Graduates of Texas A&M University are known for their fierce loyalty to the school and its traditions — so much so that they refuse to be called “ex students,” but refer to themselves as “former students.” It is no wonder then that George P. Mitchell, Class of 1940, wanted to support the school that set him on a very successful course in the oil industry through a special gift to his alma mater.
George P. Mitchell is the former chairman and chief executive officer of Mitchell Energy & Development Corp., a Fortune 500 Company, prior to its 2002 merger with Devon Energy Corporation. Mitchell graduated from Texas A&M University with a degree in petroleum engineering, with additional emphasis in geology. Following services as a captain in the Army Corps of Engineers during World War II, he joined a newly formed wildcatting company, first as a consulting geologist and engineer and later as a partner. Under his leadership, the company grew into one of the nation’s largest independent oil and gas producers.
Mitchell has long had an interest in cosmology and fundamental physics research, even bringing world-renowned theoretical physicist Stephen Hawking to Texas for a sold-out lecture at the University. Seeking to set Texas A&M on a course toward excellence at the forefront of physics research, Mitchell and his wife, Cynthia, generously donated more than $40 million to fund the institute that bears his name and the buildings that will house it. Mitchell also has an appreciation for sophisticated design, so he commissioned world-renowned architect Michael Graves & Associates (MGA) to design the buildings.
The George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy (Institute Building) and the George P. Mitchell ’40 Physics Building (Physics Building) are housed in two interconnected buildings at the northern edge of the Texas A&M University campus in College Station. The configuration of the plans negotiates the irregular shape of the confined site. The Institute is a six-story, 43,770-square-foot, elliptical-shaped building at the intersection of Ireland Street and University Avenue, a major entrance to the campus. The Physics Department is housed in an adjoining five-story, 160,000-square foot, L-shaped building wrapping around a semicircular 500-seat main auditorium.
The complex serves several user groups including undergraduates, graduate students, faculty, administrators, and attendees at conferences and special events. The buildings are planned to manage these overlapping uses by providing alternative circulation paths. At the same time, the location of stairs, lounges, and conference rooms encourages social interaction and a sense of community.
From the ground up
Soils in this part of Texas are notoriously difficult to work with because of the high plasticity index and, therefore, a great propensity to shrink and swell with changes in moisture content. In keeping with University construction practice, the lower (basement) level structure is built over a minimum 2-foot 6-inch-high crawl space that allows for free movement of the subgrade and also provides convenient access to lower-level mechanical and plumbing services.
Basements are not frequently constructed in the area, so several options were explored for the excavation retention system and basement wall structure. The final decision to use steel H-pile and wood lagging with grouted tie-backs was a result of collaboration with the contractor during early phase design meetings. The basement wall was set several feet away from the face of retention to allow for two-sided forming of the wall and installation of waterproofing and a gravel drainage medium on the outer face. Both buildings are supported by drilled and under-reamed piers bearing in hard clay approximately 40 feet below the lower-level floor.
Institute Building: The showpiece
Designed as the architectural showpiece of the project, the Institute includes conference facilities, pre-function, and gallery space on the first floor; faculty offices on the upper four floors; and a 200-seat auditorium named for Stephen Hawking at the lower level. A six-story atrium with a communicating stair provides easy access between floors and facilitates interaction among user groups.
The floor system is a combination of one-way and two-way cast-in-place concrete slabs supported by two rings of circumferential beams with additional radial beams, where required, to support openings. A large elliptical opening in the middle of each elevated floor delineates the six-story atrium that allows natural light to penetrate the full height of the building through clerestory windows above.
Concrete was chosen for the bulk of the Institute Building frame, both for its economy in the region and to accommodate the radial geometry. Setting formwork over the atrium seemed impractical and therefore the design and construction teams agreed on a steel-framed roof over the atrium. The atrium roof steel beams and metal roof deck are supported by the inner ring of concrete columns that extend from the sixth level below, and a concrete ring beam interconnects these columns to resist lateral loads efficiently.
