PSI - Issue 37

Mihaela Iordachescu et al. / Procedia Structural Integrity 37 (2022) 203–208 Iordachescu M. et al./ StructuralIntegrity Procedia 00 (2019) 000 – 000

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Fig. 6.(a) Fatigue strength curves of EC3; (b) Experimental Paris law of bolt steel vs EC3 Paris law

4. Conclusions Environmental action can ease the initiation of fatigue cracking and shorten the fatigue life of exposed constructional steel structures details. This explains the fatigue failure occurred in the analyzed bolted joint of the traffic-signal supporting structure. The long fatigue life of the failed bolts, made of galvanized high-strength steel, and the fatigue tests performed allowed the fatigue crack growth resistance to be discarded as failure origin. The fatigue tests carried out with cylindrical notched specimens machine cut from the threaded bolts showed that fatigue crack growth resistance, as given by the Paris-Erdogan law triplicates that one underling the Eurocode 3. On the contrary, from the fracture surfaces examination it was found that the environmental action propitiated the fatigue crack initiation by local dissolution and microcracking of the protective Zn-layer. This originated the decrease of the fatigue limit of the bolts and shorten the fatigue life of some of them. Acknowledgements The authors gratefully acknowledge the financial support received from Ministry of Science and Innovation in Spain through the project RTI2018-097221-B-I00. References AASHTO - American Association of State Highway and Transportation Officials (2001). Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, 4th Edition, Washington, D.C. USA. AASHTO - American Association of State Highway and Transportation Officials (2004). LRFD Bridge Design Specifications, 3rd Edition, Washington, D.C. USA. Zuo D., Letchford C.W., Wind-induced vibration of a traffic-signal-support structure with cantilevered tapered circular mast arm. Engineering Structures 32 (2010), 3171-3179. Dexter R. J., Ricker M.J., Fatigue resistant design of cantilevered signal, sign and light supports, NCHRP Report 469 (2002). Transportation Research Board, Washington, D.C., USA. Weston McLean T., Park J.S., Stallings J.M., Fatigue evaluation of two variable message sign structures, Final report (2004), The Alabama Department of Transportation, USA. EN 1993-1-8 (2005) Eurocode 3: Design of steel structures - Part 1-8: Design of joints De Abreu M., Iordachescu M., Valiente A., 2018. On hydrogen-induced damage in cold-drawn lean-duplex wires, Eng Fail Anal 91, 516-526. https://doi.org/10.1016/j.engfailanal.2018.04.036 Iordachescu M., De Abreu M., Valiente A., 2021. Effect of environmentally assisted damage on fatigue resistance of tie-down cables after 30 years of service in a cable-stayed bridge, Eng Fail Anal 126:105455. https://doi.org/10.1016/j.engfailanal.2021.105455 Toribio J., Álvarez N., González B., Matos J.C., A critical review of stress intensity factor solutions for surface cracks in round bars subjected to tension loading, Eng Fail Anal 16 (2009) 794 – 809. Paris P.C., Erdogan F. A critical analysis of crack propagation laws. J Basic Eng85D(1963) 528 – 34. Shih Y.S, Chen J.J. The stress intensity factor study of an elliptical cracked shaft. Nucl Eng Des 214(2002) 137 – 45. Valiente A., Fracture and fatigue failure in Spanish codes for design of steel structures, Eng Fail Anal, 16(2009) 2658 – 2667.