How do you build a plaza over the busiest set of railroad tracks in the busiest city in America, without bringing traffic to a screeching halt? Go with a precast concrete design, says Amir Ulislam, of Jersey Precast. Ulislam was the precast concrete producer on the Manhattan West project to erect a massive platform over the tracks leading into Manhattan’s Pennsylvania Station without disrupting the 55 live rail lines running constantly underneath. “The number of trains passing on these tracks is unbelievable,” he says.
Along with not stopping traffic, a key component of the project was finding a way to span the 240 feet (73 m) without installing intermediate steel columns, which would be too close to the rails to be safe. They also needed the structure to be highly fire resistant. The designer achieved all of these high performance design goals using massive precast concrete spans in a segmental box and lift design. Each span consists of between 36 and 37 segments that weigh 1100 tons (98 kN) in total.
Due to the strength of precast concrete, no additional supports were needed, and because precast concrete is noncombustible, no fire-proofing was necessary, Ulislam explains, “If we had gone with a steel design, we would have needed extra support columns, and a lot of fire proofing.”
The project also included a 2400 ton (21,000 kN) launching gantry, which was designed by DEAL, a subsidiary Rizzani de Eccher, USA, the general contractor for the project. “Rizzani de Eccher added tremendous value to this project,” Ulislam says.
A total of 612 precast concrete pieces were manufactured at the precast concrete producer’s Hamilton, New Jersey facility, each weighing roughly 56 tons (500 kN). They were then delivered into Manhattan by trucks over the course of five months, where the erection crew assembled them over night when there is minimal train traffic. Though getting the pieces to the site was not easy. Because of different state transportation laws regarding movement of oversized loads, each truck had to cover the first leg of the trip through New Jersey during the day, and then wait at the George Washington Bridge until dusk to finish the trip into Manhattan. “It took a lot of planning and coordination to make it work,” Ulislam says.
In the end, the owner and all key stakeholders were thrilled. “We got everything done without interrupting service, and the entire team did a fantastic job,” he says. “I’m very proud of this project.”