The already deteriorating Pier 54 was further damaged by Superstorm Sandy in 2012. Hudson River Park Trust, the public agency that oversees the parks along the Hudson River in lower Manhattan and converts existing piers into public parks, decided to replace the pier with a new kind of public park on the river. A philanthropic foundation generously funded the project, and Heatherwick Studio in London was commissioned to guide the vision of creating informal, playful, and educational public space into a reality. The idea was to create an undulating landscaped park with a plaza, performing spaces, and overlooks surrounded by the lawn and trees.
Automated Design Using Parametric Scripts
It was evident from the moment we saw the early renderings from the architect that the conventional way of engineering and documenting would not work for this highly complex geometry. Heatherwick Studio actively used the parametric Grasshopper scripts in Rhino 3D to generate the entire geometry. As we were aware of the potential of the parametric design to automate the process and respond to changes very efficiently, we decided to adopt the same strategy. We worked closely with Heatherwick to develop the scripts. Heatherwick became responsible for outer curved surfaces with our inputs on how to make them structurally sound and fabrication-friendly and achieve economy by grouping some ‘pots’ into the same geometry. At the same time, they could have different heights to make elevation changes. We then took over the script and appended it to generate inside and side faces, allowing the pots to have the required structural sections. We also made all our surfaces flat, so the curved formwork is only needed for the outer surface. As a result, all surfaces were generated by the script. Not a single surface was created manually in Rhino software.
We took the further step to generate all rebar details, such as sizes, locations, lengths, hooks, and splices, with the scripts. The outcome was a full rebar detail model with each bar identified with a unique mark. The fabricator could then bend and cut the bars exactly as needed at the suitable locations.
During construction, two of the total 132 pots had to be re-designed because obstructions required some piles to be relocated. Within a couple of weeks, along with Heatherwick, we could generate the pots’ full design, including all the element geometry, steel connections joining the precast elements, and concrete reinforcing, and feed into the fabrication. Without the automated scripts, a significant delay would have occurred.
Electronic Information Transfer
The need for electronic information transfer was identified during the mock-up in the construction phase. It took days to convey the geometry of the pots and rebar to the precast contractor in 2D drawings and to provide explanations via telephone calls. The contractor decided to invest in learning 3D software and scripts, and when the production for the project started, they could receive the Rhino files of the pots and rebar and turn them into 2D drawings for the shop and the engineer’s review.
Fabrication Methods
Casting precast elements that have two-way curved surfaces was the major challenge. Various methods were proposed and tested, and CNC-milled foam for formworks were chosen since the exact geometry information was available in the 3D models. When the sourcing for the milled foam formwork was found unable to meet the project schedule, the fabricator decided to invest and set up a milling shop for the project. This shop eventually spun off into a separate business as the demand was very high.
Off-Site Assembly
Another challenge in the construction was the assembly of the pots. The construction manager and the marine contractor had numerous discussions with the client, designers, and the precast fabricator to develop the best possible way. The plan was to set up the assembly stations in a remote yard near the precast fabricator to minimize the land transportation of the fabricated precast. A yard at the Hudson River shore was chosen so that the assembled pots could be barged to the site. This method proved to be best as the assembly required lots of welding and could be done in an almost indoor condition.
Collaborations
The importance of collaboration and trust among team members for this project must be addressed more. It was the true driver that made the landmark project a reality. Several challenges were evident from the beginning. The design team worked together rigorously to develop and share the scripts to generate, rationalize, and transmit the complex geometry. The contracting team was open-minded and willing to try, embrace, and invest in new digital fabrication technologies which were critical to the project. The client team trusted and encouraged the whole team to develop innovative ways to deliver the project. We appreciate all project team members’ great collaboration and the opportunity to be part of the new icon on the Hudson River.