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Keywords: fatigue damage, fatigue life estimate, crack growth, reliability assessment, steel bridges, temporary bridges.

Summary

This paper presents the recalculation of the fatigue life prediction of a temporary tramway bridge in Prague, now based on today's normative specifications, the linear elastic fracture mechanics (LEFM) approach and fully probabilistic concepts. The temporary four-span tramway bridge was built over the Vltava river in Prague in 1977. After a relatively short time the first cracks were discovered and after about three and a half years of use the bridge had to be removed. While the theoretical data (design according to current specifications) and experimental results (loading tests of a completed bridge) proved the required safety with respect to the strength criterion, the prediction of fatigue life, considering the actual loading and response history, was not required.

The analysis executed showed the unsuitability of such a structure for long-term heavy public traffic without adequate prediction of fatigue life. This default could lead to a very dangerous situation. The results obtained correspond to the bridge behaviour and the observed crack growth and confirm the decision to terminate the traffic. The bridge was dismantled and substituted with a new temporary lattice girder tramway bridge.

The analysis indicated the possibility of an initial crack defect of about 4.0 mm in the weld affected zone in the lower flange, which may represent real crack sizes related to problems with welding technology. In connection with the possibility of existing initial cracks, the calculation with a definition of an initial crack as an input random variable may be a progressive approach.

Knowledge of the initial crack defect, obtained by backward construction, may be used for simulation of fatigue tests and the determination of real detail. The reduced detail obtained for category 50 represents adequate prediction of the fatigue life for 3.066 years.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 91 PROCEEDINGS OF THE TWELFTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping, L.F. Costa Neves and R.C. Barros Paper 73 A Probabilistic Approach to the Fatigue Life Estimate of a Temporary Steel Bridge M. Rieger¹ and P. Marek² ¹VSB Technical University of Ostrava, Czech Republic ²Institute of Theoretical and Applied Mechanics, Academy of Sciences, Czech Republic doi:10.4203/ccp.91.73 purchase the full-text of this paper Full Bibliographic Reference for this paper M. Rieger, P. Marek, "A Probabilistic Approach to the Fatigue Life Estimate of a Temporary Steel Bridge", in B.H.V. Topping, L.F. Costa Neves, R.C. Barros, (Editors), "Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 73, 2009. doi:10.4203/ccp.91.73 Keywords: fatigue damage, fatigue life estimate, crack growth, reliability assessment, steel bridges, temporary bridges. Summary This paper presents the recalculation of the fatigue life prediction of a temporary tramway bridge in Prague, now based on today's normative specifications, the linear elastic fracture mechanics (LEFM) approach and fully probabilistic concepts. The temporary four-span tramway bridge was built over the Vltava river in Prague in 1977. After a relatively short time the first cracks were discovered and after about three and a half years of use the bridge had to be removed. While the theoretical data (design according to current specifications) and experimental results (loading tests of a completed bridge) proved the required safety with respect to the strength criterion, the prediction of fatigue life, considering the actual loading and response history, was not required. The analysis executed showed the unsuitability of such a structure for long-term heavy public traffic without adequate prediction of fatigue life. This default could lead to a very dangerous situation. The results obtained correspond to the bridge behaviour and the observed crack growth and confirm the decision to terminate the traffic. The bridge was dismantled and substituted with a new temporary lattice girder tramway bridge. The analysis indicated the possibility of an initial crack defect of about 4.0 mm in the weld affected zone in the lower flange, which may represent real crack sizes related to problems with welding technology. In connection with the possibility of existing initial cracks, the calculation with a definition of an initial crack as an input random variable may be a progressive approach. Knowledge of the initial crack defect, obtained by backward construction, may be used for simulation of fatigue tests and the determination of real detail. The reduced detail obtained for category 50 represents adequate prediction of the fatigue life for 3.066 years. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £140 +P&P)
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