The understanding of controlled demolition methods is closely related to the explosive products development, from the the first use of the black powder, and the discovery of the dynamite by Alfred Nobel . Through the history of demolition – it’s fairly illegal status (1605 – British Parliament demolition attempt) was eventually gentrified (1900 Delaware City Hall demolition, Ohio, USA) and evolved into a technology highly valued by industry and military as it is today . According to the technical means available, demoltion may be classified as follows:
1. Mechanical demolition; 2. Thermal method demolition; 3. Demolition by expansion or explosion 4. Electrical and abrasive demolition.
Many of these are either beyond the scope in some way or are far too expensive for most applications – and so we are left with two main methods for building explosive demolition:
1. The Vertical collapse method
2. The Side collapse method.
The Use of Exposives
Many factors come into consideration when it comes to the successful application of industrial and military grade explosives in dismantling buildings – no matter their size. The following is a broad list of considerations, most of which must be thoroughly addressed in the design of a successful controlled demolition.
Physical – chemical characteristics
Mechanical work of explosion (potential)
Explosive charging density
Specific volume and covolume
Heat and temperature of explosion
Brisance (breaking power)
Explosions’ gases pressure
PLANNING A CONTROLLED DEMOLITION
Fig.1 Type of elementary mechanisms: a – girder, b – mid-floor, c – floor; d – joint
Fig. 2 Analysis of Joint and Support removal.
VIDEO: Controlled Demolitions
A textbok controlled demoliton.
On September 13th 2009 at South Padre Island Texas, the doomed 31 story Ocean Tower building was imploded at 9:02 am. This video was shot from the top floor of hotel next to Ocean Towers.
VIDEOS: Controlled Demolitions of Two Separate High Rise Tower Projects
Here are two more classic style controlled demoltions. Note the ‘squibs’ or locally placed explosives at major structural joints, whose characteristic ‘puff’ shapes give them away. Please also note how, once the major structural joints have all been compromised, how the previously stiff structure collapses in on itself at a rate of freefall not different from that of an object, dropped from the roof of a similar height.
VIDEOS: Controlled Demolition FAILURES
As a counterpoint to the above – please note how a high degree of structural integrity is retained even in these buildings – for whom especially – structural integrity was not any sort of particular concern in terms of their design or construction.
Even buildings of low structural integrity generally retain a high degree of stiffness until the bitter end.