Model tree approach for prediction of pile groups scour due to waves   总被引：1，自引：0，他引：1  

A. Etemad-Shahidi  N. Ghaemi 《Ocean Engineering》2011,38(13):1522-1527

Scour around piles could endanger the stability of the structures placed on them. Hence, an accurate estimation of the scour depth around piles is very important in coastal and marine engineering. Due to the complex interaction between the wave, seabed and pile group; prediction of the scour depth is not an easy task and the available empirical formulas have limited accuracy. Recently, soft computing methods such as Artificial Neural Networks (ANNs) and Support Vector Machines (SVMs) have been used for the prediction of the scour depth. However, these methods do not give enough insight about the process and are not as easy to use as the empirical equations. In this study, new formulas are given that are easy to use, accurate and physically sound. Available empirical equations for estimating the pile group scour depth such as those of Sumer et al. (1992) and Bayram and Larson (2000), are less accurate compared to the given equations. These equations are as accurate as other soft computing methods such as ANN and SVM. Moreover, in this study, safety factors are given for different levels of acceptable risks, which can be so useful for engineers.  相似文献   

Evaluation of wave impact loads on caisson breakwaters based on joint probability of impact maxima and rise times     

Giovanni Cuomo  Rodolfo Piscopia  William Allsop 《Coastal Engineering》2011

When waves break against seawalls, vertical breakwaters, piers or jetties, they abruptly transfer their momentum into the structure. This energy transfer is always spectacular and perpetually unrepeatable but can also be very violent and affect the stability and the integrity of coastal structures. Over the last 15 years, increasing awareness of wave-impact induced structural failures of maritime structures has emphasised the need for a more complete approach to dynamic responses, including effects of impulsive loads. At the same time, movement of design standards toward probabilistic approaches requires new statistical tools able to account for uncertainties in the variability of wave loading processes. This paper presents a new approach to the definition of loads for use in performance design of vertical coastal structures subject to breaking wave impacts.  相似文献   

Uncertainty assessment for watershed water quality modeling: A Probabilistic Collocation Method based approach     

Yi Zheng  Weiming WangFeng Han  Jing Ping 《Advances in water resources》2011,34(7):887-898

Watershed water quality models are increasingly used in management. However, simulations by such complex models often involve significant uncertainty, especially those for non-conventional pollutants which are often poorly monitored. This study first proposed an integrated framework for watershed water quality modeling. Within this framework, Probabilistic Collocation Method (PCM) was then applied to a WARMF model of diazinon pollution to assess the modeling uncertainty. Based on PCM, a global sensitivity analysis method named PCM-VD (VD stands for variance decomposition) was also developed, which quantifies variance contribution of all uncertain parameters. The study results validated the applicability of PCM and PCM-VD to the WARMF model. The PCM-based approach is much more efficient, regarding computational time, than conventional Monte Carlo methods. It has also been demonstrated that analysis using the PCM-based approach could provide insights into data collection, model structure improvement and management practices. It was concluded that the PCM-based approach could play an important role in watershed water quality modeling, as an alternative to conventional Monte Carlo methods to account for parametric uncertainty and uncertainty propagation.  相似文献   

亚高斯贝叶斯预报处理器及其初步试验     

陈法敬  矫梅燕  陈静 《气象学报》2011,69(5):872-882

为用户提供概率天气预报信息是公共气象服务的发展趋势,概率天气预报技术的不断改进实现了概率天气预报信息的不断优化。在众多概率天气预报技术方法中,贝叶斯预报处理器是一种新近出现的、基于贝叶斯统计理论的概率预报技术;贝叶斯预报处理器可以根据一个确定性预报系统的预报值与观测值之间代表着这个系统预报性能的统计关系,借助于贝叶斯统计理论,把一个确定性预报转化为一个概率预报,从而实现对预报不确定性的定量化。由于亚高斯似然模型可以适用于多种单调似然比随机依赖结构,故采用该似然模型的亚高斯贝叶斯预报处理器,它在气象、水文等领域具有较强的适用性。在简要介绍了连续型二维随机变量情形下的贝叶斯定理及正态-线性贝叶斯预报处理器之后,详细论述了采用单一预报因子的连续型预报量亚高斯贝叶斯预报处理器,并以长沙站和武汉站2008年1月每日00时(世界时)地面气温(T2m)的中国国家气象中心、欧洲中期天气预报中心、美国国家环境预测中心集合预报中的控制预报资料(预报时效选为96h)作为确定性预报样本,对亚高斯贝叶斯预报处理器进行了初步试验。结果表明,亚高斯贝叶斯预报处理器可以将T2m各集合预报中的控制预报转化为能定量地表达各控制预报不确定性的T2...  相似文献   

Probabilistic analysis of soil‐structure interaction effects on the seismic performance of structures          下载免费PDF全文

Fariborz Mirzaie  Mojtaba Mahsuli  Mohammad Ali Ghannad 《地震工程与结构动力学》2017,46(4):641-660

