robert mullen | University of South Carolina (original) (raw)

Papers by robert mullen

Research paper thumbnail of An Interior-Constraint BEM for Regularization of Problems with Improper Boundary Conditions

A well-posed problem in analysis of elastic bodies requires the definition of appropriate constra... more A well-posed problem in analysis of elastic bodies requires the definition of appropriate constrains of the boundary to prevent rigid body motion. However, one is sometimes presented with the problem of non-self-equilibrated tractions on an elastic body that will cause rigid body motion, while the boundary should remain unconstrained. One such case is the analysis of multi-particle dynamics where the solution is obtained in a quasi-static approach. In such cases, the motion of the particles is governed by the dynamic equilibrium while the contact forces between particles may be computed from elastostatic solutions. This paper presents two regularization methods of Interior-Constraint Boundary Element techniques for elastostatic analysis with improper boundary supports. In the proposed method rigid body modes are eliminated by imposing constrains on the interior of an elastic body. This is accomplished through simultaneously solving the governing Boundary Integral Equation and Somigl...

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Research paper thumbnail of Geometric misfitting in trusses and frames: an interval-based approach

International Journal of Reliability and Safety, 2015

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Research paper thumbnail of Interval finite elements for nonlinear material problems

Applications of Statistics and Probability in Civil Engineering, 2011

Interval Finite Elements (IFEM) has been developed to handle load, material, and geometric uncert... more Interval Finite Elements (IFEM) has been developed to handle load, material, and geometric uncertainty introduced in a form of interval numbers defined by their lower and upper bounds. However, previous methods limited to linear problems. The present work introduces an IFEM formulation for problems involving material non-linearity. The algorithm is based on the previously developed high accuracy interval solutions. The solution is obtained using an iterative method that generates successive approximations to the secant stiffness. Examples are presented to illustrate the behavior of the formulation.

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Research paper thumbnail of Solution of uncertain linear systems of equations with probability-box parameters

International Journal of Reliability and Safety, 2018

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Research paper thumbnail of Geometric Misfitting in Structures–An Interval-Based Approach

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Research paper thumbnail of Non-Linear Analysis of Beams with Large Deflections–An Interval Finite Element Approach

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Research paper thumbnail of Nonlinear Interval Finite Elements for Beams

Vulnerability, Uncertainty, and Risk, 2014

The present study focuses on the development of Nonlinear Interval Finite Elements (NIFEM) for be... more The present study focuses on the development of Nonlinear Interval Finite Elements (NIFEM) for beam and frame problems. Three constitutive models have been used in the present study viz. bilinear, Ramberg-Osgood, and cubic models, to illustrate the development of Nonlinear Interval Finite Elements (NIFEM). Interval Finite Element Method (IFEM) has been developed to handle load, material, and geometric uncertainties that are introduced in a form of interval numbers defined by their lower and upper bounds. However, the scope of the previous methods was limited to linear problems. The present work introduces an IFEM formulation for problems involving material nonlinearity under interval loads. The algorithm is based on the previously developed high accuracy interval solutions. An iterative method that generates successive approximations to the secant stiffness is introduced. Examples are presented to illustrate the behavior of the formulation. It is shown that bounding the response of non-linear structures for a large number of load combinations can be computed at a reasonable computational cost.

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Research paper thumbnail of Better Construction Project Management through Better Scheduling

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Research paper thumbnail of Interval Householder Method for Complex Linear Systems

Reliable Computing, 2006

We consider interval Householder method for outer estimation of solution sets for interval linear... more We consider interval Householder method for outer estimation of solution sets for interval linear algebraic systems with complex interval parameters. A numerical example is presented showing that interval Householder method may work better than interval Gaussian algorithm.

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Research paper thumbnail of Nonlinear Fea of Frames Under Interval Material and Load Uncertainty

ASCE-ASME J. Risk and Uncert. in Engrg. Sys., Part B: Mech. Engrg., 2015

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Research paper thumbnail of Mechanical properties of thick, surface micromachined polysilicon films

Polycrystalline silicon is the most widely used structural material for surface micromachined mic... more Polycrystalline silicon is the most widely used structural material for surface micromachined microelectromechanical systems (MEMS). There are many advantages to using thick polysilicon films; however, due to process equipment limitations, these devices are typically fabricated from polysilicon films less than 3 μm thick. In this work, microelectromechanical test structures were designed and processed from thick (up to 10 μm) undoped

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Research paper thumbnail of A new interval finite element formulation with the same accuracy in primary and derived variables

