The State of Florida acquires over 300 cutaway buses every year. The increasing popularity of such buses raised concerns about passenger safety and overall crashworthiness of this transportation mode. Dimensions of the cutaway buses and their two-stage manufacturing process made them exempted from safety standards which were developed for smaller passenger cars as well as for large coaches. To fill this gap, cutaway bus manufacturers try to demonstrate the strength of their bus roof structures by using FMVSS 220 standard, which follows conservative quasi-static load tests for school buses in the US. However, more advanced, dynamic based safety standard - Regulation 66, was developed in Europe. It is based on a dynamic rollover test which more closely resembles an actual rollover accident. A cutaway bus is placed on a tilt table 800 mm above a concrete slab. The bus is tilted until it falls and impacts the concrete deck and the deformation of the sidewalls is measured in order to check if there is any intrusion into a so called 'survival space'. This standard was endorsed by 44 countries through the United Nation resolution. However, the Regulation 66 standard does not specify all the parameters regarding the rollover test. From multiple tests it can be observed that the friction between the vehicle and the concrete slab which is being impacted by the bus has an influence on the outcomes of the experiment and has great contribution to either a positive or negative assessment of the crashworthiness of a tested vehicle. This Master thesis focuses on the friction parameters between the impacting cutaway bus and a concrete slab used in the Regulation 66 standard. Due to dynamic nature of the experiment, the impact of the bus exerts a high normal force on the concrete slab. Together with an uneven and non-standard geometry of the elements in contact with the concrete deck the standard coefficient of friction found in the literature or obtained using standard tests may not hold. The proper assessment of this coefficient is important since many rollover tests are carried out numerically using Finite Element Methods. The use of numerical analysis reduces the cost of an expensive full scale rollover test. However, it requires verified and validated parameters in order to consider the results trustworthy. The experimental part of this thesis consists of designing and carrying out experiments to evaluate the coefficient of friction for an impacting cutaway bus and a concrete slab. The results from the experiments are incorporated into an explicit computer code LS-DYNA, which is used for numerical analysis of the cutaway buses. The final outcome of this thesis will be validating the coefficient of friction used in the Finite Element Analysis which will lead to improvement of the Finite Element models and will be used to check the influence of the coefficient of friction on vehicle structure deformation (Deformation Index) during rollover accidents. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the Master of Science. / Fall Semester 2015. / November 5, 2015. / coefficient of friction, crashworthiness, structure deformation, vehicle rollover / Includes bibliographical references. / Sungmoon Jung, Professor Directing Thesis; Michelle Rambo-Roddenberry, Committee Member; Lisa Spainhour, Committee Member; Jerry W. Wekezer, Committee Member.

As it stands, many of Florida’s roads have already reached their designed service life and are now in the process of being renewed. The current method in rehabilitation of concrete pavement requires the expired piece of pavement to be cut and removed, place new dowel bars, and then epoxied into the surrounding slabs. Once the slab area has been prepared, fresh concrete is poured, and finished. The concrete is then cured and monitored to achieve a strength requirement of 2,200 psi in the shortest possible time before the lanes can be opened for traffic. This event has been known to take a long time and on major highways lane where lane closure may not exceed 8 hours. This restriction limits the number of slabs that can be replaced. The types of concrete used on these projects are also problematic. In the past, high amounts of cementitious material was used and this can lead to premature cracking. To improve production levels, accelerate construction time at a reduced cost, and provide long lasting pavement, the current research study presents an alternative method of using precast slab panels and self-consolidating concrete. This was accomplished by testing several SCC mixes in the laboratory to achieve concrete with high workability without, high early strength and without segregation. Then, precast panels were designed and built for quick installation and removal. This study also necessitated full scaled field tests where precast slab panels with the proper SCC mix were used. The slabs were tested by a loaded truck moving over it repeatedly and the slab was monitored for any movement and displacements caused by driving and braking on it. After the data was collected from the precast panels, the slabs were then removed and fresh SCC was then poured into the empty pit. The SSC slab was left to cure and the maturity of the concrete was monitored to achieve the required strength for lane opining. In this study, three techniques were used to monitor the concrete maturity. These techniques involved the use of the conventional thermocouples, thermal camera, and laser gun. The traffic load was then applied by driving a dump truck loaded to 25000 pounds over the track for 100 laps. The SCC mix behaved as designed and presented in this study. It achieved a high workability and retained a high slump for nearly an hour. It also exceeded the required FDOT strength requirement of 2200 psi for lane opening. The precast panels proved to be highly durable during the installation, testing, removal and can be reused for other similar applications. Results from this study proved proved that using this method has several benefits including greater productivity, reduced maintenance of traffic, shorter project completion time. Further, it may reduce the case of premature cracking due to the increase amount of curing time. / A Thesis submitted to the Department of Civil and Environmental Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester 2018. / July 23, 2018. / Includes bibliographical references. / Kamal Tawfiq, Professor Directing Thesis; Michelle Rambo-Roddenberry, Committee Member; Lisa Spainhour, Committee Member; Raphael Kampmann, Committee Member.

