper presents an extensive validation of four analytical solutions for the seismic design of circular tunnels. The validation is performed with a quasi-static finite element (FE) model which conforms to the assumptions of the analytical solutions. Analyses are performed for a wide range of flexibility ratios, slippage conditions at soil–lining interface, assuming both drained and undrained behaviour. Based on the numerical predictions the relative merits of the considered analytical solutions are discussed and recommendations are given for their use in design. The second part of this paper explores the use of equivalent linear soil properties in analytical solutions as an approximate way of simulating nonlinearity. The results of equivalent linear site response analyses are used as an input for the analytical solutions. The comparison of the analytical predictions with nonlinear numerical analysis results is very satisfactory. The results of this study suggest that analytical solutions can be used for preliminary design using equivalent linear properties and the corresponding compatible strain as an approximate way of accounting for nonlinear soil response.  相似文献