Intelligent Cladding of Tall Buildings

Following the World Trade Centre disaster of 11 September 2001 when two Boeing 767 aircraft were flown into the Twin Towers, and when one was flown into the Pentagon, many questions have been asked. The International Council for Research and Innovation in Building and Construction (CIB) the Council for Tall Buildings, and other interested groups have met to discuss strategies for the future.

This article briefly discusses ideas for a new intelligent cladding system that may be installed on buildings that will warn of an imminent approach of aircraft, and automatically alter their flight-path, thereby deflecting the plane from the building.

The CIB meetings and Task Group (TG 50) – Tall Buildings – from 2002 met to discuss what happened during the 11 September incident in order to develop strategies for coping with any future such disasters.

The discussions were comprehensive and it is likely that some worthwhile recommendations will result over a period of time. The meetings of CIB discussed areas including structural performance, evacuation issues, insurance/reinsurance perspectives, fire service access and operations, megacities/megastructures, city planning issues, regulatory considerations, risk perception and fire engineering.

These items fall within our present way of thinking, but it appears that there needs to be a paradigm shift in order for society to deal with threats that were previously beyond the imagination of most people.

My proposal is to use the concepts of three existing and separate technologies in combination to arrive at new building and aircraft defence strategies. These technologies are photovoltaic solar heating for buildings, radar and aircraft anti-collision devices.

Radar is an electromagnetic system for the detection and location of objects, and it has numerous uses. Since electromagnetic energy propagates at the speed of light it is compatible with combining with photovoltaic technology. Photovoltaic electricity generation for buildings has now developed to an advanced state whereby small solar cells that produce electric pulses from the sun’s ultraviolet rays are fitted in close proximity to each other allowing them to be fitted to a building as the external cladding system. Such cells can be fitted over any desired areas of buildings when used for solar heating purposes. Silicon cells are manufactured by reducing sand to metallurgical-grade silicon. After oxygen, silicon is the most abundant element in the earth’s crust.

Commercial passenger aircraft are presently fitted with anti-collision devices. These deflect aircraft from their flight path in the event of them being on a collision course with another aircraft. There have been many reported incidents of this sort over the years.

Based on these three main current applications of technology my concept is of Intelligent Cladding of Buildings (ICB) that needs to be developed.

In my view, ICB may be applied to any building. It will be a system applied at the choice of building owners who wish to have protection against their buildings becoming targets of aircraft being used as missiles.

Typical radar systems can detect objects the size of birds and insects. This means that ICB panels may be installed judiciously on buildings in relatively small areas to ensure that the whole building elevation is protected and to provide for the desired architectural appearance.

Using conventional terrain-following (TF) systems aircraft successfully change direction to avoid collisions with mountains. When ICB is fitted to a building, it will automatically cause the path of the approaching aircraft to be altered thereby avoiding a collision. Because this would then pose a potential danger to a neighbouring building it would be necessary in future to ensure that tall buildings are separated by a distance greater than the wing span of the design aircraft, plus an additional factor of safety.

If such an ICB intelligent cladding system has not been developed, then it seems to me to be a viable proposition. I would be interested to hear from anyone who is able to advise me of the state of the art in that regard.