Download or read book Initial Analytical Investigation of Overhead Sign Trusses with Respect to Remaining Fatigue Life and Predictive Methods for Inspection written by Husam Aldeen Alshareef and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most state highway agencies do not perform routine fatigue inspections on highway signs, luminaires, and traffic signals, thereby increasing the potential for unnoticed fatigue cracking. The Kansas Highway System utilizes over 450 sign trusses, most of which have been in service for 30-45 years. In addition to aging support structures, the structural designs of these signs and signals sometimes result in significant cyclical loading due to wind gusts. This study conducted fatigue evaluations using nominal axial member-specific stress ranges corresponding to a wind speed database for a 45-year period, as well as hundreds of structural analysis simulations. Potential fatigue failure was assessed for each member of the support structure by evaluating the ratio of consumed fatigue cycles to ultimate fatigue cycles using Miner's rule to estimate finite life. If the ratio was close to zero after 45 years or any number of actual service years, the member was expected to have a practically infinite life. If the ratio was close to 1 after the service years, the member was expected to be at the end of its life. This information can help inspectors identify for critical spots that may have developed fatigue cracks that otherwise would be difficult to detect. Two approaches were hypothesized to account for fatigue life deterministically and probabilistically. Fatigue Life Simulator Software (FLSS) was developed to manage hundreds of simulations and determine the fatigue life of all members in a structure in specific areas of Kansas. FLSS is compatible and works simultaneously with STAAD. Pro software and Sign Truss Interface provided by KDOT to generate results. Users apply the results to study the behavior of overhead structures and identify critical spots that should be physically inspected and potentially replaced. Results in Kansas indicated a range of structural fatigue life varying by city. Modifications were made to the output files of Sign Truss Interface to incorporate American Association of State Highway and Transportation Officials (AASHTO) load cases 1 and 2 and simulate wind speed into wind pressure using the effect of the two load cases. The modification also automatically incorporated 45 years' worth of wind speed data into the Sign Truss Interface to simulate and generate structural models to determine corresponding stresses to the wind effect.

Download or read book Initial Analytical Investigation of Overhead Sign Trusses with Respect to Remaining Fatigue Life and Predictive Methods for Inspection written by Husam Aldeen Alshareef and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Most state highway agencies do not perform routine fatigue inspections on highway signs, luminaires, and traffic signals, thereby increasing the potential for unnoticed fatigue cracking. The Kansas Highway System utilizes over 450 sign trusses, most of which have been in service for 30-45 years. In addition, to aging support structures, the structural designs these signs and signals sometimes result in significant cyclical loading due to wind gust. This study conducted fatigue evaluations using nominal axial member-specific stress ranges corresponding to a wind speed database for a 45-year period, as well as, hundreds of structural analysis simulations. Potential fatigue failure was assessed for each member of the support structure by evaluating the ratio of consumed fatigue cycles to ultimate fatigue cycles using Miner's rule to estimate finite life. If the ratio was close to zero after 45 years or any number of actual service years, the member was expected to have a practically infinite life. If the ratio was close to 1 after the service years, the member was expected to be at the end of its life. This information can help inspectors identify for critical spots that may have developed fatigue cracks that otherwise would be difficult to detect. Two approaches were hypothesized to account for fatigue life deterministically and probabilistically. Fatigue Life Simulator Software (FLSS) was developed to manage hundreds of simulations and determine the fatigue life of all members in a structure in specific areas of Kansas. FLSS is compatible and works simultaneously with STAAD Pro Software and Sign Truss Interface provided by KDOT, to generate results. Users apply the results to study the behavior of overhead structures and identify critical spots that should be physically inspected and potentially replaced. Results in Kanas indicated a range of structural fatigue life varying by city. Modifications were made to the output files of Sign Truss Interface to incorporate American Association of State Highway and Transportation Officials (AASHTO) load cases 1 and 2 and simulate wind speed into wind pressure using the effect of the two load cases. The modification also automatically incorporated 45-years of wind speed data into the Sign Truss Interface to simulate and generate structural models to determine corresponding stresses to the wind effect.

