Demolition of buildings and structures are needed for different reasons. Demolition methods and processes for buildings and other architectures are described. As Hyper Fixes demolition experts know that every design or structure of a building has a duration known as design life. The building is designed considering a period of life, say 80 -100 years. When the given design life of the structure or edifice is over, the structure is not safe for the living people and also dangerous for neighboring buildings.
There can be more reasons for the demolition of an edifice, old structures of buildings are to be changed by new ones. The structure lost its strength, stability, or having any structural damage. Mostly small buildings are demolished to construct the big buildings etc.
Now the question arises: what is demolition? So to understand the demolition we simply jump to its definition.
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What is Demolition?
Definition: The term demolition means destruction, eradication, breaking down, or removal. Demolition of the edifice (structure or building) is the process of destroying or dismantling a building after its life of serviceability by some pre-planned and controlled methods.
Implosion in Demolition: When explosives are used in the demolition of a structure, it is known as Implosion.
Demolition Process of a Building
Various steps are involved in the process of demolition of a building structures which are:
- Survey of the Structure
- Removal of hazardous materials from site
- Preparation of plan
- Safety measures
Surveying of Buildings for Demolition
Surveying means study of various parameters of the building and its surroundings. There are two types of surveying normally conducted. They are
- Building surveying
- Structural surveying
Building Surveying
In survey of buildings or edifice for demolition, generally these processes are carried out:
- Which types of construction materials are used
- Prior and current usage of building during the process of demolition.
- The presence of hazardous materials, wastewater, matters arising from toxic chemicals, flammable material or explosives and radioactive materials, etc.
- Drainage conditions and all possible problems regarding flooding, water pollution and erosion.
- Shared facilities with neighbouring buildings, including common partition walls, staircases etc.
- Neighbouring pedestrian and vehicular traffic conditions.
- The sensitivity of the neighbourhood with respect to dust, noise, traffic impact and vibration.
Structural Surveying
In structural survey, those process which are involved in demolition are mentioned below:
- Construction method
- The structural system and structural conditions like basements, underground vaults or underground tanks.
- The original structural system was occupied in the design.
- Current building condition.
Removal of Hazardous Materials
If some hazardous materials like asbestos minerals, petroleum pollution and radioactive metals are found during the investigation of the site for demolition. Specialised personnel are called for the elimination of the hazardous materials from the site previous to the demolition of the structure.
Preparation of Demolition Plan for Structures
A comprehensive demolition plan is made which clarifies the different process involved and they are:
- Location of the building which is going to be demolished.
- Distances from the building to be demolished to its neighbouring buildings, structures, streets and important street furniture.
- The support systems of the building to be demolished.
- A demolition plan shows the whole process for the building demolition (step by step sequence of demolishing structural members and the method of demolition to be executed).
- A plan displaying all precautionary measures for the safety of the public including hoardings, catch platforms, covered walkways, catch fans, protective screens, scaffolding, and safety nets.
- Handling demolished building debris.
- Time needed for the complete demolition process etc.
Demolition Methods for Buildings and other Structures
There are two types of methods used for buildings and structures demolition.
- Explosive demolition
- Non-Explosive demolition.
Explosive Demolition Method
Implosion Method of Building Demolition
Implosion is the procedure of demolition of a building by using explosives. If the supports of the edifice are removed then the structure is destroyed. By Using implosion technique, the main supports of buildings like column’s, slab and beams are collapsed with explosive materials. When these explosives are exploded, the columns collapse and then the whole structure also collapses. Types of implosion depends on how the structure of the building falls. Generally there are two types of implosion:
Falling like a tree
In this type of implosion, the building is managed to fall like a tree to the side (oblique). This is the generally used type of implosion. When free area is available besides the building, this type of demolition is recommended. If the free area is available on the left side of the building, the explosive materials are placed on the lower level of the building on the left side columns. As the explosives are exploded, the columns crack, the building turns to fall towards the left side. Steel cables are also used to control the falling direction of the building.
Falling into its own footprint
When the free places are not available beside the building and the structure around the building are to be secured. Then this type of demolition is used. In this type of demolition, explosives are set on the ground below the middle part of the building.
These explosives must be heavy as the blast must demolish the building at once. If one part explodes and is followed by another. Then the building falls towards the first exploded part. Only few companies in the world are experienced in this type of demolition. As the explosions explode, the upper part of the building damages and falls upon the lower part of the building. Due to the heavy load and force of debris the lower part of the building also destroys and falls on its own footprint.
Non-Explosive Demolition Method
This type of structure demolition is carried out with the help of some equipment without use of any explosives. Different types of equipments are used for the demolition activity, which are:
Sledge hammer
This small handheld hammer is used for the demolition of small walls or single columns.
Excavators and Bulldozers
Excavators and Bulldozers are big machines used for demolition of small size buildings. For example used for excavation of soil or transferring of debris to trucks etc.
Wrecking Balls
A 6 -7 story building cannot be demolished only with the help of excavators or bulldozers. In such cases cranes with wrecking balls are used for the demolition process. The wrecking ball crack is a crack attached with a big steel ball hanging from a steel cable. The steel ball is stretched and then released towards the building. When a steel ball with heavy force collides the building then that part of the building is demolished. Generally this process is not recommended as the trajectory of the steel ball cannot be controlled after it collides the structure.
High Reach Excavators
High Reach Excavator machines are used in the demolition process of big buildings where demolition through explosives is not possible. The building with a height of 300ft can easily be demolished by this type of machine. High reach excavators can be used for various use by doing some extra attachments for example:
- Excavators with shear attachments.
- Hydraulic hammers and remove steel reinforcement.
Safety Measures during Demolition of Building Structures
All the workers, supervisors and engineers including plant and equipment operators are explained with the potential difficulties and process of demolitions. All items that are flammable are removed from the site unless it can be reused in the work involved. All the combustible materials (like fuel, timber, woods etc) are stored for future use in proper storage facilities. Firefighting appliances are stationed in the demolition spot till the procedure is completed.
During the process of structure demolition, many problems are experienced by the workers, such as exposure to dust, chemical exposure, noise exposure, medical and first aid facilities, heat stress and ventilation, sanitation and occupational diseases. To reduce these problems proper measures are undertaken.