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Typically, foundation piles are made of materials such as steel, concrete, and timber. Problems associated with use of these traditional pile materials in harsh marine environments include steel corrosion, concrete deterioration, and marine borer attack on timber piles. It has been estimated that the U.S. spends over $1 billion annually in repair and replacement of waterfront piling systems. Such high repair and replacement costs have led several North American highway agencies and researchers to investigate the feasibility of using composite piles for load bearing applications, such as bridge substructures. As used here, the term "composite piles" refers to alternative pile types composed of fiber reinforced polymers (FRPs), recycled plastics, or hybrid materials. Composite piles may exhibit longer service lives and improved durability in harsh marine environments, thereby presenting the potential for substantially reduced total costs. Composite piles have been available in the North American market since the late 1980's, but have not yet gained wide acceptance in civil engineering practice. Potential disadvantages of composite piles are high initial cost and questions about engineering performance. At present, the initial cost of composite piles is generally greater than the initial cost of traditional piles. Performance questions relate to driving efficiency, axial stiffness, bending stiffness, durability, and surface friction. These questions exist because there is not a long-term track record of composite pile use and there is a scarcity of well-documented field tests on composite piles. This research project was undertaken to investigate the engineering performance of composite piles as load-bearing foundation elements, specifically in bridge support applications. The objectives of this research are to: (1) evaluate the soil-pile interface behavior of five composite piles and two conventional piles, (2) evaluate the long-term durability of concrete-filled FRP composite piles, (3) evaluate the driveability and the axial and lateral load behavior of concrete-filled FRP composite piles, steel-reinforced recycled plastic composite piles, and prestressed concrete piles through field tests and analyses, and (4) design and implement a long-term monitoring program for composite and conventional prestressed concrete piles supporting a bridge at the Route 351 crossing of the Hampton River in Virginia. A summary of the main findings corresponding to each of these objectives is provided below. A laboratory program of interface testing was performed using two types of sands and seven pile surfaces (five composite piles and two conventional piles). The interface behavior of the different pile surfaces was studied within a geotribology framework that investigated the influence of surface topography, interface hardness, and particle size and shape. In general, the interface friction angles, both peak and residual, were found to increase with increasing relative asperity height and decreasing relative asperity spacing. The interface shear tests for the three pile types tested at the Route 351 bridge showed that, for medium dense, subrounded to rounded sand, with a mean particle size of 0.5 mm, the residual interface friction angles are 27.3, 24.9, and 27.7 degrees for the FRP composite pile, the recycled plastic pile, and the prestressed concrete pile, respectively. Interface shear tests on these same piles using a medium dense, subangular to angular sand, with a mean particle size of 0.18 mm, resulted in residual interface friction angles of 29.3, 28.8, and 28.0 degrees for the FRP composite pile, the recycled plastic pile, and the prestressed concrete pile, respectively. A laboratory durability study was completed for the FRP shells of concrete-filled FRP composite piles. Moisture absorption at room temperature caused strength and stiffness degradations of up to 25% in the FRP tubes. Exposure to freeze-thaw cycles was found to have little effect on the longitudinal tensile properties of saturated FRP tubes. Analyses were performed to investigate the impact of degradation of the FRP mechanical properties on the long-term structural capacity of concrete-filled FRP composite piles in compression and bending. The impact was found to be small for the axial pile capacity due to the fact that the majority of the capacity contribution is from the concrete infill. The impact of FRP degradation was found to be more significant for the flexural capacity because the FRP shell provides most of the capacity contribution on the tension side of the pile. Full-scale field performance data was obtained for two composite pile types (concretefilled FRP composite piling and steel-reinforced recycled plastic piling), as well as for conventional prestressed concrete piles, by means of load test programs performed at two bridge construction sites: the Route 351 bridge and the Route 40 bridge crossing the Nottoway River in Virginia. The field testing at the two bridges showed no major differences in driving behavior between the composite piles and conventional prestressed concrete piles. Pile axial capacities of the composite piles tested at the Route 351 bridge were between 70 to 75% of the axial capacity of the prestressed concrete test pile. The FRP and prestressed concrete piles exhibited similar axial and lateral stiffness, while the steel-reinforced plastic pile was not as stiff. Conventional geotechnical analysis procedures were used to predict axial pile capacity, axial load-settlement behavior, and lateral load behavior of the piles tested at the Route 351 bridge. The conventional analysis procedures were found to provide reasonable predictions for the composite piles, or at least to levels of accuracy similar to analyses for the prestressed concrete pile. However, additional case histories are recommended to corroborate and extend this conclusion to other composite pile types and to different soil conditions. A long-term monitoring program for composite and conventional prestressed concrete piles supporting the Route 351 bridge was designed and implemented. The bridge is still under construction at the time of this report, therefore no conclusions have been drawn regarding the long-term performance of concrete-filled FRP composite piles. The longterm monitoring will be done by the Virginia Department of Transportation. In addition to the above findings, initial cost data for the composite piles and prestressed concrete piles used in this research were compiled. This data may be useful to assess the economic competitiveness of composite piles. The initial unit cost of the installed composite piles at the Route 40 bridge were about 77 % higher than the initial unit cost for the prestressed concrete piles. The initial unit costs for the composite piles installed at the Route 351 bridge were higher than the initial unit cost of the prestressed concrete piles by about 289% and 337% for the plastic and FRP piles, respectively. The cost effectiveness of composite piles is expected to improve with economies of scale as production volumes increase, and by considering the life-cycle costs of low-maintenance composite piles. / Ph. D.

The conventional design methods for sheet-pile cellular cofferdams were developed in the 1940's and 1950's based on field and limited experimental observations. The analytical techniques of the day were unable to account for the complexities involved. The procedures used only rudimentary concepts of soil-structure interaction which do not exhibit the true response of the cofferdam for most circumstances. During the past decade it has been demonstrated that with proper consideration of the soil-structure interaction effects, the two-dimensional finite element models can be powerful tools in the investigation of cellular cofferdam behavior. However, universal implementation of the findings of these analyses was difficult to justify, since uncertainties remain about the assumptions made in arriving at the two-dimensional models. The only way to address these uncertainties was to perform a three-dimensional analysis. This investigation has focused on the study of the three-dimensional behavior of Lock and Dam No. 26 (R) sheet—pile cellular cofferdam. The work involved the development of a new three-dimensional soil-structure interaction finite element code for cellular cofferdam modeling, and the application of the new code to the study of the behavior of the first- and second-stage cofferdam at Lock and Dam No. 26 (R). The new code was used to study the cell filling process where the main cell is filled first with the subsequent filling of the arc cell. The finite element results show that interlock forces in the common wall were 29 to 35 percent higher than those in the main cell which are less than those calculated by conventional methods and compare well with the observed values. After cell filling, the new code was used to model the cofferdam under differential loading due to initial dewatering of the interior of the cofferdam and changes in river levels. The finite element analysis results show that increasing differential water loads cause the confining stresses in the cell fill to increase which results in a decrease in the level of mobilized shear strength in the cell fill. This explains why the cellular cofferdam can withstand extremely high lateral loads and lateral deformations without collapsing. / Ph. D.

An alternative to the displacement finite element method, the hybrid stress model, is applied to problems in geomechanics. A two-dimensional finite element procedure based on the hybrid stress model is developed for simulation of construction sequences including underground and surface excavations. In this procedure, an eight-node isoparametric element is employed. In the analysis, the effect of soil-structure interaction is incorporated by using a special interface element for behavior at the contact between two different materials. In the elastic-plastic analysis, the Drucker-Prager model is used as a constitutive law. In order to verify the computer program and to examine the accuracy of the hybrid stress model, several problems such as a beam, a plate with circular hole, and footings are analyzed, and the results are compared with those from the displacement method and closed-form solutions. The proposed procedure for simulation of excavation is verified by performing an excavation in linear elastic material. Finally, two field cases of excavation are solved and the results are compared with the displacement method and the field observations. It is believed that the proposed (stress) hybrid method can have significant potential of application for various problems in geomechanics, and it can be particularly appropriate for a situation where computation of stresses is important. / Ph. D.

