Background
As a family-owned business that has served Chicagoland for over 84 years, Loeber Motors has always provided a customer experience that was first-class, and it would be no different when they set out to remodel their long-time Porsche dealership in Lincolnwood, Illinois. The two-story, 45,000 square-foot next-generation Porsche facility epitomizes luxury, offering clients a one-of-a-kind interactive experience and the ultimate Porsche brand immersion. However, engineering the exterior cold-formed wall as well as the interior walls that would frame the newly designed interior were a bit of an engineering challenge specifically the frameless glass design aspect of the interior framing. The team at ClarkDietrich Engineering Services (CDES), led by Matthew Mancl, P.E., was up to the task.
Challenge
The design included multiple rooms with frameless glass partition walls, many of which had windows that turned corners and left no room for full height framing. While there was a drop ceiling in these areas, the frameless glass partitions could not accommodate any kind of vertical movement of the primary structure, which meant a typical kicked frame bulkhead suspended from the floor above would not be acceptable. As such, the deflection of the primary structure needed to be accommodated by cold-formed framing at the head of the wall and underside of the slab.
Solution
CDES came up with a straightforward framing concept that involved the use of continuous strongbacks and girts to provide adequate support for the weight of the wall framing over the frameless glass partitions while still providing a clear load path for all interior lateral loading as well. These strongbacks/girts in turn were supported by full-height posts. The basic free-body diagram of the strongback/girt was a simple span beam with a cantilever.
By utilizing both studs and tracks as strongbacks/girts, CDES was able to provide details that resulted in structurally sound connections at all the respective intersections of these elements, such as stud strongback to fit inside track strongback. Fortunately, most of these rooms had repetitive framing conditions, which helped to streamline some of the engineering efforts. However, during the design process, an addendum was issued which significantly widened one of the side frameless glass partitions. At this location, an additional lateral strut was required to utilize every space of wall and minimize the lengths of the cantilever(s).
While the overall concept was relatively straightforward, clearly depicting all information on a 2-D set of shop drawings required some additional artistry (no BIM or 3-D modeling was used). To help portray all of this to the carpenter, CDES produced multiple plans, sections, and elevation views. Furthermore, CDES was intentionally diligent with the naming convention throughout the shop drawings for all the respective elements such as gravity strongback, track girt, and lateral strut.
For their work on this project, the team at CDES won the first-place award for Creative Design from the Cold-Formed Steel Engineering Institute (CFSEI). The annual CFSEI Design Excellence and Creative Detail awards honors projects that exemplify excellence in the structural design of new or renovated structures utilizing cold-formed steel (CFS). Entries are judged on design creativity, technical innovation and overall product excellence in CFS utilization in the categories of: Residential/Hospitality, Municipal, and Commercial.
Click here to read more about the award-winning CFSEI Design Excellence projects.
Owner: Loeber Motors
Architect of Record: Praxis3, LLC
Engineer of Record: Palmer Engineering Co.
General Contractor: Pepper Construction Co.
Subcontractor: Pepper Construction Co.
Cold-Formed Steel Specialty Engineer: Matthew Mancl, P.E., ClarkDietrich Engineering Services LLC