O sucesso dos trabalhos protéticos, executados sobre os implantes osseointegrados, depende da estabilidade da conexão entre implante e pilar protético. Dentre as conexões protéticas existentes, as conexões cônicas têm demonstrado um desempenho melhor, tanto em termos mecânicos, como biológicos. A retenção friccional do pilar cônico é a grande responsável pela resistência aos movimentos laterais e oclusais da mastigação. Com a introdução de indexadores no desenho dessas conexões a característica mecânica mudou, levantando dúvidas em relação a sua atuação. Neste trabalho, avaliou-se o efeito do jateamento e uso do adesivo no torque de desaperto dessas conexões. Vinte e oito pilares synOCta® da marca Straumann® foram avaliados quanto ao torque de aperto inicial de 35 N.cm e torque de desaperto após ciclagem mecânica. Três grupos experimentais foram testados em relação ao grupo controle: modificação da superfície cônica por jateamento com óxido de alumínio, aplicação de adesivo entre as partes e o jateamento mais o adesivo. O grupo jateamento com aplicação do adesivo foi o único que apresentou valores de desaperto superiores quando comparado ao grupo controle. A rugosidade criada pelo jateamento, associada ao adesivo, elevou significantemente os valores de torque de desaperto do parafuso em comparação ao torque de aperto. / The success of the prosthetic work performed over dental implants depends on the stability of the connection between implant and abutment. Among the existing prosthetic connections, the conical connections have shown better performance, both mechanical and biological. The frictional retention of the morse taper is largely responsible for the resistance to lateral and occlusal movements of mastication. With the introduction of indexes in the design of these connections, the mechanical characteristic changed, raising doubts about its performance. In this study, we evaluated the effect of blasting and use of adhesive on abutment screw loosening torque of these connections. Twenty-eight synOcta® pillars Straumann® brand were evaluated for initial tightening torque of 35 N.cm and loosening torque after mechanical cycling. Three experimental groups were tested related to the control group: modification of the conical surface by blasting with aluminum oxide, aplication of adhesive between the parties and blasting added to the adhesive. The group blasted with adhesive application was the only one that showed values of loosening torque higher when compared to control group. The roughness created by blasting associated with the adhesive, significantly elevated values of abutment screw loosening torque against the tightening torque.

Although its use has become more widespread, controlled low-strength material, or CLSM, has fallen through the crack between geotechnical engineering and materials engineering research. The National Ready Mix Association states that CLSM is not a low strength concrete, and geotechnical engineers do not consider it as a conventional aggregate backfill. The use of CLSM as a bridge abutment backfill material brings up the need to understand the passive force versus backwall displacement relationship for this application. To safely account for forces generated due to seismic activity and thermal expansion in bridge design, it is important to understand the passive force versus backwall displacement relationship. Previous researchers have pointed out the fallacy of designing skewed bridges the same as non-skewed bridges. They observed that as the bridge skew angle increases, the peak passive force is significantly diminished which could lead to poor or even unsafe performance. The literature agrees that a displacement of 3-5% of the wall height is required to mobilize the peak passive resistance. The shape of the passive force displacement curve is best represented as hyperbolic in shape, and the Log Spiral method has been confirmed to be the most accurate at predicting the peak passive force and the shape of the failure plane. All of the previous research on this topic, whether full-scale field tests or large-scale laboratory tests, has been done with dense compacted sand, dense granular backfill, or computer modeling of these types of conventional backfill materials. However, the use of CLSM is increasing because of the product's satisfactory performance as a conventional backfill replacement and the time saving, or economic, benefits. To determine the relationship of passive force versus backwall displacement for a CLSM backfilled bridge abutment, two laboratory large-scale lateral load tests were conducted at skew angles of 0 and 30°. The model backwall was a 4.13 ft (1.26 m) wide and 2 ft (0.61 m) tall reinforced concrete block skewed to either 0 or 30°. The passive force-displacement curves for the two tests were hyperbolic in shape, and the displacement required to reach the peak passive resistance was approximately 0.75-2% of the wall height. The effect of skew angle on the magnitude of passive resistance in the CLSM backfill was much less significant than for conventional backfill materials. However, within displacements of 4-5% of the backwall height, the passive force-displacement curve reached a relatively constant residual or ultimate strength. The residual strength ranged from 20-40% of the measured peak passive resistance. The failure plane did not follow the logarithmic spiral pattern as the conventional backfill materials did. Instead, the failure plane was nearly linear and the failed wedge was displaced more like a block with very low compressive strains.

