PSI - Issue 22

Carlos D.S. Souto et al. / Procedia Structural Integrity 22 (2019) 376–385 Author name / Structural Integrity Procedia 00 (2018) 000–000

384

9

Parameters

S-N curve 71

Detail category, ∆ σ C [MPa] Fatigue limit, ∆ σ D [MPa] Cut-o ff limit, ∆ σ L [MPa]

71

52.31 28.74

3 5

First slope, m 1 Second slope, m 2

Repetitions [trains / year]

11 461

Table 1: Parameters

For the shown parameters, FDT outputs a damage of D = 2 . 03 × 10 − 3 per year, which means that the bridge has a lifetime of around 492 years since its construction (after 492 years, D > 1). According to Boavida-Barroso (2019), for the same conditions of the analysis, it was estimated a damage of D = 2 . 07 × 10 − 3 per year and a lifetime of 483 years. Thus, an error of just 1.86% between the two assessments was verified.

6. Conclusions

The development of FDT gives engineers and designers a practical and e ff ective way for assessing fatigue damage of steel structures based on the global S-N approaches and the linear damage accumulation rule. In this software, the users can define the following parameters: the design fatigue curve more suitable for the structural detail; the partial safety factors for loading and fatigue strength; the stress-time history from the global structural analysis; the number of repetitions of the stress-time history; and, the design fatigue factor where is possible to indicate an extra global safety factor. Results from the numerical analysis of a case-study of the Va´rzeas railway bridge were used to make the validation of the developed FDT program. A comparison was made with the fatigue evaluation presented by Boavida-Barroso (2019) and a good agreement was verified. In this way, engineers and designers can rely on this tool in their fatigue verifications applied to structural details of any engineering structures.

Acknowledgements

The authors would like to thank the support from the CONSTRUCT Unit (Institute of R&D in Structures and Construction – UID / ECI / 04708 / 2019), the post-doctoral grant SFRH / BPD / 107825 / 2015, FiberBridge project – POCI-01-0145-FEDER-030103), as well as to the doctoral programme iRail (Innovation in Railway Systems and Technologies) funding by the Portuguese Foundation for Science and Technology (FCT) through the PhD grant (PD / BD / 150306 / 2019).

References

AASHTO LRFD, 1995. Bridge Design Specification. American Association of State Highway and Transportation O ffi cials. Alencar, G., Ferreira, G., De Jesus, A., Calc¸ada, R., 2018. Fatigue assessment of a high-speed railway composite steel-concrete bridge by the hot-spot stress method. International Journal of Structural Integrity, vol. 9, issue 3, pp. 337-354. AREMA, 2006. Manual of Engineering. American Railway Engineering and Maintenance-of-Way Association, Lanham. ASTM E739-10, 2015. Standard Practice for Statistical Analysis of Linear or Linearized Stress-Life and Strain-Life Fatigue Data. ASTM Interna tional, West Conshohocken, PA. ASTM E1049-85, 2017. Standard Practices for Cycle Counting in Fatigue Analysis. ASTM International, West Conshohocken, PA. Barbosa, J., Correia, J., Ju´nior, R., Zhu, S., De Jesus, A., 2019a. Probabilistic S-N fields based on statistical distributions applied to metallic and composite materials: State of the art. Advances in Mechanical Engineering, 11:8, 1-22. Barbosa, J., Correia, J., Montenegro, P., Ju´nior, R., Lesiuk, G., De Jesus, A., Calc¸ada, R., 2019b. A comparison between S-N logistic and kohout veˇchet formulations applied to the fatigue data of old metallic bridges materials. Frattura ed Integrita Strutturale, vol. 13, no. 48, pp. 400-410. Boavida-Barroso, J., 2019. Dynamic Analysis and Fatigue Assessment of an Existing Railway Steel Bridge. MSc Thesis, University of Porto, 112 pages. BS 5400, 1980. Steel, Concrete and Composite Bridges: Part 10: Code of Practice for Fatigue. BSI, British Standards Institution, London.