Hunks of curved metal resembling a broken airplane wing sat on a snow-covered parking lot across from the Minneapolis Central Library. But no plane had crashed and there was not a pilot in sight.

This was the state a week ago of “Nimbus,” a massive steel sculpture by Atlanta-based artist Tristan Al-Haddad that was brought to Minneapolis in pieces, and is being welded together near its eventual home.

A crane will gently lift sections of the 20,000-pound halo-like structure into position above a small concrete amphitheater on the Nicollet Mall between 3rd and 4th streets. When it’s completed, colored light will stream through perforations in its skin, offering a singularly immersive experience for those who sit in the “Theater in the Round” beneath it.

The process of building “Nimbus,” however, was hardly as smooth as the weathering steel it’s made of. It was supposed to be installed last spring, but a shortage of construction workers in Atlanta delayed its completion.

“The fabricator we were working with in Atlanta made a prototype in my studio that turned out great,” said Al-Haddad. “But when you do multiple sections versus a single section, it’s a different thing. We gave them 5 percent of the sculpture to try and mock up at full scale, and they just murdered it. Not in a good way.”

The search for the perfect welder/fabricator continued for several months until Mary Altman, public arts administrator for the city of Minneapolis, recommended Seven Bailey, a welder/instructor at Dunwoody College of Technology.

After a visit in May to Al-Haddad’s Atlanta studio, the two agreed to work together. Bailey spent most of the summer down there, working round the clock with the artist. When school started up in September, she came back to the Twin Cities, but continued going to Atlanta every weekend. They were determined to make “Nimbus” happen.

The hardest project ever

Together the team of Al-Haddad, Bailey, three female welders who are Dunwoody alumnae and one welder from Atlanta (a guy) got to work.

One of the things that makes “Nimbus” more complex is that it had to be up to D1.1 structural steel welding codes, basically designed to the level of a building. Most large-scale art sculptures do not have to contend with such requirements but this piece will appear to levitate off the ground.

“There’s more complexity in this sculpture than there is in that building,” said the artist, pointing to a downtown skyscraper.

Al-Haddad, who is also trained as an architect, has created 15 to 20 site-specific works. His most recent is “Stealth,” a towering, folded black form installed three years ago in downtown Atlanta. That was a difficult project, he said, but “Nimbus” has been his most challenging, in part because of Minneapolis’ weather. Snow fell the day they started installing the sculpture. Their equipment has locked up at times because of the cold, which has drastically altered the welding process.

“At zero degrees Fahrenheit, welding becomes a challenge,” said Bailey. “If that happens, we have to create some sort of warming-house effect to weld on that metal.”

Ambient airflow over 5 miles per hour and any sort of moisture make welding harder, too. There’s also a ton of rigging and lifting needed to place the oddly shaped pieces. The 45-foot-wide curved structure will be anchored on one side to an 80,000-pound concrete footing deep below the sidewalk.

Nevertheless, “Nimbus” is supposed to be done around the end of November or early December.

City administrator Altman doesn’t want to put a debut date on the calendar just yet, though. “I am always a little superstitious about planning the event until the work is done,” she said.

A mall of our own

“Nimbus” was selected from a list of three finalists by the Nicollet Mall Public Art Steering Committee.

It will become one of nine sculptures on the mall — 136 objects in all (some of the works are multiples, including 12 lanterns featuring poems by Minneapolis writers).

Originally constructed in 1968, the mall was last renovated in the late 1980s. Spanning the 12 blocks of Nicollet between Washington Avenue and Grant Street, it is home to three Fortune 500 companies and 34 million square feet of offices. Every day, 14,000 Minnesotans walk the mall.

It also has the largest collection of public artworks in Minneapolis, after the Minneapolis Sculpture Garden. Most are owned by the city, including Jack Nelson’s 1968 “Sculpture Clock,” which is newly restored, and George Morrison’s 1992 granite pavement installation “Tableau, A Native American Mosaic,” which has moved from the library plaza to the entrance of the Loring Greenway.

Al-Haddad views his “Nimbus,” which he said had a “modest” budget of $226,000, as being in conversation with the nearby “Ptolemy Wedge,” a sculpture by Beverly Pepper made of the same weathering steel material, which develops a rusty patina over time. It also speaks to the post-industrial condition of the American city, which was previously run on mills and agriculture.

He is inspired by large-scale public art/sculptor makers like Anish Kapoor, known for the giant reflective silver bean in Chicago’s Millennium Park, and Olafur Eliasson, a master of light-filled installations.

But despite its massiveness, there is something very gentle about “Nimbus.” In fact, it’s inspired by gestures of the human form, not the seeming coldness of metal. And the steel itself will literally warm up, rusting and bonding to the base metal over time.

“You’ll even see the facets of each of these sections, and each one of them has an expression of the forces moving through it,” he said. “That all goes back to the idea of the pose and the body.”

Which is a good thing, because plenty of warm bodies will soon be sitting underneath it, posing, waiting for something to happen.