Download or read book Analytical Investigation of Saddle Connections for Overhead Sign Trusses with Respect to Strength and Fatigue Performance written by Danqing Yu and published by . This book was released on 2021 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bridge-type overhead truss sign structures (OHTSS) are widely used over active highways across the United States. An OHTSS is comprised of a 3D truss and two support frames at each end. The structures are usually made of steel or aluminum. Many state DOTs use their own types of connections that are not documented in specifications. Since 2015, the Kansas Department of Transportation (KDOT) has used a type of 'saddle connection' at the joints of truss chords and support frame pipes. Wind loads are the primary type of load a sign structure resists besides the gravity load. Since wind loads are periodic, fatigue properties are important in the design of OHTSS. As a newly developed connection, KDOT sought information regarding the mechanical performance of the saddle connection. Studies were needed to verify the safety of the connections, particularly regarding its fatigue susceptibility. This report presents a study mainly aimed at evaluating the fatigue susceptibility of the saddle connections using finite element analysis (FEA). The study consisted of the following four parts: Part 1: Global behavior analysis: an analysis aimed at determining the global behavior of the structures and the location of critical connections. Linear-elastic material properties were used. Part 2: Structural Hot Spot Stress analysis: an analysis was performed to determine structural Hot Spot Stresses along each weld in the critical connections identified in Part 1. Linear-elastic material properties were used. Part 3: Effective notch stress analysis: a linear-elastic analysis using the effective notch stress method to evaluate three welds identified to have larger stresses in Part 2. Linear-elastic material properties were used. Part 4: Extreme loading analysis: An analysis to evaluate the behavior of the saddle connections and the overall structures under extreme loading and provide comments regarding the strength-related safety of the saddle connections. Elastic-perfectly plastic material properties were used. Sign structures of four span lengths, including 60 ft, 83 ft, 110 ft, and 137 ft, were analyzed in Part 1 and Part 2. The 137-ft span structure was analyzed in Part 3 using the effective notch stress method. The 60-ft and 137-ft span structures were analyzed in Part 4. In Part 1 and Part 2, AASHTO fatigue loads, including natural wind gusts and truck-induced gusts, were applied in six load modes. They included: natural wind blowing from the back, front, and side of sign structures; and truck-induced gusts acting on the right, middle, and left 12 ft of sign trusses. In Part 3, the AASHTO fatigue load of the natural wind blowing from behind the sign structure was applied. In Part 4, the overall structures and the saddle connections were loaded until the analysis terminated. The termination of analysis was governed by loss of stiffness due to the yielding of material. The study resulted in conclusions that the natural wind in the direction facing the sign panel almost always governed the fatigue demand. The bottom saddle connections were more susceptible to fatigue damage than the top saddle connections, especially the stiffener-to-pipe weld in the bottom saddle connection. Fatigue failures of the saddle connections are not likely to occur in expected real use, but attention should be paid to the stiffener-to-pipe weld in the bottom saddle connection. The analysis of the structures under extreme loading suggests that the ultimate strength of saddle connections do not govern the strength of the overall structures.

Download or read book Fatigue Strength and Evaluation of Sign Structures Volume 1 written by Xuejun Li and published by . This book was released on 2006-06-15 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Determination of Remaining Fatigue Life of Welded Stud Details on Overhead Aluminum Sign Panels in Virginia written by Jeremy L. Lucas and published by . This book was released on 2005 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Some overhead highways signs in Virginia using a specific welded threaded stud and clip connection have failed while in service. From inspection of the signs it was determined that the failure was caused by fatigue of the weld connecting the threaded stud to the back of the sign panel. It was also observed that lower edge connections failed first and the failures progressed upwards in an unzipping pattern. A combination of natural and truck-induced wind gusts is the cause for the fatigue failure. Although signs with these connections are no longer produced by VDOT and all production was halted in early 2004, there are still approximately 4,000 signs in Virginia with this connection detail. The objective of the research project described here in was to determine priorities for an inspection and retrofitting plan for the remainder of the signs in Virginia. Specifically an S-N curve, which is a plot of stress range versus the number of cycles to failure, was to be developed to aid in predicting the remaining service life of sign panels using this connection detail. The authors opted to test single connections instead of multiple connection systems (i.e., an entire sign or portion thereof) because of material availability, the timeliness of testing, and the readily available equipment for testing. Connections simulating interior and exterior connections were tested under a pseudo-static load as well as for fatigue. Fatigue tests of interior and exterior sign connections developed failures of the aluminum panel instead of the expected weld fracture. Because the failure and fatigue threshold were not representative of failures found in the field, a proper S-N curve to help develop retrofitting priorities could not be developed. Recommendations from this program include increasing retrofit and inspection efforts, gauging and monitoring full-scale signs in service to understand loading conditions, and testing full-scale signs.