Extensive collaboration with MGA and the mechanical engineer, Shah Smith & Associates, was required at the mezzanine due to the restricted space, numerous floor openings, and large pieces of mechanical equipment. Further complicating this area is another steel platform that hangs from the mezzanine level to provide support for a vibration-sensitive, 235-pound Foucault pendulum that hangs 85 feet down to the first floor level. Coordination of this area was facilitated by the use of building information modeling by Walter P Moore and Shah Smith.
Physics Building: The workhorse
The Physics Building contains state-of-the-art teaching and research laboratories including six general purpose physics labs, five laser research labs, and a Class 100 clean room for nanotechnology research, in addition to lecture halls, classrooms, and meeting and office spaces. A 500-seat auditorium is located in the middle of the L-shaped structure.
The Physics Building is connected to the Institute by short, steel-framed bridges at levels two through five and shares a common lower level. An efficient 25-inch deep pan-formed beam and slab system spans nominal 36-foot bays, and 25-inch-deep post-tensioned girders were chosen to limit structural depth and maintain a constant structural soffit depth through most of the building. In isolated areas, girders and beams as deep as 42 inches were required where heavy loads, column transfers, or longer spans occurred. As at the Institute, the mechanical penthouse roof is steel framed and supported by extensions of the concrete building columns where possible; the concrete columns carry lateral loads down to the main building frame without need for supplemental bracing that might limit future flexibility.
The main teaching auditorium is a 110-foot radius quarter circle-shaped space set between the two wings of the building with access provided at the first and second levels. The auditorium can be divided into three smaller sections by means of two Skyfold Classic partitions that descend from the ceiling above. These partitions were recommended by Walter P Moore based on positive experiences on past projects. Steel rakers were chosen for support of the auditorium seating structure with curved risers comprised of concrete on metal form deck. The auditorium roof structure is composed of composite steel beams supporting a concrete slab on composite metal deck, all supported by steel columns bearing on the Level 1 concrete structure below. In addition, the roof structure must support the load of an intensive green roof with planters containing soil as deep as 30 inches. The combination of heavy roof loading, long spans, and deflection-sensitive partitions requires a heavy roof structure with 40-inch-deep, 64-foot-long main girders.
Challenging design, creative solutions
Vibration — The basement of the department building houses research labs where faculty and students probe the limits of theoretical physics with a variety of sophisticated equipment including scanning electron microscopes and cryostats capable of generating near-absolute zero temperatures. These tools are extremely sensitive to vibrations, so Walter P Moore designed the basement level concrete floor structure to meet a 2,000 micro-inches per second (mips) maximum vibration velocity criteria, a criteria commonly used in research institutions utilizing precision optical and electronic imaging equipment. To meet these criteria without using a deeper structure, additional piers were added to shorten girder spans, add additional lines of girders, and shorten beam spans. Since certain labs have even more stringent criteria, such as for an electron microscope, a specialty vibration consultant was engaged to assist with the design of five “floating slabs” in these labs. When the slabs are finally loaded and tuned, vibration velocity on the floating slabs is expected to be reduced to a maximum of 250 mips.
Sustainability — Green design was very important to Mitchell and a project requirement from the beginning. In addition, Texas A&M requires all new major campus construction to seek LEED Silver certification. Walter P Moore’s structural and civil engineers participated in several early sustainable design charrettes hosted by Houston Advanced Research Center (HARC), the project’s sustainability consultant. While the team was experienced in sustainable design and the LEED system in particular, HARC pushed for higher goals wherever possible. A first step was specifying 40-percent replacement of cement with flyash in the foundation elements, as well as minimum percentages of flyash content in all other concrete frame elements. Walter P Moore also worked closely with team members to support other sustainable design initiatives including an extensive under-floor air distribution system and the aforementioned green roof. The various systems find synergy in their design: condensate from the building HVAC units together with rain water collected on the roofs feed an underground cistern buried beneath a beautiful terraced garden on the south side of the building. The cistern, in turn, supplies all of the landscape water required for the site, and the team anticipates earning a LEED innovation credit for exceptional performance in reducing the use of potable water for landscape watering.
