University of Illinois Project Features Innovative Energy Piles and Smart Suspension Bridge Built on Cramped Site
Smart Construction and a Small Site: University of Illinois Civil and Environmental Engineering Department’s Project Designed for LEED Gold, with Research Opportunities to Expand Future Campus Sustainability
With geothermal energy foundations and a “smart” bridge featuring a range of infrastructure sensing, the $32 million expansion and renovation of the Civil and Environmental Engineering (CEE) Department’s Hydrosystems Laboratory at the University of Illinois at Urbana-Champaign serves as both a modernization of instructional facilities and research into cutting-edge sustainable solutions.
Designed for LEED Gold certification, the project includes the Kavita and Lalit Bahl Smart Bridge connecting the Hydrosystems Lab addition to the Nathan Newmark Civil Engineering Laboratory across the street. The enclosed, pedestrian suspension bridge will function as a living laboratory to teach students about the effects of dynamic forces on the built environment. Beneath the bridge, unique energy piles will reduce greenhouse gas emissions with less expense in a smaller footprint than traditional geothermal applications.
“This project is an invaluable opportunity for the department and the university to conduct a scalability study from lessons learned during the installation,” said Dr. Mohamed Attalla, the university’s Executive Director, Facilities and Services. “Outcomes from this project will be converted into design guidelines for future installation of energy foundations, which will significantly contribute to the sustainability of the campus.”
Scheduled for completion in September, the project expands the Hydrosystems Lab from one level to a basement topped by three floors and a mechanical penthouse, adding more than 51,000 square feet of hands-on laboratory, classroom, and collaboration space. The bridge extends from the third floor of the addition.
In hiring professional services consultants for the project, the university used their standard design-bid-build delivery, with contracts awarded to the lowest responsible and responsive bidder. After a feasibility study concluded in January 2016, the team began schematic design in April 2017. Demolition of the south half of the Hydrosystems Lab, built in the late 1960s, started in October 2018. The north portion of the building, which houses a large water resources experimental lab, remains in service throughout the project. The official groundbreaking occurred in March 2019 and crews installed the geothermal energy foundations last summer.
Energy from Confined Spaces
Those installations came with a few challenges in the small worksite surrounded by buildings, streets, and sidewalks. For instance, to complete drilling for caissons near the Hydrosystems Lab, “The contractor built a short, wide, and steep dirt ramp to support the weight of the drilling equipment moving into and out of the excavated basement area, approximately 15 feet below finish grade,” Attalla said. “Because the footprint of the basement is very small, maneuvering the drill rig was a challenge with the ramp consuming the majority of the area.”
Twelve, 50-foot-deep caissons support the suspension bridge. Four of those caissons house heat exchangers for the geothermal energy system, which will circulate fluid through the exchangers to a heat pump in the Hydrosystems Lab.
“By incorporating the heat exchangers into the drilled shafts supporting the bridge, we didn’t need borehole drilling or additional excavation as with other geothermal systems, making it less expensive,” Attalla said. “It’s also an ideal solution on projects like this with confined space due to numerous building footprints and other underground infrastructures that prevent the common geothermal field application.”
DR-11 polyethylene piping connects the heat exchangers to the centralized system. The piping configuration and depth varies within each of the caissons based on soil capacity and loading condition of the structure it supports.
To maintain each unique configuration, “The piping was attached to the structural rebar cages of the individual caissons utilizing heavy-duty zip ties,” Attalla explained. “Each cage was assembled on the ground then lifted by crane, where the cages elongate due to their weight and would tear the piping if it were fully secured to the rebar. The zip ties allowed the tubing to be constrained to the desired configuration while limiting the potential risk of damage.”
Once the crane placed the rebar cages in the ground, crews filled the caissons with concrete. “With the DR-11 piping contained within the caisson structure, it resembles a single well-field configuration found in a typical geothermal system – just on a larger scale,” Attalla said.
The piping comes up through the bases of the concrete bridge buttresses and connects to a centralized manifold heating system in the building’s mechanical room.
Due to design challenges, the bridge’s buttresses stretch four feet wide and 65 feet tall, tapering from 26 feet at the base to 10 feet at the top.
“A suspension bridge typically has buttresses balanced with cables on either side, but since we couldn’t practically extend cables into the Hydro addition or the Newmark Lab, we had to use large buttresses to counteract the forces on the cables,” Attalla said. “That created challenges in fitting the massive buttresses onto the site while maintaining Main Street and the sidewalk below and not having them protrude into the Hydro addition too much and break up the interior spaces.”
For the bridge’s stainless steel cables, designers chose a locked coil design. “As load is applied, the Z-shaped cables tighten around the inner wires to provide additional corrosion resistance,” Attalla said.
Steel, concrete, storefront windows, stainless steel metal wall panels, and a Thermoplastic Polyolefin (TPO) roof assembly will also be used to complete the bridge.
When finished, the bridge’s sensing equipment will include thermistors and strain gauges to measure axial and radial strains, as well as temperature profiles, within the energy pile foundations. Accelerometers will characterize the structure’s dynamic properties. A weather station will also be mounted on top, and displacement transducers at each end will measure relative movement of the bridge with respect to the buildings at either end.
Installing the sensors created additional construction challenges. “The instruments are located in areas that aren’t easily accessible, such as within wall assemblies behind the heating units and below the floor,” Attalla said. “Access points and their methods of construction needed to be developed for each unique condition.”
Toward Greater Sustainability
In addition to research opportunities provided by the bridge’s sensors, “Information gathered from the heat pump will allow students to study how the different piping configurations and depths within the caissons affect the heating and cooling performance,” Attalla said. That information will aid in refining energy pile design guidelines.
To help this project earn LEED Gold certification, in addition to the geothermal system, the design incorporated water-reducing plumbing fixtures and tinted windows to minimize solar heat gain.
“Heat island effect credits are being achieved with white roof membranes and low-albedo site paving on the adjacent plaza and woonerf that will be utilized by vehicles and pedestrians,” Attalla added. “The bridge and the alumni center in the Hydro addition will be equipped with smart glazing that adjusts based on the amount of sunlight hitting the surface. That allows clear views when it’s dark and better heat blocking when it’s sunny.”
This project is the second phase of CEE’s modernization plan, designed to keep up with a growing student body and innovative instructional methods. The M.T. Geoffrey Yeh Student Center, an expansion of the Newmark Lab, opened in 2011 with modern classrooms, meeting rooms, and study spaces. The final two phases will further expand and subsequently renovate the Newmark Lab, with projected completion in 2024.