Bilayered material systems are common in naturally formed or artificially engineered structures. Understanding how loads transfer within these structural systems is necessary to predict failure and develop effective designs. Existing methods for evaluating the stress transfer in bilayered materials are limited to overly simplified models or require experimental calibration. As a result, these methods have failed to accurately account for such structural failures as the creep induced roofing panel collapse of Boston's I-90 connector tunnel, which was supported by adhesive anchors. The one-dimensional stress analyses currently used for adhesive anchor design cannot account for viscoelastic creep failure, and consequently results in dangerously under-designed structural systems. In this dissertation, a method for determining the two-dimensional stress and displacement fields for a generalized bilayered material system is developed, and proposes a closed-form analytical solution. A general linear-elastic solution is first proposed by decoupling the elastic governing equations from one another through the so-called plane assumption. Based on this general solution, an axisymmetric problem and a plane strain problem are formulated. These are applied to common bilayered material systems such as: (1) concrete adhesive anchors, (2) material coatings, (3) asphalt pavements, and (4) layered sedimentary rocks. The stress and displacement fields determined by this analytical analysis are validated through the use of finite element models. Through the correspondence principle, the linear-elastic solution is extended to consider time-dependent viscoelastic material properties, thus facilitating the analysis of adhesive anchors and asphalt pavements while incorporating their viscoelastic material behavior. Furthermore, the elastic stress analysis can explain the fracturing phenomenon of material coatings, pavements, and layered rocks, successfully predicting their fracture saturation ratio--which is the ratio of fracture spacing to the thickness of the weak layer where an increase in load will not cause any new fractures to form. Moreover, these specific material systems are looked at in the context of existing and novel experimental results, further demonstrating the advantage of the stress transfer analysis proposed. This research provides a closed-form stress solution for various structural systems that is applied to different failure analyses. The versatility of this method is in the flexibility and the ease upon which the stress and displacement field results can be applied to existing stress- or displacement-based structural failure criteria. As presented, this analysis can be directly used to: (1) design adhesive anchoring systems for long-term creep loading, (2) evaluate the fracture mechanics behind bilayered material coatings and pavement overlay systems, and (3) determine the fracture spacing to layer thickness ratio of layered sedimentary rocks. As is shown in the four material systems presented, this general solution has far reaching applications in facilitating design and analysis of typical bilayered structural systems.

There are many natural and man-made materials with heterogeneous micro- or nanostructure (fine-scale structure) which represent a great interest for industry. Therefore there is a great demand for computational methods capable to model mechanical behavior of such materials. Direct numerical simulation resolving all fine-scale details using very fine mesh often becomes very expensive. One of alternative effective group of methods is the homogenization methods allowing to model behavior of materials with heterogeneous fine-scale structure. The essence of homogenization is to replace heterogeneous material with some equivalent effectively homogeneous material. The homogenization methods are proven to be effective in certain classes of problems while there is need to improve their performance, which includes extension of the range of applicability, simplification, usage with conventional FE software and reducing computational cost. In this dissertation methods extending the range of applicability of homogenization are developed. Firstly, homogenization was extended of the case of full nonlinear electromechanical coupling with large deformations, which allows simulating effectively behavior of electroactive materials such as composites made of electroactive polymers. Secondly, homogenization was extended on wave problems where dispersion is significant and should be accounted for. Finally, the homogenization was extended on the case where the size of microstructure. The distinctive feature of the methods introduced in this dissertation is that they don't require higher order derivatives and can be implemented with conventional FE codes. The performance of methods is tested on various examples using Abaqus.

