Adaptive Predictive Inverse Control of Offshore Jacket Platform Based on Rough Neural Network     

崔洪宇  赵德有  周平 《中国海洋工程》2009,23(2):185-198

The offshore jacket platform is a complex and time-varying nonlinear system,which can be excited of harmful vibration by external loads.It is difficult to obtain an ideal control performance for passive control methods or traditional active control methods based on accurate mathematic model.In this paper,an adaptive inverse control method is proposed on the basis of novel rough neural networks (RNN) to control the harmful vibration of the offshore jacket platform,and the offshore jacket platform model is established by dynamic stiffness matrix (DSM) method.Benefited from the nonlinear processing ability of the neural networks and data interpretation ability of the rough set theory,RNN is utilized to identify the predictive inverse model of the offshore jacket platform system.Then the identified model is used as the adaptive predictive inverse controller to control the harmful vibration caused by wave and wind loads,and to deal with the delay problem caused by signal transmission in the control process.The numerical results show that the constructed novel RNN has advantages such as clear structure,fast training speed and strong error-tolerance ability,and the proposed method based on RNN can effectively control the harmfid vibration of the offshore jacket platform.  相似文献   

基于循环孔洞扩张模型的X型圆管节点超低周疲劳寿命预测     

刘焕才  刘亚平  张正艺  解德  何文涛 《海洋工程》2024,(2):125-136

海洋工程钢结构在服役过程中,受风、浪、流或地震等极端循环载荷的影响,易发生超低周疲劳断裂破坏,造成人员伤亡及财产损失,因此超低周疲劳断裂分析及寿命预测对于海工结构安全性评估至关重要。然而,现阶段基于累积损伤理论提出的多种超低周疲劳寿命预测模型无法对多尺度节点实现统一预测,造成了实际工程应用的不便。因此文中基于循环孔洞扩张模型开展X型圆管节点超低周疲劳寿命预测。首先,开发了基于循环孔洞扩张模型的VUSDFLD程序,实现ABAQUS与FORTRAN子程序联合应用,利用有限元分析验证循环孔洞扩张模型在X型圆管节点超低周疲劳断裂分析中的有效性;其次,根据多组X型圆管节点超低周疲劳断裂有限元分析结果,在宏观层面提出了一种基于Manson-Coffin公式的超低周疲劳寿命预测公式;最后,依据Miner理论,将适用于等幅加载的超低周疲劳寿命公式扩展至变幅加载情况,验证了多种节点尺寸下超低周疲劳公式的适用性,为工程应用提供了理论依据。  相似文献   

机械光栅式测缝计应用于无砟轨道板上拱监测的可行性分析     

张利刚  高山 《测绘工程》2022,31(1):52-57

高速铁路轨道的稳定性和平顺性是高速铁路正常运营的关键,因此对运营期高速铁路的轨下结构持续地开展变形监测是十分必要的。当前我国对轨道板变形的检测主要是依靠人工肉眼观察式的现场检查和常规水准测量方式进行监测,效率低下,难以在有限的天窗时间内完成辖区内轨道结构的全覆盖检测。基于此,从理论分析和实验测试两方面探讨机械光栅式测缝计应用于无砟轨道板上拱自动化监测的可行性,结果表明机械光栅式测缝计能够抵抗高温、淋水和振动等不良条件的影响,满足轨道板上拱监测的精度要求。  相似文献   

Fractographic determination of joint length distribution in chalk     

Dov Bahat 《Rock Mechanics and Rock Engineering》1988,21(1):79-94

Summary Measurements of fracture joint distribution combined with determinations of plume length and orientation on a vertical section of a single chalk layer near Beer Sheva, Israel, reveal that joints marked by unilateral and circular plumes are skewed towards the shorter sizes while joints decorated by bilateral plumes are skewed towards the longer sizes. The mean lengths of the unilateral and bilateral joints are 66.5 cm and 155.6 cm, with standard deviations of 30 cm and 60.6 cm, respectively. These results as well as joint length observations from other areas seem to suggest a bimodal length distribution. However, since the minor maximum is generally very weak, and due to some additional uncertainties, further confirmation of the present observations is needed.  相似文献   

Shear resistance of jointed rock masses and stability calculation of rock slopes     

Xing Zhang 《Geotechnical and Geological Engineering》1993,11(2):107-124

Summary Based on an extension to a model originally proposed by Zhang (1990), a method for estimating the shear strength of a jointed rock mass containing two joint sets is developed. Compared to the original method in which only a single en-echelon joint set was considered, the new method has the following advantages: (1) it allows a much more realistic joint pattern to be incorporated; (2) the effects of joint connectivity and intersection angle between joint sets on shear strength are included. Use of the new method is demonstrated by application to the calculation of the stability of slopes in jointed rock. The importance of joint connectivity, joint persistence and joint set intersection angle on slope stability, as predicted by the model, is revealed.  相似文献   

