Fatigue Life Evaluation of in-Service Steel Bridges by Using Bi-Linear S-N Curves

Abstract

ABSTRACT:The in-service steel bridges are often required to carry increasing volume of traffic and heavier trucks or freight trains. More attention should be paid to possible fatigue damages of such structures. It has been reported that for many structure details with an equivalent stress range below the constant amplitude fatigue limit (CAFL) and free of fatigue cracks, calculations show that the remaining fatigue life has been exhausted. This condition indicates that it could be too conservative to predict the remaining fatigue life of in-service steel bridges by utilizing the equivalent constant amplitude stress ranges with the direct extension of S-N curves of AASHTO specifications with a slope of -3 to below the CAFL. This over-prediction of fatigue damage may lead to unnecessary rehabilitation and maintenance actions. For a better fatigue life evaluation and prediction, a set of bi-linear S-N curves with a break at the CAFL for the AASHTO fatigue strength categories and with a slope of -4 below, has been proposed for fatigue life evaluation of in-service structures. This paper applies the concept of the equivalent constant amplitude stress range for bi-linear curves to AASHTO specifications and Eurocode. Cases of fatigue evaluation of in-service steel bridge components are studied by correlating the field-measured live-load stresses with the bi-linear S-N curves. Comparative results from the bi-linear S-N curve approach, the current AASHTO specifications and Eurocode approach are presented.

Fatigue design in reinforced concrete bridges according to Brazilian code

“…The principle of Cumulative Damage was chosen to be used to study the stress variations. This approach was adopted because in bridge fatigue non-uniform stress variations occur; it is recommended to a reduced number of structural members, such as beams; it has mathematical rigor, given the absence of conversion and simplification formulas; and it has been used by several authors in the national and international literature (Pimentel, Bruhwiler, Figueiras, 2008;Santos, Pfeil, 2014;Freitas, 2014;Zhang, Xin, Cui, 2012;Wang et al, 2015;Hassen, 2020).…”

Concurrent multi-scale fatigue damage evolution simulation method for long-span steel bridges

“…The S–N curve method is often adopted by design codes, such as American Association of State Highway Transportation Officials (AASHTO, 2004), BS 5400 (1980), and EN 1993-1-9 Eurocode 3 (2005), to assess the fatigue damage of steel bridges (Angelo and Nussbaumer, 2015; Fisher and Roy, 2011; Flint and Neill Partnership, 1999; Kwon et al., 2012; Wang et al., 2015) following the Palmgren–Miner linear accumulative damage rule (Miner and Calif, 1945). Nevertheless, fatigue damage accumulation during the early stage of fatigue life is different from that in the later stage, and the linear Miner's rule is confirmed to be over-conservative.…”