Browsing by Author "Dias-da-Costa, D."
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- Probabilistic Analysis of High Strength Concrete Girders Strengthened with CFRPPublication . Gomes, S.; Neves, L.; Dias-da-Costa, D.; Júlio, E.; Fernandes, PauloThe strengthening or upgrading of reinforced concrete girders with carbon fiber reinforced polymer (CFRP) composites has become a common procedure in the last years. However, the lack of standards or codes proposed within the same design philosophy of the Eurocode, and which are capable of assuring an adequate confidence level for the CFRP as for steel or concrete, often implies that the safety of prestressed girders strengthened with CFRP has to be evaluated using probabilistic tools. This manuscript presents a reliability study of a Portuguese prestressed high strength concrete (HSC) girder strengthened with CFRP. The selected bridge is representative of what has been constructed in Portuguese highways during the last two decades. First, the reliability level and the importance of design and load variables are computed using the following two codes: Portuguese RSA (1983) and European EC1 (2002). Next, partial safety factors are determined for the CFRP. © 2014 American Society of Civil Engineers.
- Time-dependent reliability analyses of prestressed concrete girders strengthened with CFRP laminatesPublication . Dias-da-Costa, D.; Neves, L.A.C.; Gomes, S.; Hadigheh, S.A.; Fernandes, PauloThis paper presents a time-dependent reliability analysis of prestressed concrete girders subjected to degradation caused by pitting corrosion. The procedure presented includes the effects of both spatial and temporal pitting corrosions on prestressing steel, as well as the degradation of the strengthening CFRP laminate used for the rehabilitation of the member. Results indicate that the correlation of corrosion in different segments of the prestressing tendons impacts on the computed safety index for the deteriorated structure. Ditlevsen bounds are proposed for a better approximation of the correlation between failure modes in the spatial discretisation. Results show that such approach produces adequate estimates of the reliability index over the full range of analysis in comparison with other tested models. It is also observed that the degradation of the CFRP laminates does not affect the reliability as significantly as corrosion, and that traffic loads, models uncertainties, corrosion error and corrosion rate are the most relevant variables in the analysis, followed by prestressing strength and concrete cover. The significance of the variables changes with time: the corrosion rate, corrosion model error and concrete cover increase in importance with the development of corrosion, whereas traffic loads become gradually less important.