Projects Transportation

South Shore over Bethlehem Steel Entrance Road

Michigan City, Indiana

DLZ utilized a rapid insertion (roll-in) design to accomplish the replacement of the existing bridge. The rapid insertion process was utilized to allow NICTD to keep the existing bridge in service for as long as possible and to minimize disruption to its passenger service. NICTD also wanted to minimize the disruption of traffic into the Bethlehem Steel Plant’s main entrance which handles approximately 9000 vehicles per day.

As a result, Bethlehem Steel required that no roadway restrictions would be permitted during the time period around shift changes and would only allow the roadway to be closed for a six-hour period between the shift changes. Bethlehem Steel, however, was agreeable to close the road for a period of one weekend to facilitate the rapid insertion. Since NICTD wanted to maintain the existing railroad alignment with minimal disruptions to its passenger service, an extensive analysis was performed on the existing abutments to ensure that they could handle the additional loads of the new superstructure. Another challenge was maintaining the existing vertical clearance.

The new superstructure is a single span, steel thru girder, ballasted deck bridge with a span of 134’-8”. The new plate girders are 11’-8” deep. Due to the use of a ballasted deck structure versus the existing open deck structure, the construction depth of the proposed superstructure was greater than that of the open deck structure. (A ballasted deck structure was selected since it would require less long term maintenance). In order to maintain the existing vertical clearance, the existing roadway had to be lowered by approximately 6 inches.

In conjunction with lowering the roadway, vertical camber was built into the girders to reduce the amount that the road needed to be lowered. As a result of lowering the roadway, an existing storm sewer also needed to be replaced. The corridor following the NICTD tracks is utilized by several major utilities, the most prominent of which are NIPSCO’s power lines, these presented another challenge for this project.  NIPSCO’s power lines supply power to many of the industrial plants in the region and could not be taken out of service.

As a result, the project had to be designed so it could be constructed without impacting these facilities. On-site construction began in September 2000 with the construction of temporary pile bents just north of the existing structure.

The temporary pile bents were designed to support the new superstructure during the erection of the structural steel. Prior to the rapid insertion weekend, the entire superstructure was erected on these bents which included the waterproofing, ballast, rails, and painting.  By completing the superstructure prior to the rapid insertion, minimal work was required after the structure was rolled into its final position. While the new superstructure was being constructed, new precast abutment caps were cast on site. The new 115 ton precast abutment caps were designed to be set on top of the existing abutments and doweled and grouted in place.

The rail service was suspended east of Miller Station on Friday, November 3, 2000 at 3 a.m. and the main entrance road to the Bethlehem Steel Plant was closed. The existing truss was lowered to the ground, disassembled and hauled away overnight. The existing abutment caps were removed and replaced with the new precast abutment caps during the day on Saturday and Sunday morning. On Sunday afternoon the new superstructure was rolled approximately 32 feet into its final position and lowered onto the new precast abutment caps. The final track and ballast work was finished in time to permit NICTD to transport its fleet to Michigan City Sunday night and have it ready for the Monday morning rush hour commute.