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Evaluation of Remaining Fatigue Life of a Non-Cantilever Highway Truss With Tubular Joints

Haroon, Abdullah
http://orcid.org/0000-0001-5180-4728
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1556235660877763

Abstract Details

2019, Master of Science, University of Toledo, Civil Engineering.
Non-cantilevered support structures have been widely used in the transportation department for supporting overhead traffic signs and signals. Several of them exhibit fracture failure at the welded connections, with the most likely cause being fatigue failure due to wind-induced vibrations. The failure usually occurs at “T”, “Y”, “K” tube to tube welded connections. The crack initiates at the welded junction of chord and diagonal and propagates circumferentially. A similar crack was observed at a truss on Alum Creek Drive at the interchange of I-270 in the state of Ohio. An investigation, funded by ODOT, was conducted at the University of Toledo into the cause of failure. Finite element modeling of the structure was conducted using SAP2000. External loadings from natural wind gusts were considered. It was presumed that the effects of other loadings such as vortex shedding, galloping, and truck gusts are negligible for this structure. Both static and transient dynamic analyses were performed. Weather data of daily variation in wind speed and direction were obtained from NCDC and a probabilistic wind distribution was performed. Using Kaimal spectrum load time histories of natural wind was generated, and a transient dynamic analysis was performed. Stress histories of critical members were extracted, and Palmgren-Miner rule was applied to evaluate the fatigue life of the critical members. The analysis results indicated that if the weld is assumed to be of sound quality, the fatigue life of the critical members under the effect of natural wind gust greater than the service life of the truss. Simulated damage scenarios were introduced by reducing the load carrying capacity of the members at failed joints and fatigue life was compared in undamaged and damaged states. Damage was introduced by reducing the mechanical strength of failed members and deterioration due to poor weld quality was not considered Compared to the undamaged state, the fatigue life in all the three damage scenarios was found to reduce by only 10%. This suggests that assuming the welds are done as per code requirements, the truss is redundant enough to sustain some damage without affecting the overall fatigue life of the structure. Even though the findings of this report predict the fatigue life to be greater than the service life of the truss, it should be noted that this result is only valid with the presumption that welded connections between members of the truss are sound and no defect in weld quality is considered in the present analysis. A quantitative assessment of the effects of weld defects on the fatigue life of the structure could give a better understanding of the failure mode, but such a venture was beyond the scope of this study.
Douglas Nims (Committee Chair)
Serhan Guner (Committee Chair)
Luis Mata (Committee Member)
84 p.
Civil Engineering

Recommended Citations

Citations

  • Haroon, A. (2019). Evaluation of Remaining Fatigue Life of a Non-Cantilever Highway Truss With Tubular Joints [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1556235660877763

    APA Style (7th edition)

  • Haroon, Abdullah. Evaluation of Remaining Fatigue Life of a Non-Cantilever Highway Truss With Tubular Joints. 2019. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1556235660877763.

    MLA Style (8th edition)

  • Haroon, Abdullah. "Evaluation of Remaining Fatigue Life of a Non-Cantilever Highway Truss With Tubular Joints." Master's thesis, University of Toledo, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1556235660877763

    Chicago Manual of Style (17th edition)

toledo1556235660877763
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This open access ETD is published by University of Toledo and OhioLINK.