检索结果-南通市图书馆

A three-dimensional coupled numerical model of nonlinear waves in a harbor

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2008年第12期51卷 2185-2196页

作者： L.G.THAM department of civil and structural engineering The University of Hong Kong

A 3-D time-domain numerical coupled model for nonlinear waves acting on a ship in a harbor has been developed in the present *** whole domain is divided into the inner domain and the outer *** inner domain is the area around the ship,where the flow is expressed by the Laplace equation and numerically solved by the finite element *** other area is the outer domain,where the flow is described by the higher-order Boussinesq equations and numerically solved by the finite difference *** matching conditions on the interfaces between the inner domain and the outer domain,the procedure of coupled solution,the length of common domain and the mesh generation in the inner domain are discussed in *** other coupled model with the flow in the inner domain governed by the simplified linear Euler equations and relevant physical experiment are adopted to validate the present coupled model,and it is shown that the numerical results of the present model agree with the experimental data,so the present model can be used for the study on the effect of nonlinear waves acting on a fixed ship in a large area and provide a reference for the time-domain simulation of nonlinear wave forces on an arbitrary object in a large harbor and the 3-D district computation in the future.

关键词： 3-D coupled model nonlinear waves boussinesq equations laplace equation

Towards multiple hazard resilient bridges:a methodology for modeling frequent and infrequent time-varying loads Part I,Comprehensive reliability and partial failure probabilities

在线全文

学校读者我要写书评

暂无评论

Earthquake engineering and engineering Vibration 2012年第3期11卷 293-301页

作者： Zach Liang George C.Lee department of Mechanical and Aerospace engineering University at Buffalo department of civil Structural and Environmental EngineeringUniversity at Buffalo

The current AASHTO load and resistance factor design （LRFD） guidelines are formulated based on bridge reliability, which interprets traditional design safety factors into more rigorously deduced factors based on the theory of probability. This is a major advancement in bridge design specifications. However, LRFD is only calibrated for dead and live loads. In cases when extreme loads are significant, they need to be individually assessed. Combining regular loads with extreme loads has been a major challenge, mainly because the extreme loads are time variables and cannot be directly combined with time invariant loads to formulate the probability of structural failure. To overcome these difficulties, this paper suggests a methodology of comprehensive reliability, by introducing the concept of partial failure probability to separate the loads so that each individual load combination under a certain condition can be approximated as time invariant. Based on these conditions, the extreme loads （also referred to as multiple hazard or MH loads） can be broken down into single effects. In Part II of this paper, a further breakdown of these conditional occurrence probabilities into pure conditions is discussed by using a live truck and earthquake loads on a bridge as an example. There are three major steps in establishing load factors from MH load distributions：（1） formulate the failure probabilities; （2） normalize various load distributions; and （3） establish design limit state equations. This paper describes the formulation of the failure probabilities of single and combined loads.

关键词： multiple hazards bridge probability-based design comprehensive reliability partial failure probability

同方期刊数据库

Dynamic earth pressure on rigid retaining walls induced by a neighboring machine foundation,by the meshless local Petrov-Galerkin method

在线全文

学校读者我要写书评

暂无评论

Earthquake engineering and engineering Vibration 2015年第4期14卷 647-661页

作者： Mehdi Veiskarami Arash Bahar Erfan Zandi Lak Geotechnical engineering Division Department of Civil EngineeringUniversity of Guilan department of civil and Environmental engineering School of Engineering No.1Shiraz University structural engineering Division Department of Civil EngineeringUniversity of Guilan

Dynamic earth pressure induced by machine foundations on a neighboring retaining wall is analyzed with emphasis on factors which control the intensity and location of the design forces. The meshless local Petrov-Galerkin (MLPG) method is used to analyze the problem for a variety of retaining wall and machine foundation geometries. The soil medium is assumed to be homogeneous and visco-elastic. The machine foundation is idealized as a harmonic sinusoidal dynamic force often encountered in practice. A number of analyses have been made to reveal the effect of the loading frequency, the location and size of the foundation and the soil shear wave velocity on the distribution and magnitude of the dynamic earth pressure. Results indicate that there is a critical frequency and a critical location for which the passive pressure takes the maxima in the entire duration of the dynamic load.

