Abstract
The extension of fatigue life of ageing welded steel structures is an important challenge faced by the industry. Herein, a detailed framework was developed to assess and improve the performance of these aged structures (pre-fatigued) using tungsten inert gas (TIG) dressing. Within this framework, relevant damage theories and models were applied to assess the state of pre-fatigued structures. Based on the results of this assessment and TIG dressing parameters, the extended fatigue life was estimated. Particular attention is paid to the deterministic study of the TIG dressing parameters, which are the fusion depth, weld toe radius, and residual stress. The resulting data, especially longitudinal and transversal attachments, were analysed to verify the proposed framework. The improved fatigue life was found to be at least 3.4 times the as-welded fatigue life when the cracks were completely re-melted. A significant dependency of the extended fatigue life on the remaining crack length after treatment was observed. A comparison of my predictions with experimentally obtained fatigue lives in other studies showed an absolute error of 20%.
Highlights
The last decades of the 20th century witnessed an increase in the construction of steel bridges
Aeran et al [4] presented a detailed framework for fatigue assessment of steel-based offshore structures, which can be extended to other steel structures
This study proposes a detailed framework for assessing and strengthening ageing welded steel structures using tungsten inert gas (TIG) dressing
Summary
The last decades of the 20th century witnessed an increase in the construction of steel bridges. Kühn [6] summarised this report with an astute guideline for the estimation of the remaining fatigue life These studies ([1,2,3,4,5,6,7]) provide a general assessment technique for existing steel structures without recommending models for damage calculations and crack propagation, which is required for an accurate prediction of the remaining fatigue life. Manai [29] summarises these studies These studies, had the following limitations: (1) they do not provide a detailed framework to assess and repair welded steel structures by TIG dressing; (2) they do not provide recommendations to estimate the damage distribution in pre-fatigue structures; and (3) they do not predict the extended fatigue life by TIG dressing treatment. A recommendation to extend the fatigue life is presented
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