Download or read book Mitigating Wind Induced Fatigue in Steel Traffic Signal Support Structures written by Kyle Thomas Wieghaus and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Traffic signal structures undergo wind-induced vibrations that result in fatigue damage accumulation and reduced service life. Mast arms have failed and required removal while in service. A dual experimental and analytical modeling approach is taken to mitigate fatigue and fracture in steel traffic supporting structures. A full-scale prototype structure is instrumented to study natural wind response. Excitation mechanisms are identified, and response is characterized statistically by a lognormal distribution. Helical strakes are found to reduce the vortex-induced vibration of cantilevered traffic signal structures, however are not a panacea for fatigue mitigation as marginal service life gains occur in severe wind environments. A probabilistic framework is extended to assess the risk of wind-induced fatigue and estimate service life while considering uncertainties in fatigue demand and capacity. The framework is successfully demonstrated against compiled inspection records. Locations with higher prevailing winds are susceptible to wind-induced fatigue, but the prevalence of low-speed vortex-induced response is primarily responsible for the early fatigue failures in more mild environments. A low-cost damage avoidance system is proposed to mitigate fatigue and fracture in steel traffic supporting structures. Applied prestress introduces a fail-safe, supplementary load path to balance dead load moment, eradicating the detrimental tensile mean stress found in traffic signal structure connections. Field observations are made without and with the proposed system installed. The benefit of applied prestress is quantified by determining service life without and with the system based on changes in response and fatigue resistance using: (i) a code-based technique; and (ii) the proposed probabilistic framework. Fatigue performance is modeled as mean stress-dependent by modifying nominal stress-life relationships. Service life is shown to increase by an order of magnitude, regardless of wind environment. The concept shows potential to reduce the detrimental effects of non-redundancy for a variety of similar, fatigue-critical infrastructure components. The validity of simplified mean stress-dependent connection modeling is explored. A fracture mechanics-based, total life (initiation-propagation) model is used to demonstrate the detrimental effect mean stress has on tube-to-transverse base plate fatigue resistance. Using fatigue strength curves derived from total life analyses, probabilistic analyses are repeated to justify the use of simplified models. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155395
Download or read book Fatigue resistant Design of Cantilevered Signal Sign and Light Supports written by Robert Joseph Dexter and published by Transportation Research Board. This book was released on 2002 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the XV Conference of the Italian Association for Wind Engineering written by Francesco Ricciardelli and published by Springer. This book was released on 2019-03-12 with total page 755 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume gathers the latest advances, innovations, and applications in the field of wind engineering, as presented by leading international researchers and engineers at the XV Conference of the Italian Association for Wind Engineering (IN-VENTO 2018), held in Naples, Italy on September 9-12, 2018. It covers highly diverse topics, including aeroelasticity, bluff-body aerodynamics, boundary layer wind tunnel testing, computational wind engineering, structural dynamics and reliability, wind-structure interaction, flow-induced vibrations, wind modeling and forecast, wind disaster mitigation, and wind climate assessment. The contributions, which were selected by means of a rigorous international peer-review process, highlight numerous exciting ideas that will spur novel research directions and foster multidisciplinary collaboration among different specialists.
Download or read book Risk Assessment Model for Wind induced Fatigue Failure of Cantilever Traffic Signal Structures written by C. W. Letchford and published by . This book was released on 2008 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Guide Design Specification for Bridge Temporary Works written by American Association of State Highway and Transportation Officials and published by AASHTO. This book was released on 1995 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mitigating Fatigue of Cantilevered Overhead Sign Structures Due to Natural and Truck induced Wind Gusts written by Mohamed Salah Gallow and published by . This book was released on 2014 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cantilevered overhead sign structures (COSS) are widely used across highways in the U.S. Several cases of failures have been reported for such structures due to fatigue wind loads. The structure's dynamic characteristics such as natural frequency and critical damping are responsible for its behavior during those loads. When the frequency of wind gusts load matches the fundamental frequency of the OSS, resonance occurs, which causes excessive vibrations. Consequently, fatigue stresses in crease and may exceed the fatigue critical limit, resulting in failure. Vibrations and fatigue stresses amplitudes are dependent on the structure's natural frequency. The objective of this study is investigating natural frequencies of COSS in order to mitigate fatigue stresses due to natural and truck-induced wind gusts. Investigating damping and other fatiguee wind loads are out of the scope in this study. Alterations in factors such as the members' configuration, arrangement, sizes, and layout of the structure control its stiffness and mass distribution which controls its natural frequency and consequently, fatigue stresses. A parametric study was considered in order to investigate the effect of these factors and recommend the best layout between 4-chord, 2-chord, and monotube CSS in mitigating fatigue. Structures were designed according to the American Association of State Highway and Transportation Officials (AASHTO) 2013, Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals (mentioned hereafter as the AASHTO Support Specifications (2013)) and modeled using commercial finite element analysis software. Wind pressure power spectral density and time history loading functions were applied on these structures to simulate natural and truck-induced wind gusts, respectively. Eventally, on the contrary of the 2-chord structure, slanted monotube CSS with curved end post was found to have least mass, highest frequency and nearly smallest fatigue stresses.
