PSI - Issue 37

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia 00 (2019) 000 – 000 il l li t . i i t. tr t r lI t rit r i ( )

www.elsevier.com/locate/procedia . l i r. /l t / r i

ScienceDirect

Procedia Structural Integrity 37 (2022) 203–208

ICSI 2021 The 4th International Conference on Structural Integrity In-service failure of a support structure for traffic signaling Mihaela Iordachescu a *, Andrés Valiente a , Maricely De Abreu a a Material Science Dpt., ETSI Caminos, Universidad Politécnica de Madrid, 5 Prof. Aranguren St., 28040-Madrid, Spain a a a a t i l i t., I i , i i lit i i , f. t., - i , i

Abstract

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© 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Pedro Miguel Guimaraes Pires Moreira Traffic signals and their supporting structures are an essential complement in highways and local roadways all around the world. Their accurate operation is today a well-recognized issue by the respective transportation authorities, especially when located on major roadways because of exposure to fatigue cracking by wind-induced large-amplitude vibrations and severe environmental conditions or wind gusts resulting from the passing trucks. The present paper describes the research undertaken to analyze the fatigue failure of a bolted joint in an overhead porticoed structure for traffic signaling located close to a highway entrance to a tunnel. The structure had been in use for more than 25 years and the failure was preventively detected, during a maintenance inspection. The research is a forensic engineering analysis of failure involving optical and scanning electron microscopy observations of the in-service fractured bolts together with the experimental characterization of the fatigue behavior of the bolt steel by means of non-standardized fatigue tests. The failure analysis pointed to the existence of environmentally-induced fatigue initiators as the failure origin, the galvanized condition of the bolts and environment aggressivity gave rise to local dissolution and microcracking of the Zn-coating, damaging and weakening specific zones at the steel interface that acted as fatigue initiators. © 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Pedro Miguel Guimaraes Pires Moreira Keywords:High-strength steel; Fracture micro-mechanisms; Fatigue; 1. Introduction Today, traffic signals are extensively present all around the world on highways and local roadways. According to the bridge design specifications of AASHTO (2001 and 2004), the supporting structures can be manufactured in many sizes and shapes, with one of the most commonly used being of overhead span-type and referred to as cantilever bridge supports. These structures are often positioned over major roadways, which entails a significant risk of fatigue cracking due to wind-induced large-amplitude vibrations under severe environmental conditions or by wind gusts resulting from i t ti i t ll i i t ti t t ti t iti , i ll l t j t ti i i i l lit i ti i t l iti i t lti t i t . t i t t t l t ti il lt j i t i ti t t t i i li l t l t i t t t l. t t i t t il ti l t t , i i t i ti . i i i i l i il i l i ti l i l t i ti t i i t lt t t it t i t l t i ti t ti i t lt t l t i ti t t . il l i i t t t i t i t ll i ti i iti t t il i i , t l i iti t lt i t i it i t l l i l ti i i t ti , i i i i t t t l i t t t t ti i iti t . t . li . . This is an ess article under the CC BY-NC-ND license (https://creativecommons.org/license / / . i i ilit i l i i i : i - t t t l; t i - i ; ti ; . i , t i i l t i l t ll t l i l l . i t t i i i i ti , t ti t t t i i , it t t l i t t til i t . t t t iti j , i t il i i i t i ti i t i i l lit i ti i t l iti i t lti

* Corresponding author. Tel.: +0-000-000-0000 ; fax: +0-000-000-0000 . E-mail address: mihaela.iordachescu@upm.es i t r. l.: - - - ; f : - - - . - il : i l .i r . rr

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2452-3216© 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Pedro Miguel Guimaraes Pires Moreira i i rti l r t - - li ( tt :// r ti . r /li / - - / . ) r-r i r r i ilit f r i l i r ir r ir

2452-3216 © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Pedro Miguel Guimaraes Pires Moreira 10.1016/j.prostr.2022.02.048