PSI - Issue 5

Hołowaty J. et al. / Procedia Structural Integrity 5 (2017) 1035 – 1042 Wichtowski and Hołowaty. / Structural Integrity Procedia 00 ( 2017) 000 – 000

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The calculations for service stresses under real loadings have very low values in relation to the stresses calculated for the code traffic model and consist approximately of 60 – 80 % of these values. A similar value was obtained during field load test measurements for bridge No. VIII. Resistance analysis explains why the bridges could remain in further operation without the necessity for strengthening or replacement. The infinite life fatigue strength from fatigue tests on butt welds with internal cracks has the value Z rj = 90 MPa. This consists of 28 % of the yield strength value for the tested steel f y = 320 MPa. Each time, the value of Z rj is larger than the service stresses calculated in the butt welds with cracks from the bridges under analysis (see Table 1, col. 5). This means that the initiated crack stress is lower than the stress necessary for the cracks to increase. Steel structures always contain internal cracks or other discontinuities which make them susceptible to fatigue and fracture. The adaption of the simplified fatigue verification approach for the infinite life check is justified in the initial assessment as the future loading should not be predicted precisely. If the infinite-life verification is satisfied, no more complex finite-life verification is required [Dexter and Fisher (2000), NCHRP (2012)]. Dexter, R.J., Fisher, J.W., 2000. Fatigue and fracture . In: " Bridge Engineering Handbook ". Chen, W.F., Duan, L. (Eds.). CRC Press, Boca Raton, pp. 23. Hołowaty, J., Wichtowski, B., 2015. Testing of welded joints in steel bridges to European standards , 8th International Symposium on: Steel Bridges: Innovation & New Challenges 2015 (SBIC - 2015). Istanbul, 14 - 16 September 2015, 305 - 314. Kühn, B. , Lukić , M. , Nussbaumer , A., Günter, H.P. , Helmerich , R., Herion, S., Kolstein , M.H., Walbridge , S., Androic, B., Dijkstra, O, Bucak, Ö. , 2008. Assessment of existing steel structures: Recommendations for estimation of remaining fatigue life. ECCS & JRC, European Communi ties: Luxembourg, pp. 92. National Cooperative Highway Research Program (NCHRP), 2012. Fatigue evaluation of steel bridges. Report 721. Transportation Research Bo ard, Washington, DC, pp. 65. Neiber, G., 1947. Stress concentration (in Russian). Gastiechnizdat, M o skwa, pp. 204. Nussbaumer, A., Borges, L., Davaine, L., 2011. Fatigue design of steel and composite structures. Wiley , Berlin, pp. 311. Wichtowski, B. , Hołowaty, J., 2016 . Quality of butt welds in bridges and fatigue classes according to European codes and testing. XIII International Conference on "Metal Structures – Zielona Góra 2016". Zielona Góra, 15 - 17 June 2016, 130 - 131 Wichtowski, B., 2002. Fatigue strength of welded butt splices in steel railway bridges (in Polish ). Research Works, PS No. 572, Szczecin, pp. 210. Wiśniewski, D., Casas, J.R., Ghosn, M., 2012. Codes for s afety asses sment of existing b ridges – Current state and further d evelopment. Structural Engineering International, No. 4, 552 - 561. Wiśniewski, D., Majka, M., Bień, J., 2013. Capacity assessment of existing bridges during their service life – national and international experience (in Polish). Inżynieria i Budownictwo, No 5, 436 - 441 . SB -LRA. 2007. Gu ideline for l oad and resistance a ssessment of existing European r ailway b ridges. Advices on the use of advanced m ethods. Sustainable Bridges, 6 th Framework Programme, Brussels, pp. 428 . References