Located in Lincoln, Neb., the Pinnacle Bank Arena is a new multi-purpose arena equipped to host community and regional events. It serves as home to the University of Nebraska men’s and women’s basketball programs and will accommodate events such as NCAA championships, concerts, circuses, boxing, and ice skating. The arena, completed in 2013, was part of a $344 million redevelopment of the historic Haymarket downtown district.
Built using construction materials including mass concrete, structural steel, masonry, fireproofing, earthwork operations, and more, the arena structure is supported on deep foundation pile extending into sandstone bedrock located at depths of up to about 100 feet below grade, with the superstructure comprised of structural poured-in-place concrete, structural steel, and precast concrete. The client brought Terracon in to perform construction materials testing, and special inspections on construction materials used in the area, but as the project unfolded, Terracon’s role expanded.
Terracon project manager Russell Wilson and office manager Bradley Levich, P.E., worked closely with Mortenson Construction, the Construction Manager at Risk (CM); the City of Lincoln; and the design team to set up and perform the day-to-day testing of the construction materials. As many as five technicians were on site at any given time to ensure that we were able to meet demands and stay responsive to the client’s needs, and Terracon completed every inspection as scheduled. The client received test results from these inspections in real time and final reports within one day, a milestone achievement that sets a new standard in the materials testing industry. Each technician is equipped with a laptop and a smartphone so that they are seamlessly connected to the project manager, the office, and the client at all times. This project was particularly complex in design and Terracon worked with the CM to provide technicians with up-to-the minute plans and specifications to technicians.
Most of the observations Terracon completed met requirements; however there were some deviations that were uncovered. A deviation is a non-conformance or a failed test. As a large-scale project, keeping track of deviations could have become a huge problem. This challenge was met with great success because of the company’s proprietary Construction Materials Engineering and Laboratory Management System (CMELMS™), which automates the delivery of information so that test results and inspection information can be quickly transferred from the field to the office.
Terracon noticed that a rebar tail extending from the top of a column had broken. Eventually a few tails were noticed to have failed, and the client asked the team to perform additional testing and observations to help solve the problem.
Digging deeper into the rebar problem
Terracon began a more extensive survey of bent rebar that was formed in some cast-in-place columns and discovered evidence that there were issues with the integrity of the reinforcing steel. To determine the cause, Terracon worked closely with the structural engineering consultants, and brought in a metallurgy expert to perform laboratory testing on the reinforcing steel. Results showed the bars met the criteria of American Society for Testing Materials (ASTM) A615 for deformed reinforcing steel bars. Since much of the rebar was comprised of recycled steel, the team performed a laboratory test to check both chemical makeup and to look for foreign material or microscopic inclusions that could lead to failures.
The laboratory test showed the reinforcing steel was acceptable, which was good news for the project because it meant that the straight reinforcement already placed was likely sound, but what about the broken bent bars? What was the source of this issue? After researching production procedures and consulting additional experts within Terracon, it was found that the issue was originating during manufacture. Specifically, bending reinforcing steel over too small of a pin for the bar size caused undue stresses at the bend in the reinforcing steel. This resulted in the development of stress cracks at the outer radii of the bends, which propagated through the bars, and caused the bars to fracture.
Terracon worked closely with the design team, providing observations and testing during the repairs. The structural engineers designed a fix for all the pile caps that called for pouring a structural band of concrete around each pile cap. The Terracon team carefully observed and performed testing on each fix, which was now under the scrutiny of not only the project team, but also the mayor of Lincoln and the general public.
Citizens in the Lincoln community are truly excited about what the Pinnacle Bank Arena means to the downtown area and to the future of their hometown. Terracon is pleased to have been a part of the team that kept this high-profile arena project moving forward.