This paper addresses the main challenge in interval computations, which is to minimize the overes... more This paper addresses the main challenge in interval computations, which is to minimize the overestimation in the target quantities. When sharp enclosures for the primary variables are achievable in a given formulation, such as the displacements in interval finite elements, the calculated enclosures for secondary or derived quantities, such as stresses and strains, are usually obtained with significantly increased overestimation. One should follow special treatment in order to decrease the overestimation in the derived quantities. In this work, we introduce a new formulation for Interval Finite Element Methods (IFEM) where both primary and derived quantities of interest are included in the original uncertain system as primary variables. The formulation is based on the variational approach and the Lagrange multiplier method by imposing certain constraints that allows the Lagrange multipliers themselves to be the derived quantities. Numerical results of this new formulation are illustrated in a number of example problems.

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Research paper thumbnail of Nonlinear Interval Finite Element for Structural Mechanics Problems

Abstract: Interval Finite Element Method (IFEM) has been developed to handle load, material, and ... more Abstract: Interval Finite Element Method (IFEM) has been developed to handle load, material, and geometric uncertainties that are introduced in a form of interval numbers defined by their lower and upper bounds. However, the scope of the previous methods was limited to linear problems. The present work introduces an IFEM formulation for problems involving material nonlinearity. The algorithm is based on the previously developed high accuracy interval solutions.

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Research paper thumbnail of Primary and Derived Variables with the Same Accuracy in Interval Finite Elements

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Research paper thumbnail of Geometric misfitting in trusses and frames: an interval -based approach

In this work, the issue of predicting structural behaviour in the presence of geometric uncertain... more In this work, the issue of predicting structural behaviour in the
presence of geometric uncertainty arising out of fabrication errors and/or thermal changes in trusses and frames is addressed. Geometric uncertainty is expressed as deviations of actual dimensions of system components from their
corresponding nominal dimensions (misfitting) and is expressed in interval form. Such geometric uncertainty is converted into an equivalent nodal load uncertainty. The present work eliminates the element force overestimation
resulting in the previous formulation of Muhanna et al. The mixed interval finite element formulation developed earlier by Rama Rao et al. is utilised to obtain sharp bounds to displacements and element forces in the presence of
geometric, material and load uncertainties. The present work also computes an exact enclosure to the final system geometry. Results are illustrated in example
problems. Dependency due to the presence of geometric uncertainty is eliminated using the M matrix approach developed earlier by Mullen and Muhanna.

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Research paper thumbnail of Geometric Misfitting in Structures–An Interval-Based Approach

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Research paper thumbnail of Numerical and analytical study of fluid dynamic forces in seals and bearings

Journal of vibration, …, 1988

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Research paper thumbnail of Experimental and computational methods for shape memory alloys

15th ASCE …, 2002

... EXPERIMENTAL AND COMPUTATIONAL METHODS FOR SHAPE MEMORY ALLOYSGuruprasad Ramanathan1 Dr.Vassi... more ... EXPERIMENTAL AND COMPUTATIONAL METHODS FOR SHAPE MEMORY ALLOYSGuruprasad Ramanathan1 Dr.Vassilis P. Panoskaltsis2, ASCE Member Dr. Robert L. Mullen3, ASCE Member Dr. Gerhard Welsch4 ABSTRACT ...

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Research paper thumbnail of Introductory Remarks on Reliable Engineering Computing

Reliable Computing, 2006

Introductory Remarks on Reliable Engineering Computing RAMON E. MOORE 40 Orchard Dr., Worthington... more Introductory Remarks on Reliable Engineering Computing RAMON E. MOORE 40 Orchard Dr., Worthington, OH 43085, USA, e-mail: rmoore17@columbus.rr.com ... 11. Lin, X., Melo, OT, Hastie,DR, et al.: Case Study of Ozone Production in a Rural Area of Central Ontario, Atmos. ...

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Research paper thumbnail of Discussion of “ Digital Imaging Concepts and Applications in Pavement Management ” by Stephen G. Ritchie (May/June, 1990, Vol. 116, No. 3)

Journal of Transportation Engineering, 1992

... Discussion of "Digital Imaging Concepts and Applications in Pavement Management". S... more ... Discussion of "Digital Imaging Concepts and Applications in Pavement Management". See original paper by J. Adolfo Acosta , (Grad. Student, Dept. of Civ. Engrg., Case Western Reserve Univ., Cleveland, OH 44106) , Robert L. Mullen , (Assoc. Prof., Dept. of Civ. ...

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Research paper thumbnail of An Interior-Constraint BEM for Regularization of Problems with Improper Boundary Conditions

A well-posed problem in analysis of elastic bodies requires the definition of appropriate constra... more A well-posed problem in analysis of elastic bodies requires the definition of appropriate constrains of the boundary to prevent rigid body motion. However, one is sometimes presented with the problem of non-self-equilibrated tractions on an elastic body that will cause rigid body motion, while the boundary should remain unconstrained. One such case is the analysis of multi-particle dynamics where the solution is obtained in a quasi-static approach. In such cases, the motion of the particles is governed by the dynamic equilibrium while the contact forces between particles may be computed from elastostatic solutions. This paper presents two regularization methods of Interior-Constraint Boundary Element techniques for elastostatic analysis with improper boundary supports. In the proposed method rigid body modes are eliminated by imposing constrains on the interior of an elastic body. This is accomplished through simultaneously solving the governing Boundary Integral Equation and Somigl...

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Research paper thumbnail of Geometric misfitting in trusses and frames: an interval-based approach

International Journal of Reliability and Safety, 2015

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Research paper thumbnail of Interval finite elements for nonlinear material problems

Applications of Statistics and Probability in Civil Engineering, 2011

Interval Finite Elements (IFEM) has been developed to handle load, material, and geometric uncert... more Interval Finite Elements (IFEM) has been developed to handle load, material, and geometric uncertainty introduced in a form of interval numbers defined by their lower and upper bounds. However, previous methods limited to linear problems. The present work introduces an IFEM formulation for problems involving material non-linearity. The algorithm is based on the previously developed high accuracy interval solutions. The solution is obtained using an iterative method that generates successive approximations to the secant stiffness. Examples are presented to illustrate the behavior of the formulation.

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Research paper thumbnail of Solution of uncertain linear systems of equations with probability-box parameters

International Journal of Reliability and Safety, 2018

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Research paper thumbnail of Geometric Misfitting in Structures–An Interval-Based Approach

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Research paper thumbnail of Non-Linear Analysis of Beams with Large Deflections–An Interval Finite Element Approach

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Research paper thumbnail of Nonlinear Interval Finite Elements for Beams

Vulnerability, Uncertainty, and Risk, 2014

The present study focuses on the development of Nonlinear Interval Finite Elements (NIFEM) for be... more The present study focuses on the development of Nonlinear Interval Finite Elements (NIFEM) for beam and frame problems. Three constitutive models have been used in the present study viz. bilinear, Ramberg-Osgood, and cubic models, to illustrate the development of Nonlinear Interval Finite Elements (NIFEM). Interval Finite Element Method (IFEM) has been developed to handle load, material, and geometric uncertainties that are introduced in a form of interval numbers defined by their lower and upper bounds. However, the scope of the previous methods was limited to linear problems. The present work introduces an IFEM formulation for problems involving material nonlinearity under interval loads. The algorithm is based on the previously developed high accuracy interval solutions. An iterative method that generates successive approximations to the secant stiffness is introduced. Examples are presented to illustrate the behavior of the formulation. It is shown that bounding the response of non-linear structures for a large number of load combinations can be computed at a reasonable computational cost.

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Research paper thumbnail of Better Construction Project Management through Better Scheduling

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Interval Householder Method for Complex Linear Systems

Reliable Computing, 2006

We consider interval Householder method for outer estimation of solution sets for interval linear... more We consider interval Householder method for outer estimation of solution sets for interval linear algebraic systems with complex interval parameters. A numerical example is presented showing that interval Householder method may work better than interval Gaussian algorithm.

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Research paper thumbnail of Nonlinear Fea of Frames Under Interval Material and Load Uncertainty

ASCE-ASME J. Risk and Uncert. in Engrg. Sys., Part B: Mech. Engrg., 2015

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Research paper thumbnail of Mechanical properties of thick, surface micromachined polysilicon films

Polycrystalline silicon is the most widely used structural material for surface micromachined mic... more Polycrystalline silicon is the most widely used structural material for surface micromachined microelectromechanical systems (MEMS). There are many advantages to using thick polysilicon films; however, due to process equipment limitations, these devices are typically fabricated from polysilicon films less than 3 μm thick. In this work, microelectromechanical test structures were designed and processed from thick (up to 10 μm) undoped

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Research paper thumbnail of A new interval finite element formulation with the same accuracy in primary and derived variables

This paper addresses the main challenge in interval computations, which is to minimize the overes... more This paper addresses the main challenge in interval computations, which is to minimize the overestimation in the target quantities. When sharp enclosures for the primary variables are achievable in a given formulation, such as the displacements in interval finite elements, the calculated enclosures for secondary or derived quantities, such as stresses and strains, are usually obtained with significantly increased overestimation. One should follow special treatment in order to decrease the overestimation in the derived quantities. In this work, we introduce a new formulation for Interval Finite Element Methods (IFEM) where both primary and derived quantities of interest are included in the original uncertain system as primary variables. The formulation is based on the variational approach and the Lagrange multiplier method by imposing certain constraints that allows the Lagrange multipliers themselves to be the derived quantities. Numerical results of this new formulation are illustrated in a number of example problems.

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Research paper thumbnail of Nonlinear Interval Finite Element for Structural Mechanics Problems

Abstract: Interval Finite Element Method (IFEM) has been developed to handle load, material, and ... more Abstract: Interval Finite Element Method (IFEM) has been developed to handle load, material, and geometric uncertainties that are introduced in a form of interval numbers defined by their lower and upper bounds. However, the scope of the previous methods was limited to linear problems. The present work introduces an IFEM formulation for problems involving material nonlinearity. The algorithm is based on the previously developed high accuracy interval solutions.

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Research paper thumbnail of Primary and Derived Variables with the Same Accuracy in Interval Finite Elements

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Research paper thumbnail of Geometric misfitting in trusses and frames: an interval -based approach

In this work, the issue of predicting structural behaviour in the presence of geometric uncertain... more In this work, the issue of predicting structural behaviour in the
presence of geometric uncertainty arising out of fabrication errors and/or thermal changes in trusses and frames is addressed. Geometric uncertainty is expressed as deviations of actual dimensions of system components from their
corresponding nominal dimensions (misfitting) and is expressed in interval form. Such geometric uncertainty is converted into an equivalent nodal load uncertainty. The present work eliminates the element force overestimation
resulting in the previous formulation of Muhanna et al. The mixed interval finite element formulation developed earlier by Rama Rao et al. is utilised to obtain sharp bounds to displacements and element forces in the presence of
geometric, material and load uncertainties. The present work also computes an exact enclosure to the final system geometry. Results are illustrated in example
problems. Dependency due to the presence of geometric uncertainty is eliminated using the M matrix approach developed earlier by Mullen and Muhanna.

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Research paper thumbnail of Geometric Misfitting in Structures–An Interval-Based Approach

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Numerical and analytical study of fluid dynamic forces in seals and bearings

Journal of vibration, …, 1988

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Research paper thumbnail of Experimental and computational methods for shape memory alloys

15th ASCE …, 2002

... EXPERIMENTAL AND COMPUTATIONAL METHODS FOR SHAPE MEMORY ALLOYSGuruprasad Ramanathan1 Dr.Vassi... more ... EXPERIMENTAL AND COMPUTATIONAL METHODS FOR SHAPE MEMORY ALLOYSGuruprasad Ramanathan1 Dr.Vassilis P. Panoskaltsis2, ASCE Member Dr. Robert L. Mullen3, ASCE Member Dr. Gerhard Welsch4 ABSTRACT ...

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Research paper thumbnail of Introductory Remarks on Reliable Engineering Computing

Reliable Computing, 2006

Introductory Remarks on Reliable Engineering Computing RAMON E. MOORE 40 Orchard Dr., Worthington... more Introductory Remarks on Reliable Engineering Computing RAMON E. MOORE 40 Orchard Dr., Worthington, OH 43085, USA, e-mail: rmoore17@columbus.rr.com ... 11. Lin, X., Melo, OT, Hastie,DR, et al.: Case Study of Ozone Production in a Rural Area of Central Ontario, Atmos. ...

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Research paper thumbnail of Discussion of “ Digital Imaging Concepts and Applications in Pavement Management ” by Stephen G. Ritchie (May/June, 1990, Vol. 116, No. 3)

Journal of Transportation Engineering, 1992

... Discussion of "Digital Imaging Concepts and Applications in Pavement Management". S... more ... Discussion of "Digital Imaging Concepts and Applications in Pavement Management". See original paper by J. Adolfo Acosta , (Grad. Student, Dept. of Civ. Engrg., Case Western Reserve Univ., Cleveland, OH 44106) , Robert L. Mullen , (Assoc. Prof., Dept. of Civ. ...

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