Download or read book Structural Supports for Highway Signs Luminaires and Traffic Signals written by Fouad H. Fouad and published by Transportation Research Board. This book was released on 2003 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue resistant Design of Cantilevered Signal Sign and Light Supports written by Mark R. Kaczinski and published by Transportation Research Board. This book was released on 1998 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Traffic Signal Pole Research damping written by University of Wyoming. Department of Civil and Architectural Engineering and published by . This book was released on 2001 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Researches the weakness and failure potential of cantilevered traffic signal structures due to wind-induced fatigue cracks.
Download or read book Full scale Investigation of Wind induced Vibrations of Mast arm Traffic Signal Structures written by Hung Nguyen Sinh and published by . This book was released on 2014 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because of their inherent flexibility and low damping ratios, cantilevered mast-arm traffic signal structures are susceptible to wind-induced vibrations. These vibrations cause structural stresses and strains to develop in a cyclical fashion which can lead to reduced service life due to fatigue and, in extreme cases, full collapse. In 2001, after the collapse of several of these structures throughout the United States, American Association of State Highway and Transportation Officials (AASHTO) code standards were updated to include fatigue provisions for traffic signal supporting structures. In New York State, there is particular concern regarding structures spanning longer than 14 meters which currently do not meet these updated fatigue provisions. To address this concern, a full-scale experiment was conducted using an existing 25 meter mast-arm traffic signal structure, located in Malta, NY, in which the response of the structure was observed in relation to in-situ wind conditions. In previous studies, high-amplitude vertical vibrations of mast-arm traffic signal structures have been shown to be due to vortex shedding, a phenomenon in which alternatingly shed, low-pressure vortices induce oscillating forces onto the mast-arm causing a cross-wind response. When the frequency of vortices being shed from the mast-arm corresponds to the natural frequency of the structure, a resonant condition is created. The resonant condition causes the long-lasting, high amplitude vibrations, which may lead to the fatigue failure of these structures. Turbulence in the approach flow is known to affect the cohesiveness of vortex shedding. Results from this full-scale experiment indicate that the surrounding terrain conditions, which affect the turbulence intensity of the wind, greatly influence the likelihood of occurrence of long-lasting, high-amplitude vibrations and also impact whether reduced service life due to fatigue is likely to be a concern.
Download or read book AE Evaluation of Fatigue Damage in Traffic Signal Poles written by TJ. Fowler and published by . This book was released on 1999 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two traffic signal structures recently collapsed in Wyoming. The collapse was a result of brittle fracture of the connection between the cantilever signal light support arm (mast arm) and the vertical pole (post) caused by wind-induced, largeamplitude vibrations of the mast arm. This paper presents the problem, the proposed test program, the results of initial development tests, and the effort to develop a viable AE testing technique along with evaluation criteria that can be used to screen in-service traffic signal poles.
Download or read book Reducing Fatigue in Wind excited Traffic Signal Support Structures Using Smart Damping Technologies written by Richard Christenson and published by . This book was released on 2011 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Loading and Design Methodology for High Mast Lighting Towers written by Robert J. Connor and published by Transportation Research Board. This book was released on 2012 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB’s National Cooperative Highway Research Program (NCHRP) Report 718: Fatigue Loading and Design Methodology for High-Mast Lighting Towers provides criteria for the fatigue design of high-mast lighting towers.
Download or read book Fatigue Risks in the Connections of Sign Support Structures written by and published by . This book was released on 2008 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the International Conference on Advances in Computational Mechanics 2017 written by Hung Nguyen-Xuan and published by Springer. This book was released on 2018-02-20 with total page 1137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview of state-of-the-art methods in computational engineering for modeling and simulation. This proceedings volume includes a selection of refereed papers presented at the International Conference on Advances in Computational Mechanics (ACOME) 2017, which took place on Phu Quoc Island, Vietnam on August 2-4, 2017. The contributions highlight recent advances in and innovative applications of computational mechanics. Subjects covered include: biological systems; damage, fracture and failure; flow problems; multiscale multiphysics problems; composites and hybrid structures; optimization and inverse problems; lightweight structures; computational mechatronics; computational dynamics; numerical methods; and high-performance computing. The book is intended for academics, including graduate students and experienced researchers interested in state-of-the-art computational methods for solving challenging problems in engineering.
Download or read book Structural Supports for Highway Signs Luminaires and Traffic Signals written by Fouad Hilmy Fouad and published by . This book was released on 1998 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Use of Wind Power Maps to Establish Fatigue Design Criteria for Traffic Signal and High mast Structures written by Richard Lee Price and published by . This book was released on 2008 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent design requirements for traffic signal and sign structures incorporated fatigue load criteria related to wind that are producing significant increases in size and cost. The Fourth Edition of the AASHTO Luminaire and Traffic Signal Specification (2002 with interims) specification is a significant change to past practice and often results in much larger and more costly structures. Here conservative principles (envelope wind demands and infinite fatigue life) for design at increased cost even for those regions not adversely affected by wind-induced fatigue. The states that do not have steady, sustained winds and have not experienced significant fatigue failures have concerns with the larger and more costly structures. A rationale basis for lowering the fatigue design loads may be appropriate. This study compares fatigue failures with respect to wind power (expressed as a function of average wind velocity). Inspection reports for approximate 2500 cantilevered traffic structures and 700 high-mast luminaires were collected and analyzed for suspected fatigue cracking. Each structure was located spatially and the associated wind power classification for that location was noted. (Wind power classifications are used to site wind generators.) This research is limited to traffic signal structures.