The rocking motion of a solid block on a moving deformable base is a dynamic problem, that despite its apparent simplicity, involves a number of complex dynamic phenomena such as impacts, sliding, geometric and material nonlinearities and, under some circumstances, chaotic behavior. For that reason, since the first model proposed by G. W. Housner in 1963, a number of alternative models have been proposed for its mathematical simulation. Although, with very few exceptions, the previous models in the literature make the simplified assumption that this motion is planar, this is usually not true since a body will probably not be aligned with the direction of the ground motion. Thus, even in the case where the body is fully symmetric, the rocking motion involves three dimensional rotations and displacements. Moreover, for reasons more related to functionality than safety, it is not uncommon for heavy mechanical and electrical equipment to be placed on wheels. Examples of such devices are medical carts, mechanical equipment in hospitals, electrical transformers and recently even supercomputers. Although wheels facilitate the operation of these devices, they also affect the response of these objects during earthquakes; not necessarily in a beneficial way. This dissertation develops suitable models for simulating the previous dynamic problems. The equations of motion and suitable contact models are developed for each case. The importance of phenomena often neglected in the literature is stressed. Suitable examples illustrate the complex dynamic character of the problems examined. Finally, a static contact problem is examined. A model is developed for systems of multiple jointed elastic beams, using exact shape functions. A special application of the method for the definition of pressure loads in the wires of the main cable of a suspension bridge is presented. Examples illustrate the robustness of the method and the special properties associated with pressure loads.

Structural Health Monitoring (SHM) is central to the goal of maintaining civil engineering structures safely and efficiently, and thereby securing people's lives and property. Furthermore, it plays an essential role in infrastructure design at a fraction of the capital cost of construction. In this thesis, we seek to address two of the central concerns of the SHM: parametric system identification and damage detection. The first proposed method seeks to identify the physical parameters of an analytical model. First, the connection coefficients for the scaling function were developed for deriving the responses of the velocity and displacement from the acceleration responses. Next, defining the dominant sets based on the relative energies of the Wavelet Components of the acceleration responses, the equations of motion of the system in the time domain were converted to a reduced representation of the equations of motion in terms of the DWT and of the DWPT. Finally, the least square error minimization was conducted over the dominant sets to estimate the best estimation of the physical parameters. The second proposed method seeks to detect damage in a structure. Motivated by the fact that the Empirical Mode Decomposition is seen to have different features from the Discrete Wavelet Transform when one investigates nonstationary signals, we have combined the Empirical Mode Decomposition with the Discrete Wavelet Transform to enhance the performance of the proposed method for identifying damage in the structure.