Download or read book Structural Analysis of Sign Bridge Structures and Luminaire Supports written by and published by . This book was released on 2004 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluation of Remaining Fatigue Life of a Non cantilever Highway Truss with Tubular Joints written by Abdullah Haroon and published by . This book was released on 2019 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Fatigue Life Calculation of Overhead Sign Structure Due to Thermal Loading written by Lucky K C and published by . This book was released on 2019 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis analytically investigates the effects of thermal loading on the aluminum overhead sign structure and calculates the remaining fatigue life of the structure. Overhead sign structures are widely used across freeways and highways to support traffic signals and signposts and monitor the proper flow of traffic. The Ohio Department of Transportation (ODOT) is responsible for the inspection and safe operation of the overhead sign structures in Ohio. However, sudden failure of an overhead sign structure on Alum Creek Drive in Columbus, Ohio, lead ODOT to initiate an investigation to determine the cause of failure. From the study done by a research team from the University of Toledo, Ohio, it was concluded that the failure was fatigue failure. Fatigue failure occurs due to the repetitive cyclic load acting on the structure. The cyclic loading can be thermal loading, wind loading, wind galloping and so on. This research concentrates on the effects of thermal loading on the structure and mainly illustrates about the fatigue stresses that are generated by the daily temperature variations and calculation of the fatigue life of the overhead sign structure due to these stresses. The research was done by creating an analytical model (based on the standard drawing provided by ODOT) of the structure using finite element software SAP2000, so that it resembled the structure that was erected in the field. Cyclic loading due to daily temperature variations was considered. The data of the daily temperature change were obtained from the National Climatic Data Center (NCDC) and a temperature histogram was plotted. These temperature variations were applied to the structure as thermal loads and corresponding thermal stresses were generated. Finally, using the Palmgren-Miner's rule, the fatigue life of the structure was calculated. This calculation of fatigue life assumed that the welded joints were in sound condition and there were no structural defects in the structure. Therefore, for pristine geometry and proper welded condition, the result indicated the fatigue life of the structure due to thermal loading to be greater than the service life of the structure.

Download or read book Study of Fatigue Damage in Overhead Sign Supports and High Light Towers written by W. H. Parcells and published by . This book was released on 1981 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stability Analysis and Reliability based Assessment of Truss Highway Sign Support Structures written by Jun Yang and published by . This book was released on 2000 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Determination of Fatigue Resistance of Coupler Connections in Aluminum Overhead Truss Structures written by Danqing Yu and published by . This book was released on 2021 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Overhead truss sign structures (OHTSS) are widely used over highways across the nation. An overhead truss sign structure is comprised of a truss and two supporting frames at each end, and can be made using aluminum or steel. Aluminum overhead truss sign structures are generally more prone to vibration issues due to their light weight (Fouad et al. 2003). Before 2015, aluminum overhead truss sign structures constructed in Kansas used an identical type of coupling assembly to provide connection between vertical poles and horizontal trusses. There are approximately 450 sign structures that use this type of connection over active highways in the State of Kansas. The coupler connection was designed in the early 1970s. At that time, experimental tests were conducted to determine the static strength of the connection (McCollom, 1973), however, no prior research has been conducted to evaluate the fatigue performance of the coupler connection. Many of these connections have now been in service for 30–40 years and research is needed to evaluate the fatigue performance of the connections. This report presents a study aimed at evaluating the fatigue performance of the coupler connections used in bridge-type overhead truss sign structures. It consists of two parts. The first part describes a series of finite element (FE) analyses that were used to determine the behavior of the coupler connections in expected real use. The results indicated that among all loading cases analyzed in this study, the out-of-plane responses of the sign structures were more significant than in-plane responses. The coupler connections behaved like idealized pinned connections, with little to no capability to transfer moments; therefore, the rivets connecting the interior two couplers were found to undergo mostly direct tension and shear. A rational experimental testing plan was developed according to the findings of the finite element analyses. The second part of this study included performing 22 fatigue tests on newly-fabricated coupling assemblies obtained from Steve Johnson Fabrication, Inc. (Wichita, KS), the company that manufactures most OHTSS in Kansas. The experimental tests were conducted to characterize the fatigue performance of the coupler connection, utilizing AASHTO S-N curves. The fatigue tests were conducted in three directions, such that the rivet was loaded in: 1) tension, 2) vertical shear, and 3) horizontal shear. These loading conditions on the rivet represented, respectively: 1) truss out-of-plane shear, 2) truss in-plane shear, and 3) truss chord axial force. The testing program revealed that the coupler connection has much better fatigue resistance when loaded in shear than in tension. Despite poor tensile fatigue performance, fatigue failure is still considered to be unlikely in OHTSS applications, due to very low stress demands found from finite element analyses.

