Glazing, fire protection & structural integrity

Published:  01 April, 2006

In the USA, New York’s Freedom Tower is set to rise 1,776 feet from ashes of the World Trade Center now that the final designs have been agreed and the ‘ground breaking’ inauguration ceremony is over.

The new tower is to include 2.6 million square feet of commercial space and will cost $1.5 billion, or US$1m per 500 square feet. It will be built at the site of the destroyed World Trade Center in Lower Manhattan and when completed will be the world’s highest building.
On September 11th, 2001, two hijacked passenger jets levelled the 110-storey Twin Towers and five smaller buildings, and killed 2,752 people in the tragedy.
More than 350 fire and emergency responders were among those killed, the largest loss of life for this sector in a single incident.
Architects from Skidmore, Owings and Merrill believe they have now designed a structure tough enough to prevent the sort of catastrophic failures which brought down the original Twin Towers five years ago. 
Creating a structure which is fire-resistant and physically tougher is not easy: the building’s core will be reinforced with a thick concrete-and-steel wall with a web-like structure for the exterior. This is designed to redistribute weight if support columns are damaged by impact or explosion.
Fire-safety features
The Freedom Tower’s developer has promised to go beyond the safety measures required for a New York City highrise. Inside, the building will have biological and chemical filters and two sprinkler systems (to provide a backup if one is destroyed).
Other features include upgraded elevators for use by emergency responders, fire-resistant steel members (capable of coping with temperatures up to 800°C) and blast-resistant refuge rooms where people can survive until rescue comes.
As well as extra-wide emergency stairs and a dedicated staircase just for firefighters, communication systems, sprinklers and elevators will be encased behind 3-foot-thick walls.
Probably the most innovative feature of the building will be the use of high-performance concretes and glazing which falls into bits rather than delaminating into crystalline shards.
“The tower will have a solid concrete core and state-of-the-art fireproofing on its steel beams. We embrace the recommendations of the US National Institute of Standards and Technology, which found that the dislodging of fireproofing material when the hijacked planes crashed into the Twin Towers contributed greatly to their collapse,” comments real estate developer, Larry Silverstein.
According to a description of the redesign by the Lower Manhattan Development Corp the tower’s cubic base will be constructed of luminous materials - probably a combination of stainless steel and titanium - that will be shimmering and light-reflective as well as blast-resistant. As in the original design, the structure outlined in the latest plan exceeds city fire code requirements, and will have biological and chemical filters in its air supply system.
 W. Gene Corley , the man who headed the Federal Emergency Management Agency investigation into the Twin Towers’ collapse, comments:  “It’s not feasible to design any building, of any height at least, that will resist anything that might happen in the future. Whatever you do to provide resistance in a building, there’s somebody that will come up with a way to bring it down if they get a hold of the materials.”
A spectacular topping
A broadcast antenna will also be attached to the tower is to bring the structure’s total height above 2,000 feet.
Governor George Pataki had ordered design changes because police were worried that the tower’s placement near West Street, a vital route by Manhattan’s west side, could potentially make it a target for a would make a truck bomb.
Now, instead of being 25 feet from West Street, the tower will be set back 90 feet, and its 200-foot base will be a reinforced concrete wall covered in steel and titanium.
Ultimately, Freedom Tower is to rise 70 floors and be topped by wind-harvesting turbines that designers predict will provide 20% of the building’s energy.
“We build the Freedom Tower in honour of the memories of the heroes we lost,” Pataki said at the unveiling ceremony near Ground Zero. “We will build it to show the world that freedom will always triumph over terror and that we will face the 21st Century and beyond with tremendous confidence.”
Terminal velocity
Terminal 5 at London’s Heathrow Airport is one one of Europe’s largest construction projects. Costing an estimated £4.2 billion, when fully built T5 will handle 30 million passengers a year.
