Resumo em Inglês:

Abstract This article presents a theoretical and numerical study of an innovative joint using cold-formed steel sections. The motivation for the study of this connection is the ease of manufacturing and assembly that it provides. The profiles are made of cold-formed lipped channel sections, which are welded to form closed built-up sections on the columns and open built-up lipped sections to the beams. The beams use endplates connected by bolts (threaded bars) to the columns. The study evaluates the connection’s initial stiffness of 19 models, where the following parameters were varied: the thickness of the profiles and endplates, the height of the column sections and the diameter of the bolts. A theoretical and a numerical study were developed: the numerical study was performed using finite elements through the commercial software ANSYS, whereas the theoretical study was made based on the component method, prescribed by Eurocode 3, that does not include the design of the connection analyzed herein. Thus, aiming to enable the design of joints composed of cold-formed lipped channel sections, the analysis results were compared and an adjustment coefficient, proportional to the slenderness of the column’s plates, was proposed. The coefficient was introduced to the stiffness component that represents the column web in compression in the mechanical model. The ratio between the coefficients’ numerical and theoretical values presented a maximum variation of 11%, which was considered satisfactory.

Resumo em Inglês:

Abstract With the advances in computational analysis techniques and development of new design methods, new interests have arisen in structural engineering. In the last few years, with the increasing numbers of terrorist attacks, the study of robustness, progressive structural collapse and ultimate resistance of structures has grown exponentially, with various studies being published all over the world. In order to perform this study through computational analysis, it was necessary to develop a calibrated numerical model capable of representing the behaviour of structures in their final stage of resistance. This article presents an evaluation of semi-rigid connections through a numerical model considering the implementation of collapse and damage progression criteria calibrated against experimental tests. Afterwards, a parametric study was developed by varying the bolt diameters and endplate thickness of a flush endplate semi-rigid connection. The main parameters and criteria that rules the simulation of flush end-plate joints subject to damage were assessed, allowing that many different kind of studies with similar components could be performed, such as impact, explosion and column loss analysis. As an outcome, the bending moment-rotation curves of these connections are presented and it is shown that those with a larger bolt diameter were able to produce greater rotation, while an increase in the endplate thickness was able to provide a greater bending moment capacity.

Resumo em Inglês:

Abstract In this study, a ground anchored wall located in Belo Horizonte containing 295 anchorages in a sandy silt soil was analyzed. The load capacity of all the anchors was calculated by extrapolation of the receipt tests by the Van der Veen method through the CsAGeo web application. The shear strength in the soil-anchor interface was obtained from a semi-empirical method. Two criteria to analyze the extrapolated curves of Van der Veen were used. In the first criteria, the shear strengths of all the extrapolated curves were calculated. In the second criteria, only those curves from the extrapolations considered as reliable were used to calculate the shear strengths. The main objective of this work is to set up the value of shear strength at the soil-anchor interface through extrapolation of the mathematical and semi-empirical methods. The semi-empirical method was carried out in soil and executive methodology equal to the work analysed, which increases the accuracy of these values contributing to containments using anchors. The results were grouped according to the ranges of the penetration resistance (NSPT). An increasing tendency was identified in the shear strength as the value of the resistance to penetration increased. In addition, the linear tendency was observed for the reliable curves.

Resumo em Inglês:

Abstract The management and monitoring of mechanized tunnel excavation parameters are crucial for ensuring the safety, quality and project's time/costs, since these parameters are the only existing elements that enable the evaluation of the performance of the excavation itself. In this study, will be presented the computational tool christened as SAPE (Support System and Monitoring of Underground Excavation Parameters), an innovative tool meant to assist the monitoring of ongoing or completed mechanized tunneling projects. The tool was designed to be a flexible and simple management tool, which means that it can be customized as a function of the characteristics of each project. The default version comprises the most important excavation parameters (a total of 14). Besides, it has important functions, such as geolocation (GoogleEarth program), historical production data and basic excavation statistics. The software was tested in the recently completed twin tunnels of the Subway Line 5 - Lilac in the city of São Paulo, Brazil.

Resumo em Inglês:

Abstract The industrial development and the advance of the primary sector in Brazil generated an increase in the cases of structures damaged by sulfate attacks. A reduction in material lifetime is one of the most costly factors in the construction field. Therefore, it is necessary to understand the sulfate attack mechanism in order to provide repairs and prevent further attacks. This article aims to understand how the environmental condition and the material properties influence the attack’s severity. Hence, it combined an experimental program and analytical model to measure those parameter effects. Experiments show that cement with a higher amount of tricalcium aluminate (C3A), as the CP V ARI, presented a more pronounced deterioration. Visual changes such as cracking, crystallization of expansive products and a complete disintegration were also observed. In addition, loss of resistance occurred in the specimens with low slag content. Moreover, the model is useful to predict the delamination depth and to identify the most critical factors influencing the attack through sensitive analysis. Its results were compared with real cases based on literature and verifying the model reliability.

Resumo em Inglês:

Abstract Soil provides important support for anthropogenic activities, and earthen trails, which have always been present in the natural landscape, are routes of access to various tourist attractions. In recent decades, trails have been widely used as a method of access and visitation to geotouristic attractions. Because trails are restricted routes, transit along these paths also transforms the route into a pathway for the spread of various negative environmental impacts, including compaction and soil erosion of the trailbed. Soil compaction is caused by changes in the soil structure that are partly induced by the use of agricultural or geotechnical machinery and traffic, and the damage is also manifested in a remarkable decrease in porosity, which has clear implications for the infiltration and percolation of water and air associated with the functional porosity of soil. Soil micromorphological characteristics contribute to the analysis of soil porous systems, and the macroporous characteristics visible at this scale include the size, shape and connectivity among voids, which can be studied using different methods of identification, measurement and interpretation. Such methods are applied to understand the pore genesis and, more importantly, the physical behavior of soil-water order management. This work presents the results of analyses of the macromorphological and micromorphological characteristics, porosity, texture and penetrometry resistance of soil profiles on the Farofa Waterfall trail in the Serra do Cipó National Park, and the aim is to provide recommendations for compaction studies along special trails. The results showed that most of the trailbed is more compressed than at the margins, which suggests the need for geoindicator studies of soil quality to monitor the visitation of the trail and improve the conservation of natural resources.

Resumo em Inglês:

Abstract The mining industry can be one of the most impacting human activities. In the southern region of Santa Catarina (Brazil), open pit coal mining has left an extensive environmental impact. Since there was no topsoil in the abandoned open pit sites, it is necessary to provide a substrate for vegetation growth. However, the selection of the best substrate between multiple options is difficult. Thus, a fuzzy logic-based model is proposed. The proposed model was compared to reference models and to experts’ knowledge. Statistical analysis and validation were carried out with a correlation coefficient, a Kappa coefficient, along with the Accuracy, Precision, Sensibility Specificity, F-Score and Mathews correlation coefficients. The data set used to assess the proposed model presented a wide range of data, but for values such as aluminum saturation, higher values were common. The fuzzy logic-based expert system presented better results when assessing the behavior of the defuzzified output values with the crisp input values. The fuzzy model also followed the trend of the reference models (with R2 between 0.3639 and 0.5250). The comparison to the experts’ opinion demonstrated that agreement comes easily with extreme values (such as not suitable and suitable). However, using a Winner-Takes-All approach, the proposed fuzzy model had high scores for suitable soils for land reclamation’s soil construction. The proposed model can be used to define the best substrate for land reclamation. Some improvements, such as different parameters and increases in the number of interviews rounds, should be also tested.

Resumo em Inglês:

Abstract In Brazil, natural caves in iron lithotypes have increasingly been discovered in iron mining areas and its surroundings. Mining companies attempt to study them according to the Federal Decree 6640/2008 and the Normative Instruction 2/2009 of the Ministry of the Environment, which is concerned with the preservation of the Brazilian Speleological Heritage. This research is within one of those studies in which a geophysical campaign methodology is established for an attempted prospection of caves, in an area located on the north flank of Mariana's Anticlinal, Quadrilátero Ferrífero. The flank, which is sustained by iron formations from the Itabira Group and covered by the product of alteration and sedimentary redistribution, experienced extensive and compressive tectonics, generating, respectively, the main structuration in the NW-SE direction and schist thrust slices from the Nova Lima Group. Caves are mainly developed in the lithological contacts and in fault zones. In the regional stage, the methodology uses aeromagnetometric (identification of iron lithotypes, structural and statistical analysis of magnetic lineaments) and aeroradiometric (structural-geological mapping and setting of lithological contacts) methods. Results have shown some caves in lateral contact zones between lithologies, and the structural control imposed by a shear zone in the area. At the local stage, the electrical resistivity method - EL was used, dipole-dipole array, data mathematical inversion, presentation of pseudo-depth sections and tridimensional modeling. The results, in accordance with the topographic data, show the possible limits of the geometric contour and the tendency for cave deepening. However, studies of the moisture, of similar caves with different spacings, and the use of Ground Penetration Radar - GPR are suggested.

Resumo em Inglês:

Abstract The Córrego dos Boiadeiros Body (CBB) comprises a metaultramafic-metamafic sequence located in the vicinities of Nova Lima town, central area of the Quadrilátero Ferrífero province. The main rock type is a serpentinite that grades upwards to weathering mantles with well-preserved pedogenetic horizons composed, from bottom to top, of four facies: the R Horizon (Fresh rock facies), the C Horizon (Alterite facies), the B Horizon (Transition facies) and the A Horizon (Solum facies). This article presents the results of geochemical and mass balance studies along a representative pedogenetic profile in order to evaluate the chemical transformations concerning major, trace and Rare Earth Elements. From bottom to top of the selected profile, there is enrichment in Fe2O3, Al2O3 and depletion in MgO and SiO2. There are also relative gains of metallic elements as Ni, Co, V and loss of Au. Cr is enriched at the uppermost horizon. Pt is enriched at the basis of the profile, but decreases towards the upper layers. The weathering mantle is REE-enriched and shows major fractionating of LREE over HREE. In order to evaluate the economic potential of the lateritic deposits, especially concerning Cr content, additional chemical analyses should be distributed over the entire body and its surroundings.

Resumo em Inglês:

Abstract Machining is one of the most important manufacturing processes used worldwide in the mechanical industry, and in order to optimize productivity, cutting fluids can be used in the process. Vegetable based fluids present low toxicity as well as good biodegradability and environmental sustainability; however, they also have low oxidative stability. Esters which are obtained from different vegetable oils, maintain the qualities mentioned and provide the required stability. This study presents a production and characterization of the raw materials, methyl esters and epoxidized methyl esters, as well as mainly the comparative evaluation of the cutting fluid formed by these esters with commercial fluids derived from minerals. The emulsions were evaluated regarding the mechanical properties resulting from their use in the process, registration of the temperature obtained during machining, the rough surface the dimensional deviation of the final product and also the evaluation of surface oxidation occurred on the pieces in the medium term. Emulsions containing 5% of esters (methyl and epoxidized methyl) seemed to be the best option, presenting less oxidation of machined pieces, lower working temperature during the process and better surface completion, demonstrating the best performance over the tested fluids.

Resumo em Inglês:

Abstract The developed model is an association of thermodynamic calculations for dissolution of alloys, slag formers and the deoxidation reaction in the molten steel with two artificial neural network (ANN) models trained with industrial data, to predict the molten steel temperature drop from the blowing end of the BOF until the first measurement at secondary metallurgy. To calculate the associated energy for deoxidation, an experiment was designed to set up the parameters for oxygen partitioning among deoxidants, with timed aluminum addition during teeming being the main parameter. The temperature control in the teeming stage presented a standard deviation for the error of prediction of 5.46 ºC, for transportation from the rinsing station to the secondary metallurgy of 2.79 ºC. The association of all calculations presented an error standard deviation of 7.49 ºC. The operational validation presented superior accuracy compared with the current method for controlling the temperature, resulting in a reduction in the aluminum consumption for heating at secondary metallurgy with a potential economy of U$ 4.07 million per year for a steel shop producing 5 million tons of steel yearly. The artificial neural network model confirmed its capacity for modeling a complex multivariable process and the separation of thermodynamic calculation provides a better adaptability to different steel grades with different teeming strategies.

