We sat down with Tom Greenough, Associate, to talk about a unique project, the Buddy Holly Hall of Performing Arts and Sciences in Lubbock, Texas.
The Buddy Holly Hall of Performing Arts and Sciences is a world-class, multipurpose cultural venue that recently opened its doors (for some limited events). It includes a 2,300-seat main theater, a 425-seat studio theater, a multipurpose event room, ballet studios, and a bistro café. The facility is acoustically flexible to accommodate opera, symphonic and rock music, and other performances, such as Broadway shows and the ballet, as well as educational activities, banquets, and community events.
Entuitive served as the Structural Engineering Consultant for the above-grade work on the Helen DeVitt Jones Main Theater, Christine DeVitt Main Lobby, including the feature stair, and the front entrance canopy.
Thanks so much for sitting down with us, Tom. Can you tell us about some of the challenges of this beautiful performance center?
Tom: Absolutely. This was a truly unique, community-building project that required uncompromising performance. A few of the challenges we solved during the design of Buddy Holly Hall included: the feature stair in the main lobby; the balconies in the main theater; and the main entrance elevation, which includes a dramatic set-back in the façade at the sloping roof line.
Let’s start with the feature stair in the lobby.
The dramatic helical staircase in the Christine DeVitt Main Lobby is over 17 meters (56 feet) tall across three stories and features a central spine that supports cantilevering stair treads that vary in length between 2.4 meters (8 feet) and 4.2 meters (14 feet).
The stair is constructed from Hollow Structural Sections (HSS) and steel plates. At the exterior edge of the stair an HSS member connects all the risers. The treads are formed from a steel plate and support polished concrete treads. All told, the stair represents approximately 145 tons of steel.
To achieve the desired aesthetic for the stair, the HSS had to be bent in two directions to create the central spine and outer ring. Given the large section sizes and tight radii required, only two facilities in the United States had the ability to roll these sections, which also came with a six-month lead time.
The fabrication sequence involved bending the HSS chords and then welding the plate on afterwards. The stair was temporarily erected in the shop in two parts to test the fit and complete the fabrication process prior to erection on site. A temporary support tree was used to support the stair during erection as it was installed in five pieces and required significant field welding between the connections.
The feature stair also presented vibration challenges. The long spans, slender profile, and low mass, in conjunction with a low damping ratio, resulted in a low-frequency system that was particularly vulnerable to vibrations from human activity. A finite element model of the stair, including all supporting framing, was analyzed to capture its full behaviour. The natural frequency of the stair segments between Level 2 and 3 and Level 3 and 4 was found to be approximately 2Hz. People can descend stairs at up to a 4-Hz step frequency without much effort.
This combination of low natural frequency and high step frequency means almost all slender stairs are excitable by the second or third harmonic of the walking force. Harmonic forces due to descents are high compared to most other forces from human activity, and stair damping and mass are often also very low. Finally, rapidly descending groups can cause significant amplification compared to just one person.
Through our analysis it was found that supplementary damping was required to meet the vibration limits. An effective means for providing additional damping for a structural mode of vibration whose motion is deemed excessive is the addition of a tuned mass damper (TMD) to the base structure.
This way, we were able to ensure that the stair would not be subjected to excessive vibration from performance center patrons ascending and descending the stair.
Wow, the feature stair required quite a few special considerations. Of course, the final product is a beautiful stair adorning the lobby of this special center. Can you tell us about the second challenge?
Tom: Of course. The second challenge of bringing this performance hall to life involved the use of structural steel for the balconies in the main theater. Typically, such theaters are constructed with reinforced concrete. But based on advice from the construction manager on the local market conditions, we opted for structural steel as the primary framing system. The look and functionality of polished concrete in the main theater for the risers and treads was still a design requirement, however.
In addition, Diamond Schmitt, the architect, wanted to ensure that every seat is the best seat in the house while adhering to the required seat count. So, the profile of each balcony was fine-tuned and as result each is unique. No obstructed views here!
Since the theater is a curved, bowl shape, the structural steel members composing the seating balconies had to be bent to fit the curvature of the space. The columns were placed behind the back wall of the theater, which meant the balcony rakers cantilever up to 9.6 meters (31’-6”). To follow the profile of the balcony, the 1000-mm (40”) rakers are cranked in several locations, and a shallower 350-mm (14”) section is added at the end to create the front section of the balcony.
On the uppermost balcony, the height of the risers meant that the use of standard steel sections was not practical or cost efficient, so a custom steel profile was created to span between the rakers, support concrete on deck for the treads, and serve as formwork for the concrete risers. This custom steel profile was not only bent but varied in height to follow the profile of the seating and incorporated web openings to allow for air distribution below each of the seats. This required detailed up-front coordination between us, the architect, the mechanical engineer, and the theater consultant as the fabrication of the structural steel needed to start early in the process.
Can you tell us about that final challenge you mentioned, regarding the main entrance?
Tom: Absolutely. The building elevation at the main entrance will be the first thing most patrons see but they may not understand or appreciate its inherent complexity. Starting at the top is a truss that spans over 46 meters (153 feet). This truss starts by supporting the roof over the lobby to keep the lobby column-free.
‘Hangers’ then extend down from the truss to support the exterior cladding, which is a combination of solid panels and linear windows and the one side of the sloping roof that pushes out from this exterior cladding line. From here, slender ‘hangers’ emerge from below the exterior cladding line to extend down and support the lobby side of the level 2 lounge area at the front of the building.
From the level 2 floor, custom tapered plate girders cantilever out 7.6 meters (25 feet) to form the main entrance canopy. Between the force effects from the sloping roof and main entrance canopy these ‘hangers’ go into compression under some loading scenarios.
Since the truss supports many different elements, including the back spans of large cantilevers and the building enclosure, it necessitated a very finely calibrated design to meet a number of different loading conditions with different requirements and criteria.
Wow! Thank you so much for chatting with us about this amazing project, Tom. We’re amazed at the incredible work it took to help bring this performance center to life. Any final thoughts?
Tom: You’re so welcome. It was a privilege to work on the project and visit the city of Lubbock during the design and construction phases. My last thought is simply that I hope that once COVID restrictions are lifted, and we’re allowed to travel again that I can go to see the completed Buddy Holly Hall. This was truly a once-in-a-lifetime project, and I’m excited to see a show there!
Thanks for chatting with us, Tom. If you'd like to learn more about the project, reach out to Tom here.
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