Structural Engineers Association of New York, Excellence in Structural Engineering, 2014
It is “an outstanding example of a Beaux-Arts style skyscraper,” according to the New York State Historic Preservation Office, and has been described by the New York City Landmarks Preservation Commission as “one of the most recognizable and most admired skyscrapers in New York.” The Helmsley Building at 230 Park Avenue, originally known as the New York Central Building, is the skyscraper counterpart to New York’s Grand Central Terminal.
The building consists of a 16-story podium and a slender 32-story tower capped by a pyramidal roof and a crowning cupola. It features ornamentation by American sculptor Edward McCartan, including its iconic Park Avenue clock flanked by heroic-sized figures of Mercury and Industry. The façade is characterized by distinct terra-cotta elements, including 32 free-standing, three-story fluted columns consisting of hollow terra-cotta masonry cladding around brick encasement, supported by a central core of built-up laced steel columns. The façade also has 74 seven-foot tall terra-cotta bison heads that make up the cornice of the podium structure.
We provided historic preservation and structural renewal services to RXR for the building, which was designated a New York City Landmark in 1987.
Historical Preservation Highlights
- Restoration of the entire façade that included repairs to the brick masonry, granite, limestone and terra cotta elements. All façade repairs were designed for maximum retainage of historic fabric.
- New storefronts that accurately replicate the original storefronts.
- Implementation of a impressed current cathodic protection system (ICCP) at the steel built-up laced columns to arrest corrosion and monitor for future section loss. The use of the ICCP system allowed for retaining most of the original historic terra-cotta fabric which provided the client with significant long term cost savings.
- Delicate removal and reinstallation of the upper portions of the terra-cotta bison heads to repair and waterproof the continuous steel shelf angles that run the length of the cornice.
- Restoration and resurfacing of the crowning cupola, which included resealing the joints, relining the gutters and installing new waterproofing membranes.
- We provided inspection services as per NYC façade safety regulations.
- Investigation into the cause of large-scale systemic cracking at the twelve-foot tall terra-cotta brackets that project four feet outboard of the façade.
- The investigation included non-destructive evaluation techniques such as impact echo, ultrasonic pulse velocity and infrared scanning.
- A finite element model was developed to analyze the behavior of these cracks, which revealed high stress concentration.
- We designed appropriate cost-effective repairs to restore these historic brackets that included specially designed six-foot long stabilization anchors to relieve the stress concentration.
- This solution reduced the schedule and saved the client significant costs, while addressing the underlying cause of deterioration.
- Ten-years later, the restored brackets are performing well, with no signed of deterioration.