Erleen Hatfield on engineering the 9/11 Memorial Museum Pavilion
The National September 11 Memorial Museum Pavilion, acts as an open and transparent entry for visitors to the below-grade museum from the memorial site. BuroHappold Engineering, selected by the Pavilion’s architect, Snøhetta, provided integrated mechanical, electrical, plumbing and structural engineering services that contributed to the realization of this 47,000 sq ft cultural facility that orients the visitor within the memorial grounds and belies the complexity of the site.
Overcoming the many constraints of a site that is situated in dense urban infrastructure and that has been continually transforming since September 11, 2001, required rigorous coordination and interplay among architect, engineer and other project teams working on site. Integrated structural systems, both above and below grade impacted the building’s design as well. The team had to take into consideration support for the museum below and other underground infrastructure when calculating structural loads.
The majority of the pavilion is supported over the PATH train station and tracks, while the remainder sits atop the museum. Analysis of these below-grade structures, the memorial pools, and surrounding infrastructure identified, in addition to the pavilion’s concrete core, limited the supports capable of carrying the loads of the pavilion. A full-story-tall steel truss extends from the pavilion’s core to effectively cantilever the building over the PATH station hall.
The reinforced concrete core provides lateral stability for the pavilion, however, its location above the PATH tracks and station hall complicated the transfer of lateral forces to the ground. To solve this issue, the pavilion is ringed with steel and reinforced-concrete composite drag beams that transfer the forces to the museum’s shear walls.
As plans for the site evolved the structural design was recalculated and adjusted, a feat advanced by the team’s understanding of the tremendous importance of the pavilion, both as a physical presence within the memorial plaza and as the visitors’ entry to the museum.
Craig Dykers, architect and Founding Partner of Snøhetta said the design of the pavilion building was born out of 'a desire to allow visitors to find a place that is a naturally occurring threshold between the everyday life of the city and the uniquely spiritual quality of the Memorial'.
“It is important that the people physically engage with the building and feel that it helps lead them on to other areas of the site and other thoughts about their experiences there,” Dykers continued.
Elegant and slender-looking steel tubes support the transparent and reflective glass façade, which contributes to the lightness and levity of the pavilion. The pavilion’s 30ft-tall freestanding grand stairs appear to float in space and widen as they descend bringing visitors within close proximity to the tridents. Careful consideration to performance and vibrational aspects of the hollow steel section stair was required to ensure visitor comfort as they descend and potentially pause along this feature stair. Mechanical, electrical and plumbing systems are subtle and unnoticed, but contribute to visitor comfort, proper ventilation, and the energy efficiency of the building.
In addition to coordination during the design of the pavilion, carefully planned and phased construction was critical to the project’s success. Due to their size, the tridents were installed in 2010, prior to the installation of the atrium. Throughout the process, BuroHappold Engineering and Snøhetta worked closely with the National September 11 Memorial & Museum Design and Construction staff to plan logistics.
Erleen Hatfield, PE, AIA, LEED AP is a Partner and the North American Structural Discipline Leader for BuroHappold Engineering. She has over twenty years of experience leading the structural design of large-scale and complex commercial, cultural and educational facilities including the Pinnacle Bank Arena in Lincoln, NE; the Foster + Partners designed Yale University School of Management; the new Atlanta Falcons Stadium; in addition to the National 9/11 Memorial Museum Pavilion. She has a passion for tackling important and ambitious engineering challenges with innovative, elegant and economical design solutions.