Field demonstration of new bridge approach slab designs and performance.

Details

• Creators:
  Abu-Farsakh, Murad Y. ; Chen, Qiming
• Corporate Creators:
  Louisiana Transportation Research Center
• Corporate Contributors:
  United States. Federal Highway Administration
• Subject/TRT Terms:
  • Bridge design
  • Bridge approaches
  • Slabs
  • Field tests
  • Performance tests
  • Settlement (Structures)
  • Flexural strength
  • Bridge foundations
  • Bearing capacity
  • Traffic loads
• Publication/ Report Number:
  FHWA/LA. 13/520
• Resource Type:
  Tech Report
• Geographical Coverage:
  Louisiana
• Corporate Publisher:
  Louisiana Transportation Research Center
• Abstract:
  The Louisiana Department of Transportation and Development (DOTD) has initiated a major effort to minimize the bridge end bump problem associated ; with differential settlement. As a result, a new design for the approach slab was proposed, which requires increasing the slab flexural rigidity (EI), and ; using reinforced soil foundation (RSF) to support the slab and traffic loads at the roadway pavement/approach slab joint (R/S joint). Reinforcing the soil ; underneath the strip footing will result in increasing the soil’s bearing capacity and reducing the embankment settlement by redistributing the loads ; imposed by the slab and traffic over a wider area. Bayou Courtableau Bridge was selected as a demonstration project to evaluate, validate, and verify the ; new bridge approach slab design method proposed in a previous study. The east and west approach slabs at Bayou Courtableau Bridge are 40 ft. long by 40 ; ft. wide. The west approach slab was designed using the proposed new method with slab thickness of 16 in., while the east approach slab was designed ; using the traditional method with slab thickness of 12 in. The pavement end side of the approach slab was supported by a 4.0-ft. wide strip footing with the ; soil underneath it reinforced by six layers of geogrid placed at a vertical spacing of 12 in. The geosynthetic reinforced soil below the strip footing was ; designed according to the methodology proposed in previous study. The west approach slab was instrumented with pressure cells to measure the pressure ; distribution underneath the footing and contact pressure underneath the slabs. Strain gauges were used to measure strain distribution along geogrid ; reinforcement and sister-bar strain gauges to measure strains within the slab. The east approach slab was instrumented with pressure cells to measure the ; contact pressure underneath slab. Two static load tests were conducted on both the west and east approach slabs at two different times after construction. ; The performance of the approach slabs, including deformation and internal stresses of concrete slab, contact stresses between slab and embankment, stress ; distributions within reinforced soil foundation, and strain distributions along the geogrid, was monitored during the tests. The test results indicated that the ; west approach slab (with new design) lost most of its supports from the soil; while the east approach slab (with traditional design) kept losing its contacts ; from the soil starting from the bridge side towards the pavement side after about a year and half. The roughness profiles show better performance of the ; new approach slab system with much lower International Roughness Index (IRI) values. The year and a half monitoring program at Bayou Courtableau ; Bridge demonstrated much better performance of the new approach slab design system (west approach slab) compared to the traditional design. ; The magnitude and rate of embankment settlement at Bayou Courtableau Bridge site was also monitored (for the two embankment sides) during and after ; the construction, and the results were compared with the laboratory calculated settlements and the piezocone penetration test (PCPT)-based settlement ; prediction methods. The results showed better predictions using PCPT methods as compared to laboratory results.
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• Format:
  PDF
• Funding:
  LTRC Number: 05-1GT ; SIO Number: 30000116
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/27323/dot_27323_DS1.pdf
• File Type:
  [PDF - 1.58 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:72a3ee7ff65d1319d86d3652bb53ab2ba805113d109cf5c9fb14c2016cb365d8