In Australia a class of soils known as sodic duplex soils covers approximately 20% of the continent. Their defining characteristic is a sharp texture contrast between the A (or E) and B horizon. The upper B horizon at the point of contact with the E horizon is often highly sodic and of such a high strength that root growth and proliferation, water conductivity, aeration, water storage and water uptake are restricted. Roots growing in these soils rely on channels created by previous roots or cracks arising from shrink– swell forces associated with seasonal wetting and drying. It has been suggested that by increasing the number of these channels in the subsoil, the structure and permeability of the subsoil would be increased as would be the number of preferential pathways for following generation roots. A biological approach for improving soil macroporosity would be to use plants that can grow through that hostile layer creating new channels. This is known as the primer plant concept. This concept is based on a better understanding of root soil interactions. It is accepted that root growth is influenced by the soil structure and the soil structure is influenced by root growth. However, a lot of these dynamics are still unknown. This project aims to contribute to improving that knowledge by investigating the use of modern techniques to study plant/root interactions in duplex soils. First macroporosity and mesoporosity were characterized in three dimensions using medical computer tomography and micro-tomography. Then the imaging methodology was improved by using a local and adaptive threshold technique based on indicator kriging instead of a global threshold. Using this new methodology, changes in porosity were analysed in intact samples when three different plant species were grown for 12 weeks. The plants were canola (Brassica napus); lucerne (Medicago sativum) and saltbush (Atriplex nummularia) hypothesizing saltbush would change the porosity more because it is a native plant species based on the primer plant concept. The results showed that the porosity changed significantly after root growth but no ii differences were found between plant species. The changes could also not all be attributed to root growth because cracks were also formed after 12 weeks. Therefore, the living roots were visualized and characterized using a new tracing algorithm 'rootviz'. This revealed that saltbush was growing more roots down through the profile. Lucerne seemed to grow roots down the profile as well but to a lesser extend. Both of these plants seemed to have more geotropic features than canola that seemed to grow more laterals and had a more exploratory behaviour.

The term ???Integral Abutment Bridges??? is used broadly all over the world these days. While the expansion joints used in bridges were once a scientifically proved cure to the problem of natural expansion and contraction, there are the excessive maintenance costs being accumulated annually due to the deterioration of essential functions from deicing chemicals and debris. This drawback triggered the advent of Integral Abutment Bridges. The performance of Integral Abutment Bridges at almost no extra costs in seasonal and daily cyclic contraction and expansion can be assessed as a monumental landmark of civil engineering technologies with respect to the massive budget reductions. However, since Integral Abutment Bridges are destined to expand or contract under the laws of nature, the bridge design became more complicated and sophisticated in order to complement the removal of expansion joints. That is why numerous researchers are attracted to Integral Abutment Bridges with deep interests. Accordingly, in designing the piled abutments of Integral bridges, it is essential to precisely predict the bridge???s behavior in advance. Researchers have been broadly carried out during the last several decades on the behavior of piled bridge abutments. However, most of the studies have been analyzed with focus on structural elements or soils, respectively for the static and dynamic loads such as thermal variations and earthquake loads. This presented research developed 3D numerical models with 3 m, 4 m, 5 m, 6 m, 7 m, and 8 m-tall abutments in the bridge using the finite element analysis software MIDAS CIVIL that simulate the behaviors of Integral Abutment Bridges to study the soil-structure interaction mechanism. In addition, this work evaluated and validated the suitability to the limit of the abutment height in Ontario???s recommendations for Integral Abutment Bridges by a parametric study under the combined static loading conditions. In order to be a balanced research in terms of a multidisciplinary study, this research analyzed key facts and issues related to soil-structure interaction mechanisms with both structural and geotechnical concerns. Moreover, the study established an explanatory diagram on soil-structure interaction mechanisms by cyclic thermal movements in Integral Abutment Bridges.

