Department Of Civil And Environmental Engineering .

FATIGUE FAILURE AND CRACKING IN HIGH MAST POLESbyRaka GoyalResearch AssistantHemant B. DhondeResearch Assistant ProfessorandMina DawoodAssistant ProfessorResearch Project Number 0-6650Fatigue Failure and Cracking in High Mast PolesPerformed in cooperation with theTexas Department of Transportationand theFederal Highway AdministrationOctober 2011Published: March 2012Department of Civil and Environmental EngineeringUniversity of HoustonHouston, Texas

Technical Report Documentation Page1. Report No.2. Government Accession No.3. Recipient's Catalog No.FHWA/TX-12/0-6650-14. Title and Subtitle5. Report DateFATIGUE FAILURE AND CRACKING IN HIGH MASTPOLES7. Author(s)October 2011Published: March 20126. Performing Organization Code8. Performing Organization Report No.Raka Goyal, Hemant B. Dhonde, and Mina Dawood9. Performing Organization Name and AddressReport 0-6650-110. Work Unit No. (TRAIS)Department of Civil & Environmental EngineeringCullen College of EngineeringUniversity of Houston4800 Calhoun RoadHouston, TX 77204-400311. Contract or Grant No.Project 0-665012. Sponsoring Agency Name and Address13. Type of Report and Period CoveredTexas Department of TransportationResearch and Technology Implementation OfficeP.O. Box 5080Austin, TX 78763-5080Technical Report:September 2010–August 201114. Sponsoring Agency Code15. Supplementary NotesProject performed in cooperation with the Texas Department of Transportation and the FederalHighway Administration.Project Title: Fatigue Failure and Cracking in High Mast PolesURL: http://tti.tamu.edu/documents/0-6650-1.pdf16. AbstractThis report presents the findings of a comprehensive research project to investigate the fatiguecracking and failure of galvanized high mast illumination poles (HMIP). Ultrasonic inspection ofpoles throughout the state has revealed the presence of weld toe cracks at the shaft-to-base-plateconnections of some galvanized poles that the Texas Department of Transportation (TxDOT)owns.However, the effect of these galvanization-induced cracks on the fatigue life of the poles has notbeen clearly defined. The first phase of this research involved extensive review of published andunpublished data, to identify key factors that contribute to galvanization-induced cracking. Bestfabrication practices to minimize such cracking are recommended. In the second phase, acomprehensive reliability analysis of several TxDOT pole configurations was conducted fordifferent regions in Texas to predict the fatigue lives of the cracked poles. Critical poleconfigurations and locations are identified to facilitate cost-effective decisions related toinspection, repair, and replacement of poles.17. Key Words18. Distribution StatementHigh Mast Illumination Pole, Galvanization,Fatigue Cracking, FEM Analysis, Fatigue Life19. Security Classif. (of this report)UnclassifiedForm DOT F 1700.7 (8-72)No restrictions. This document is available to thepublic through the NTIS:National Technical Information Service,Alexandria, Virginia 22312http://www.ntis.gov20. Security Classif. (of this page)Unclassified21. No. of Pages22. Price270Reproduction of completed page authorized

FATIGUE FAILURE AND CRACKING IN HIGH MAST POLESbyRaka GoyalResearch AssistantHemant B. DhondeResearch Assistant ProfessorandMina DawoodAssistant ProfessorReport 0-6650-1Project 0-6650Project Title: Fatigue Failure and Cracking in High Mast PolesPerformed in cooperation with theTexas Department of Transportationand theFederal Highway AdministrationOctober 2011Published: March 2012Department of Civil and Environmental EngineeringUniversity of HoustonHouston, Texas

DISCLAIMERThis research was performed in cooperation with the Texas Department of Transportation andthe U.S. Department of Transportation, Federal Highway Administration. The contents of thisreport reflect the views of the authors, who are responsible for the facts and accuracy of the datapresented here. The contents do not necessarily reflect the official view or policies of the FederalHighway Administration (FHWA) or the Texas Department of Transportation (TxDOT). Thisreport does not constitute a standard, specification, or regulation, nor is it intended forconstruction, bidding, or permit purposes.TRADE NAMES/MANUFACTURERS’ NOTICEThe United States Government and the State of Texas do not endorse products or manufacturers.Trade or manufacturers’ names appear herein solely because they are considered essential to theobject of this report. Trade names were used solely for information and not product endorsement.v

ACKNOWLEDGMENTSProject 0-6650 was conducted in cooperation with the Texas Department of Transportation andthe U.S. Department of Transportation, Federal Highway Administration. The authors gratefullyacknowledge the contributions of the project monitoring committee, which consisted of TimBradberry (Project Director), John Harper (Project Advisor), Teresa Michalk (Project Advisor),Jim Yang (Project Advisor), Yuan Zhao (Project Advisor), Sandra Kaderka (Contract Specialist),and Wade Odell (Research Engineer).The researchers thank Mr. J. Wood of the North Texas Tollway Authority (NTTA) and Mr. E.Starnater of Lamb-Star Engineering for sharing their inspection data and invaluable experience.vi

