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

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.

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Sliding response of gravity dams including vertical seismic accelerations

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Earthquake engineering and engineering Vibration 2003年第2期2卷 189-200页

作者： Constantin Christopoulos PierreLéger André Filiatrault department of Civil engineering University of TorontoCanada Assistant Professor department of Civil engineering Ecole PolytechniqueMontrealCanada Professor department of Civil Structural and Environmental EngineeringUniversity at BuffaloUSA Professor

Seismic safety assessment of gravity dams has become a major concern in many regions of the world while the effects of vertical seismic accelerations on the response of structures remain poorly *** paper first investigates the effect of including vertical accelerations in the sliding response analysis of gravity dams subjected to a range of historical ground motion records separated in two groups according to their source-to-site *** showed that the incidence of vertical accelerations on the sliding response of gravity dams is significantly higher for near-source records than for far- source *** pseudo-static 30% load combination rule,commonly used in practice to account for the non-simultaneous occurrence of the peak horizontal and vertical accelerations,yielded good approximations of the minimum safety factors against sliding computed from time-history analyses.A method for empirically estimating the vertical response spectra based on horizontal spectra,accounting for the difference in frequency content and amplitudes between the two components is *** from analyses using spectrum compatible horizontal and vertical synthetic records also approximated well the sliding response of a gravity dam subjected to series of simultaneous horizontal and vertical historical earthquake records.

关键词： vertical accelerations sliding gravity dams synthetic accelerograms pseudo-static combinations frequency

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Analytical solutions for dynamic pressures of coupling fluid-solid-porous medium due to P wave incidence

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Earthquake engineering and engineering Vibration 2004年第2期3卷 263-271页

作者：王进廷张楚汉金峰 department of Hydraulic engineering Tsinghua UniversityBeijing 100084China Assistant Professor department of Hydraulic engineering Tsinghua UniversityBeijing 100084China Professor

Wave reflection and refraction in layered media is a topic closely related to seismology,acoustics,geophysics and earthquake *** solutions for wave reflection and refraction coefficients in multi-layered media subjected to P wave incidence from the elastic half-space are derived in terms of displacement *** system is composed of ideal fluid,porous medium,and underlying elastic *** numerical examples,the effects of porous medium and the incident wave angle on the dynamic pressures of ideal fluid are *** results show that the existence of the porous medium,especially in the partially saturated case,may significantly affect the dynamic pressures of the overlying fluid.

关键词： porous medium ideal fluid dynamic pressure elastic half-space layered media P wave reflection refraction

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Disbond detection with piezoelectric wafer active sensors in RC structures strengthened with FRP composite overlays

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Earthquake engineering and engineering Vibration 2003年第2期2卷 213-223页

作者： Victor Giurgiutiu Kent Harries Michael Petrou Joel Bost Josh B.Quattlebaum department of Mechanical engineering University of South CarolinaUSA Associate Professor department of Civil and Environmental engineering University of South CarolinaUSA Assistant Professor department of Civil and Environmental engineering University of South CarolinaUSA Associate Professor department of Mechanical engineering University of South CarolinaUSA Undergraduate Research Assistant department of Civil and Environmental engineering University of South CarolinaUSA Graduate Research Assistant

The capability of embedded piezoelectric wafer active sensors(PWAS)to perform in-situ nondestructive evaluation(NDE)for structural health monitoring(SHM)of reinforced concrete(RC)structures strengthened with fiber reinforced polymer(FRP)composite overlays is ***,the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite *** was found that the presence of a disbond crack drastically changes the electromecfianical(E/M)impedance spectrum lneasurcd at the PWAS *** spectral changes depend on the distance between the PWAS and the crack ***,large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer(CFRP)composite *** beam was subject to an accelerated fatigue load regime in a three-point bending configuration up to a total of 807,415 *** these fatigue tests,the CFRP overlay experienced disbonding beginning at about 500,000 *** PWAS were able to detect the disbonding before it could be reliably seen by visual *** correlation between the PWAS readings and the position and extent of disbond damage was *** preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite overlays.

