Quatro juntas tubulares de uma plataforma offshore fixa foram modeladas em elementos finitos para o cálculo das vidas à fadiga e comparação com os resultados obtidos através de modelos convencionais em elementos de barras. Foram também cotejados os fatores de concentração de tensões (SCF's), obtidos com base nas formulações paramétricas, com os calculados através dos modelos em elementos finitos. Os objetivos foram averiguar a validade do refinamento do cálculo da fadiga em juntas críticas da plataforma e avaliar as suas conseqüências na elaboração do plano de inspeção. Os resultados permitiram concluir que a análise por elementos finitos torna-se recomendada para juntas que não apresentam tipo e/ou comportamento compatíveis com as configurações padronizadas, normalmente utilizadas pelos programas. Das quatro juntas analisadas, duas delas não necessitariam fazer parte do plano de inspeção da plataforma.
Four tubular joints of a fixed offshore platform were modelled using finite elements to evaluate respective fatigue lifes and comparison with the results obtained from conventional models in frame elements. Stress concentration factors (SCF's) calculated from parametric formulas were also compared with those obtained from finite elements models. The results of this work have the intention of verifying the validity of the refinement of fatigue analysis on critical joints of the platform and the evaluation of its consequences in the inspection plan. Obtained results show that finite elements analysis is recommended for joints whose type and/or behaviour is not consistent with standard models, used by computational programs. From four analised joints, two of them would not need to be part of inspection plan
-Four tubular joints of a fixed offshore platform are modelled using finite elements to evaluate respective fatigue lives and comparison with the results obtained from conventional models in frame elements. Stress concentration factors (SCF's) calculated from parametric formulas are also compared with those obtained from finite elements models. The results of this work have the intention of verifying the validity of the refinement of fatigue analysis on critical joints of platforms and the evaluation of its consequences in the inspection plan. Results show that finite elements analysis is recommended for joints whose type and/or behaviour is not consistent with standard models, used by computational programs. From four analised joints, two of them would not need to be part of inspection plan.
Nesse trabalho apresenta-se um estudo comparativo entre os sistemas de estabilizações verticais em pórticos rígidos e os sistemas em treliças em `K' e em `X'. A eficiência estrutural é analisada através do relacionamento entre o número de pavimentos com os deslocamentos horizontais, esforços solicitantes e os perfis adotados no dimensionamento dos modelos. Nos sistemas rígidos, os esforços solicitantes e os deslocamentos horizontais são maiores do que nos sistemas contraventados. Nesse caso, leva-se a estruturas mais pesadas e, portanto, menos econômicas. A partir de 24 pavimentos, para se garantirem deslocamentos aceitáveis nos modelos rígidos, a rigidez necessária do sistema fica impraticável. Usaram-se as teorias linear e não-linear (Efeito P-delta) para análise comparativa dos modelos adotados. Nesse contexto, verificou-se que a análise não-linear é fundamental para os modelos com maior número de pavimentos, pois proporciona resultados de esforços e deslocamentos mais coerentes.
This paper compares rigid-frame vertical bracing systems against "K" or "X" truss systems, according to height variation. The adopted models used were based on technical information from a standard project. Structural efficiency was analyzed by comparison of the ratio of the number of pavements to their horizontal dislocation, structural strain and perfiles adopted in dimension models. In the rigid-frame vertical bracing systems, structural strain and horizontal dislocation were greater than in the truss systems. The rigid-frame vertical bracing system also requires more steel, providing for a heavy, less economic structure. After 24 floors, the rigid-frame vertical bracing system becomes impractible, since at this point it no longer meets acceptable dislocation standards. For structural calculations, comparisons between the linear and non-linear analysis (P-delta effect) were used. It was concluded that non-linear analysis should be considered in the design of buildings, particularly those very tall, since it indicates true strain and major structural displacement. This paper proves that there are advantages in using the truss systems for multiple-story buildings and that it is necessary to analyse the P-delta effect for more efficient building design
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