O presente trabalho se propôs a estudar os esquemas estruturais alternativos para pontes esconsas e avaliar as modelagens matemáticas possíveis através de softwares especializados, como o SAP2000 e STRAP2010, a fim de identificar as melhores soluções e modelos para cada caso. O objetivo foi o de aprimorar os modelos de cálculo, especialmente no que diz respeito à previsão das reações de apoio e das forças cortantes, ponto mais delicado de obras esconsas. O estudo baseou-se em soluções de superestrutura em laje e em grelha, com ou sem transversinas, com esconsidade variável entre zero e sessenta graus, eixo longitudinal reto, modeladas por barras e elementos finitos. Não foi objeto deste estudo a influência da meso e da infraestrutura dessas pontes nos esforços na superestrutura. / The present work is proposed to study alternative structural schemes for skew bridges and to evaluate possible mathematical modeling through specialized software, such as SAP 2000 and STRAP2010, in order to identify the best solutions and models for each case. The aim was to improve the calculation models, especially with regard to the prediction of the support reactions and shear forces, most delicate point in skew bridges. The study was based on slab or grid, with or without transversal beams, superstructure solutions, with variable skew between zero and sixty degrees, straight longitudinal axis, modeled through bars and shell elements. It was not purpose of this study the influence of meso and infrastructure of the bridge on its superstructure.

Recently a large amount of interest has developed around separating out impurities of small size; pertinent examples are found within fuel and solvent processing. For such applications a leading candidate process is nanofiltration. This thesis focuses on SRNF (solvent resistant nanofiltration) composite membranes consisting of a dense polymer active layer bonded to a stronger, but ultimately more porous, support layer. The composite membranes that have been produced during the course of this work consist of a PDMS (polymdimethylsiloxane) active layer bonded to a commercially available support layer of PAN (polyacrylonitrile). To create the membrane a monomer was spread over the support layer and then polymerised to form the matrix which was responsible for separation. Commercially, either heat or radiation is often applied to cause polymerisation, however the membranes in the current work have been formed by the used of a homogeneous catalyst. This thesis investigates the transport and separation dynamics of the produced membranes for a series of fuel simulants composed of organometallics and poly-nuclear aromatic solutes dissolved in aromatic and alkane solvents. Membrane composition and the extent of polymer swelling were found to be the two key factors which had the greatest influence on solvent flux and solute rejection. By increasing catalyst concentration it was found that the dual effects of increased rejection and reduced flux occurred, with the converse also being true. The effective pore size of the membrane could also be controlled by varying the catalyst amount during manufacture as this directly affected the limit of crosslinking which formed. Polymer swelling was the most pronounced using solvents with a solubility parameter close to that of the polymer. The membrane transport mechanism was most accurately forecast by the solution diffusion model for flux predictions and the convection diffusion model for rejection predictions, however all the models tried were in close agreement. This was postulated to be due to the swelled polymer matrix which allows for both convective and diffusive transport to occur.

The Andean Cordilleran orogenic system stretches over 7,000 km along the western margin of South America and serves as a useful laboratory to evaluate the causes of spatial and temporal variations in orogenic processes. Although the geology of the Andean margin is fundamentally controlled by the subduction of the Nazca plate beneath the South American plate, the style of deformation, basin morphology, exhumation history, and volcanic activity along this margin are remarkably heterogeneous in both time and space. My Ph.D. work presents new data from the Miocene – Pliocene along-strike depocenters bounding the basement block uplifts of the Sierras Pampeanas and the fold and thrust belt of the Andean Precordilleran in the south Central Andes between ca. 27.5°S and 30.5°S. I use new observations from sedimentology, detrital zircon U-Pb data, and low-temperature thermochronology to evaluate the mechanisms driving basin organization, sedimentation, and exhumation. Geohistory analysis supports flexurally controlled basins between ca. 18 and 6 Ma with detritus derived exclusively from the active Precodillera to the west. Accelerated deformation in the Precordillera produced accelerated sedimentation from ca. 10 – 8.5 Ma. A deceleration of sedimentation from ca. 6 – 5 Ma was most likely controlled by heightened aridity. Around the same time, low-temperature thermochronometers record the widespread exhumation of the foreland basin system for over 300 km along strike, this may be driven by dynamically controlled uplift related to Miocene flat-slab subduction. Low-temperature thermochronometers suggest that the geothermal gradient throughout the late Miocene was ca. 35°C/km – 25°C/km and had not been significantly depressed as previously proposed. Granite-cored ranges in the Sierras Pampeanas were sampled for low-temperature thermochronology to constrain the exhumation history of the region. Modeling of both apatite fission track and apatite (U-Th-Sm)/He thermochronometers demonstrates that these rocks have been close to the surface since the late Paleozoic. Reheating during the Cretaceous is attributed to elevated geothermal gradients due to back-arc rifting. Final exhumation (1- 2 km) occurred in the mid to late Miocene and may have been controlled by the onset of flat-slab subduction. These results suggest that the Sierras Pampeanas may have had inherited positive topography that has controlled basin organization and sediment distribution patterns since the Paleozoic.

