Strong innovative courthouse design
by Danielle Beaugureau from Southwest Contractor Magazine / October 1997 / (602) 258-1641

As part of the nation's first large federal courthouse construction program in almost 50 years, the United States Courthouse in Albuquerque has veered from the traditional courthouse to incorporate regional style along with innovative courtroom design.

The $43 million project, located on a 4.5-acre site on the edge of downtown Albuquerque, has broken away from the traditional individual courtroom design to provide a more modern, efficient building.

Designed by architects Flatow Moore Shaffer McCabe Architects, Albuquerque, this 254,000-sq.-ft. courthouse is the first to incorporate both a shared courtroom and a "collegial floor" design concept. Because a typical courtroom dedicated to an individual judge may only be used 25 percent of its available time, the shared courtroom concept make the courtrooms equally accessible to all judges, both Federal District and Federal Magistrate. The judges' chambers are grouped together and remote from the courtrooms.

In order to make this unique design a reality, structural engineers Red Mountain Engineers, Inc., Albuquerque, designed a composite beam design in which steel beams and a 4.5-in. concrete floor slab are the primary structural unit. This system required the use of 49-ft. spans to accommodate the courtroom layout.

According to Tom Bauhan, a design engineer with Red Mountain Engineers, more than four million pounds of Grade 50, A572 steel will be used to complete the project. The steel was supplied by North Texas Steel, Fort Worth, Texas. Bauhan explained that designing the bracing frames to accommodate the building's architectural features was one of several structural challenges on the project. "We had to shorten brace frames, in a couple of instances, which increased the footing loads a great deal. In addition, we had to control the amount of story drift, which was induced by going to a shorter bracing frame."

Designing the framing for the central rotunda, and the support framing for the dome was also complex. More than 144 steel columns were used on the project, weighing as much 18,000 lbs. each.

The perimeter walkways of the sixth and seventh floors are recess three in. from the floor elevation. Which meant that Red Mountain Engineers had to specially design tapered floor beams to accommodate the difference in elevation. "We had to take a beam that supported the main elevation and actually cut the top flange of the beam off and then weld in another tapered flange. Essentially, we went from a 21-in. section to about an 18-in. section." Bauhan said. More than 100 beams were tapered in this manner.

According to George Bosiljevac, president of the steel erection company Structural Services Inc., Albuquerque, the most difficult aspect of the steel erection was relocating the spiral stairway into the Rotunda. "We had to get some special 'skates' to move the stairs into place," Bosiljevac said. Because the six prefabricated staircase pieces arrived at the site later than expected, logistical problems arose for the steel erector. "Had it arrived earlier, we would have been able
to hang it down though the rotunda with a crane and positioned it without a problem. But they came after the rotunda was closed off, so then we had to move them from the outside wall across the floors. Then, we needed to figure out how to swing them out over the edge without them dropping four floors," he said.

A system of chain falls was used to hand the stairs over the side and then pull them into place on each floor. "Once we figured out how to do it and got the skates to move it, it went quite nicely," Bosiljevac explained.

Using a 25-man crew, steel erection at the courthouse began in February and is expected to be completed in November. The largest steel pick, a beam used to support the cooling towers, was located at the center of the building near the roof. The 10,000-lb. piece was lifted using a 125-ton crane.

"Another real challenge was getting the electrified deck system in place on the first (two) floors because they had only a .8-in. tolerance on location." Bosiljevac said.

Built as a battered dry-stack Anasazi-style sandstone masonry wall, the main south facade of the building was also sloped and required special reinforcing design. Using a series of setbacks with transfer girders and high capacity connections, Red Mountain Engineers was able to support the 92-ft. high wall.

In addition to the shared courtroom layout, this structure was the first federal courthouse to be designed after the Oklahoma City bombing. Naturally, the safety and structural design was re-evaluated, incorporating such blast resistant features as an extra-heavy floor slab reinforcement and simply supported floor framing.

Bauhan explained that this reinforcement system is capable of bridging, by catenary action, relatively large areas of loss of steel framing, thus preventing progressive collapse. The single-span simply supported floor framing with simple shear connections reduces the potential for progressively damage from one bay to adjacent bays.

The general contractor for the courthouse is Centex Construction Co., Dallas. Owned by General Services Administration, Fort Worth, Texas, the project is expected to be completed in September 1998. Abide International Inc., Kirkland, Wash., is the construction manager for the project.

2001 Red Mountain Engineers, Inc.