Development and Validation of Methodologies for Rapid Inspection and Assessment of Fatigue Damage
-
2020-09-01
-
By Roy, Sougata
Details:
-
Creators:
-
Corporate Creators:
-
Corporate Contributors:United States. Department of Transportation. Office of the Assistant Secretary for Research and Technology ; New Jersey Turnpike Authority (NJTA) ; United States. Department of Transportation. Federal Highway Administration ; United States. Department of Transportation. University Transportation Centers (UTC) Program
-
Subject/TRT Terms:
-
Publication/ Report Number:
-
Resource Type:
-
Geographical Coverage:
-
Edition:Final Report, 09/01/2018- 12/31/2019
-
Corporate Publisher:
-
Abstract:Causes of unusual fatigue cracking of a steel bridge owned by the New Jersey Turnpike Authority (NJTA) was investigated by Finite Element Analysis (FEA). The bridge is located on a strategic commerce route and is subjected to high Average Daily Truck Traffic (ADTT) consisting of significant fraction of overloaded trucks having Gross Vehicle Weight as high as twice the legal limit. The bridge originally built in 1950s and widened in 1971 is in service for more than 60 years. Fatigue cracking was observed in the top flange of the floor beams at deck expansion joints. The cracks developed at bearing stiffeners under the stringers and grew through the flange at some locations. Based on Weigh-in-Motion (WIM) studies performed at a nearby bridge, the bridge model was analyzed for 2.25 times the AASHTO fatigue design truck load plus 15% impact. The analysis showed that the maximum stress in the floor beam flange developed when the rear tandem axle of the truck loading crossed over to the deck on one side of the expansion joint. The maximum stress range occurred under the loaded bearing on the floor beam bracket, which was remnant from the original construction and was incorporated into the deck widening. The fatigue cracking in the flange adjacent to the bearing stiffeners was due to cyclic plastic straining. The local stresses at the holes for the bearing retaining bolts also exceed the yield limit of the material leading to fatigue cracks in the flange emanating from the holes. Due to significantly larger section modulus of the interior floor beam, the stresses in the flange was less than the AASHTO CAFT for Category A or base metal. No fatigue crack growth was observed nor was expected at this location. The analysis showed that the fatigue cracking was due to frequently occurring overloaded trucks in the truck traffic spectrum. The fatigue cracking was expected to be localized under the widened section of the bridge carrying the two exterior lanes mostly traversed by truck traffic, where the section modulus of the floor beam was significant less than that of the floor beams between the interior girders. Based on the findings, it is recommended that the exterior floor beam between the exterior and the first interior girder be strengthened to reduce the stresses in the flange below the CAFT of respective details.
-
Format:
-
Funding:
-
Collection(s):
-
Main Document Checksum:
-
Download URL:
-
File Type: