For the hordes of tourists stuck in lines for the Colosseum or queuing up to enter the Sistine Chapel, Rome’s 2,000-year history acts as a powerful magnet.

Many museum buildings have incorporated systems that allow daylight to illuminate their galleries, but none as robustly as MAXXI, where almost every roof surface is glazed. To support such a roof above the museum’s winding galleries, whose bays average 40 feet wide, reinforced-concrete walls on either side sandwich a series of trusses. While these trusses run parallel to the gallery walls, transversal steel beams connect the walls. Originally conceived as a precast-concrete element, each of these longitudinal sections, typically six per bay, is composed of a steel truss encased in 1⁄2-inch-thick fiberglass-reinforced concrete panels. The nearly 8-foot-deep assembly, which rises