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facility for healthcare professionals. As the building owner/developer and a public agency, the medical center wants a healthy indoor environment and a sustainable building, but without the typical budget increase of nearly 10 to 20 percent.Eleven prerequisites are specified by the building owner with an emphasis on the following outcomes: The new facility must last more than 100 years; it must sustain economic efficiencies by mandating that utility costs be 70 percent lower than those of an existing facility; it must incorporate all-natural opportunities presented by the physical site to design economy for long-term maintenance and operational costs; it must use to the fullest extent possible natural, recycled, and reclaimed materials from sources and manufacturers in Texas; and the actual construction costs of the facility must not exceed 105 percent of the costs of a conventionally constructed building.
Additionally, the site itself would require protection from future flood damage, given that it was situated within a 100-year floodplain and had experienced flooding from tropical storm Alison in 2001.
Moreover, the new building involved numerous internal clients and external consultants: 60 experts in total representing 17 outside firms and an equally large number of internal clients who would be engaged in the project. At the same time, the building’s owner/developer, The University of Texas Health Science Center, required a design team that would not only collaborate to create a forward-looking sustainable design project, but make every effort to achieve the highest level of LEED (Leadership in Environmental and Energy Design) certification possible.
In tandem with these goals for the new facility, the project team, under the direction of BNIM Architects in collaboration with Lake | Flato Architects, understood that the building systems and their components must contribute individually and collectively to the project’s overall sustainability.
The result: an anticipated LEED gold rating for the building—one of the first LEED gold recipients in the state of Texas—with the potential of earning LEED platinum.
The UT School of Nursing was also recognized last year as one of the American Institute of Architects (AIA) Committee on the Environment (COTE) Top Ten Green Projects in the nation. Additional recognition has been bestowed on the facility from the Houston; San Antonio; Central States region, and Kansas City, Mo., AIA chapters, as well as the Texas Society of Architects for its sustainable achievements.
From a structural engineering viewpoint, the UT School of Nursing and Student Community Center was nearly an improbable proposition that succeeded because of the integrated team approach and the commitment by all parties to excel in the sustainability outcomes.
Overview of the project
At first glance, the UT School of Nursing and Student Community Center seems unimposing among the structures that comprise Houston’s Texas Medical Center. The 195,000-square-foot, 8-story building occupies a relatively small lot size of 34,177 square feet with a north-south orientation because of the site’s long axis. An adjacent 8,150-square-foot, 2-story service building and yard house the mechanical equipment and rainwater cisterns.
The School of Nursing features most of its public spaces—including the student lounge, café, student center, auditorium, and bookstore—on the two lowest floors for convenience to foot traffic. The third and fourth levels consist of classrooms, laboratories, and patient rooms. Research facilities and offices are on the upper four floors.
The building structure essentially consists of a concrete mat foundation supporting a cast-in-place concrete frame and structural steel roof. The elevated floors are 10-inch-thick, mild-reinforced flat slabs, with 8-inch-deep (18-inch overall depth) drop panels at the columns. Round columns were used to support bays that are approximately 30 feet by 30 feet. The steel roof takes on a "sawtooth" configuration, which allows for natural light to enter the building and filter down to lower floors through large openings in the interior bays of the elevated floors, creating an atrium effect. There are also steel frames in place at the roof level for the future installation of photovoltaic arrays. All of the material specifications for the building dictated the use of recycled and regionally obtained materials, including structural steel (containing a minimum of 75 percent recycled material), reinforcing steel (containing a minimum of 90 percent recycled material), and concrete constituents.
Jaster-Quintanilla (JQ) designed and documented the structural framing, foundation members, and structural connections to the building frame for sustainable design elements. The elements include photovoltaic panel arrays, curtainwall sunshade/sunscreen devices, a rainwater harvesting system with storage cisterns at grade, a "green roof," and a customized rainscreen exterior skin. The firm also consulted on the integrated building system issues and helped to identify and select appropriate structural building materials with regard to both environmental impact and proximity to the project site.
Some of the most challenging work, however, consisted of working closely with the construction manager Jacobs/Vaughn and the concrete supplier to develop high-volume fly ash (HVFA) concrete design mixes and concrete placement strategies that would achieve an overall project goal of 50 percent replacement of cement with fly ash. Structural engineers have historically allowed up to 25 percent of the cementitious materials in concrete to be replaced with fly ash, so this was an ambitious goal.
Fly ash is a by-product of coal-fired electric generating plants. According to a white paper written by Vaughn Construction titled, "High Volume Fly Ash Concrete," even as cement production falls behind demand, the majority of fly ash produced in the United States continues to be disposed of in landfills. Ready-mix concrete producers often utilize fly ash to produce the higher-strength concretes that are becoming more and more common in larger projects. However, the design and construction team had to develop, test, and implement concrete mix designs containing far more fly ash than conventional concrete in order to meet the rigid demands of the building program.
Green construction challenges: high-volume fly ash
Much of the background research on the new HVFA concrete mix designs was gleaned from case studies of green building projects completed in California and Canada accessed via the Internet, according to Scott Francis, P.E., of JQ/Austin, who managed the firm’s efforts on the project. Lenny Enderle, chief estimator and project manager for Vaughn Construction, and Joe Lucas of Hanson Concrete took the lead roles in developing and testing the new mixes.
The appropriate mix designs were identified after 47 different mixes were batched, using various percentages of fly ash with normal-, mid-, and high-range water reducers, and the mixes were analyzed for both compressive strength and initial set data. Two ready-mix companies were utilized in the final re-testing of the mixes; TXI Concrete was selected because the company used all-Texas ingredients that performed better in the testing stages. The use of local/regional materials helped to satisfy LEED credits MR 5.1 and 5.2. These credits stipulate that 20 percent of all materials used are manufactured regionally within a 500-mile radius. Of the 20 percent regional materials requirement, at least 50 percent of the content is extracted regionally.
In general, HVFA concrete will usually exceed specified compressive strength by a large margin. However, the rate of strength gain is slower than a conventional mix design. For that reason, 56-day compressive strength tests were specified instead of the traditional 28-day breaks. In addition, HVFA concrete tends to set and cure at a slower rate, especially in cooler weather, making the timing and performance of the concrete-finishing operations less predictable than that of a more conventional mix. In order to take advantage of the properties of HVFA concrete without potentially jeopardizing the contractor’s construction schedule, JQ strategically specified different percentages of fly ash replacement for each of the structural elements.
For example, because initial set, curing, and concrete finishing is not particularly important in the mat foundation and drilled piers, 65 percent fly ash replacement was specified in these elements. This high fly ash content in the mat also helped lower the internal heat generated during the curing process, which minimized the risk of thermal-related cracking. The columns and walls contained 50 percent fly ash. Forty percent maximum fly ash content was specified for the elevated slabs and beams. This allowed the contractor to finish the concrete using conventional techniques, and to strip forms in a cycle that maintained the construction schedule.
During the two-year construction period, approximately 19,000 yards of concrete were placed. Although the university sought an original project goal for the building of 50 percent fly ash replacement, 48 percent of the cement was replaced, which eliminated 34.8 percent of the cement that would have been used with traditional concrete mixes. For the environment, that difference is significant because it equates to a savings of approximately 1,808 tons of carbon dioxide that would have been released into the atmosphere.
Other steps to engineering success
Various deep and shallow foundation systems were considered. Ultimately, a 5-foot-thick concrete mat foundation bearing approximately 8 feet below existing
natural grade was selected. There are several underground utility lines along the west side of the building that are actually below the footprint of the mat foundation. The utility lines could not be re-routed, so construction of the mat required the use of supplemental, deep-drilled piers to safely transfer loads and avoid undermining the building foundation if excavation below the mat was necessary to maintain or repair the utility lines in the future.Although the typical floors are fairly rectangular in plan, the architect manipulated the slab edges on the lower floors to create visual interest. For example, the slab edges are pulled outward at portions of the second and third level to create a band of exposed concrete that is expressed in the elevations. However, the same slab edges are pushed inward at the building corners, essentially to the column centerlines. This creates a dramatic intersection of materials, and exposes the round concrete columns, but it also creates an engineering challenge to resolve the transfer of shears and moments from the slab to a column that is only partially engaged with the slab.
JQ used the SCS Floor software package (now called RAM Concept), which is a finite element program for the analysis and design of the reinforced concrete floor systems and mat foundation. The program allows engineers to define floor systems with any degree of irregularity, including slabs of any arbitrary shape, drop panels, beams, and openings. This methodology was far more efficient than using a traditional equivalent-frame technique. It also provided an additional means for JQ to study the shear and moment transfer to the columns. These results were compared to hand calculations to develop the reinforcing details at the corners of the building.
Turning green into gold
The building envelope, lighting, and mechanical systems were all designed to minimize cooling loads. Strategies included high-performance glazing and shading devices; high-efficiency, right-sized mechanical systems; day-lit work spaces; and devices to reduce lighting loads, along with operable windows.
The UT School of Nursing and Student Community Center is expected to use 80 percent less energy per square foot than the adjacent UT School of Public Health Building built in 1977, and 41 percent less energy than a conventional, minimally code-compliant building. Anticipated energy savings alone is more than $38,000 per year.
Because the School of Nursing is a critical-use facility on the Texas Medical Center campus, it is equipped with backup generators that can operate without traditional grid power, which are located above the highest floodplain levels.
A green roof system, natural linoleum flooring, waterless urinals, and recycled-content carpet tiles were among the green products used for the building. Most importantly, 75 percent of the building’s total construction waste was recycled.
Leading the way in higher education
The University of Texas System medical branches plan to spend $1.3 billion in construction over the next five years, consisting of substantial teaching and lab components. With pressure from the healthcare industry regarding shortages among medical and other healthcare professionals, the UT School of Nursing and Student Community Center was designed to leverage its useful and efficient life over the next century, while serving as a good steward of our natural resources.
At a total project cost of $57 million, 20 percent of which was financed through the university’s capital campaign, the UT School of Nursing presents the best case for going green by providing a healthy and productive environment for its healthcare professionals—faculty, students, and administrators—with as little impact on the environment as possible while generating significant savings through its ongoing operations and maintenance.
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Project &Construction Team
Project name: UT School of Nursing and Student Community Center, Houston
Owner: The University of Texas System, Austin, Texas
User group: University of Texas Heath Science Center, Houston
Architect: BNIM Architects, Houston, in collaboration with Lake | Flato Architects, San Antonio
Structural engineer: Jaster-Quintanilla & Associates, Austin, Texas
Civil engineer: Epsilon Engineering, Houston
Construction manager: Jacobs/Vaughn, Inc., Houston
Testing agency: PSI, Houston
MEP engineer: Carter & Burgess, Inc., Houston
Geotechnical engineer: Ulrich Engineers, Houston
Landscape architect: Coleman & Associates, Austin, Texas
Parking engineer: Walter P Moore, Houston
Concrete supplier: TXI Concrete, Houston
Concrete contractor: Vaughn Construction, Houston
Sustainable strategies: Elements, a division of BNIM Architects, Kansas City, Mo.
