Dowco/TSD has recently completed detailing of the canopy structures for the North Texas Tollway Authority, part of the project known as the NDT Extension Phase 3 for the fabricator Hirschfeld Steel Group LP, in San Angelo, Texas and AUI Contractors of Ft. Worth, Texas.
The canopy details consist of ten Ramp Canopies and one Main Lane Plaza Canopy integrated with a 6000 sf administration building and catwalk.
The Main Lane canopy is a long span truss of approximately 270 feet utilizing 22” diameter top and bottom chord members along with 11-3/4” diameter side chord members interlaced with 9-5/8” and 10” diameter pipe.
On each side of the truss, Teflon coated fiberglass fabric is stretched between 15 tapered built-up steel spars supported at the bottom truss chord and side chord with additional 6-5/8” diameter pipe hangers.
The truss also supports pipe brackets for cameras, directional lighting, AVI antennae and lane signage, as well as a full length access canopy thru the center of the truss.
The truss is supported at each end by one oval shaped, variable diameter plated column.
The Ramp Canopies are much smaller in size with a built up plate girder for the bottom chord member with similar design for the fabric and support arms.
The collaborative design efforts of Architectural and Structural firms Murphy/Jahn and Werner Sobek Ingenieure along with Thornton-Tomesetti Engineers have created a very significant and challenging structure for modeling and detailing.
Many delays and changes have extended completion of this project thru the summer and fall with proposed changes to the fabric and supporting structure looming in the near future.
The Information request and drawing approval procedure was a lengthy process as all information was required to pass thru the firm of Werner Sobek Ingenieure in Germany.
As the main structural elements noted on the design drawings could only be procured in Germany the first hurdle was to obtain acceptance of alternate substitutions. This done, the challenge was left to model the project in Tekla Structures.
The crew has done an amazing job modeling these trusses to suit the camber and geometry requirements on the curved Main Lane Truss and Ramp Truss.
The 3-D modeling of Tekla Structures was a definite asset due to the many views and details required to layout and produce the necessary information for the pipe details, many of which have multiple profile end cuts.
Congratulations to everyone involved in this challenging project.
Don Shaver
Senior Project Manager
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