Numerical analyses of two different geotechnical problems, namely a bridge abutment and a geosynthetic reinforced embankment are presented in this thesis. Settlement, bearing capacity and slope stability are the major factors that need to be considered in the design of a foundation near a sloped fill. In this thesis, the behaviour of a small scale model footing located near the shoulder of a sloped fill was investigated numerically. Single and multiple layers of geogrid were used to reinforce the sloped fill, and their effects on the load-deformation behaviour and bearing capacity of the footing were explored. The analyses showed 80%, 168%, 295% and 375% maximum improvement in the ultimate bearing capacity with 1, 2, 3 and 4 reinforcement layers respectively. This maximum improvement depends on the embedment depths of the reinforcement layers below the foundation and the suggested optimal depths are discussed. Typically, greatest improvement in ultimate bearing capacity with a single layer of reinforcement was obtained when the reinforcement was at a depth between 0.50 and 0.75 times the foundation width. Similarly, highest ultimate bearing capacity with 2 reinforcement layers was predicted when the spacing between them was 1.0 times the width of the foundation. However, higher settlement was estimated at failure for the reinforced sloped fill than the unreinforced one. The second problem investigated was the three-dimensional (3D) analysis of Sackville embankment, a geosynthetic reinforced embankment on soft soil. Previous analyses using two-dimensional (2D) numerical modelling of Sackville embankment indicated potential 3D effects affecting the performance of this embankment. Therefore, 3D analysis incorporating geometric variations of Sackville embankment foundation soil, anisotropic model for fluid flow, mobilization of geotextile stresses in minor direction and the boundary effects (lateral directions) were taken into account in this analysis. The predicted performance of Sackville embankment were compared with the field data and the previously reported 2D analysis results in terms of vertical and horizontal displacements and excess pore pressures in the foundation soil, and geotextile stresses, strains and displacements. Better overall predictions of the Sackville embankment performance was obtained from this 3D analysis than the previous analysis reported in the literature.

Integral abutment bridges are jointless bridges in which the deck is continuous and connected monolithically with the abutment walls supported typically by a single row of piles. This thesis focuses on the effects of two major parameters on the seismic behavior of an integral abutment bridge in Tennessee by considering soil-structure interaction around the piles and in back of the abutments: (1) clay stiffness (medium vs. hard) around the piles, and (2) level of sand compaction (loose vs. dense) of the abutment wall backfilling. Modal and nonlinear time history analyses are performed on a three dimensional detailed bridge model using the commercial software SAP2000, which clearly show that (1) compacting the backfilling of the abutment wall will increase the bridge dominant longitudinal natural frequency considerably more than increasing the clay stiffness around the piles; (2) the maximum deflection and bending moment in the piles under seismic loading will happen at the pile-abutment interface; (3) under seismic loading, densely-compacted backfilling of the abutment wall is generally recommended since it will reduce the pile deflection, the abutment displacement, the moments in the steel girder, and particularly the pile moments; (4) under seismic loading, when the piles are located in firmer clay, although the pile deflection, the abutment displacement, and the maximum girder moment at the pier and the mid-span will decrease, the maximum pile moment and the maximum girder moment at the abutment will increase.

Vibration-based damage detection (VBDD) comprises a family of non-destructive testing methods in which changes to dynamic characteristics are used to track the condition of a structure. Although VBDD methods have been successfully applied to various mechanical systems and to simple beam-like structures, significant challenges remain in extending this technology to complex, spatially distributed structures such as bridges. <p> In the present study, numerical simulations using a calibrated finite element model were used to investigate the use of VBDD methods to detect small-scale damage on a two-span, integral abutment overpass structure located in Saskatoon, Saskatchewan. The small scale damage was defined in this study as the removal of a concrete element from the top surface of the bridge deck, resembling the spalled clear cover of concrete deck of the overpass. Five different VBDD techniques were evaluated, including the Change in Mode Shape, Change in Flexibility, Change in Mode Shape Curvature, Change in Uniform Flexibility Curvature and Damage index methods. In addition, the influence of the size of damage, the orientation of damage geometry, sensor spacing (3 m, 5 m and 7.5 m), the approach used for mode shape normalization, and uncertainty in the measured mode shapes was investigated. <p> It was found that localized damage could be reliably detected and located if the sensors were located within 3 m of the damage (the distance between adjacent girders) and if uncertainty in the mode shapes was attenuated through the use of a sufficient number of repeated trials. Furthermore, studies using a limited sensor installation that could be achieved without interrupting the flow of traffic indicated that small scale damage could be detected and potentially located using sensors that are placed well away from the damaged area, provided uncertainty in mode shape was attenuated.

In this master thesis the connection between the two major parts of an osseointegrated prosthesis system for lower limb amputees has been investigated by finite element (FE) analysis. The prosthesis system is developed by Integrum and the current design consists of a fixture, which is integrated in the residual bone, an abutment that penetrates the skin and an abutment screw that holds the parts together. The connection between the fixture and the abutment has a hexagonal section and a press-fit section that together form the connection. Due to wear and fracture problems it is desired to improve the connection. A tapered connection could be an alternative and three different taper angles, the effect of the length of the taper and the smoothness of the outer edge of a tapered fixture have been investigated. The results show that the taper has potential to function well and that a longer connection will give lower stresses in the system, but further investigations are needed.

