Engineering Commons^™

A Parametric Study Of Lateral-Torsional Buckling In Pultruded Frp Beams Using Abaqus, Robert Nathaniel Baylor

Graduate Theses, Dissertations, and Problem Reports

Fiber Reinforced Polymer (FRP) composites continue to gain popularity in civil and mechanical infrastructure due to a high strength-to-weight ratio, corrosion-resistance, and low maintenance requirements. FRP can also fulfill niche roles requiring non-conductivity and magnetic transparency. The longitudinal forming of pultruded FRP makes it a natural choice for lightweight beams. Although FRP composites have a high strength for their weight, the elastic and shear moduli for glass FRP may only be 1/7 and 1/30 that of steel, respectively. These low stiffnesses make FRP composite beams particularly susceptible to lateral-torsional buckling (LTB). In addition, the low shear to elastic stiffness amplifies …

Structural Behavior Of Steel Plate Embedded Hybrid Gfrp Shapes, Piyush R. Soti

Graduate Theses, Dissertations, and Problem Reports

The civil infrastructure industry has been dominated by traditional materials such as steel, timber, and concrete. Although these materials offer great advantages, they have major durability issues in terms of corrosion, decaying, and cracking. Traditional material-based structures deteriorate frequently and require regular-interval repairs with huge expenditures. To resolve these maintenance and durability issues associated with traditional materials, fiber reinforced polymer (FRP) composites have gained some popularity in the past few decades because of their superior mechanical properties and durability. Carbon-FRPs (CFRPs) and glass-FRP (GFRPs) are the most commonly used FRPs in the market. However, in civil engineering applications, CFRPs are …

Effective Post-Tensioned Splicing System For Prestressed Concrete Piles, Zhongxin Wu

USF Tampa Graduate Theses and Dissertations

Precast prestressed concrete piles are widely used in deep foundation construction. Due to unexpected site soil conditions and difficulties associated with transportation and handling long precast piles, splicing is sometimes necessary at the construction site.

Available splicing methods utilize steel type connections that are more suitable for reinforced concrete construction and result in limited tensile capacity at the splice. This dissertation describes studies associated with the development of a new post-tensioned splicing system using staggered, embedded anchorages. The new system has the potential to provide the same tensile capacity as a one piece prestressed pile.

To develop the post-tensioned splicing …

Evaluation And Validation Of A Model To Predict The Effect Of Asphalt Mixtures And Vehicle Speed On Fuel Consumption Excess, Nirmal Dhakal

LSU Master's Theses

The primary objective of this study is to evaluate the effects of asphalt concrete (AC) properties and vehicle speed on fuel consumption excess using a Three-Dimensional (3D) Finite Element (FE) approach. Secondarily, the effect of pavement design characteristics on energy dissipation was studied. Finite element modeling was used to simulate three flexible pavements typically used for low traffic volume, medium traffic volume, and high traffic volume. The effect of asphalt concrete mixes with different binders and varying percentages of Reclaimed Asphalt Pavement (RAP) on fuel consumption excess was studied. The FE models were validated based on field stress and strain …

Innovative Techniques For Seismic-Resistant Bridge Columns Under Ground Motion Excitations, Ayman A. Moustafa

Doctoral Dissertations

“This dissertation provides innovative alternative solutions for replacing conventional reinforced concrete columns. The proposed columns displayed enhanced seismic resistance and properties compared to their counterpart conventional columns. Two main techniques were followed and proposed to develop seismic-resistant columns. The first technique utilized rubberized concrete to internally enhance energy dissipation and damping. Materials testing of rubberized concrete with scrap tire replacement of fine aggregates were performed to evaluate its dynamic properties. Shaking table testing of a rubberized concrete column was performed and the behavior was compared to that of the conventional one. The rubberized column showed an increase of 16% in …

Feasibility Of Cathodic Protection In Grouted Post Tensioned Tendons - Exploratory Model Calculations, Jacob Dharma Bumgardner

USF Tampa Graduate Theses and Dissertations

Recent corrosion related failures of grouted post tensioned tendons, even after the introduction of improved grouts, have led to renewed interest in supplemental or backup means of corrosion control for these systems. A finite element model is presented to explore feasibility of impressed current cathodic protection of strand in grouted tendons. The model examines polarization evolution as function of service time and includes consideration of anode placement and size, grout porosity, pore water alkalinity, electrochemical species diffusivity and applied voltage on the polarization efficacy and durability of such a system. The exploratory model projections suggested that, within the context of …

Multiplatform Analysis Seismic Evaluation Of A Non-Seismically Detailed Nonlinear Rc Structure Retrofitted With Magneto-Rheological Dampers, Eric R. Lovejoy

Master's Theses

In prior research, the MR damper's dynamic characteristics are typically modeled in the MATLAB/Simulink environment. Creating a structural model with nonlinear material properties, however, may be challenging in the MATLAB/Simulink environment without approximating the material behavior and neglecting effects such as P-∆ or panel zone behavior. More behaviorally accurate models of these structures can be produced using nonlinear finite element analysis tools such as Abaqus, OpenSees or ZuesNL. These analysis tools, however, are not traditionally used to model the complex nonlinear and controllable behavior of MR dampers, nor their associated control algorithms. One solution is to facilitate communication between these …

Modeling Of Shear Strengthening Of Reinforced Concrete Beams Retrofitted With Externally Bonded Fiber Reinforced Polymers, Srinivasa Anusha Bellamkonda

LSU Master's Theses

This thesis presents a study on the shear retrofit of reinforced concrete (RC) beams with externally bonded fiber reinforced polymers (FRP), since it is very important for RC beam to have a shear strength that is higher than the flexural strength in order to ensure ductile flexural failure mode. The study proposes a new model to predict the FRP shear strength contribution for different modes of failure, i.e., bending, shear with FRP rupture, shear with FRP debonding, and mixed shear-flexure and various retrofit techniques, i.e., side-bonding, U-jacketing, and full wrapping. The proposed model is compared to other existing models for …

Geometric Optimization Of Retroreflective Raised Pavement Markers, Lukai Guo

USF Tampa Graduate Theses and Dissertations

As the field service life of retroreflective raised pavement marker (RRPM) is much shorter than expected, it is necessary to identify the causes and thus improve the RRPM structural design to mitigate the main failure modes, such as poor retention from pavements, structural damage, and loss of retroreflectivity. One strategy for extending RRPM service life is to enhance RRPM geometric characteristics to decrease critical stresses in markers. The main purpose of this thesis is to analyze the relationship between stresses, failure modes, and RRPM profiles. Based on this research, some measures are suggested in order to avoid corresponding failure modes …

Comparison Between Three Types Of Cable Stayed Bridges Using Structural Optimization, Olfat Sarhang Zadeh

Electronic Thesis and Dissertation Repository

Cable stayed bridges have good stability, optimum use of structural materials, aesthetic, relatively low design and maintenance costs, and efficient structural characteristics. Therefore, this type of bridges are becoming more and more popular and are usually preferred for long span crossings compared to suspension bridges. A cable-stayed bridge consists of one or more towers with cables supporting the bridge deck. In terms of cable arrangements, the most common type of cable stayed bridges are fan, harp, and semi fan bridges. Because of their large size and nonlinear structural behaviour, the analysis of these types of bridges is more complicated than …

Finite Element Modeling Of Seismic Wave Propagation In Earthen Embankments, Binyam Tadese

Electronic Theses and Dissertations

The detection of internal seepage zones in embankments (dams and levees) by geophysical seismic techniques such as seismic refraction is limited by a number of factors. Some factors are associated with inversion and smoothing problems during processing, while others are associated with the natural characteristics of embankments and seepage anomalies. In this research, changes in the seismic response associated with: embankment soil compositions and moisture, characteristics of the seepage zone, presence of water in the reservoir, and shape of embankment was studied via 2D and 3D finite element (FE) embankment models. Artificial reflections from external boundaries and numerical dispersion were …

Behavior Of The Next-D Beam Shear Key: A Finite Element Approach, Armando Flores

All Theses

State Departments of Transportation have been using adjacent precast bridges for many years. A vital component of this type of bridges is the connection between the members, which is typically done with a grouted shear key. Shear keys have changed through time to adapt to the requirements of bridge design. An assessment of the Northeast Extreme Tee with integral deck (NEXT-D) was performed for the SCDOT as a development possibility for short span bridges. This research focuses on the finite element analysis study of the NEXT-D's specific shear key configuration.
A review of shear key configurations used by different DOTs …

Optimum Design Of Cable-Stayed Bridges, Mahmoud M. Hassan

Digitized Theses

Owing to their excellent structural characteristics, aesthetic appearance, low maintenance cost, and efficient use of structural materials, cable-stayed bridges have gained much popularity in recent decades. Stay cables of a cable stayed bridge are post-tensioned to counteract the effect of the bridge dead load. The solution for an optimum distribution of post-tensioning cable forces is considered one of the most important and difficult tasks in the design of cable-stayed bridges. A novel approach that utilizes the finite element method, B-spline curves, and real coded genetic algorithm to determine the global optimum post-tensioning cable forces is developed. The effect of geometric …

An Adaptive Multi-Scale Computational Method For Modeling Nonlinear Deformation In Nanoscale Materials, Wenming Wang

LSU Doctoral Dissertations

In this dissertation a coupled multi-scale computational model for simulating nonlinear deformation processes in crystalline metals at finite temperatures is developed. The computational model uses the finite element method to model the coarse scale response of the material. The constitutive response in the finite element will be modeled through interatomic potentials acting on the underlying homogeneous crystal lattice that characterizes its nanostructure. An adaptive remeshing technique is proposed to automatically delineate regions of severe deformation where homogeneity of the microstructure/deformation is violated. In these regions the finite element will be replaced by a set of deformed atoms which interact with …

A New Paradigm Of Modeling Watershed Water Quality, Fan Zhang

Electronic Theses and Dissertations

Accurate models to reliably predict sediment and chemical transport in watershed water systems enhance the ability of environmental scientists, engineers and decision makers to analyze the impact of contamination problems and to evaluate the efficacy of alternative remediation techniques and management strategies prior to incurring expense in the field. This dissertation presents the conceptual and mathematical development of a general numerical model simulating (1) sediment and reactive chemical transport in river/stream networks of watershed systems; (2) sediment and reactive chemical transport in overland shallow water of watershed systems; and (3) reactive chemical transport in three-dimensional subsurface systems. Through the decomposition …

An Application Of The Finite Element Method And Two Equation (K And E) Turbulence Model To Two And Three Dimensional Fluid Flow Problems Governed By The Navier-Stokes Equations, John I. Finnie

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Finite Element computer codes in two and three dimensions were written that solve both laminar and turbulent flow. These codes use the two equation (k and E) turbulence model to evaluate turbulent viscosity. They were tested with 29 different flow problems. The largest two dimensional turbulent problem solved is flow under a sluice gate. A three dimensional vortex flow problem was attempted but was not feasible due to the size of the available computer. The Harwell sparse matrix subroutines of the United Kingdom Atomic Energy Authority were used to solve the set of simultaneous equations. The performance of these subroutines …