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New Jersey Turnpike Bridge Over Mill Lane

Students:

  1. Isaac Garcia,
  2. Joseph King (Team Leader),
  3. Jonathan Raybould,
  4. Michael Trull

Advisors: A. Bechtel, V. Krstic

As part of the New Jersey Turnpike Exit 6-9 Widening program, a new structure was designed adjacent to the existing bridge in order to accommodate more lanes of traffic. Due to the increased capacity of the bridge, the structure will need to accommodate 6 lanes of high speed (65 mph) traffic. The scope of the project called for both a structural and geotechnical design.

The structural team adopted a total number of 6 girders for the super structure by optimizing scale factors of the moment of inertia. The final design for built-up I-beam section incorporated two 1.5”X12” flanges and a 3/8”X55”web with a nominal capacity of 8700 ft.-kip.  The exterior I beams also required 6 stiffeners. To achieve a fully composite section that does not fail to transverse shear, a total of 234 ¾” shear studs were added to the design.

Using boring logs, the geotechnical team identified upper fill and granular layers with cohesive soil underneath. Using calculated soil properties, the foundation was designed for the abutment. Using the design program Driven, the estimated tip elevation was found to be 41 ft. and 39 ft. for the South and North Abutments respectively. The pile drivability for 24” square concrete piles was satisfied by using an ICE 640 Hammer with a power of 55 Kj for the given soil conditions at both abutments when used with a 6” plywood hammer cushion. Due to the cohesive nature of the soil, and subsequent settlement, a MSE wall was designed. The 27’x19’x72’ MSE wall was found to be stable for both sliding and overturning conditions. The bearing capacity for the MSE wall at the abutment was checked using the Meyerhof bearing capacity method. It was determined that the applied load of 4868.2 psf was satisfied by the 71,752 psf capacity of the soil.

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