September 2002 saw construction begin on the new terminal; Phase One of the project is scheduled to be completed and opened by April 2008, with the Second Phase opening in 2011.
The timescale is just one of the construction challenges. Improving fire engineering design by following the lessons learned at Dusseldorf Airport - and building-in safety features against the ever-present risk of terrorist attacks are two other essentials.
Heathrow is one of the busiest airports in Europe and passenger numbers are expected to grow by 27 million per year as a result of Phase One, and then by a further 3 million per year after Phase Two.
Essentially a large infrastructure project involving over 60 contractors, Terminal 5 is the focus for 16 major projects and 147 sub-projects over a 260 hectare site.
Glazing & insulation suppliers
One of the principal suppliers of the special glazing option for the exterior of T5 is Schmidlin, best-known for its creation of the protective EL4003 facade system used on the first three BAA projects at London Heathrow and Edinburgh airports.
Working with partners Hek Manufacturing, Schmidlin (UK) Ltd devised a safe and cost-efficient working method to provide a flexible solution to installing fire & blast protective façade elements to all four sides of the structure. 
Andy Turnbull, Schmidlin (UK) Ltd Contract Manager commented: “Work is progressing on both West and East facades and Schmidlin (UK) Ltd is exceeding its 10 glazing elements per day.”
Schmidlin (UK) is also installing Knauf Insulation’s new, fire protective insulated soffit lining board. Polyfoam Soffit Linerboard was selected as it provides the high level of insulation performance and aesthetic appearance needed in just one product.
Polyfoam Soffit Linerboard - a high-performance, extruded polystyrene (XPS) foam board with a high strength, fire resistant, decorative cement facing - was chosen as it met all three requirements.
“We needed to insulate the underside of a concrete soffit,” explains Paul Martin-Jones, Schmidlin’s Project architect at Heathrow T5. “It was vital that whatever we used gave the thermal performance we needed and, at the same time, preserved the design integrity of the building’s exterior.”
Knauf Insulation is the UK’s only manufacturer of both mineral wool and extruded polystyrene (XPS) insulation.
Both are available bonded to a tough, 6 mm thick, cement facing board which has been classed as ‘Class 1’ to BS 476-7: 1997 (Surface Spread of Flame).
Rocksilk Soffit Linerboard uses a layer of Rocksilk rock mineral wool to provide a board with excellent all-round insulation performance. Rock mineral wool is justifiably well known for its outstanding combination of thermal, acoustic and fire insulation properties.
What about inside T5?
If the T5 exterior is fire-resistant - what about the interior? Internally, the structure has Foamglass non-combustible insulation materials made by Pittsburgh Corning.
It’s well-known that the catastrophic fire at Dusseldorf airport on April 11th 1996 was caused by the use of plastic-foam insulation in ceiling voids - this had been ignited by sparks from welding equipment. The fire and smoke generated killed 17 people and caused an estimated £200m of damage. A German court ordered  the Dusseldorf Airport Authorities to pay US$11m in compensation.
The airport itself admitted failures and delays in preventing and dealing with the fire, including an acknowledgement that the wrong evacuation message was played, directing passengers to their deaths in the Arrivals Lounge where the seat of the fire was located.
When Dusseldorf airport was rebuilt Foamglas cellular glass was specified for the roof, terraces, basements, ventilation and air conditioning ducts - all places reckoned to be at greatest risk from fire.
It is also used in other areas. T5’s 862-tonne control room and upper mast section for the £50m steel air traffic control tower were fabricated offsite and have been lifted into their final position on top of a 4.8m diameter 65m high steel mast.
Fire-resistant Foamglas cellular glass insulation has been attached to the inner faces of the upper mast section and underneath the floors. A fire engineering spokesman told IFJ:  “It was picked because of its complete non-combustibility. Foamglas is the only truly 100% closed-cell, non-combustible (Euroclass A1) insulation material; its thermal conductivity is uniquely constant over time.”

  • Operation Florian

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