关键词： FRP composite overlays composite strengthening and rehabilitation structural health monitoring piezoelectric wafer active sensors E/M impedance aging infrastructure disbond damage PWAS

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Study of narrow waterways congestion based on automatic identification system(AIS)data:A case study of Houston Ship Channel

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Journal of Ocean engineering and Science 2022年第6期7卷 578-595页

作者： Masood Jafari Kang Sepideh Zohoori Maryam Hamidi Xing Wu Research assistant Department of Industrial EngineeringLamar University2607 Cherry Engineering BuildingBeaumontTX 77710United States assistant professor Department of Industrial EngineeringCenter for Advances in Port ManagementLamar University2210 Cherry Engineering BuildingBeaumontTX 77710United States Associate professor Department of Civil and Environmental EngineeringLamar University2032 Cherry Engineering BuildingBeaumontTX 77710United States

Using automatic identification system(AIS)data,this article first has extended the definition of three widely used roadway congestion indices to maritime transportation systems(MTS),traffic speed index(TSI),traffic rate index(TRI),and dwell time index(DTI).Next,a methodology is developed to measure the indices based on AIS data,considering various factors,including path geometry,time of day,and the type and size of vessels,and finally the method has been applied to the AIS data of the Houston Ship Channel(HSC)to evaluate the applicability in real *** results show that although average TSI and TRI cannot represent waterway congestion,the real-time values(rather than the average)at the micro level can help finding location,time,and severity of traffic ***,while TSI and TRI have shortcomings,both average and real-time dwell time index(DTI)can quantify traffic congestion and highlight severity in different waterway segments for different types of *** congestion happens at some narrow waterways,vessels need to wait at sea buoy or docks,thus dwell time index(DTI)can quantify traffic congestion better than in-transit indices such as travel speed,*** to HSC DTI,most tankers experience long waiting times at the sea buoy and Galveston Bay,while cargo vessels experience delays at Bayport and Barbour’s Cut *** paper helps the decision-makers quantify congestion in different sections of a waterway and provides measures to compare congestion for national competing projects at different waterways.

关键词： Maritime transport system Waterway congestion Quantifying congestion AIS data Houston Ship Channel

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Probabilistic seismic response and reliability assessment of isolated bridges

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Earthquake engineering and engineering Vibration 2005年第1期4卷 95-106页

作者： Giuseppe Carlo Marano department of Environmental engineering and Sustainable Development Technical University of BariTarantoItalyAssistantProfessor

Bridge seismic isolation strategy is based on the reduction of shear forcestransmitted from the superstructure to the piers by two means: shifting natural period andearthquake input energy reduction by dissipation concentrated in protection devices. In this paper,a stochastic analysis of a simple isolated bridge model for different bridge and device parametersis conducted to assess the efficiency of this seismic protection strategy. To achieve this aim, asimple nonlinear softening constitutive law is adopted to model a wide range of isolation devices,characterized by only three essential mechanical parameters. As a consequence of the random natureof seismic motion, a probabilistic analysis is carried out and the time modulated Kanai-Tajimistochastic process is adopted to represent the seismic action. The response covariance in the statespace is obtained by solving the Lyapunov equation for a stochastic linearized system. After asensitivity analysis, the failure probability referred to extreme displacement and the mean value ofdissipated energy are assessed by using the introduced stochastic indices of seismic bridgeprotection efficiency. A parametric analysis for protective devices with different mechanicalparameters is developed for a proper selection of parameters of isolation devices under differentsituations.

关键词： bridge seismic isolation stochastic analysis nonlinear softeningconstitutive law reliability assessment

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Grey Wolf Optimizer to Real Power Dispatch with Non-Linear Constraints

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Computer Modeling in engineering & Sciences 2018年第4期115卷 25-45页

作者： G.R.Venkatakrishnan R.Rengaraj S.Salivahanan assistant professor Department of Electrical and Electronics EngineeringSSN College of EngineeringChennai-603110India Associate professor Department of Electrical and Electronics EngineeringSSN College of EngineeringChennai-603110India professor Department of Electronics and Communication EngineeringSSN College of EngineeringChennai-603110India

