First National Bank Tower

The First National Bank Tower follows a postmodern design with a granite facade.[1]Externally, the building has a central tapering structure and an upward-curving base along its eastern side. The bottom six stories are designated as the building's base and host a parking garage nearby.[3] Underneath the building is a series of tunnels that connect the parking garage to the main building.[5]

Lightweight concrete on metal decks was used to form the floor slabs of the building. This was done to minimize dead loads and support planned office and storage spaces. A two-hour fire-rated floor was constructed with 5.25 in (13.3 cm) concrete. The perimeter girder slabs were reinforced with steel, while the rest were reinforced with synthetic fiber. Exterior steel columns were spaced at 10 ft (3.0 m) around the building's perimeter, and composite wide-flange beams extended 47 ft (14 m) between the building's core and the exterior columns.[5] The original core plan had dimensions of 91 ft 5 in × 39 ft 6 in (27.86 m × 12.04 m).[1] The core was a self-climbing style, housed an elevator shaft, and was constructed with 8000-psi (approximately 5.5 million pascal) concrete to provide lateral resistance to the structure. The core was supported by a 120 ft × 76 ft × 12 ft (36.6 m × 23.2 m × 3.7 m) concrete pile cap and 950 tons (862 metric tons) of steel to combat shear and uplift forces. Construction of the pile cap took 11 hours of continuous concrete pouring and was the "largest single placement of concrete in the state of Nebraska".[5] The foundations of the building were supported by 28 shafts, 90 in (230 cm) in diameter, that were drilled in the limestone bedrock by the Big Stan drilling rig.[5]

The steel support structure of the parking garage was encased in concrete to emulate a cast-in-place style of construction, while the rest of the parking garage was built with cast-in-place concrete. This was done because the design lacked expansion joints, separation joints, and post-tension concrete; thus, the concrete design was connected to form one single structure. The parking garage was supported by 70 ft-deep (21 m), 30–60 in-diameter (76–152 cm), drilled shafts with cast-in-place concrete.[5]

Inside the building are two fountains, with a third one located in the tower's front plaza. The lobby was built to feature a 60 ft (18 m) glass winter garden, constructed with bowed tube trusses and a curved cast-in-place concrete wall. The wintergarden also contains a mezzanine that leads to the building's second floor. This is supported by two tapered, cantilevered, cast-in-place concrete supports from a fountain.[1][5] The lobby also includes the original terracotta facade from the former Medical Arts Building along the lobby's southern wall.[1]

Following the completion of the building, its use of cast-in-place concrete and steel during the construction of the building's framework was the recipient of the Nebraska Chapter ACI Award of Excellence for Use of Concrete, the Engineering Excellence Honor Award from the Nebraska Chapter of ACEC, and National Finalist Recognition by the national ACEC organization.[5] The building also won fifth place for the 2002 Emporis Skyscraper Award.[1]