Safety first as developer executes concrete plan.

Taking the lead among New York City high-rise office building owner and developer, Dr. Axel Stawski of Kipp/Stawski Group has elected to emphasize SAFETY in his new 28-story office building designed by renowned architects Kohn Pedersen Fox Associates, PC.

The structure at 505 Fifth Avenue is being constructed with a concrete core and a flat plate reinforced concrete framing system.

Cast-in-place reinforced concrete was chosen over steel for this office building because it is terror-resistant, blast resistant, fire-resistant and sound-proof.

The concrete columns used at 505 Fifth Avenue are spaced 30-feet-on-center and they support an 11-inch-deep concrete slab with 22-inch-deep capitals at the columns.

The 11-inch slab at the spandrel meets the stringent architectural requirements for the curtain wall design while still allowing impressive 15-foot dual cantilevers at the south-west corner.

The new 300,000-square-foot structure, which will contain approximately 275,000 square feet of office space and 25,000 square feet of retail space, will also contain a 12-inch-thick concrete shear wall that will completely encase the fire stairs above the building's mezzanine floor.

The shear wall will be located at the rear of the property to maximize rentable space with views on 42nd Street and Fifth Avenue. Any eccentricity in the lateral load resistance system is handled by the reinforced concrete slab-frame system.

An additional safety measure being taken by the owner is to have the office building's ground floor perimeter columns jacketed in a steel plate to maximize the building's structural integrity against explosive loads. In the event of local overloading and failure of a slab-column connection, sufficient steel is provided to arrest progressive collapse.

The owner is going one step further to ensure safety by having an 8-inch reinforced concrete curb at the first floor as a barrier against vehicle intrusion.

The use of a concrete hardened core and cast-in-place reinforced concrete framing system also increases the clear ceiling heights and/or lowers the floor-to-floor heights allowing for less electrical wiring, ducts, piping and building skin.

At the lower levels where the owner anticipates the possibility of interconnected floors, provision has been made for tenants' future stairs.

Supporting the owner's decision to construct a high-rise office structure using a concrete core and high-strength concrete is research by the National Institute of Standards and Testing that steel, when exposed to fire, loses its strength and stiffness much quicker than high-strength concrete. High-strength concrete, which has a lower thermal conductivity, will maintain its strength and stiffness much longer. This means that in the event of natural or unnatural disasters, tenants will have more time to evacuate the building should evacuation become necessary.

In addition to safety, the mass of a concrete structure such as this makes it a significant thermal reservoir with the ability to store larger amounts of energy. In the heating months, concrete walls and floors absorb the interior heat during the day, and then radiate warmth back into the space at night. The same holds true for cooling. This thermal inertia allows concrete to help maintain a relatively steady interior temperature.

By storing and releasing energy needed for heating and cooling, concrete delivers year-round energy benefits.

Furthermore, "concrete is a durable material that gains strength over time. Such an extended life span conserves resources by reducing maintenance and the need for reconstruction," explained Alfred G. Gerosa, president of the Concrete Alliance, Inc.

"A cast-in-place reinforced concrete high-rise office building such as 505 Fifth Avenue enhances homeland security by ensuring a safer place to work. The Concrete Alliance salutes Dr. Stawski for putting the safety of New Yorkers first and foremost. The example they have set will serve as a precedent to all owners and developers planning to construct high-rise office structures in New York City," Gerosa added.