I-35 NB/SB Over IAIS Railroad

WHKS was the prime consultant for replacing the existing I-beam bridges with dual 194’-0” x 63’-4” prestressed concrete beam bridges. The bridges span the Iowa Interstate Railroad, requiring coordination with the railroad and an evaluation of horizontal and vertical clearance.

A continuous pier cap, 134’ long with 7 columns, is used to support both bridges at each pier. The 3’-6” diameter pier columns are supported by 4’ diameter drilled shafts to minimize excavation and disturbance near the railroad. The shafts are 56’ long and socketed approximately 20’ into rock.

To maintain at least two lanes of traffic in each direction during construction, a median bridge was built between the existing bridges, followed by sequential replacement of the southbound and northbound bridges in subsequent years. The median bridge was incorporated into the final structure to create three lanes in each direction. The plans included staging layouts, special stage construction joint details, and temporary shoring details.

Construction deviations of the deck thickness, which occurred in Stage 1, required special revisions to the Stage 2 and 3 plans so that the deck elevations and cross slope would match at the stage construction joint.