In modern days, construction projects have become more and more complex and intriguing. One source of the complexity arises from the large number of parties involved. This is especially the case for large-scale construction projects. Because of such complexity, disputes are almost inevitable and implementation costs associated with dispute resolution have become increasingly expensive. Because most projects operate on tight budgets, cost effective dispute resolution plays an important role in the success of a construction project. For this purpose, Alternative Dispute Resolution (ADR) techniques such as negotiation, mediation, and arbitration are being widely adopted in large-scale construction projects to resolve disputes in more effective and cost-saving ways. However, the risk of incurring dispute-related cost overruns always exists because of the uncertainty in the distribution of dispute occurrence and the effectiveness of contractually-predetermined ADR techniques. As a result, the traditional self-insured structure which simply retains all dispute resolution costs to the project through contingency fees is no longer considered economical. While many insurance policies cover the settlement of a dispute, such as professional liability insurance, no specific insurance policy is dedicated to cover the ADR implementation costs such as fees and expenses that are paid to the owner/contractor's employees, lawyers, claims consultants, third party neutrals, and other experts involved in the resolution process. To fill the gap, this dissertation proposes an insurance model to reduce the potential variations in the dispute resolution budget by pricing ADR techniques as an insurance product. It is designed to transfer the risk of dispute-related cost overruns from the project to a third-party insurance company. To achieve this goal, this dissertation focuses on three major tasks: 1) investigate the role of ADR implementation insurance in construction risk management, 2) construct a mathematical model to represent the risk attitudes of project participants using utility theory and derive the basic premium of ADR implementation insurance using insurance pricing theory, and 3) develops a comprehensive framework to determine the optimal insurance premium by considering two additional insurance limits a Deductible Limit (DL) and a Maximum Payment Limit (MPL). The objective of this dissertation is to provide project participants with an advantageous insurance policy that minimizes their total expected subjective loss. The model can serve as a decision-making support system to help project participants determine whether an ADR implementation insurance policy is attractive for a certain project. To illustrate the benefits of the proposed model, numerical examples are provided for simulation purpose. The results show that ADR implementation insurance, although not a tool to eliminate dispute resolution costs, is a powerful alternative in risk management to transfer the financial implications of ADR implementation risk to a third party.

In past years, railroad transportation has been of growing interest due to its efficiency and advancement in railway technologies. However, many issues arise due to the variability in subsurface conditions along the sizeable lengths of track that exist. One very important issue is the need for significant upkeep and maintenance for railways passing over areas of poor soil conditions due to continuous deformation and a lack of stiffness from the ballasted foundation. One general solution for lack of substructure integrity has been confinement, applied through a variety of reinforcement types, including geocell. To investigate the effectiveness of geocell confinement on ballasted substructure integrity, a series of embankment model tests with different configurations of geocell placement (one layer and two layers of geocell) were constructed and loaded monotonically and cyclically for comparison to unreinforced, control tests. Upon the completion of these tests, the model embankments were simulated numerically using finite element procedures. The results were then used as validation for a parametric study, observing the effects of less competent geocell material, ballast and foundation conditions and their implications. Further numerical simulations were then performed on railroad embankments reinforced with and without geocell to model realistic railroad conditions and the effects of confinement on performance.The tests and numerical simulations demonstrate that geocell confinement effectively increased stiffness and strength of a ballast embankment, while reducing vertical settlement and lateral spreading. Additionally, the parametric study shows that the use of geocell provides a composite, "mattressing" effect that distributes subgrade stress more uniformly than without reinforcement, increasing bearing capacity and reducing settlement, especially on soft foundations or when using weaker ballast. The results suggested that in some site conditions, use of geocell might be an economical alternative to frequent maintenance and/or lower train speeds. Additionally, it implies that geocell might be cost-effective when used in combination withed degraded, weaker ballasts, i.e. inferior local or recycled materials. The use of geocell in ballast stabilization could prove to a sustainable solution for a common and expensive problem.

We present a unified, homogenization framework for computational analysis of heterogeneous materials consisting of multiple length scales, multiple time scales and coupled-multiple physics. The research efforts also addresses the technological issues associated with modeling the morphological details of microstructures with randomly distributed inclusions. The Random Sequential Adsorption (RSA) algorithm is improved to accurately and effectively model the morphological details of materials with randomly distributed inclusions. The proposed algorithm is more robust; computational efficient and versatile in comparison to the existing methods. A temporal homogenization scheme is developed and integrated with the previously developed spatial homogenization theory for fatigue life analysis of heterogeneous materials. The unified space-time multiscale homogenization model is validated for fatigue life prediction of elevated temperature Ceramic Matrix Composites (CMCs). In the final phase of the research a mathematical model for coupled moisture diffusion-mechanical deformation is developed. This model is integrated with the spatial homogenization framework to analyze problems consisting of multiple length scales and coupled-multiple physics. The unified multiscale-multiphysics model is validated for evaluating the degradation of physical and mechanical properties of short glass fiber and carbon fiber filled thermoplastic material systems.