Vibration-based damage detection (VBDD) comprises a family of non-destructive testing methods in which changes to dynamic characteristics are used to track the condition of a structure. Although VBDD methods have been successfully applied to various mechanical systems and to simple beam-like structures, significant challenges remain in extending this technology to complex, spatially distributed structures such as bridges. <p> In the present study, numerical simulations using a calibrated finite element model were used to investigate the use of VBDD methods to detect small-scale damage on a two-span, integral abutment overpass structure located in Saskatoon, Saskatchewan. The small scale damage was defined in this study as the removal of a concrete element from the top surface of the bridge deck, resembling the spalled clear cover of concrete deck of the overpass. Five different VBDD techniques were evaluated, including the Change in Mode Shape, Change in Flexibility, Change in Mode Shape Curvature, Change in Uniform Flexibility Curvature and Damage index methods. In addition, the influence of the size of damage, the orientation of damage geometry, sensor spacing (3 m, 5 m and 7.5 m), the approach used for mode shape normalization, and uncertainty in the measured mode shapes was investigated. <p> It was found that localized damage could be reliably detected and located if the sensors were located within 3 m of the damage (the distance between adjacent girders) and if uncertainty in the mode shapes was attenuated through the use of a sufficient number of repeated trials. Furthermore, studies using a limited sensor installation that could be achieved without interrupting the flow of traffic indicated that small scale damage could be detected and potentially located using sensors that are placed well away from the damaged area, provided uncertainty in mode shape was attenuated.

The bridge scour depths in cohesive soil have been predicted using the scour equations developed for cohesionless soils due to scarce of studies about cohesive soil. The scour depths predicted by the conventional methods will result in significant errors. For the cost effective design of bridge scour in cohesive soil, the Scour Rate In COhesvie Soil (SRICOS) for the singular circular pier in deep water condition was released in 1999, and has been developed for complex pier and contraction scour. The present study is the part of SRICOS-EFA method to predict the history of contraction scour, and local scours, such as abutment scour and pier scour. The main objective is to develop the prediction methods for the maximum and the uniform contraction scour depth, the maximum pier scour depth and the maximum abutment using flume test results. The equations are basically composed with the difference between the local Froude number and the critical Froude number. Because the scour happens when the shear stress is bigger than the critical shear stress, which is the maximum shear stress the channel bed material can resist from the erosion, and continues until the shear stress becomes equal to the critical shear stress. All results obtained from flume tests for pier scour have been conducted in Texas A&M University from 1997 to 2002 are collected and reanalyzed in this study. Since the original pier scour equation did not include soil properties. The effect of water depth effect, pier spacing, pier shape and flow attack angle for the rectangular pier are studied and correction factors with respect to the circular pier in deep water condition were newly developed in present study. For the abutment scour, a series of flume tests in large scale was performed in the present study. Two types of channel - rectangular channel, and compound channel - were used. The effect of abutment length, shape and alignment of abutment were studied and the correction factors were developed. The patterns of velocity and of scour were compared, and it was found that the maximum local scour occurred where the maximum turbulence was measured. For the contraction scour, the results obtained from a series of flume tests performed in 2002 and a series of flume tests for the abutment scour in the present study are analyzed. The methodologies to predict the maximum contraction scour and the uniform contraction scour in the compound channel was developed. Although all prediction methods developed in the present study are for the cohesive soils, those methods may be applicable to the cohesionless soils because the critical shear stress is included in the methods. All prediction methods were verified by the comparison with the databases obtained from flume test results and field data.

Computation of temporal variation of clear water scour is important for the design of bridge foundations. Previous studies conducted for determining equilibrium scour depth at bridge abutments indicated that very long flow duration was needed to achieve equilibrium scouring situations. However, the corresponding durations in the prototype conditions may yield considerably greater values than time to peak of the design flood. Therefore, there is a need to estimate the temporal variation of scour depth. An experimental study was carried out to observe temporal variation of scour depth and contours around vertical-wall and wing-wall abutments. The results of the experiments have been interpreted. A semi-empirical model has been developed for determining time-dependent variation of clear water scour depth at vertical-wall abutments. This approach is based on the application of sediment continuity equation to the scour hole around the vertical-wall abutment. To this end, time-dependent geometric features of the scour hole were investigated and a recent sediment pickup function was used to formulate the rate of sediment transport out of the scour hole. The results of the proposed model were compared with those of some empirical models. The findings of the model agree well with the experimental results.

Deterministic scour prediction equations for bridge abutments do not involve uncertainties coming from scouring parameters and they only consider effects of hydraulic parameters. However, in order to safely design bridge abutments, treatment of these uncertainties and evaluation of possible risks are required. Two artificial neural network (ANN) models are constructed to describe scouring phenomenon using the parameters of two different equations. The equation to be used in the reliability analysis is then determined according to ANN modeling results. To conduct reliability analysis, Monte Carlo simulation technique is used in which different distributions and coefficients of variations are used for random variables to examine their effects on reliability. It is observed that probability distributions of governing variables have no impact on reliability. However, coefficients of variations of these variables influence reliability.