Neste trabalho são realizadas análises estruturais de edifícios de paredes de concreto moldadas no local e de alvenaria estrutural considerando a interação solo-estrutura e a sequência construtiva. Com solução de fundação em estacas pré-moldadas, cada edifício piloto com 45 metros de altura, formado por 15 pavimentos de parede com pé-direito de 2,80m, apoiado sobre um pilotis de concreto armado de 3 metros de altura é modelado com base em 4 metodologias de análise: (i) O AI_AF, modelo clássico de referência, que admite apoios indeslocáveis e ações instantâneas; (ii) O AE_AF, modelo que inclui as ações evolutivas, incorporando o aumento gradativo de carregamento e rigidez; (iii) O AI_ISE, modelo que incorpora a interação com o solo a partir da aplicação instantânea de ações e (iv) o AE_ISE, modelo mais refinado, que considera a interação com o solo no tempo de construção. As paredes são modeladas em elementos finitos de casca, os pilares de concreto, vigas de transição, estacas e blocos em elementos finitos de barra e o maciço de solo em elementos finitos sólidos isoparamétricos, com o auxílio do software comercial DIANA®. O trabalho evidencia que o modelo clássico de referência, que desconsidera a interação com o solo, não alerta para a necessidade de aumentar a ductilidade das paredes dos pavimentos iniciais em ambos os sistemas construtivos. / This study consist of a structural analyses of concrete walls and masonry building including the soil-structure interaction and the construction process. Each pilot building is 45 meters high, consisting of 15 floors with 2.80 m high. Each floors are seated on pillars of reinforced concrete with 3 meters of height, which were modeled using 4 methodologies: (i) The AI_AF, classic reference model, which adopts fixed foundations and instantaneous action; (ii) The AE_AF is a model, that includes construction loads and incorporates a gradual increasing in load and stiffness; (iii) The AI_ISE model incorporates interaction with the soil and the instantaneous application of actions; and, (iv) AE_ISE, which consists of a more refined model with soil interaction and the time of construction. The concrete walls are modeled based on shell finite elements, the concrete pillars, transition beams, stakes and blocks are modeled based on bar finite element and the soil mass is modelled as an isoparametric solid finite elements. The numerical modelling is conducted using commercial software DIANA®. Results show that the classic reference model, in which the soil-structure interaction is not considered, does not attent to the need of increasing the ductility of the walls in initials floor.

Ce travail de thèse présente une contribution à l'analyse des effets dynamiques des interactions sol-structure sur le mouvement sismique du sol et des bâtiments. Il repose essentiellement sur une approche numérique qui utilise la méthode des éléments spectraux et une représentation simplifiée des bâtiments par des modèles « par blocs » dont la réponse est ajustée par comparaison à plusieurs jeux de données expérimentales. L'objectif principal est de définir un cadre permettant une modélisation réaliste des effets macroscopiques d'interactions sol-structure et structure-sol-structure dans le calcul du mouvement du sol et des bâtiments. Après une présentation du cadre théorique de l'interaction sol-structure et des principales méthodes utilisées pour sa modélisation, divers exemples, comprenant le site Euroseistest / Volvi (Grèce), les tours de l'Ile Verte à Grenoble et Anchorage (Alaska), sont étudiés en détail pour identifier les difficultés de modélisation et proposer une procédure d'ajustement des paramètres des modèles par blocs au comportement réel des structures. Cela inclue une discussion sur les caractéristiques dynamiques les plus importantes à reproduire (fréquence de résonance, amortissement et mouvement de bascule) et sur la façon d'adapter les propriétés fictives des modèles par blocs afin de reproduire le comportement dynamique de structures dont les propriétés mécaniques varient fortement sur des