This thesis covers several topics within computational modeling and simulation of problems arising in Civil Engineering and Applied Mechanics. There are two distinct parts. Part 1 covers work in modeling and analyzing heterogeneous materials using the eXtended Finite Element Method (XFEM) with arbitrarily shaped inclusions. A novel enrichment function, which can model arbitrarily shaped inclusions within the framework of XFEM, is proposed. The internal boundary of an arbitrarily shaped inclusion is first discretized, and a numerical enrichment function is constructed "on the fly" using spline interpolation. This thesis considers a piecewise cubic spline which is constructed from seven localized discrete boundary points. The enrichment function is then determined by solving numerically a nonlinear equation which determines the distance from any point to the spline curve. Parametric convergence studies are carried out to show the accuracy of this approach, compared to pointwise and linear segmentation of points, for the construction of the enrichment function in the case of simple inclusions and arbitrarily shaped inclusions in linear elasticity. Moreover, the viability of this approach is illustrated on a Neo-Hookean hyperelastic material with a hole undergoing large deformation. In this case, the enrichment is able to adapt to the deformation and effectively capture the correct response without remeshing. Part 2 then moves on to research work in simulation of random processes and fields. Novel algorithms for simulating random processes and fields such as earthquakes, wind fields, and properties of functionally graded materials are discussed. Specifically, a methodology is presented to determine the Evolutionary Spectrum (ES) for non-stationary processes from a prescribed or measured non-stationary Auto-Correlation Function (ACF). Previously, the existence of such an inversion was unknown, let alone possible to compute or estimate. The classic integral expression suggested by Priestley, providing the ACF from the ES, is not invertible in a unique way so that the ES could be determined from a given ACF. However, the benefits of an efficient inversion from ACF to ES are vast. Consider for example various problems involving simulation of non-stationary processes or non-homogeneous fields, including non-stationary seismic ground motions as well as non-homogeneous material properties such as those of functionally graded materials. In such cases, it is sometimes more convenient to estimate the ACF from measured data, rather than the ES. However, efficient simulation depends on knowing the ES. Even more important, simulation of non-Gaussian and non-stationary processes depends on this inversion, when following a spectral representation based approach. This work first examines the existence and uniqueness of such an inversion from the ACF to the ES under a set of special conditions and assumptions (since such an inversion is clearly not unique in the most general form). It then moves on to efficient methodologies of computing the inverse, including some established optimization techniques, as well as proposing a novel methodology. Its application within the framework of translation models for simulation of non-Gaussian, non-stationary processes is developed and discussed. Numerical examples are provided demonstrating the capabilities of the methodology. Additionally in Part 2, a methodology is presented for efficient and accurate simulation of wind velocities along long span structures at a virtually infinite number of points. Currently, the standard approach is to model wind velocities as a multivariate stochastic process, characterized by a Cross-Spectral Density Matrix (CSDM). In other words, the wind velocities are modeled as discrete components of a vector process. To simulate sample functions of the vector process, the Spectral Representation Method (SRM) is used. The SRM involves a Cholesky decomposition of the CSDM. However, it is a well known issue that as the length of the structure, and consequently the size of the vector process, increases, this Cholesky decomposition breaks down (from the numerical point of view). To avoid this issue, current research efforts in the literature center around approximate techniques to simplify the decomposition. Alternatively, this thesis proposes the use of the frequency-wavenumber (F-K) spectrum to model the wind velocities as a stochastic "wave," continuous in both space and time. This allows the wind velocities to be modeled at a virtually infinite number of points along the length of the structure. In this work, the relationship between the CSDM and the F-K spectrum is first examined, as well as simulation techniques for both. The F-K spectrum for wind velocities is then derived. Numerical examples are then carried out demonstrating that the simulated wave samples exhibit the desired spectral and coherence characteristics. The efficiency of this method, specifically through the use of the Fast Fourier Transform, is demonstrated.