The board of directors for the three-auditorium Ronald O. Perelman Performing Arts Center—the final piece of the puzzle for Lower Manhattan’s 16-acre World Trade Center redevelopment—says construction on the project is expected to begin in 2018 and be completed in 2020. Earlier this month, the Perelman board unveiled a design for a 90,000-sq-ft venue by local designer REX, with structural engineer Magnusson Klemencic Associates. MKA was the engineer for the original scheme for the WTC performing-arts center, designed by Gehry Partners. But, in 2014, the board tossed Gehry’s decade-old concept and started from scratch. The boxy Perelman center, to be clad in marble, will produce and premiere theater, dance, music, film, opera and multidisciplinary works.