échelles spatiales beaucoup plus faibles. Une attention particulière est consacrée à la modélisation par blocs de bâtiments ayant des propriétés dynamiques non-isotropes et des réponses mêlant flexion et cisaillement (de type « poutre de Timoshenko ») via l'introduction de propriétés hétérogènes au sein des éléments spectraux, et sans modification de la section géométrique globale. Ce travail comprend également une comparaison détaillée des différences entre modèles 2D et 3D et une discussion de leur origine physique : pour des bâtiments ayant des rapports d'aspect (longueur sur largeur) inférieurs à 6, les modèles 2D sont non-conservatifs, dans le sens où ils surestiment de façon significative l'amortissement et le mouvement de bascule. Cette thèse comprend également une grande partie sur les effets de l'interaction de structure à structure au travers du sol. De nombreuses situations sont étudiées, depuis le cas de 2 bâtiments à 2D ou 3D jusqu'au cas de zones densément urbanisées en 3D, avec divers types d'excitations (« pull-out », source superficielle ou profonde). Les effets de la distance inter-bâtiments sont étudiés dans diverses gammes de fréquence. La tendance générale obtenue est une diminution du mouvement du sol et des bâtiments autour de la fréquence de résonance fondamentale et une augmentation autour de la fréquence du premier harmonique. Des effets significatifs de réduction de la sollicitation sismique apparente sont obtenus en raison de l'effet de bouclier joué par les bâtiments vis à vis des ondes de surface. / This work is a contribution to investigations on the effects of dynamic soil-structure interaction on the seismic motion of both ground surface and buildings. It is based mainly on a numerical approach using the spectral element method and a simplified representation of buildings with "block models", calibrated however on a comparison with various sets of instrumental data. One of the main goals is to set the frame for a relevant macroscopic modeling of SSI and SSSI effects on ground and structural dynamic response. After a presentation of the background theoretical framework of soil-structure interaction and the main modeling approaches, various examples from Euroseistest / Volvi (Greece), Grenoble Ile Verte towers (France) and Anchorage (Alaska) are investigated in detail to identify the main modeling issues and to propose a procedure to best tune the model and its parameters to the actual behavior. It includes a discussion on the main relevant macroscopic dynamic characteristics to fit (frequency, damping and rocking ratio), and on the way to use "block models", i.e., models consisting of blocks full of fictitious material, to satisfactorily reproduce the macroscopic response of actual buildings having highly variable slenderness ratios, with frames or shear walls. A special attention is devoted to the "block-modeling" of buildings with non-symmetrical dynamic properties and Timoshenko beam like behavior, through the introduction of material heterogeneities within the spectral elements of block models, while keeping unchanged the geometrical cross-section. It also includes a thorough comparison on the major differences between 2D and 3D models and their physical origins: for long buildings with aspect ratios (length over width ratio) lower than 6, 2D models are shown un-conservative, as they tend to significantly overestimate the damping and rocking ratios. This work also includes a large part on the effects of Structure-to-Structure interaction through the soil. Various cases are considered, from the 2 building case in 2D and 3D geometries to an idealized, densely urbanized 3D area, with various types of excitations (pull-out, surface or deep source). Effects of inter-building distance and frequencies are investigated. The general trend is a reduction of the ground and building motion around the fundamental frequency, with however opposite effects for the first higher mode. The reduction effects are found of particular importance because of the shielding effects of building clusters for surface waves.

Neste trabalho são realizadas análises estruturais de edifícios de paredes de concreto moldadas no local e de alvenaria estrutural considerando a interação solo-estrutura e a sequência construtiva. Com solução de fundação em estacas pré-moldadas, cada edifício piloto com 45 metros de altura, formado por 15 pavimentos de parede com pé-direito de 2,80m, apoiado sobre um pilotis de concreto armado de 3 metros de altura é modelado com base em 4 metodologias de análise: (i) O AI_AF, modelo clássico de referência, que admite apoios indeslocáveis e ações instantâneas; (ii) O AE_AF, modelo que inclui as ações evolutivas, incorporando o aumento gradativo de carregamento e rigidez; (iii) O AI_ISE, modelo que incorpora a interação com o solo a partir da aplicação instantânea de ações e (iv) o AE_ISE, modelo mais refinado, que considera a interação com o solo no tempo de construção. As paredes são modeladas em elementos finitos de casca, os pilares de concreto, vigas de transição, estacas e blocos em elementos finitos de barra e o maciço de solo em elementos finitos sólidos isoparamétricos, com o auxílio do software comercial DIANA®. O trabalho evidencia que o modelo clássico de referência, que desconsidera a interação com o solo, não alerta para a necessidade de aumentar a ductilidade das paredes dos pavimentos iniciais em ambos os sistemas construtivos. / This study consist of a structural analyses of concrete walls and masonry building including the soil-structure interaction and the construction process. Each pilot building is 45 meters high, consisting of 15 floors with 2.80 m high. Each floors are seated on pillars of reinforced concrete with 3 meters of height, which were modeled using 4 methodologies: (i) The AI_AF, classic reference model, which adopts fixed foundations and instantaneous action; (ii) The AE_AF is a model, that includes construction loads and incorporates a gradual increasing in load and stiffness; (iii) The AI_ISE model incorporates interaction with the soil and the instantaneous application of actions; and, (iv) AE_ISE, which consists of a more refined model with soil interaction and the time of construction. The concrete walls are modeled based on shell finite elements, the concrete pillars, transition beams, stakes and blocks are modeled based on bar finite element and the soil mass is modelled as an isoparametric solid finite elements. The numerical modelling is conducted using commercial software DIANA®. Results show that the classic reference model, in which the soil-structure interaction is not considered, does not attent to the need of increasing the ductility of the walls in initials floor.

Forest biomass burned for energy purposes does not need to be accounted for under IPCC rules. This has led to a number of countries considering tree stump harvesting as a source of forest biomass. However there are concerns that the soil disturbance that this may entail could have adverse environmental effects, including the loss of sequestered carbon from the soil. Published results differ in the degree and nature of stump harvesting soil disturbance. Two widely used measures employed in stump harvesting soil disturbance studies are visual assessment of disturbance extent and bulk density measures of the nature of disturbance. Each of these has limitations. This study seeks to extend the insight into both the nature and extent of soil disturbance resulting from stump harvesting by the application of additional techniques. In this way the physical effects of soil disturbance by stump harvesting will be compared with those of other forestry practices. To overcome the two-dimensional and subjective nature of visual assessment, a radiometric approach was adopted, utilising residual Chernobyl 137Cs fallout to determine the degree of soil mixing. To complement bulk density measurements, micromorphological analyses of soil thin sections taken from field samples were carried out to investigate the impact of compressive force on pore space. Low-cost tracer devices were deployed in the soil around stumps prior to extraction to permit the monitoring of the lateral movement of soil during stump extraction. These methods were applied to a stump harvesting operation carried out under current UK guidance at a UPM Tilhill managed site in south west Scotland. The radiometric method demonstrated its capacity to recognise differing degrees of soil disturbance in an operational forest environment, including some disturbance that might escape visual assessment. Analysis of soil thin sections provided the evidence of a significant increase in the pore capacity of disturbed soil. The soil movement tracers developed for this project provided the capability to examine the various trajectories of soil during stump extraction as well as dimensioning the resulting disturbance crater. The study indicated that under current UK management and operational practice, stump harvesting generated a higher level of soil disturbance compared to ground preparation by trench mounding, with an estimated 1260 m3 ha-1 of soil disturbed by stump harvesting compared to 250 m3 ha-1 from trench mounding. Stump harvesting was found to generate a net reduction in soil bulk density in the affected areas, contrary to the findings of some other studies. This outcome is dependent on adhering to particular site management and operational procedures. The practice of raking over the site following stump harvesting is estimated to add a further 10% to the volume of soil disturbed, and is a questionable activity under soil sustainability guidance. This work was part-funded and actively supported by the UK Forestry Commission and UPM Tilhill.