by Gautam Shah ➔
Buildings take long time to plan and execute, and are designed as long lasting assets. However, the rapid pace of technology has forced designers to conceive buildings as a fast replaceable entity. Buildings that are common and emotionally unattached (like, departmental stores, industrial plants, bridges, offices and housing complexes), as soon as become economically unviable or location wise irrelevant, are quickly replaced. Buildings of doubtful structural integrity are also demolished immediately. New structures are often designed with considerations of not only the likely mode of collapse, but also including the means and methods of demolition.
Demolition contrasts with Deconstruction, which involves taking a building apart while carefully preserving valuable elements for re-use. Material recycling or reuse practices are becoming part of material selection strategies.
Other options to demolitions are few. Displacements or Relocations of the buildings have been tried, but involve a great expense and risk. Relocation of building is carried out in two basic ways. Buildings are dismantled and reassembled, or transported as a whole at another location.
The first approach requires building to be consisting of separable and re-unite-able parts, whereas the later one requires building to be an integrated entity. In reality buildings are exclusively neither of these. It was possible to shift the Egyptian temple from the Aswan dam site as it consisted of small units of rock. A modern integrated RCC frame structure cannot be disassembled. A small structure may be shifted as a whole but a large structure may not have the required street width in an urban location. Displacements are conceived for highly sentimental entities, and only as a last resort.
Displaced building sited in a new setting makes it an alien entity, almost like an artefact on display in a museum. A building’s environment is part of the building, and when surroundings are changed, the building looks strange. Buildings with substantially changed surroundings look misplaced. A castle with a dry moat, or historical monument set in a lush green lawn, Khajuraho temples with multi coloured flower beds and hedges, Stonehenge in vast lawn, are also examples of such displacements.
Demolitions involve, the costs of, pulling down the structure, debris removal and safe disposal, and risks management, in all far more expensive then the value of the neutralized asset. Atomic and toxic chemical plants are an example of very costly disposal.
For small buildings, of two or three stories is rather easy to demolish. Larger buildings, however, need a wrecking ball or a heavy knocker weight. These tools are useful for masonry work but cement concrete and steel frames require special strategies. Demolition strategies for very tall structures such as chimney stacks, towers and high-rise buildings, mainly centre on minimizing the collateral damage. Manual scavenging is carried out to lighten its debris mass, followed by implosion with explosives to reduce the spread of collapse. Post demolition sub sizing of large components into a transportable entity and removal of debris from a core area of a city, are all part of demolition strategies.
Disaster management strategists work primarily on avoidance of collapse and disposal of remains, besides safe evacuation of goods and people. Yet, their strategies often include demolition of buildings and structures.
Old buildings, being destroyed, have materials that may require specific removal and disposal strategies, these include Asbestos products, Fibre glass, PU insulation foams.