Another important sustainable design element is also a signature component of the building architectural design. A unique window system consisting of precast vertical pilasters and large precast sunshades on the southern and western façades shade the low-e glazing, which reduces solar heat gain on the building during hot Texas summers. The structural support system for these façade elements combines cold-formed metal framing, structural steel, cast-in-place concrete, and the precast elements themselves to achieve an elegant and easily constructible solution.
George Mitchell’s intent to establish a significant architectural home for the Physics department on the College Station Campus led to the selection of Michael Graves & Associates as the designer for the new building. Walter P Moore’s past collaboration with both Michael Graves and Texas A&M University on other important projects naturally led to our partnership for the project. This established collaborative design relationship is fitting in that an important driver of the University’s site selection for the Mitchell buildings was the desire to encourage creative collaboration across many disciplines through close proximity to other university departments. In the end, the addition of the Mitchell Physics buildings to Texas A&M University creates a world-class home for the Physics Department as it continues to grow and meet the needs of its faculty and students, within the context of the Texas A&M community and its continuing tradition of excellence.
The Mitchell Physics Buildings at Texas A&M University
JG: What was the first task you needed to do to get started on the design?
JS: Design criteria for the laboratory areas was not well defined at the outset, so we spent some time evaluating the department’s existing space to gain an understanding for the actual usage of the space and the kinds of demands their work would place on the structure. A tour of the laboratory with Physics Department faculty was particularly enlightening, and we quickly determined that a live load of 150 psf was appropriate to allow for both flexibility of usage and the density of equipment observed in the existing labs.
JG: What was the most challenging aspect of the structural design?
JS: Definitely the façade support system. We spent an extraordinary amount of time working out the details of the structural backup for all the various elements of the façade, which included standard brick masonry, heavy precast pieces with large support eccentricities, glazing infill, and curtain wall. We typically are able to leave the details of façade attachment to subcontractors and their specialty engineers, but because of the complex interplay of the various pieces and parts, prudence dictated that we design the bulk of the support framing. The resulting systems used structural steel, heavy-gage cold-formed metal framing, and cast-in-place concrete in various combinations to provide a safe, constructible system in the space of a typical wall cavity.
JG: what was the most unique problem to solve on the project?
JS: The equipment supported by the floating slabs is also very sensitive to electromagnetic interference, so we weren’t allowed to use standard steel rebar in the floating slab or in the suspended pits beneath them. We decided early in the project to use glass-fiber reinforced polymer (GFRP) reinforcing bars, so I had to spend some time learning how to design and detail with this material. In the end, stainless steel reinforcing bar turned out to be more economical, so I was able to redesign the area using a more familiar material.
JG What engineering ideas did you implement to save costs?
JS: Our time spent coordinating the façade system was time well used: the contractor reported that erection of the system went very smoothly. Our early-stage collaboration with the contractor on the façade and other structural design issues resulted in a system that was cost-effective and constructible.
JG: Did you have any other comments regarding the challenges of this project?
JS: One of the most enjoyable aspects of working on this project was the time spent with other members of the design team. Mark Sullivan, Michael Graves’ project manager, was a particular pleasure to work with, both for his devotion to the design and his appreciation of the difficulties his consultants faced in delivering his firm’s vision. The other engineers, consultants, and builders were equally talented and made for a truly enjoyable experience throughout the course of design and construction. The engineering challenges and their innovative solutions were icing on the cake! Through it all I gained a deeper understanding and appreciation of the building’s other engineered systems, because of the diverse program and the intense collaboration required to fit everything in to a tight space.
Firm Facts: Walter P Moore
The firm has consistently ranked in the top structural engineering firms for all seven years of the Structural Engineer’s Best Structural Engineering Firms To Work For competition.
Jamison Smith, P.E., LEED AP, was project manager and structural engineer-of-record for this project. Dennis Wittry, P.E., S.E., was principal-in charge. Both are with Walter P Moore and can be reached at 713-630-7300.