关键词： MLPG retaining wall dynamic loading visco-elastic soil machine foundation

Three-scale stochastic homogenization of elastic recycled aggregate concrete based on nano-indentation digital images

在线全文

学校读者我要写书评

暂无评论

Frontiers of structural and civil engineering 2018年第4期12卷 461-473页

作者： Chen WANG Yuching WU Jianzhuang XIAO department of structural engineering College of Civil EngineeringTongji UniversityShanghai 200092China

In this paper, three-scale stochastic elastic finite element analyses are made for recycled aggregate concrete (RAC) based on nano-indentation digital images. The elastic property of RAC contains uncertainties across scales. It has both theoretical and practical values to model and predict its mechanical performance. Based on homogenization theory, effective stochastic elastic moduli of RAC at three different scales are obtained using moving window technique, nano-indentation digital images, and Monte-Carlo method. It involves the generation of a large number of random realizations of microstructure geometry based on different volume fraction of the inclusions and other parameters. The mean value, coefficient of variation and probability distribution of the effective elastic moduli are computed considering the material multiscale structure. The microscopic randomness is taken into account, and correlations of RAC among five phases are investigated. The effective elastic properties are used to obtain the global behavior of a composite structure. It is indicated that the response variability can be considerably affected by replacement percentage of recycled aggregates.

关键词： RAC nano-indentation digital image multiscale microscopic randomness homogenization

Parallel finite element modeling of earthquake ground response and liquefaction

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Earthquake engineering and engineering Vibration 2004年第1期3卷 23-37页

作者：陆金池彭军 Ahmed Elgamal 杨朝晖 Kincho H.Law department of structural engineering University of California department of civil and Enviromental engineering Stanford University department of civil and Enviromental engineering Stanford University

Parallel computing is a promising approach to alleviate the computational demand in conducting large-scale finite element *** paper presents a numerical modeling approach for earthquake ground response and liquefaction using the parallel nonlinear finite element program,ParCYCLIC,designed for distributed-memory message-passing parallel computer *** ParCYCLIC,finite elements are employed within an incremental plasticity,coupled solid-fluid formulation,A constitutive model calibrated by physical tests represents the salient characteristics of sand liquefaction and associated accumulation of shear *** elements of the computational strategy employed in ParCYCLIC include the development of a parallel sparse direct solver,the deployment of an automatic domain decomposer,and the use of the Multilevel Nested Dissection algorithm for ordering of the finite element *** results of centrifuge test models using ParCYCLIC are *** results from grid models and geotechnical simulations show that ParCYCLIC is efficiently scalable to a large number of processors.

关键词： parallel finite element domain decomposition liquefaction parallel speedup earthquake site amplification

The effect of micro-structural uncertainties of recycled aggregate concrete on its global stochastic properties via finite pixel-element Monte Carlo simulation

在线全文

学校读者我要写书评

暂无评论

Frontiers of structural and civil engineering 2018年第4期12卷 474-489页

作者： Qingpeng MENG Yuching WU Jianzhuang XIAO department of structural engineering College of Civil EngineeringTongji UniversityShanghai 200092China

In this paper, the effect of micro-structural uncertainties of recycled aggregate concrete (RAC) on its global stochastic elastic properties is investigated via finite pixel-element Monte Carlo simulation. Representative RAC models are randomly generated with various distribution of aggregates. Based on homogenization theory, effects of recycled aggregate replacement rate, aggregate volume fraction, the unevenness of old mortar, proportion of old mortar, aggregate size and elastic modulus of aggregates on overall variability of equivalent elastic properties are investigated. Results are in a good agreement with experimental data in literature and finite pixel-element method saves the computation cost. It is indicated that the effect of mesoscopic randomness on global variability of elastic properties is considerable.

关键词： RAC Monte Carlo analysis stochastic finite pixel-element method homogenization coefficient of variation

Voronoi Based Discrete Least Squares Meshless Method for Heat Conduction Simulation in Highly Irregular Geometries

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical engineering 2016年第1期29卷 98-111页

作者： LABIBZADEH Mojtaba Assistant Professor of structural engineering Civil Engineering DepartmentFaculty of EngineeringShahid Chamran University

