Steel Framing, vibration Analysis, Plates
The design of the new headquarters of Carson Group, located in Omaha, Nebraska, aimed to create an open office space that embodied the company’s culture, while providing an elevated experience for employees and clients alike. The 200,000 SF project’s amenities (such as a rooftop bar, gym, and balconies) have drawn additional companies to the inviting, open workspace. The project consists of two buildings, with a six and four-story structure, connected by a two-story amenity hub and “sky-bridge”. The buildings’ clear glass envelopes provide two distinct attributes: Carson Group’s emphasis on transparency, reflecting the trust shared with financial services, and as a way to highlight the Omaha landscape, which Carson Group has made their home for over 35 years.
"With RISA, you can gain that (engineering) trust quite quickly with its outputs."
— Tim Morrison, SE
One of the most noted features of the buildings’ profiles are their distinctive, upward-sweeping rooflines. The sweeping shape is meant to reference the financial services positive-growth curves and serves as an enclosure for the buildings’ mechanical systems. The steel canopy is an open-framed structure supported by the roof structure below, and the roof canopy has no metal deck to act as a diaphragm for distribution of the lateral forces. The structural engineers at LEO A DALY, designed a system of horizontal bracing members to transfer the lateral canopy loads in lieu of utilizing decking. Additionally, the structure's monumental stair posed a structural design opportunity due to the balancing of vibration concerns and the element’s architectural profile. The monumental stair serves as the main architectural feature that connects the lobby to the two-story amenity hub space. With glass cladding much of the building, the stair profile can also be viewed from outside and as a result, needed to be very sleek and slender. To accomplish this, the engineers needed an analysis tool, like RISA-3D, to help meet the tight performance and architectural constraints.
For the project's structurally complex areas such as the monumental “sit-stair”, roof-top canopies, and sky-bridge, LEO A DALY turned to RISA-3D. For the design of the folded forms making up the roof-top canopies, as well as the “inverted V” truss elements used in the sky-bridge, RISA-3D was able to easily perform static and dynamic analysis, while also providing accurate results in a timeframe that fit the project schedule. Additionally, the transparent results available in RISA-3D allowed engineers to better understand how these ancillary structural elements interacted with the main building structure. As both the architect and engineer on the project, LEO A DALY required an enhanced level of collaboration. The flexibility and ease-of-use of RISA-3D proved critical and enhanced overall collaboration on the project, specifically as engineers reviewed various loading criteria and alternative designs. These alternative designs were used to collaborate with the contractor to circumvent the steel member procurement strain caused by the onset of the 2020 COVID pandemic.
Images: ©LEO A DALY / Photos by A.J. Brown Imaging