This thesis presents the results of an experimental, numerical and analytical study to develop a design method to calculate punching shear resistance for a new shearhead system between tubular steel column and reinforced concrete flat slab. This shearhead system enables two of the most popular structural systems, i.e. reinforced concrete flat slab floor and steel tubular column, to be used to produce efficient structures of low cost and short construction time. This research investigates slabs without and with a service hole adjacent to the column. The new shearhead system should not only possess sufficient punching shear resistance, but should also be efficient for construction. The main methodology for this project was based on numerical finite element simulations verified by two full scale tests. These two tests were carried out in the University of Manchester's Structural Testing Laboratory. The two specimens had the same slab size, thickness and reinforcement ratio, but differed in the column shape (rectangular or circular), central reinforcement arrangement (continuous or discontinuous), shearhead position in the slab thickness and shearhead fabrication arrangement. Recorded load-deflection and load-strain relationships, crack development and critical perimeter were used for detailed validation of using the commercial finite element software ABAQUS. The validated ABAQUS model was used to conduct a comprehensive parametric study to investigate the effects of a number of design parameters, including the effect of varied column size, shearhead arm length, shearhead arm cross section, shearhead arm angle, amount of flexural reinforcement, slab thickness, shearhead positions and hole positions. The main conclusion from the parametric study was that the shearhead system could be treated as an enlarged column in normal flat slab structure. The parametric study enabled pressure distribution below the shearhead arms to be approximated for checking whether the shearhead arms would be sufficient for the enlarged column assumption to be valid. The parametric study results were also used to determine the effective depth of the flat slab and critical punching shear perimeter of the slab with and without a service hole.Using the enlarged column assumption, the punching shear resistance of all structures used in the parametric study were re-calculated using Eurocode 2 (EC2), British stand 8110 (BS8110) and American Concrete Institute code 318 (ACI 318). Comparison of calculation results using these three design methods indicates that both EC2 and BS8110 predicted very close value which reached very good agreement with the ABAQUS simulation (normally within 10%). Among these three design methods, ACI 318 was the only code that explicitly considered shearhead system. ACI 318 was not able to predict the slab critical perimeter length with good accuracy, however, its prediction of slab punching shear resistance achieved reasonably good agreement with numerical analysis results and were on the safe side. Based on these studies, a design method for calculating punching resistance of the proposed shearhead system between reinforced concrete flat slab and steel tubular column has been developed in this thesis.

The thesis presents the structural behaviour of fibre reinforced polymer (FRP) laminated composites based on 3D elasticity formulation and finite element modeling using Abaqus. This investigation into the performance of the laminate included subjecting it to various parameters i.e. different boundary conditions, material properties and loading conditions to examine the structural responses of deformation and stress. Both analytical and numerical investigations were performed to determine the stress and displacement distributions at any point of the laminates. Other investigative work undertaken in this study includes the numerical analysis of the effect of flexural deformation of the FRP strengthened RC slab. The formulation of 3D elasticity and enforced boundary conditions were applied to establish the state equation of the laminated composites. Transfer matrix and recursive solutions were then used to produce analytical solutions which satisfied all the boundary conditions throughout all the layers of the composites. These analytical solutions were then compared with numerical analysis through one of the commercial finite element analysis programs, Abaqus. Out of wide variety of element types available in the Abaqus element library, shells and solids elements are chosen to model the composites. From these FEM results, comparison can be made to the solution obtained from the analytical. The novel work and results presented in this thesis are the analysis of fully clamped laminated composite plates. The breakthrough results of fully clamped laminated composite plate can be used as a benchmark for further investigation. These analytical solutions were verified with FEM solutions which showed that only the solid element (C3D20) exhibited close results to the exact solutions. However, FEM gave poor results on the transverse shear stresses particularly at the boundary edges. As an application of the work above, it is noticed that the FEM results for the FRP strengthened RC slab, agreed well with the experimental work conducted in the laboratory. The flexural capacity of the RC slab showed significant increase, both at service and ultimate limit states, after FRP sheets were applied at the bottom surface of the slab. Given the established and developed programming codes, exact solutions of deflection and stresses can be determined for any reduced material properties, boundary and loading conditions, using Mathematica.

