The Mississippi River Bridge project will create a new gateway between Illinois and Missouri to provide better connections to and through St. Louis. The project includes a landmark bridge structure, and the realignment and reconstruction of Interstate 70.
The joint venture building the bridge, MTA, is made up of Massman Construction, Kansas City; Traylor Brothers, Evansville, Ind.; and Alberici Constructors, St. Louis. The design includes two pylons projecting vertically from the river bed with 20-foot-deep footings. The lower pylon is 68 feet high, 22 feet 2 inches wide, and 129 feet long, projecting from the river in a Y configuration. The tower elevates to 402 feet above the footing.
MTA used Doka’s D22 dam formwork to construct the lower portion of the pylon. This part of the project was completed in seven lifts with gang forms fabricated by Doka for nearly every lift. The formwork provided a working platform with ample space for the laborers, as well as an area for equipment staging. The forms were suspended on climbing shoes that encompass the entire perimeter of both pylons.
A total of twenty-two lifts using automatic climbing systems SKE 100 and SKE 50 were used for the four tower legs. Using the automatic climbing systems allowed for faster overall completion time because raising the formwork could proceed in all weather and wind conditions (up to 40 mph) and allowed gangs to lift without having to rely on a tower crane.
To provide an area to pour footings, MTA installed a coffer dam and pumped out the river water. The contractor used Doka’s Steel Girder Forms for the 88x55x20-foot footing. All standard girder forms are the same depth, which eliminated shimming the form joints. These forms are modular, and can be ganged and picked in large sections. With capabilities to form concrete and support concrete loads on structures, such as beams or bridge pier caps, the steel girder form spans large distances without any additional support or shoring. The biggest advantages of the formwork was that the girders for the footings offered MTA a heavy-duty gang system that was easily installed and required a minimal number of form ties.
Heavy duty spindle struts and custom channels provided maximum security when hanging forms from the pylon face. There were areas located at the eyebrow where the concrete face projected out at a 35-degree angle. At lifts five through seven of the lower pylon eyebrow, separate large-area gang forms were assembled for all three lifts.
Custom steel brackets and splice plates were used to connect gang forms. Additionally, a custom aluminum pouring platform was incorporated, which MTA installed above the +1 platform. The +1 platform provided a secure, lightweight surface and allowed laborers to work safely well above gangs, while pouring concrete into each wall cell.
Safety and flexibility
A custom protection screen was used on the outside face of the climbing system as a method to cocoon working platforms and keep workers safe and comfortable during harsh winter weather. The climbing systems offered MTA a way to easily climb all four legs safely, efficiently, and independent from a crane. The flexibility of the climbing formwork systems easily adapted to the bridge geometry and contractor’s requirements. Engineering support, know-how, and experience on previous and current bridge projects around the globe reassured the contractor’s decision to go with Doka.
Dave Monnot is key account manager for the Doka Midwest Branch of Doka USA Ltd. He can be reached at 815-521-3700 or email@example.com.
Engineering support, know-how, and experience on other bridge projects, along with competitive pricing, gave the contractor confidence in the decision to use Doka forms.