Gregory R. Miller

An object-oriented approach to structural analysis and design

Abstract This paper considers the application of an object-oriented perspective in developing software for structural engineering applications. A basic introduction to object-oriented programming is given followed by an overview of how issues of concurrency and persistence can be addressed and exploited within an object-oriented framework. A more in-depth presentation is then given of a structural analysis program being developed using an object-oriented approach, which provides a further illustration of the usefulness and potential of the object-oriented perspective.

An algorithmic framework for flexible finite element-based structural modeling

Abstract A framework is presented that provides new levels of computational flexibility for general finite element-based structural modeling. The approach is based on object-oriented programming methods in which the classes defining the framework represent both traditional and non-traditional finite element modeling abstractions. The framework supports a wide range of algorithmic methods and techniques: degree of freedom- and element-based, iterative and direct algorithms are accommodated for solving linear and non-linear problems in static and dynamic contexts. In order to adapt the solution to factors including the modeling assumptions, the required levels of efficiency and accuracy, and variations in a model in space and over time, algorithms can be selected and changed dynamically, and distinct algorithms can be used in different parts of a model. An evaluation of the framework using various criteria shows that in addition to enabling new kinds of efficiencies, it exhibits performance comparable to traditional implementations in executing fundamental computations.

Mitigating kinematic locking in the material point method

The material point method exhibits kinematic locking when traditional linear shape functions are used with a rectangular grid. The locking affects both the strain and the stress fields, which can lead to inaccurate results and nonphysical behavior. This paper presents a new anti-locking approach that mitigates the accumulation of fictitious strains and stresses, significantly improving the kinematic response and the quality of all field variables. The technique relies on the Hu-Washizu multi-field variational principle, with separate approximations for the volumetric and the deviatoric portions of the strain and stress fields. The proposed approach is validated using a series of benchmark examples from both solid and fluid mechanics, demonstrating the broad range of modeling possibilities within the MPM framework when combined with appropriate anti-locking techniques and algorithms.

Avalanche and landslide simulation using the material point method: flow dynamics and force interaction with structures

In this paper, the material point method (MPM) is presented as a tool for simulating large deformation, gravity-driven landslides. The primary goal is to assess the interaction of these flow-like events with the built environment. This includes an evaluation of earthen mounds when energy dissipating devices are placed in the path of a snow avalanche. The effectiveness of the embankments is characterized using displacement, velocity, mass, and energy measures. A second example quantifies the force interaction between a landslide and a square rigid column. Multiple slide approach angles are considered, and various aspects of the impact force are discussed.

3D Scene Reconstruction for Robotic Bridge Inspection

AbstractThis paper provides a comparative study of two methods for reconstructing three-dimensional (3D) scenes from monocular two-dimensional (2D) images with respect to their applicability to rob...

Localized tensor-based solvers for interactive finite element applications using C++ and Java

This paper presents techniques for solving systems of equations arising in finite element applications using a localized, tensor-based approach. The approach is localized in that a major part of the solution responsibility is delegated to vector degree-of-freedom objects, rather than residing solely in a global solver working on a monolithic data structure. The approach is tensor-based in that the fundamental quantities used for computation are considered to be second-order tensors. The localized data structure strategy provides the benefits of an efficient sparse and symmetric storage scheme without requiring complex implementation code. The tensor-based aspect of the approach can bring substantial performance benefits by increasing the granularity at which solution algorithms deal with their data. Java and C++ implementations of interactive finite element programs are used to demonstrate performance that is competitive with other available solvers, especially in the case of problems for which interactive analysis is feasible on commonly available hardware.

An adaptable finite element modelling kernel

Abstract This paper describes a finite element kernel designed to provide high levels of adaptability and flexibility for modelling and analysis. The kernel is based on high-level abstractions that can be used to create a variety of interactive finite element-based modelling applications. The structure and functionality of the kernel are embedded in frameworks and classes of objects which encapsulate modelling and computational capabilities in modular form. Sample uses of the kernel are illustrated via prototype modelling applications, including a direct manipulation modelling environment, which exemplifies the type of application for which the modelling capabilities of the kernel are well suited.

A suite of computer-based tools for teaching mechanics of materials

In this article we describe an integrated suite of multimedia and simulation software developed to support the teaching of mechanics of materials. The materials are designed to support both classroom presentation and student-directed learning, provide direct manipulation and visualization, and foster exploration and experimentation.

Coordinate-free isoparametric elements

Abstract Formulations for general solid elements are presented which do not rely explicitly on an arbitrary global coordinate system, and which are independent of the dimension of the embedding space. Abstract data types corresponding to points, vectors and tensors replace matrix representations, allowing the coordinate-free nature of the derivation to be carried over into the implementation. The formulations are oriented primarily toward applications involving general geometric and material nonlinearities, iterative solution algorithms and element-by-element implementations, but traditional linear applications are considered as well.

Robust Automated Concrete Damage Detection Algorithms for Field Applications

This paper presents a computer vision framework supporting automated infrastructure damage detection, with a specific focus on surface crack detection in concrete. The approach presented is designed to provide a significant increase in robustness relative to existing methods when faced with widely varying field conditions while operating fast enough to be used in large scale applications. In particular, a clustering method for segmentation is developed that exploits inherent characteristics of fracture images to achieve consistent performance, combined with robust feature extraction to improve recognition algorithm classifier outcomes. The approach is shown to perform well in detecting cracks across a broad range of surface and lighting conditions, which can cause existing techniques to exhibit significant reductions in detection accuracy and/or detection speed.