LeanSteel: Design. Build. Better.

Martin Drake Power Plant

Colorado Springs, Colorado

2015 Tekla BIM Award Winner.

Colorado Springs Utilities constructed and commissioned innovative technology to reduce SO2 emissions at one of its power plants. During pilot testing of the technology, researchers determined the best configuration of ductwork for the system was a combination of reinforced fiberglass (FRP) with a steel exoskeleton.

The benefits of FRP come with drawbacks that had to be overcome by a structural steel exoskeleton. The skeleton had to provide strength and stiffness for the duct while at the same time allowing for thermal expansion of the FRP. This meant no internal bracing typical of steel ductwork, and the only connection between the two materials was with slotted clips and UHMW shims. Because the steel would be galvanized, then mated to the FRP panels at a shop, it had to be designed in 8’ to 10’ wide modules for shipping, while minimizing loose field pieces.

The system is made up of six duct units between 20 feet and 55 feet high and weighing up to 130,000 lbs. The team built custom components to streamline connecting the model and FRP attachments, and wrote custom reports to communicate material and shipping lists in a format the client could more easily use. They detailed the structural steel in-house due to the complexity of the geometry and FRP mating and to minimize the project schedule.

Tekla Structures was essential to the successful completion of this pairing. A 3D model of the original ductwork was used for reference, but the new system was wider and clearances tighter. Seeing the product in 3D allowed the design team to make decisions to make the project constructible in the field, like switching to an inside-out expansion joint or using Hollo-Bolts in tight corners. The steel model was shared in STEP format for the company to complete the FRP design, and converted to Revit format for overall project coordination. Internal and external model reviews ensured any hiccups would be found before their impact could grow.

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