This thesis presents the development and validation of a new wireless Impact Echo (IE) system for condition assessment of reinforced concrete slabs. The new IE prototype was compared with other commercially available non-destructive testing (NDT) devices used for similar purposes, namely Ground-Penetrating Radar (GPR) and Ultrasonic Pulse Echo (UPE). Monitoring and structural inspections are critical to effective management of civil infrastructure and NDTs can enhance the quality of condition assessments by providing objective visualizations of the interior of a structural element. The IE method, first developed in the 1980s, has seen few advancements in the last 20 years. The method has been standardized and used on site, but the underlying technology has become outdated. The data obtained from the transducer is difficult to interpret and requires a computer to post-process it before being usable, thus limiting the direct feedback of the method when conducting tests on-site. Because of those limitations and the test being relatively more time consuming than other alternatives, the method is lacking in usability. A new prototype IE device was designed and built by the project industry partner, FPrimeC Solutions. The methodology followed the traditional approach, but it was designed to work with today’s technology. The device is operated wirelessly via a Bluetooth connection, uses smaller-sized electronic components, and connects with a user-friendly interface on a small tablet to set-up the tests and compute the results immediately. The first part of the project focused on product development by testing iterations of the prototype and providing user feedback to improve the device and accompanying software. The second part of the project aimed to validate the new technology using a set of three large reinforced concrete slabs containing artificial defects. The studied points of interest were sound concrete, effect of boundaries and steel reinforcements, vertical cracks, presence of a hollow conduit, artificial voids and delamination. The IE results were also compared with those from commercial GPR and UPE devices. GPR was found to be the quickest method by far, although the results gathered seemed to be limited by the presence of steel reinforcement and also failed to locate certain defects. UPE was a bit slower than GPR, but was generally able to locate more accurately the artificial flaws created in the test specimens. The results showed poor definition of the flaws making it difficult sometimes to properly locate them. The UPE results also seemed to be negatively affected by the presence of reinforcement which were causing frequent abnormal values. Lastly, the IE method was used. This method was greatly improved during the first phase, but it is still a time-consuming method. The value of the data, however, has great potential when compared to the other options. It accurately located most of the flaws generated and was practically unaffected by the presence of steel reinforcing bars. Also, with further analysis of the data, it was possible to determine the depth of some of the flaws accurately. Due to the time-consuming testing phase and the longer analysis of the data required to obtain the higher quality of results, this study suggests that IE is not likely to be the best choice for a general inspection of a large area (depending on the nature of the information needed). Rather, it is suggested to first conduct a general review of the structure using a quicker method like GPR to locate the problematic areas. After that, refining the grid at key locations to test with IE should provide the best quality of data in a reasonable amount of time.

No description available.

<p> The advantages of Thin-Slab Cast Direct-Rolling (TSCDR) process include reduced capital, energy, labour and inventory costs, as well as the ability to roll thinner strip compared to the conventional process of thick slab casting, reheating and hot rolling. There is great interest in utilizing this technology to produce microalloyed steels which can meet American Petroleum Institute (API) standards. However, whereas the conventional approach can produce APIX80, APIXlOO, and even APIX120 steels; the TSCDR process can only produce APIX70 and APIX80. The main obstacles in the way of achieving high API grades are the non-uniform initial as-cast microstructure and the large grains that result from grain growth at high temperature. The production of APIX80 and higher grade steels can only be achieved through a comprehensive research initiative that combines careful control of solidification, homogenization, thermomechanical-processing, cooling and coiling. </p> <p> This contribution examines the solid state microstructure evolution of microalloyed steels under simulated TSCDR conditions. The grain growth kinetics in delta-ferrite and austenite were studied separately using two model alloys. At high temperatures and in the absence of precipitation, the growth kinetics in both delta-ferrite and austenite appeared to follow a simple parabolic growth law. The measured grain growth kinetics was then applied to the problem of grain-size control during the process of TSCDR. Several strategies of controlling and refining the grain size were examined. The kinetics of delta-ferrite to austenite phase transformation was investigated using a quenching dilatometer; the results showed that the austenite phase formed along the original delta grain boundaries, and that the precipitation of austenite at the delta-ferrite grain boundaries effectively pins delta grain growth. The kinetics of the phase transformation was modeled using a local equilibrium model that captures the partitioning of the substitutional elements during the transformation. </p> <p> A novel delta-ferrite/austenite duplex microstructure is proposed to achieve fine and uniform high-temperature microstructure. The grain growth of the matrix phase (delta-ferrite) is controlled by the coarsening mechanism of pinning phase (austenite). The effectiveness of this delta/austenite duplex microstructure was validated experimentally and analyzed in details using a physically-based model. </p> / Thesis / Doctor of Philosophy (PhD)

When designing reinforced concrete (RC) slabs with steel piles various variables must be considered, from the internal force to the distance of piles. An endless number of designs are possible, leaving space for optimizing designs. The purpose of this thesis is to analyze how different variables may affect the design and how to design for different situations. With the rising interest of the environmental impact of constructions the thesis will analyze both optimal cost and carbon footprint. The analysis is limited to the materials cost and carbon footprint excluding transportation and construction work. To analyze optimized design a method was created to calculate RC slabs using minimum amount of material. Limitations were made analyzing a range of pile distances, acting live loads, pile length, and slab thicknesses. The method used a finite element analysis software to analyze internal forces after creep and crack. A code was programmed to execute the method and extracted results presented as graphs. The results indicated that the smallest slab thickness is the optimal design up to a certain pile distancing. The curve of cost and carbon footprint dependent on the slab thickness flattens out with an increased pile distance. When pile distance is the variable of cost and carbon footprint, an exponential curve is found. The pile length impact on the result is found more prominent for lower live loads. When the slab is exposed to the highest live load (20 MPa) the optimal design is found at the lowest pile distance (2 meters). In general cost and carbon footprint is affected equally. However, there are differences in the results as materials have different ratios between cost and carbon footprint. When designing according to pile distance a shorter distance is more optimal for cost than the carbon footprint.

No description available.