A new technique is used in Discrete Least Square Meshfree（DLSM） method to remove the common existing deficiencies of meshfree methods in handling of the problems containing cracks or concave boundaries. An enhanced Discrete Least Squares Meshless method named as VDLSM（Voronoi based Discrete Least Squares Meshless） is developed in order to solve the steady-state heat conduction problem in irregular solid domains including concave boundaries or cracks. Existing meshless methods cannot estimate precisely the required unknowns in the vicinity of the above mentioned boundaries. Conducted researches are limited to domains with regular convex boundaries. To this end, the advantages of the Voronoi tessellation algorithm are implemented. The support domains of the sampling points are determined using a Voronoi tessellation algorithm. For the weight functions, a cubic spline polynomial is used based on a normalized distance variable which can provide a high degree of smoothness near those mentioned above discontinuities. Finally, Moving Least Squares（MLS） shape functions are constructed using a varitional method. This straight-forward scheme can properly estimate the unknowns（in this particular study, the temperatures at the nodal points） near and on the crack faces, crack tip or concave boundaries without need to extra backward corrective procedures, i.e. the iterative calculations for modifying the shape functions of the nodes located near or on these types of the complex boundaries. The accuracy and efficiency of the presented method are investigated by analyzing four particular examples. Obtained results from VDLSM are compared with the available analytical results or with the results of the well-known Finite Elements Method（FEM） when an analytical solution is not available. By comparisons, it is revealed that the proposed technique gives high accuracy for the solution of the steady-state heat conduction problems within cracked domains or domains with concave boundaries a

关键词： Discrete Least Squares Meshless crack Voronoi tessellation concave boundaries Steady-state heat conduction.

Introspection on improper seismic retrofit of Basilica Santa Maria di Collemaggio after 2009 Italian earthquake

在线全文

学校读者我要写书评

暂无评论

Earthquake engineering and engineering Vibration 2011年第1期10卷 153-161页

作者： Gian Paolo Cimellaro Andrei M. Reinhorn Alessandro De Stefano department of structural & Geotechnical engineering (DISTR) Politecnico di Torino department of civil Structural & Environmental Engineering University at Buffalo The State University of New York

The 2009 L’Aquila, Italy earthquake highlighted the seismic vulnerability of historic masonry building structures due to improper ＂strengthening＂ retrofit work that has been done in the last 50 years. Italian seismic standards recommend the use of traditional reinforcement techniques such as replacing the original wooden roof structure with new reinforced concrete （RC） or steel elements, inserting RC tie-beams in the masonry and new RC floors, and using RC jacketing on the shear walls. The L’Aquila earthquake revealed the numerous limitations of these interventions, because they led to increased seismic forces （due to greater additional weight） and to deformation incompatibilities of the incorporated elements with the existing masonry walls. This paper provides a discussion of technical issues pertaining to the seismic retrofit of the Santa Maria di Collemaggio Basilica and in particular, the limitations of the last （2000） retrofit intervention. Considerable damage was caused to the church because of questionable actions and incorrect and improper technical choices.

关键词： seismic vulnerability historic masonry building wooden roof structure seismic retrofit L’Aquila earthquake

Probabilistic Lifetime Assessment of Marine Reinforced Concrete with Steel Corrosion and Cover Cracking

在线全文

学校读者我要写书评

暂无评论

China Ocean engineering 2011年第2期25卷 305-318页

作者：陆春华金伟良刘荣桂 Institute of structural engineering Zhejiang University department of civil engineering Jiangsu University

In order to study the durability behavior of marine reinforced concrete structure suffering from chloride attack, the structural service life is assumed to be divided into three critical stages, which can be characterized by steel corrosion and cover cracking. For each stage, a calculated model used to predict the lifetime is developed. Based on the definition of durability limit state, a probabilistic lifetime model and its time-dependent reliability analytical method are proposed considering the random natures of influencing factors. Then, the probabilistic lifetime prediction models are applied to a bridge pier located in the Hangzhou Bay with Monte Carlo simulation. It is found that the time to corrosion initiation to follows a lognormal distribution, while that the time from corrosion initiation to cover cracking t~ and the time for crack to develop from hairline crack to a limit crack width t2 can be described by Weibull distributions. With the permitted failure probability of 5.0%, it is also observed that the structural durability lifetime mainly depends on the durability life to and that the percentage of participation of the life to to the total service life grows from 61.5% to 83.6% when the cover thickness increases from 40 mm to 80 mm. Therefore, for any part of the marine RC bridge, the lifetime predictions and maintenance efforts should also be directed toward controlling the stage of corrosion initiation induced by chloride ion.

关键词： marine reinforced concrete chloride ingress steel corrosion cover cracking probabilistic lifetime