Heavy Axle Load Effects on Fatigue Life of Steel Bridges

Unsworth, John F.

doi:10.3141/1825-06

Cited by 5 publications

(2 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Railroads want to add instrumentation to their bridges that can inform them with objective measurements about the bridge performance under revenue service traffic. Tobias and Foutch and Unsworth pointed out that steel bridges constructed over a hundred years ago need to be monitored to ensure that the loads experienced by bridge elements do not translate into fatigue failures or deficiencies. As identified in studies by Byers and Otter , future challenges and needs for bridge engineers will be better bridge performance monitoring tools to collect data from bridges in the field.…”

Section: Introductionmentioning

confidence: 99%

Railroad bridge monitoring using wireless smart sensors

Moreu

Kim

Spencer

2016

Struct. Control Health Monit.

View full text Add to dashboard Cite

Railroads carry more than 40% of the freight, in terms of tons per mile transported in North America. A critical portion of the railroad infrastructure is the more than 100,000 bridges, which occur, on the average, every 1.4 miles of track. Railroads have a limited budget for capital investment. Therefore, decisions on which bridges to repair/replace become critical for both safety and economy. North American railroads regularly inspected bridges to ensure safe operation that can meet transport demands, using inspection reports to decide which bridges may need maintenance, replacement, or further investigation. Current bridge inspection practices recommend observing bridge responses under live load to help assess bridge condition. However, measuring bridge responses under train loads in the field is a challenging, expensive, and complex task. This research explores the potential of using wireless smart sensors (WSS) to measure bridge responses under revenue service traffic that can be used to inform bridge management decisions. Wireless strain gages installed on the rail measure real-time train loads. Wireless accelerometers and magnetic strain gages installed in the bridge measure associated bridge responses. The system is deployed and validated on a double-track steel truss bridge on the south side of Chicago, Illinois, owned by the Canadian National Railway. A calibrated finite element model of the bridge with known train input load estimated the responses of the bridge at arbitrary, unmeasured locations, showing the possibility of applying the system for decision making process. These results demonstrate the potential of WSS technology to assist with railroad bridge inspection and management practice.

show abstract

Section: Introductionmentioning

confidence: 99%

Railroad bridge monitoring using wireless smart sensors

Moreu

Kim

Spencer

2016

Struct. Control Health Monit.

View full text Add to dashboard Cite

show abstract

“…1990s freight rail cars of 263,000 lb are now a standard of 286,000 lb, and we are now even seeing car loads with gross weights of 315,000 lb. Today's design capacity of railroad bridges is double what they were in the early 1900s (Unsworth, 2003). Plans may provide the age and design capacity of the structure, but a thorough field inspection helps detect deviations from the plan that may affect the structural response of the bridge, together with deterioration findings, and replaced members.…”

Section: Evaluation Of Existing Railroad Bridgesmentioning

confidence: 99%

Load testing and recommended repairs for dailey branch bridges - milepost 1.4 to 5.8

Parra-Luckert¹

View full text Add to dashboard Cite

The West Virginia Department of Transportation State Rail Authority sponsored a study to evaluate the condition of the railroad bridges on the Dailey Branch in Elkins, WV. The evaluations included field inspections, load rating, load testing, and a repair plan. A total of 2 steel bridges and 3 timber bridges were part of the study. The repair plan focused on identifying deteriorated timber bridge members for potential Glass Fiber Reinforced Polymer (GFRP) wrap repair. Information on dimensions and deterioration was gathered through field inspections. A timber specialist determined the species and grade of the timber bridges, finding most members to be Select Structural lumber of Southern Pine species. A preliminary analysis was performed to ensure that the bridges would withstand a hi-rail dump truck and a locomotive during load testing. A total of 76 strain gages were installed on all 5 bridges to record bending, shear, and axial compression data. Steel Bridge 1.4 is a 2 span steel through-girder bridge with spans of roughly 98 feet, and the measured field strains correlated well to those predicted through load rating analysis. The other steel bridge, Bridge 5.8, had field measurements of about 1.5 times lower than theoretical predictions, likely due to the contribution of the track structure on the 20' span. The field measured strains for the timber bridges were always less than theory for bending and shear, typically by a factor of about 2, due to the extra stiffness added through composite action between the ties and track together with the stringers, as evident through the shifting of the neutral axis. Field compression strains in the posts were typically higher than predicted, except for two cases, which are most likely due to the section losses in the instrumented posts and uneven bearing conditions. All bridges were load rated using AREMA standard Cooper E 80, a 286K freight railcar, and GP 38 locomotive with the analysis assumptions verified during the field load testing process. Under normal rating conditions, the bridges do not meet Cooper E 80 rating, but they can safely carry all other equipment. Recommendations for maintenance were made for the steel bridges. A cost-benefit analysis on timber bridge repair was used to recommend stringers to be replaced, and substructure members to be wrapped with GFRP, and filled with resin and bulk filler. 14'-11" to 76'-11" 21'-10" to 70'-4" 8' to 84'-3" 14'-11" to 77'-2" 22' to 70'-5" 2 17'-10" to 80' 24'-8" to 73' 10'-4" to 87'-2" 17'-10" to 80' 24'-8" to 73'-3" Floor beams run transverse to the girders riveted to the insides of their web plates, with a depth of 26.875 inches. Two rolled steel stringers run parallel to the girders and between floor beams with a depth of 20 inches. The AISC Historic Database has a few sections that closely match the dimensions of the stringers, thus section S20x64.8 is used due to it having the smallest strong axis moment of inertia. All substructures consist of concrete abutments and one concrete pier at mid span for Bridge 1.4.

show abstract