EM - Escola de Minas

Agora exibindo 1 - 4 de 4

The importance of underpaint corrosion caused by damage to paint on steel structures.
(2020) Ribeiro Filho, Guido Lessa; Ribas, Rovadávia Aline de Jesus; Paula, Geraldo Donizetti de
The impact of varying the dry paint film thickness (DFT) on the underpaint corrosion of steel plates obtained from the floor of an offshore oil platform is evaluated. The specimens were all prepared using the same material and paint scheme, and the DFT and exposure conditions in a salt spray chamber were varied and compared with the results obtained in a real situation. The results indicated that corrosion initiated at sites where the paint was damaged, may be more important than corrosion through the undamaged paint due to permeation, even in cases where the DFT is thin. In specimens whose substrates were previously damaged, there were pathological manifestations of osmotic blistering. The underpaint corrosion that occurred after the paint was damaged in the field occurred at an intensity like that observed for the tested specimens.
Large barchanoid dunes in the Amazon River and the rock record : implications for interpreting large river systems.
(2016) Almeida, Renato Paes de; Galeazzi, Cristiano Padalino; Freitas, Bernardo Tavares; Janikian, Liliane; Ianniruberto, Marco; Marconato, André
The interpretation of large river deposits from the rock record is hampered by the scarcity of direct observations of active large river systems. That is particularly true for deep-channel environments, where tens of meters deep flows dominate. These conditions are extremely different from what is found in smaller systems, from which current facies models were derived. MBES and shallow seismic surveys in a selected area of the Upper Amazonas River in Northern Brazil revealed the presence of large compound barchanoid dunes along the channel thalweg. The dunes are characterized by V-shaped, concave-downstream crest lines and convex-up longitudinal profiles, hundreds of meters wide, up to 300 m in wavelength and several meters high. Based on the morphology of compound dunes, expected preserved sedimentary structures are broad, large-scale, low-angle, concave up and downstream cross-strata, passing laterally and downstream to inclined cosets. Examples of such structures from large river deposits in the rock record are described in the Silurian Serra Grande Group and the Cretaceous São Sebastião and Marizal formations in Northeastern Brazil, as well as in Triassic Hawkesburry Sandstone in Southeastern Australia and the Plio–Pleistocene Içá Formation in the western Amazon. All these sedimentary structures are found near channel base surfaces and are somewhat coarser than the overlying fluvial deposits, favoring the interpretation of thalweg depositional settings. The recognition of large barchanoid dunes as bedforms restricted to river thalwegs and probably to large river systems brings the possibility of establishing new criteria for the interpretation of fluvial system scale in the rock record. Sedimentary structures compatible with the morphological characteristics of these bedforms seem to be relatively common in large river deposits, given their initial recognition in five different fluvial successions in Brazil and Australia, potentially enabling substantial improvements in facies models for large rivers.
A numerical model for concrete slabs under fire conditions.
(2013) Caldas, Rodrigo Barreto; Fakury, Ricardo Hallal; Sousa Junior, João Batista Marques de; Pitanqueira, Roque Luiz da Silva
A numerical model for the behavior of concrete slabs in a fire is described. This model consists of a shell finite element, a damage constitutive model for concrete with steel reinforcement and the consideration of heat transfer through the thickness of the slab. An improved damage constitutive model for concrete at elevated temperatures has been implemented considering compressive and tensile behavior through an orthotropic compliance theory. The damage in compression is based on the concrete stress–strain relationships presented by the European Committee for Standardization. Several calculations have been performed to validate the improved model. The comparison with experimental tests and numerical results confirm the validity of the approach for reinforced concrete slabs subjected to large transverse displacement.
Finite element implementation for the analysis of 3D steel and composite frames subjected to fire.
(2014) Caldas, Rodrigo Barreto; Fakury, Ricardo Hallal; Sousa Junior, João Batista Marques de
This paper presents a finite element formulation for the numerical analysis of three-dimensional framed steel, reinforced concrete or composite steel and concrete structures subjected to fire. Several specialized and commercial programs may be used for the analysis of structures in fire condition. Within this context, the purpose of this work is to present the steps taken to extend a previously developed static analysis procedure with beam elements in order to cope with the thermal and structural analysis of structures under fire action. Physical nonlinearity and material propertydegradation considering the temperature distribution are taken into account at the cross section level, which is divided into quadrilateral or triangular finite elements. Thermal strains are considered through the effective strain concept, and the resulting nonlinear system of equations is solved by the Newton-Raphson scheme. The accuracy and capability of the formulation to simulate the behavior of framed structures under fire action are assessed through comparison with various numerical and experimental results.

EM - Escola de Minas

Notícias

Navegar

Filtros

Configurações

Ordenar por

Resultados por página

Resultados da Pesquisa