Usually when a large internal fluid pressure acts on the inner walls of flexible pipes, the carcass layer is not loaded, as the first internal pressure resistance is given by the internal polymeric layer that transmits almost all the loading to the metallic pressure armor layer. The last one must be designed to ensure that the flexible pipe will not fail when loaded by a defined value of internal pressure. This paper presents three different numerical models and an analytical nonlinear model for determining the maximum internal pressure loading withstood by a flexible pipe without burst. The first of the numerical models is a ring approximation for the helically rolled pressure layer, considering its actual cross section profile. The second one is a full model for the same structure, considering the pressure layer laying angle and the cross section as built. The last numerical model is a two-dimensional (2D) simplified version, considering the pressure layer as an equivalent ring. The first two numerical models consider contact nonlinearities and a nonlinear elastic-plastic material model for the pressure layer. The analytical model considers the pressure armor layer as an equivalent ring, taking into account geometrical and material nonlinear behaviors. Assumptions and results for each model are compared and discussed. The failure event and the corresponding stress state are commented.
Dry collapse is one of the possible failure modes of flexible pipes. It refers to the situation in which no damage occurs in the flexible pipe external sheath. In this scenario, all layers of the pipe withstand the external pressure loading in a deep-water application. Such a situation is addressed in this work, which proposes some simplified modeling techniques to represent straight and curved flexible pipes subjected to external pressure, undergoing dry collapse during simulation procedure. The results of the proposed models are compared to other reference results, from a fully three-dimensional (3D) finite element model. Good agreement has been got, even with the proposed simplifications with a large reduction in computational cost when compared to full 3D model.
PURPOSE: To evaluate the incidence of fistula and stenosis of the cervical esophagogastric anastomosis with invagination of the proximal esophageal stump into the stomach after subtotal esophagectomy. METHODS:We studied 54 patients who underwent subtotal esophagectomy, 45 (83.3%) patients with carcinoma and nine (16.6%) with advanced megaesophagus. In all cases the cervical esophagogastric anastomosis was performed with the invagination of the proximal esophageal stump inside the stomach. RESULTS:Three (5.5%) patients had a fistula at the esophagogastric anastomosis, two of whom with minimal leakage of air or saliva and with mild clinical repercussion; the third had a low output fistula that drained into the pleural space, and this patient developed empyema that showed good progress with drainage. Fibrotic stenosis of anastomosis occurred in thirteen (24%) subjects and was treated successfully with endoscopic dilatation. CONCLUSION:Cervical esophagogastric anastomosis with invagination of the proximal esophageal stump into the stomach tube presented a low rate of esophagogastric fistula and stenosis, thus becoming an attractive option for the reconstruction of alimentary transit after subtotal esophagectomy. Key words: Esophagus. Esophagectomy. Constriction, Pathologic. Anastomotic Leak, Gastroplasty. RESUMOOBJETIVO: Avaliar a incidência de fístula e estenose da anastomose esofagogástrica cervical com invaginação do coto esofágico proximal no interior do estômago após esofagectomia subtotal. MÉTODOS:Foram estudados 54 pacientes submetidos à esofagectomia subtotal, 45 (83,3%) com carcinoma e nove (16,6%) com megaesôfago chagásico avançado. Em todos os casos, a anastomose esofagogástrica cervical foi realizada com invaginação do coto esofágico proximal no interior do estômago. RESULTADOS:Três (5,5%) pacientes apresentaram fístula, dois deles com saída mínima de ar e saliva pela incisão cervical que evoluíram com rápida cicatrização; o terceiro apresentou fístula de pequeno débito que drenou para o espaço pleural causando empiema que teve boa evolução após drenagem. Treze (24%) doentes apresentaram estenose fibrótica e foram tratados com sucesso com dilatação endoscópica. CONCLUSÃO:A anastomose esofagogástrica cervical com invaginação do coto esofágico proximal no interior do estômago apresentou baixa incidência de fístula e estenose tornando-se opção atraente para a reconstrução do trânsito alimentar após esofagectomia subtotal.
OBJETIVO: Os autores apresentam sua experiência com 50 pacientes operados de colecistectomia videolaparoscópica em regime ambulatorial, no Hospital de Ensino da Faculdade de Medicina do ABC. MÉTODO: Quarenta e dois pacientes (84%) eram do sexo feminino e oito (16%) do masculino, a idade variou de 23 a 60 anos, com média de 41,5 anos. Foram submetidos ao procedimento pacientes com diagnóstico de colecistite crônica calculosa, que obedeciam aos seguintes critérios: inexistência de colecistite aguda, idade máxima de 60 anos, ausência de suspeita de coledocolitíase, avaliação clínica pré-operatória ASA I ou II, aprovação do paciente quanto ao método e período de internação empregados e presença de acompanhante. O posicionamento da equipe e a técnica utilizada foram os preconizados pela escola americana. RESULTADOS: O tempo cirúrgico variou de 50 minutos a 2 horas, com média de 1 hora e 25 minutos. A colangiografia intra-operatória foi realizada em 35 pacientes (70%), demonstrando coledocolitíase em um caso (2%), que necessitou conversão para cirurgia aberta. As complicações mais freqüentes no período pós-operatório imediato foram náuseas e vômitos em três casos (6%), seguidas de dor abdominal intensa em dois casos (4%). Foram tratados com antieméticos e analgésicos e tiveram a alta hospitalar adiada para o dia seguinte à operação. Quarenta e quatro pacientes (88%) tiveram condições de alta no mesmo dia. O período de permanência hospitalar foi entre nove e 12 horas. O retorno ambulatorial era programado para o sétimo e trigésimo dias pós-operatório, não havendo necessidade de reinternação em nenhum caso. CONCLUSÕES: A colecistectomia videolaparoscópica ambulatorial é um procedimento seguro.
The present paper brings together theoretical predictions and experimental results, comparing crushing tests results as well as carcass wet collapse tests. The theoretical models are of two kinds: (i) numerical (FE) and (ii) analytical. The first kind is a restricted 3D version of a finite element model. The second kind is based on classic assumptions of equivalent ring behavior. Discussion is made on the real yield stress value to be adopted, as well as on the pertinence of geometric hypotheses. Sensitivity analyses, regarding ovalization and helical pitch are also presented.
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