An example of slip instability resulting from displacement-varying strength     

David Lockner  James Byerlee 《Pure and Applied Geophysics》1990,133(2):269-281

A rock cylinder, containing a clay-filled sawcut making an angle of 30° to the sample axis, was deformed at constant confining and pore pressures and constant remote shortening rate. The sawcut surfaces contained a series of regularly spaced ridges and grooves oriented perpendicular to the direction of shear. The interaction of these grooved surfaces resulted in a sliding strength which varied periodically with displacement. By varying the effective machine stiffness through the use of an electronic feedback circuit, a range of stable and unstable slip behavior was achieved. In this way, we examined fault slip behavior which was dominated by displacement-dependent strength.  相似文献   

Tomographic determination of 3-D crustal structure — Joint inversion of explosion and earthquake data     

Xian-Kang Zhang  Zhuo-Xin Yang  Yu-Chun Yang  Jian Yang  Jian-Li Song  Ping Zhao 《地震学报(英文版)》1995,8(4):519-529

In this paper, the theory and method, obtaining the tomographic determination of three-dimensional velocity structure of the crust by use of the joint inversion of explosion and earthquake data, are given. The velocity distribution of the crust is regarded as a continuous function of the spatial coordinates without parametrization of the velocity model ahead, so that the inversion solution would not be influenced by different parametrization procedures. The expressions of integration kernels, which relates the two kinds of data sets, are also given. The authors have processed the observed data in Tangshan earthquake region by the method proposed in this paper, and obtained the tomographic results of the middle and upper crust structures in this region. The comparison of these results with the result obtained only by the explosion data, has also been made.  相似文献   

An analytical method for determining shear stiffness of an inclined grouted bolt installed across an open discontinuity     

B. Stimpson 《Geotechnical and Geological Engineering》1987,5(3):299-305

Summary The shear stiffness of a grouted, rock bolt intersecting a discontinuity controls the amount of shear movement that can occur for a given shear force. In this paper an analytical model is developed for estimating the shear stiffness of a single bolt as a function of bolt inclination, hole and bolt diameter, bolt, grout and rock Young's moduli, and aperture (opening) across the discontinuity, and sensitivity studies conducted to determine the most significant of these variables as predicted by the model.  相似文献   

Centrifuge Modeling of Rock Slopes Susceptible to Block Toppling   总被引：2，自引：0，他引：2  

J. H. Zhang  Z. Y. Chen  X. G. Wang 《Rock Mechanics and Rock Engineering》2007,40(4):363-382

Summary This paper presents the results of centrifuge tests that were aimed at validating the Goodman-Bray method for rock slope toppling analysis. The Goodman-Bray method was extended by the authors to accommodate non-persistent basal planes of rock columns. Two gypsum column models, with and without anchors were used to represent the failure modes. Measured critical centrifuge accelerations were in agreement with the results obtained from numerical modeling. A background of the toppling slope failures associated with a large hydropower project in China instigated the need for the centrifuge study. The centrifuge model tests used an artificial rock. The observed failure mode did not follow a straight failure plane as proposed by Goodman and Bray. The failures revealed a bi-planar slip surface with a deep-seated portion near the toe of the slope. The outcomes of the centrifuge tests illustrated the need to search for the critical failure surface when performing a toppling analysis. The search technique is similar to that usually performed in a conventional sliding analysis.  相似文献   

Experimental and numerical study of soil-reinforcement effects on the low-strain stiffness and bearing capacity of shallow foundations     

Wilson Chung  Giovanni Cascante 《Geotechnical and Geological Engineering》2007,25(3):265-281

This paper presents results of meticulous laboratory testing and numerical simulations on the effect of reinforcement on the low-strain stiffness and bearing capacity of shallow foundations on dry sand. The effect of the location and the number of reinforcement layers is studied in the laboratory, whereas numerical simulations are used to study the reinforcement-foundation interaction. Laboratory tests show an increase of 100, 200, and 275% not only in bearing capacity but also in low-strain stiffness (linear load–displacement behaviour) of a square foundation when one, two, and three layers of reinforcement are used, respectively. The specimen preparation technique is found to be crucial for the repeatability and reliability of the laboratory results (less than 5% variability). Numerical simulations demonstrate that if reinforcements are placed up to a depth of one footing width (B) below the foundation, better re-distribution of the load to deeper layers is achieved, thus reducing the stresses and strains underneath the foundation. Numerical simulations and experimental results clearly identify a critical zone between 0.3 and 0.5B, where maximum benefits not only on the bearing capacity but also on the low-strain stiffness of the foundation are obtained. Therefore, soil reinforcement can also be used to reduce low-strain vibrations of foundations.  相似文献