Download or read book NCHRP Synthesis 354 written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Testing and Analysis written by Yung-Li Lee and published by Elsevier. This book was released on 2011-04-18 with total page 417 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue Testing and Analysis: Theory and Practice presents the latest, proven techniques for fatigue data acquisition, data analysis, and test planning and practice. More specifically, it covers the most comprehensive methods to capture the component load, to characterize the scatter of product fatigue resistance and loading, to perform the fatigue damage assessment of a product, and to develop an accelerated life test plan for reliability target demonstration. This book is most useful for test and design engineers in the ground vehicle industry. Fatigue Testing and Analysis introduces the methods to account for variability of loads and statistical fatigue properties that are useful for further probabilistic fatigue analysis. The text incorporates and demonstrates approaches that account for randomness of loading and materials, and covers the applications and demonstrations of both linear and double-linear damage rules. The reader will benefit from summaries of load transducer designs and data acquisition techniques, applications of both linear and non-linear damage rules and methods, and techniques to determine the statistical fatigue properties for the nominal stress-life and the local strain-life methods. - Covers the useful techniques for component load measurement and data acquisition, fatigue properties determination, fatigue analysis, and accelerated life test criteria development, and, most importantly, test plans for reliability demonstrations - Written from a practical point of view, based on the authors' industrial and academic experience in automotive engineering design - Extensive practical examples are used to illustrate the main concepts in all chapters

Download or read book Engineering for Structural Stability in Bridge Construction written by Federal Highway Federal Highway Administration and published by . This book was released on 2020-07-19 with total page 669 pages. Available in PDF, EPUB and Kindle. Book excerpt: This manual is intended to serve as a reference. It will provide technical information which will enable Manual users to perform the following activities:Describe typical erection practices for girder bridge superstructures and recognize critical construction stagesDiscuss typical practices for evaluating structural stability of girder bridge superstructures during early stages of erection and throughout bridge constructionExplain the basic concepts of stability and why it is important in bridge erection* Explain common techniques for performing advanced stability analysis along with their advantages and limitationsDescribe how differing construction sequences effect superstructure stabilityBe able to select appropriate loads, load combinations, and load factors for use in analyzing superstructure components during constructionBe able to analyze bridge members at various stages of erection* Develop erection plans that are safe and economical, and know what information is required and should be a part of those plansDescribe the differences between local, member and global (system) stability

Download or read book Fatigue and Fracture written by F. C. Campbell and published by ASM International. This book was released on 2012-01-01 with total page 699 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This book emphasizes the physical and practical aspects of fatigue and fracture. It covers mechanical properties of materials, differences between ductile and brittle fractures, fracture mechanics, the basics of fatigue, structural joints, high temperature failures, wear, environmentally-induced failures, and steps in the failure analysis process."--publishers website.

Download or read book Inspection and Management of Bridges with Fracture Critical Details written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Redundancy in Highway Bridge Superstructures written by Michel Ghosn and published by Transportation Research Board. This book was released on 1998 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: