Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

University of Kansas Opens Structural Test Facility

By Kevin Wilcox

A massive reaction wall and floor system highlights the new facility, which expands the scope of structural research that can be conducted at the KU School of Engineering.

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Ribbons of windows were employed to break up the scale of the new engineering research building, which complements the nearby Hill Engineering Research and Development Center. © Burns and McDonnell

November 25, 2014—A new engineering research facility on the west campus of the University of Kansas (KU) features a 40 ft tall, L-shaped reaction wall and reaction floor that work together to greatly expand the School of Engineering's capacity for structural research. The system, also known as a strong wall and strong floor, accommodates test specimens that can be loaded with as much as 880,000 lb bearing simultaneously in two directions.

"First and foremost, the new structural testing facility will allow us to fully support our ongoing structural engineering research and expand the scope of structural research at KU. The addition of this 10,000 square foot laboratory brings the total structural lab space at KU to over 14,000 square feet," said Michael Branicky, Sc.D., the dean of engineering at KU, who responded in writing to questions posed by Civil Engineering online.

The strong wall is robust—4 ft thick, reinforced concrete, backed by 8 ft deep buttresses spaced every 12 ft. Embedded in the wall are a series of steel sleeves that serve as anchoring points for securing hydraulic actuators that will exert forces on specimens that are anchored to the floor.

"Initial plans called for construction of the new facility adjacent to the engineering complex on the main campus. Limited space and complexities involved with integrating a substantial facility at that location led to the decision to build the new facility on west campus," Branicky said.

"Through the programming process, the school of engineering—and particularly the professors in the Civil, Environmental & Architectural Engineering (CAE) Department—really got interested in [a larger] strong wall and the potential for research enhancement and leadership for KU," says Amy J. Slattery, AIA, LEED-AP BD+C, a senior architect for Burns & McDonnell, the Kansas City-based firm that served as the architect and structural engineer of record on the West Campus facility.

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The massive strong wall can be loaded with as much as 880,000 lb bearing simultaneously in two directions. The wall and floor are perforated by anchor points on a 3 ft by 3 ft grid. © Burns and McDonnell

As the plans grew into a 40 ft tall strong wall and 10,000 sq ft strong floor, it became clear to the project team that the main campus facility could not easily accommodate the system.

"The faculty and research groups were thinking about testing large-scale specimens and full-scale multistory frames," says Jun Fei, P.E., a senior structural engineer for Burns & McDonnell. "You have to have 18-wheelers in and out for specimen delivery. In their current layout [on the main campus] there was no chance to have a truck deliver such large specimens. I believe they made a great decision to go with a bigger strong wall to serve not only their current research but also their future needs."

Branicky added that one of the bonuses of that decision was that the new site is large enough to accommodate a doubling of the size of the new lab at a future date, if needed.

The new building is a single-story, high-bay structure, 160 ft long, 65 ft wide, and 60 ft high. It is set apart from other buildings on the developing campus, which are smaller in scale. Ribbons of small windows are employed to add visual interest to the large facade.

"It needed to set itself back and be respectful of the more pedestrian scale of the other buildings on west campus," Slattery says. "That created an opportunity to make more of a graphic read. The ribbon windows are intended to be seen at a certain distance so that the scale is broken down by the ribbon."

The front of the structure is marked by large, open, flexible space that will be used to display student projects. The showcase, almost entirely glass, further breaks down the scale of the building.

The new facility complements the recently completed Hill Engineering Research & Development Center nearby, a glimmering facility with a facade of hand-fabricated, woven aluminum designed by Studio 804, Inc. Branicky explained that the Hill Engineering Research & Development Center is home to what is known as the KU EcoHawks team—a group of students engaged in a capstone and graduate-student program that focuses on a number of energy-related topics, including transportation. "The benefit of having them so close is that students will be able to share tools and resources, as well as be exposed to interdisciplinary research and collaboration opportunities," Branicky said.

The key engineering challenge of the project was the reaction wall, Fei notes. "At the very early stage of the project, we had numerous meetings with the end-user groups, including the dean of the school, the professors, and graduate students to learn their expectations and to understand their needs. We heard everything from these groups about what they were planning to use the facility for, which set the design goals for us to achieve in a constructable and economical way."

The wall and floor are perforated on a 3 ft by 3 ft grid with the anchor points. On the floor, each anchor point is rated for a vertical load of 100,000 lbs, either in tension or in compression. The high-bay steel structure housing the wall and floor was designed to accommodate the loads of two overhead cranes, each with a 20-ton lift capacity, operating at once. The whole system is founded on a 3 ft thick reinforced concrete mat foundation. A full basement enables researchers to access both sides of the anchor points.

Because of the tremendous test forces to be placed on the wall and floor, the design team and KU were concerned about potential cracking in the wall, which is an exposed concrete element.

"We had to rely on computer software to perform a stress analysis and then determine the magnitude of the calculated stresses in the concrete-analysis model under various test-load combinations," Fei says. "We had to identify those 'hot spots' where the calculated tensile stress was greater than the concrete allowed and provide constructible resolutions. That was a very challenging exercise."

The solution was to place posttensioning tendons in the vertical direction of the wall to introduce compressive forces.

One interesting element of the project for Slattery and Fei, both of whom are KU graduates, was working with a group of clients who are themselves highly skilled engineers.

"When we talked about the structure with the end-user groups, they were very enthusiastic," Fei recalls. "They had all the performance-based expectations outlined. They knew exactly what they wanted us to achieve. It was quite exciting. Most of the time we have a project in which we may need to educate the client, from the technical side, to explain the structural system selected and why it offers the best value to the client—but not in this case. The knowledge and experience of the end-user group made our life a little easier."

Once the design was complete, the strong wall presented some construction challenges, as well. The design called for the exposed concrete surfaces to be more highly finished than could be achieved by using conventional reinforced-concrete techniques. After further discussions with the general contractor, the Kansas City office of Turner Construction, the team decided to use self-consolidating concrete for the wall. Turner Construction developed a robust system of form work to use with the self-consolidating concrete.

"Imagine you are pouring a 40-foot-tall wall. There is a huge amount of pressure. So the form works had to be adequate and specialized to have the ability to hold the fresh concrete in place," Fei says.

A large-scale mock-up of the strong wall was constructed to ensure that the self-consolidating concrete was providing the desired levels of settling and the desired finish. The team encountered an uncommon problem when they went to examine it, however: they couldn't find a saw large enough to cut it in half to check how the self-consolidating concrete had performed. Eventually, by making several passes, they were able to cut the wall open and were pleased with the results.

The $14.5-million building has opened to positive reviews on campus. Branicky said research commitments are building and KU's structural labs will be fully committed by March 2015.

"An example of the research enabled by the new strong wall are a series of cyclic load tests of 30-foot-tall, reinforced-concrete, T-shaped walls containing high-strength reinforcing steel—research that has been funded since the new lab came on line," Branicky said. 

 

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