TABLE OF CONTENTSList of Figures . xList of Tables . xi1Introduction . 11.11.21.32Problem . 1Scope . 1Layout of the Report . 2Background on Galvanization-Induced Cracking . 32.1High Mast Illumination Poles—TxDOT Detail . 32.1.1 Shaft-to-Base-Plate Welding Details . 52.1.2 Materials and Fabrication . 82.1.3 Recommended Revisions to Existing TxDOT Details . 92.2Steel Chemistry . 92.2.1 Steel Manufacturing Processes . 102.2.2 Effect of Coiled Plate. 112.2.3 Steel Strength and Toughness . 112.2.4 Steel Chemistry Related Parameters Affecting Cracking . 122.2.5 Recommendations to Minimize Cracking in HMIP . 172.3Cold Working . 182.3.1 Cold Working Related Parameters Affecting Cracking . 192.3.2 Recommendations to Minimize Cracking in HMIP . 212.4Welding . 222.4.1 Welding Related Parameters Affecting Cracking in HMIP . 272.4.2 Recommendations to Prevent/Minimize Cracking in HMIP . 342.5Galvanizing . 362.5.1 Hot-Dip Galvanizing Process. 362.5.2 Galvanizing Practice in Texas. 372.5.3 Galvanizing-Related Parameters Affecting Cracking in HMIP . 382.5.4 Recommendations to Prevent/Minimize Cracking in HMIP . 453Analytical Method and Structural Response to Wind Loading . 473.13.23.33.43.53.6Introduction . 47Modal Analysis of HMIP (Step 1) . 48Pole Segments Affected by Vortex Shedding (Step 2) . 49Lock-in Velocity Range for Each Pole Segment (Step 3) . 51Creation of Wind Speed Bins across the Lock-in Plateau (Step 4) . 53Equivalent Static Wind Pressure Ranges, Pvs, for Vortex Shedding InducedVibration (Step 5) . 54vii

3.73.83.93.103.113.123.134Analytical Results and Discussions . 674.14.24.34.44.54.64.74.84.94.104.115Natural Frequencies (Step 1) . 67Velocities Causing Vortex Shedding Induced Vibrations (Step 2 to Step 4). 69Equivalent Static Pressure Ranges for Vortex Shedding Induced Vibrations(Step 5) . 70Equivalent Static Pressure Ranges for Natural Wind Gust Vibrations (Step 6) . 71Stress Ranges at the Base of the Pole (Step 7) . 71Wind Speed Distributions (Step 8). 74Number of Applied Cycles for a Given Stress Range (Steps 9 and 10). 79Vortex Shedding Induced Stress Cycles (Step 9). 80Natural Wind Gust Induced Stress Cycles (Step 10) . 80Fatigue Life and Reliability Analysis of High Mast Poles (Steps 11 and 12) . 81Limitations of the Current Study . 86Repair Alternatives and Repair/Replacement Cost Analysis . 915.15.25.36Equivalent Static Wind Pressure Ranges, PNW, for Natural Wind Gust InducedVibrations (Step 6) . 54Calculation of Stress Ranges at the Base of the Pole (Step 7) . 55Wind Speed Distributions Based on Historical Wind Data (Step 8). 56Number of Vortex Shedding Induced Vibrations during the Life of HMIP(Step 9) . 57Number of Natural Wind Gust Induced Vibrations during the Life of HMIP(Step 10) . 58Fatigue Resistance of Pole Base Connection with Galvanization-InducedCracks (Step 11) . 59Reliability Analysis to Determine Probability of Failure of Poles (Step 12) . 63Introduction . 91Repair Methods . 93Cost of Repair and Replacement of HMIP. 98Recommendations, Conclusions, and Future Work . 1016.1Recommendations . 1016.1.1 Design and Geometry . 1016.1.2 Steel Chemistry . 1016.1.3 Cold Working. 1026.1.4 Welding Processes . 1026.1.5 Galvanizing Processes. 1046.1.6 Recommendations for Inspection Scheduling Based on Reliability Analysis . 1056.2Conclusions . 1066.3Future Work . 107viii

References . 109Appendices .

FATIGUE FAILURE AND CRACKING IN HIGH MAST POLES by Raka Goyal Research Assistant Hemant B. Dhonde Research Assistant Professor and Mina Dawood Assistant Professor Report 0-6650-1 Project 0-6650 Project Title: Fatigue Failure and Cracking in High Mast Poles Performed in cooperation with the Texas Department of Transportation and the