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One of the concerns about the use of passive Infrared Thermography (IRT) for structural health monitoring (SHM) is the determination of a favorable period to conduct the inspections. This paper investigates the use of numerical simulations to find appropriate periods for IRT-based detection of subsurface damages in concrete bridge slabs under passive heating along a 1 year of time span. A model was built using the Finite Element Method (FEM) and calibrated using the results of a set of thermographic field inspections on a concrete slab sample. The results showed that the numerical simulation properly reproduced the experimental thermographic measurements of the concrete structure under passive heating, allowing the analysis to be extended for a longer testing period. The long-term FEM results demonstrated that the months of spring and summer are the most suitable for passive IRT inspections in this study, with around 17% more detections compared to the autumn and winter periods in Brazil. By enhancing the possibility of using FEM beyond the design stage, we demonstrate that this computation tool can provide support to long-term SHM.

Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution Non-Commercial, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado.Recebido: 27 Jun., 2017 Aceito: 03 Out., 2017 E-mails: ronaldo.tremarin@erechim. ifrs.edu.br (RCT), zacarias@upf.br (ZMCP)Resumo: O principal objetivo deste trabalho é mostrar aos especialistas envolvidos com estruturas soldadas submetidas a esforços cíclicos uniaxiais e multiaxiais, proporcionais ou não proporcionais, as opções existentes para previsão de vida em fadiga para juntas soldadas. Apresentam-se as normas, Eurocode 3 -IIW-AASHTO e BS 5400, com suas características específicas e uma revisão das metodologias computacionais desenvolvidas nos últimos anos. Para avaliar as normas apresentadas, analisa-se dois casos de previsão de vida em fadiga, uma chapa e uma viga I, nas diferentes normas. Identificou-se as similaridades e discrepâncias entre as normas, acerca dos principais parâmetros constitutivos, a previsível semelhança entre as previsões de vida em fadiga obtidas via IIW e Eurocode 3 e as significativas diferenças entres AASHTO e BS 5400 em decorrência da filosofia de cada norma. Palavras-chave:Fadiga; Solda; Prescrição de normas. Life Predictions Fatigue According to Technical Norms: a Critical ReviewAbstract: The main objective of this work is to show to the specialists involved welded structures subjected to cyclic uniaxial and multiaxial stresses proportional or non-proportional to the existing options for fatigue life prediction for welded joints that deals with the subject. Each of the standards (Eurocode 3 -IIW-AASHTO and BS 5400) has specific characteristics, some of them very distinct as well as a review of the computational methodologies developed in recent years. To evaluate the standards presented a case of fatigue life prediction of a plate top in I -beam I in the different standards. The similarities and discrepancies between the standards, the main constitutive parameters, the predicted similarity between fatigue life forecasts obtained through IIW and Eurocode 3, and the significant differences between AASHTO and BS 5400 were identified as a result of the philosophy of each standard. Key-words:Fatigue; Weld; Standards. IntroduçãoAo projetar juntas metálicas soldadas, visando à resistência à fadiga, é possível reduzir a ocorrência de falhas catastróficas e aumentar a vida útil do produto, proporcionando a produção de estruturas de aço, pontes, máquinas e outros equipamentos, com adequada segurança operacional e vida útil.O processo de soldagem implica na elevada taxa de transferência de calor, para formação das soldas e, por consequência, das conexões estruturais. Tal situação resulta na formação da Zona Afetada pelo Calor (ZAC), inserção de tensões residuais e outras alterações termo-metalúrgicas, ocorrendo a deterioração das propriedades mecânicas: ductilidade, tenacidade e outras no metal base -MB [1,2]. A relaçã...

This work presents a new computational approach to estimate the fatigue life in welded joints, taking into account three-dimensional, non-proportional, and out-of-phase stresses; the thermomechanical properties of steel; parameters of the welding process; and the effects of residual stresses. We use the mechanical equations of continuous and cumulative fatigue damage found from Multiaxial RainFlow, the Wang and Brown and critical plane methods, and the Findley criteria approach. The numerical finite element method, available with software, is used to simulate the formation of residual stress and quantify its influence by solving equations. Based on the analysis of numerical results, we were able to prevision the crack location and angles of propagation of a high cycle fatigue crack with totally random loads in a metallic structure. We conclude that the result of the computational method is valid and can be used to estimate and life in fatigue in welded joints.