Sign Connections, X-Rays, and Structural Engineering

If you tend to appreciate the intricacies of large-scale project installations, here’s a little tidbit that you may find interesting. As part of the intensive display installation ongoing at Circa Towers (1200 S. Figueroa) in Los Angeles, SNA Displays was tasked with installing two steel frame structural systems. The primary system is designed to reinforce the existing building slab edge while the secondary structural system is used for attaching our LED display sections to the building. (An alternative design was engineered to combine these systems into a single frame, but the dual structural frames were ultimately chosen for a slimmer profile, limiting the display’s projection off the face of the building.)

More information on this project.

Three large displays, totaling 18,000 square feet, exceed heights of 65 feet, meaning they will vertically extended through six garage floors. Given the inherent differential deflection of parking garage levels, the slab edges had to be reinforced to ensure that one floor did not deflect more than others, which of course would impose additional stresses on the display structure.

Additionally, we installed a sign frame connection (at right, top) that incorporates building drift, lateral sign deflection, and a partial release of moment forces. In fact, we designed this frame to account for 5.9 inches of seismic building drift in addition to the lateral sign deflection.

The SNA Displays project team needed to drill bolt holes through the existing post-tensioned slab. A total of 528 bolts had to be post-installed, but locating the proper place to drill was extremely critical due to the innate risks of cutting into PT slabs.

Ground penetrating radar did not yield clear results and to eliminate the risk of any variations between the design drawings and the as-built conditions, SNA Displays employed X-ray scans.

The X-ray scans yielded a much higher-quality image of the reinforcement and tendons within the concrete slab (as shown at right, bottom), providing our installation team with enough information to accurately complete the drill work.

“This was a complicated design that had to be perfectly coordinated,” said Carl Hubben, PE, who is SNA Displays director of project management. “The fact that our PM team installed both structural systems, maintained safety and quality measures throughout and completed this project on time is a great testament to our staff’s determination and expertise. We are very happy with the result.”

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