Demolition is the destruction of a building or structure. It is important to ensure this process us undertaken safely as taking down an entire building has many obvious risks.
Here are some demolition methods;
Almost any structure can be demolished via Wrecking Ball but it is a skilled practice which cannot be self taught.
The wrecking ball is a very effective method of demolition. When demolishing multi-storey structures that have suffered structural damage. After all other methods have been considered and undertaken a hazard assessment, if the plans are deemed too hazardous the wrecking ball is determined the most appropriate method.
Hazards associated with Wrecking Ball Demolition include but are not limited to:
- Vibration to adjoining structures
- Flying Debris
- Uncontrolled/Unintentional Collapse
- Limited waste minimisation
Any trainee's must be instructed by a trained and experienced worker and work under close supervision until they are competent.
Not just any crane is capable of undertaking this task, we would recommend a converted drag line crane. They are very robust and stable, a crane with a hydraulic ram should not be used when using a demolition.
A crane which is being used with a wrecking ball should be fitted with FOPS and should be enclosed, strong and debris-proof. Cranes which are used solely for lifting on a demolition project dont need to be fitted with a FOPS cab, however operations that could cause flying debris should not be carried out close to the crane.
Demolition by Implosion/Explosives
Explosion or implosion destruction is an effective and efficient method of demolition. Using this technique can reduce both cost and time to bring dangerous multi-storey structures to the ground in comparison to conventional demolition methods. In the majority of cases, implosion can reduce the whole demolition period by up to 80% with most of the time being spent in preparation and the clean up following.
The only structures which cannot be demolished in this manner are Timber-Framed and Brick Structures. Even structures which have been compromised in the past can be effectively imploded, however an expert will give instructions on any collateral damage that may occur.
The method usually used is to cut or disintegrate key structural members by fixing plaster charges to key structural supports or drill holes
The usual method is to cut or disintegrate key structural members by loading drilled holes with explosives, or fixing plaster charges to the outside of these members.
You should always take the following precautions:
- Have an experienced and approved explosives handler in charge of the work.
- Make sure that the plans are feasible by consulting an experienced IPENZ engineer.
- Use mats and small charges to stop flying debris
- Beware of strong columns as they may cause the building to sit down rather than topple.
- Advise the local authority and police of the plans.
- Ensure there are safe escape routes.
Wire Rope Pulling
This method uses wire ropes and cables which are attached to such as tractors or winches and fixed to key structural members then pulled down. This method is best suited to detached structures as there is plenty of surrounding room and less risk of damaging any other structures in the process. Wire Rope Pulling can be used for bridges, brick, stone or steel chimneys, timber-framed buildings and for spires or masts.
We would recommend the following precautions:
- Use wire ropes with a safety rating of at least 6 and with a diameter of at least 16mm.
- Make sure the machine is anchored securely and the rope is flattened to less than 1 inch.
- Ensure that no one stands between the machine and building or next to the rope.
- Do not allow anyone inside of the building while pulling.
- Make sure that all ropes are properly secured before commencing with the pull.
- Take note of any overhead power lines to make sure the rope doesn't touch them.
Grapples and Shears
If there might be a risk of fire, or where more precise cutting using a torch is not required, power shears can be used to crop and cut through concrete and metal such as beams or reinforcing steel. An additional feature of this method is that it reduces the noise on site. Any member which is to be severed should either be effectively supported or, if it is going to be allowed to fall care should be taken in order to ensure remaining structures or personnel are not endangered.
When moving waste around the site or loading it onto other vehicles to dispose of waste, power grapples can be used to handle the waste. There should be care taken to avoid overloading the equipment as some of the debris from demolition could have a high density. You should always try to avoid damage to the machine itself, do not try to do too much at once, as a heavy load could induce instability and then overturning.
Machines should only be operated in accordance with the manufacturers recommendations.