This paper revisits the phenomenon of dynamic soil‐structure interaction (SSI) with a probabilistic approach. For this purpose, a twofold objective is pursued. First, the effect of SSI on inelastic response of the structure is studied considering the prevailing uncertainties. Second, the consequence of practicing SSI provisions of the current seismic design codes on the structural performance is investigated in a probabilistic framework. The soil‐structure system is modeled by the sub‐structure method. The uncertainty in the properties of the soil and the structure is described by random variables that are input to this model. Monte Carlo sampling analysis is employed to compute the probability distribution of the ductility demand of the structure, which is selected as the metrics for the structural performance. In each sample, a randomly generated soil‐structure system is subjected to a randomly selected and scaled ground motion. To comprehensively model the uncertainty in the ground motion, a suite of 3269 records is employed. An extensive parametric study is conducted to cover a wide range of soil‐structure systems. The results reveal the probability that SSI increases the ductility demand of structures designed based on the conventional fixed‐based assumption but built on flexible soil in reality. The results also show it is highly probable that practicing SSI provisions of modern seismic codes increase the ductility demand of the structure. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Quadrature-based approach for the efficient evaluation of surge hazard   总被引：3，自引：0，他引：3  

G.R. Toro  A.W. Niedoroda  D. Divoky 《Ocean Engineering》2010,37(1):114-124

The Joint Probability Method (JPM) has been used for hurricane surge frequency analysis for over three decades, and remains the method of choice owing to the limitations of more direct historical methods. However, use of the JPM approach in conjunction with the modern generation of complex high-resolution numerical models (used to describe winds, waves, and surge) has become highly inefficient, owing to the large number of costly storm simulations that are typically required. This paper describes a new approach to the selection of the storm simulation set that permits reduction of the JPM computational effort by about an order of magnitude (compared to a more conventional approach) while maintaining good accuracy. The method uses an integration scheme called Bayesian or Gaussian-process quadrature (together with conventional integration methods) to evaluate the multi-dimensional joint probability integral over the space of storm parameters (pressure, radius, speed, heading, and any others found to be important) as a weighted summation over a relatively small set of optimally selected nodes (synthetic storms). Examples of an application of the method are shown, drawn from the recent post-Katrina study of coastal Mississippi.  相似文献   

Probabilistic modelling of long-term beach evolution near segmented shore-parallel breakwaters     

Baoxing Wang  Dominic Reeve 《Coastal Engineering》2010

This paper presents a new framework for probabilistic modelling of long-term beach evolution in the vicinity of detached breakwaters. The study focuses on the key physical processes contributing to beach variability over a range of spatial and temporal scales. Based on a one-line model, the framework is enhanced with sophisticated solutions for beach-wave-structure interaction, diffraction together with a treatment of varying tide level. The sediment transport rate is calibrated at regional and local levels using data from bespoke field campaigns and site-specific coefficients are proposed. Monte Carlo simulation is conducted for long-term shoreline simulation under a sequence of time varying sequence of waves, currents and tidal levels. The results of the Monte Carlo simulation give an insight into the statistical characteristics of beach behaviour within the defence system. In particular, regions within the scheme that are relatively stable and those that exhibit greater natural fluctuations are identified.  相似文献   

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification     

Woojae Seong  Cheolsoo Park 《Marine Georesources & Geotechnology》2001,19(1):37-50

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-waveletconvolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L 2 norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.  相似文献   

Strong motion uncertainty determined from observed records by dense network in Japan   总被引：2，自引：1，他引：1  

Nobuyuki Morikawa  Tatsuo Kanno  Akira Narita  Hiroyuki Fujiwara  Toshihiko Okumura  Yoshimitsu Fukushima  Aybars Guerpinar 《Journal of Seismology》2008,12(4):529-546

The variation of ground motions at specific stations from events in six narrow areas was inspected by using K-NET and KiK-net records. A source-area factor for individual observation stations was calculated by averaging ratios between observed values for horizontal peak acceleration and velocity, as well as acceleration response spectra for 5% damping, and predicted values using a ground-motion model (usually known as an attenuation relation) by Kanno et al. (Bull Seismol Soc Am, 96:879–897, 2006). Standard deviations between observed and predicted amplitudes after the correction factor are less than 0.2 on the logarithmic scale and decrease down to around 0.15 in the short-period range. Intra-event standard deviation clearly increases with decreasing distance due to differing paths around near source area. Standard deviations may increase with amplitude or decrease with magnitude; however, both amplitude and magnitude of the data are strongly correlated with distance. The standard deviation calculated in this study is obviously much smaller than that of the original ground-motion model, as epistemic uncertainties are minimized by grouping ground motions at specific stations. This result indicates that the accuracy of strong ground motion prediction could be improved if ground-motion models for specified region are determined individually. For this to be possible, it is necessary to have dense strong-motion networks in high-seismicity regions, such as K-NET and KiK-net.  相似文献   

Application of probabilistic neural network to design breakwater armor blocks     

Dookie Kim  Dong Hyawn Kim  Seongkyu Chang 《Ocean Engineering》2008,35(3-4):294-300

This study presents a probabilistic neural network (PNN) technique for predicting the stability number of armor blocks of breakwaters. The PNN is prepared using the experimental data of Van der Meer. The predicted stability numbers of the PNN are compared with those of previous studies, i.e. by an empirical formula and a previous neural network model. The agreement index between the measured and predicted stability numbers by PNN are better than those by the previous studies. The PNN offers a way to interpret the network's structure in the form of a probability density function and it is easy to implement. Therefore, it can be an effective tool for designers of rubble mound breakwaters.  相似文献