A new and efficient Grey Wolf Optimization(GWO)algorithm is implemented to solve real power economic dispatch(RPED)problems in this *** nonlinear RPED problem is one the most important and fundamental optimization problem which reduces the total cost in generating real power without violating the *** methods can solve the ELD problem with good solution quality with assumptions assigned to fuel cost curves without which these methods lead to suboptimal or infeasible *** behavior of grey wolves which is mimicked in the GWO algorithm are leadership hierarchy and hunting *** leadership hierarchy is simulated using four types of grey *** addition,searching,encircling and attacking of prey are the social behaviors implemented in the hunting *** GWO algorithm has been applied to solve convex RPED problems considering the all possible *** results obtained from GWO algorithm are compared with other state-ofthe-art algorithms available in the recent *** is found that the GWO algorithm is able to provide better solution quality in terms of cost,convergence and robustness for the considered ELD problems.

关键词： Grey wolf optimization(GWO) constraints power generation dispatch evolutionary computation computational complexity algorithms

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Effect of types of reinforcement on plastic hinge rotation parameters of RC beams under pushover and cyclic loading

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Earthquake engineering and engineering Vibration 2015年第3期14卷 503-516页

作者： V.V.S.Surya Kumar Dadi Pankaj Agarwal department of Civil engineering Institute of Technology Guru Ghasidas Vishwavidyalaya Bilaspur (C.G.) India Assistant Professor department of Earthquake engineering Indian Institute of Technology Roorkee

Experimental evaluation of reinforced concrete beam specimens with different characteristics of reinforcement subjected to pushover and cyclic loading is *** hinge rotation parameters are determined based on the idealization of pushover and hysteresis curves of reinforced concrete beam specimens constructed in two percentage of reinforcement(0.471%and 0.71%) with different ductile *** experimental test results provide a clear demarcation of the effect of types of loading and the types of reinforcement on the nonlinear performance characteristics of beam *** results are helpful to update the nonlinear modeling parameters of beam components for the specific type of reinforcement used in the construction of a *** updated non-linear modeling parameters of beam components in lumped plasticity model are compared with the values of ASCE/SEI 41-06(2007) used for the performance based design of structures.

关键词： concrete structures pushover loads cyclic loads hy

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Analytical exploration of γ-function explicit method for pseudodynamic testing of nonlinear systems

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Earthquake engineering and engineering Vibration 2005年第1期4卷 117-127页

作者：张顺益宋裕祺 department of Civil engineering National Taipei University of Technology Chinese Taipei 106-08AssociateProfessor department of Civil engineering National Taipei University of Technology Chinese Taipei 106-08 assistant professor

It has been well studied that the γ-function explicit method can be effective in providing favorable numerical dissipation for linear elastic systems. However, its performance for nonlinear systems is unclear due to a lack of analytical evaluation techniques. Thus, a novel technique is proposed herein to evaluate its efficiency for application to nonlinear systems by introducing two parameters to describe the stiffness change. As a result, the numerical properties and error propagation characteristics of the γ-function explicit method for the pseudodynamic testing of a nonlinear system are analytically assessed. It is found that the upper stability limit decreases as the step degree of nonlinearity increases; and it increases as the current degree of nonlinearity increases. It is also shown that this integration method provides favorable numerical dissipation not only for linear elastic systems but also for nonlinear systems. Furthermore, error propagation analysis reveals that the numerical dissipation can effectively suppress the severe error propagation of high frequency modes while the low frequency responses are almost unaffected for both linear elastic and nonlinear systems.

关键词： pseudodynamic test nonlinear error propagation numerical dissipation

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Seismic response analysis of arch dam-water-rock foundation systems

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Earthquake engineering and engineering Vibration 2004年第2期3卷 283-291页

作者：杜修力王进廷 Beijing key laboratory of earthquake engineering and struetural retrofit Beijing University of TechnologyBeijing 100022China Professor department of Hydraulic engineering Tsinghua University Beijing 100084China Assistant Professor

The effect of water compressibility on the seismic responses of arch dams is not well *** this paper,a numerical model is developed with rigorous representation of the dynamic interaction between arch dam-water- rock *** model is applied to the seismic response analysis of an arch dam with a height of 292m designed to a seismic intensity of *** is shown that consideration of the water compressibility clearly decreases the stress responses at key positions of the dam,while the added mass model gives a conservative estimate.

关键词： seismic response arch dam water compressibility dam-water-foundation interaction added mass model finite element method

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