Estudo numérico-experimental do dano produzido por fadiga em jaquetas de plataformas marítimas

This work presents a method for obtaining the acumulated fatigue damage in the welded joints of a jacket type platform, based on measurements carried on the platform during its operation. The technique of random data measurement and analysis is presented, emphazising the aspects of measuring on the sea. After this the mathematical modeling of the structure, by means of a computer, is discussed. Transfer functions are obtained between deck displacements and member stresses, with the help of a structural analysis program. Having them been determined, the fatigue damages are calculated for selected joints. The results achieved by the proposed method are compareci with those obtained by in situ measurements and with the conclusions of the structure original project.Este trabalho apresenta um método para a determinação do dano acumulado devido à fadiga nas juntas soldadas de uma plataforma do tipo jaqueta, a partir de medições realizadas na plataforma em operação. Apresenta-se a técnica de medição e análise de dados aleatórios, com ênfase aos aspectos inerentes a medições no mar. Em seguida discute-se o modelamento matemático da estrutura com o auxílio de computador. São levantadas funções de transferência entre deslocamentos de convés e tensões nos membros, com o auxílio de um programa de cálculo estrutural. De posse dessas, calculamos os danos de fadiga de algumas juntas selecionadas. Os resultados obtidos pelo método proposto são comparados com os obtidos pela medição in situ e com as conclusões do projeto original da estrutura

Stress Analysis of Pipelines With Composite Repairs

The repair of corroded pipelines with fiber reinforced composite materials is a well-developed practice in the oil and gas transportation industry. Laboratory hydrostatic burst tests and field practice of several years have shown that these repairs are effective for pipelines with external corrosion defects. This paper deals with laboratory tests carried out to compare the behavior of fiber reinforced composite repairs applied to defects machined in pipeline test specimens. The experimental results were compared to results from Finite Element Analysis (FEA) of the tubes tested. The parameters of FEA were calibrated to this specific problem, beforehand. Some hipotheses were tested during FEA trials to better explain the experimental results. The results indicated that, up to the starting of yielding of the pipe defected region, practically only the elastic pipe stresses equilibrate the pressure loading, due to the steel high Young modulus. After yielding, the composite material starts to work, carrying an important part of the pressure loading increments. Experimental results also showed that the repair systems tested allowed the pipes to achieve the original design pressure before bursting. However, only one of the repair systems was approved in all strength verification tests for both internal and external defects. This system operated for four hours under a hydrostatic pressure test associated to the specified minimum yield strength (SMYS) of the steel and was also able to support ten pressure cycles of the design pressure afterwards, without showing any visual damage

Reversible pulmonary trunk banding: Myocardial vascular endothelial growth factor expression in young goats submitted to ventricular retraining.

BACKGROUND:Ventricle retraining has been extensively studied by our laboratory. Previous studies have demonstrated that intermittent overload causes a more efficient ventricular hypertrophy. The adaptive mechanisms involved in the ventricle retraining are not completely established. This study assessed vascular endothelial growth factor (VEGF) expression in the ventricles of goats submitted to systolic overload. METHODS:Twenty-one young goats were divided into 3 groups (7 animals each): control, 96-hour continuous systolic overload, and intermittent systolic overload (four 12-hour periods of systolic overload paired with 12-hour resting period). During the 96-hour protocol, systolic overload was adjusted to achieve a right ventricular (RV) / aortic pressure ratio of 0.7. Hemodynamic evaluations were performed daily before and after systolic overload. Echocardiograms were obtained preoperatively and at protocol end to measure cardiac masses thickness. At study end, the animals were killed for morphologic evaluation and immunohistochemical assessment of VEGF expression. RESULTS:RV-trained groups developed hypertrophy of RV and septal masses, confirmed by increased weight and thickness, as expected. In the study groups, there was a small but significantly increased water content of the RV and septum compared with those in the control group (p<0.002). VEGF expression in the RV myocardium was greater in the intermittent group (2.89% ± 0.41%) than in the continuous (1.80% ± 0.19%) and control (1.43% ± 0.18%) groups (p<0.023). CONCLUSIONS:Intermittent systolic overload promotes greater upregulation of VEGF expression in the subpulmonary ventricle, an adaptation that provides a mechanism for increased myocardial perfusion during the rapid myocardial hypertrophy of young goats