Heavy rains destroy well traveled pedestrian bridge
During the summer of 2008, torrential rains hit Iowa’s Cedar River Valley. In just 24-hours, the community suffered more flood damage than they’d encountered in hundreds of years. When Charles City residents learned that the hostile waters had washed away their prized swinging pedestrian bridge, a pang of sorrow rippled through the community.
For more than a century, the Cedar River pedestrian bridge had connected one of the Charles City’s most populated residential areas with many recreational facilities, such as the public swimming pool and ball diamonds. With no bridge in place, children were forced to walk and bike an extra mile around the river, along busy streets and highways. Safety was a big concern.
After months of anticipation, residents rejoiced when news came that the Federal Emergency Management Agency (FEMA) was going to fund a replacement bridge—an estimated $3 million project. The city vowed that the new bridge would be every bit as beautiful as the old one, and enthusiastic citizens quickly came together to form a design committee. With money in hand, and a design vision in mind, they sought out a team to make it happen. The action team consisted of consultants from WHKS & Company, Iowa Bridge and Culvert as the contractors, and Big R Bridge.
Big R brings Charles City's design vision to life
After meetings with Charles City residents, the Big R team understood their vision. The outcome of the design committee was to construct a cable-stayed bridge, complete with 19.8 m (65') inverted “A” shape towers, stainless steel cables and deck made of tropical, decay-resistant IPE wood. The truss portion of the bridge was designed as an H-Section model, capable of fully supporting its own weight, with end spans of 33.5 m (110') and a center span of 60.9 m (200'). This reduced installation costs and provided a platform for future maintenance if required.
As with any project of this magnitude, the Charles City Bridge presented several challenges. Due to its unique design, a cable-stayed bridge requires the installation method to be known in advance. Since each contractor bidding on the project suggested a different installation process, the Big R design team needed to be flexible. To address this issue, we developed a complete step-by-step erection procedure.
Cable-stayed bridge design presents several challenges
Once we’d decided how to build the bridge, the next question was where to build it. Our manufacturing shop is 91.4 m long (300'), and the bridge was 128 m long (420'). The Big R team leapt over this hurdle using a leapfrog fabrication approach.
Ensuring that the cable forces remained balanced was the final challenge. A custom pivoting attachment beam, located below the truss, was designed to allow for rotational movements and cable length adjustment. Once all fabrication was completed, the entire 122-ton bridge was assembled to verify length and confirm that all pieces fit together properly. It was then disassembled for shipping.
During the installation, over 500 citizens of Charles City gathered to observe the process that they, themselves, had set in motion. The actual installation of the bridge took only two-days, with the truss being installed on the first day, and the towers and cables installed on the next.
The grand opening of the bridge was an exciting day for both the community and Big R Bridge. The new cable-stayed bridge is a triumphant sight, and our team is glad to know that Charles City’s children will once again have a safe path to travel.
Owner: Charles City
Consultant: WHKS & Company
Contractors:Iowa Bridge and Culvert
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