Resumo em Inglês:

Abstract The manufacturing of the gear profile by Metal Forming is widely used in industry due to its quality and production capability. Direct cold extrusion has this characteristic and with support of peripheral technologies allows the development of asymmetric parts with complex geometry and near net shape. These resources, added with the great experience of a Brazilian forging company with strong presence in the cold forging market, allowed to develop a cold extrusion process to produce spur gears using the low carbon steel alloy described as SAE 10B22. The goal of this study was to develop the whole process, precision tooling project and manufacture as well as the experimental availability of the process. The tools were manufactured with high speed steel AISI M2 having a hardness in a range from 61 up to 63 HRc. The shrink rings were manufactured using steels with more toughness, such as S1 and H13. The application of shrink rings for the prestressing of tooling was evaluated using two different methods. The first one is using conventional shrink rings with tool steel, while the second is the stripwinding concept developed by the company STRECON.

Resumo em Inglês:

Abstract Lab experiments were carried out to check the effect of some process parameters of nitriding, performed simultaneously with decarburization, on magnetic properties of 3%Si Grain-oriented silicon steel produced by a low slab reheating technology. The samples of (GO) 3% Si steel collected as 0.27mm cold-rolled were submitted to a continuous annealing process at two temperatures, 860 and 900ºC; three annealing times, 63.6, 95.4, and 119.25s; and three ammonia flows 0.1, 0.2, and 0.4Nm3/h. The nitrogen content obtained after the treatments was much higher than those obtained by the currently used process, and it increased as the ammonia flow rates and soaking times were increased, hindering the primary grain growth that adversely affected the magnetic properties. The increase of annealing temperature improved the decarburization and the magnetic properties. The best magnetic properties were found in the sample with the highest primary grain size and the lowest amount of absorbed nitrogen. The success of this practice, in terms of magnetic properties, was pointed out to be based on a drastic reduction on strip nitrogen increase.

Resumo em Inglês:

Abstract The 316L stainless steel (316L SS) is one of the most used metallic materials for implants, due to its high mechanical properties and low cost. However, it is bioinert. One possibility to improve its biocompatibility is the production of a composite with b-tricalcium phosphate (β-TCP) addition. This study investigated the mechanical behavior of 316L SS/β-TCP composites through powder metallurgy. For this, used were 3 compositions, with 0 %, 5 % and 20 % of β-TCP. The compositions with 5% and 20% were milled during 10 hours with a mass/sphere ratio of 1:10 and 350 rpm. All compositions were uniaxially pressed with 619 MPa and sintered during 1 hour at 1100ºC. The microstructural and mechanical evaluations were performed through scanning electron microscopy, density and compressive strength. The results indicated that, by increasing the percentage of β-TCP in the compositions, the mechanical resistance decreases, as a consequence of its low load support.

Resumo em Inglês:

Abstract The aim of this study was to evaluate the corrosion resistance of Ni-bearing carbon steels used in outdoor structures from short-term experimental techniques and compare with the long-term field test data. The carbon steels studied were two experimental steels, produced in a pilot plant, and alloyed with nickel, copper, silicon and molybdenum (Ni-Cu-Si and Ni-Cu-Mo-Si steels), one carbon steel and one commercial Cr-Cu-Si alloyed steel. The atmospheric corrosion resistance of low alloyed carbon steels was evaluated by using field tests for eight years in a marine station, and their electrochemical behavior was studied in laboratory using the electrochemical impedance spectroscopy in aqueous electrolytes containing chlorides. The Ni-Cu-Si and Ni-Cu-Mo-Si steels showed the lowest corrosion rates which decreased as the time increased after eight years of exposure in marine atmosphere. The classification of the low alloyed steels considering the corrosion resistance using electrochemical tests in 10% m/v NaCl solution was similar to rating using field tests in a marine station.

Resumo em Inglês:

Abstract Geologic modeling is an important step in determining the benefits and final pit dimensions for mining operations. Geostatistical models and distance-based functions are the main methods used to estimate the grade behavior. However, these two methods, despite their similar mean values, differ in spatial variability. The objective of this article is to prove, by comparing the two methodologies, that models with different spatial variability using the Lerchs-Grossmann algorithm will output subtly different final pit dimensions and scheduling. Furthermore, with the direct block schedule (DBS), these differences can be considerable. The tests compared the methodologies using the following three models: inverse distance (ID), ordinary kriging (OK) and turning bands simulation (TBS). The results demonstrate that the Lerchs-Grossmann algorithm is only slightly sensitive to the spatial variability of the grade; however, DBS requires the model populations to be better defined because of its greater sensitivity to spatial variability.