Demolition is the DISMANTLING,RAZING, DESTROYING orWRECKING any building or structureor any part of building by PRE-PLANNED and CONTROLLEDmethods.
Demolition is the tearing-down ofbuildings and other structures.Demolition contrasts withdeconstruction, which involves takinga building apart while carefullypreserving valuable elements for re-use.
For small buildings, such as houses, that are only two or three storieshigh, demolition is a rather simple process. The building is pulled downeither manually or mechanically using large hydraulic equipment:elevated work platforms, cranes, excavators or bulldozers.
Larger buildings may require the use of a wrecking ball, a heavy weighton a cable that is swung by a crane into the side of the buildings.Wrecking balls are especially effective against masonry, but are lesseasily controlled and often less efficient than other methods.
Code of practice for Demolition PlanWhen preparing plans for demolitionworks, reference should be made to therelevant regulations in the BuildingsOrdinance and the Code of Practice forDemolition of Buildings issued by theBuildings Department (BD)
Scope of the CoP of DemolitionOutline good practices for PLANNING andIMPLEMENATION of demolition of variousbuilding works aiming at minimizing the risk of :– damage to people and properties of the PUBLIC;– endanger the health and safety of SITEPERSONEL;– damage to the neighborhood ENVIRONMENT.
Building appraisal by means of– Building Survey– Structural Survey– Demolition Plan & StabilityReport includingCalculation– Utilities– Hazardous materials
Demolition Plan• location plan• layout plan• structural plan• procedure plan• plant routing and structural alteration• precautionary measures plan• shoring plan (outside)• shoring plan (inside)• debris disposal plan• Special safety considerations• Traffic• Post-demolition arrangement
A. Record DrawingsB. Survey ItemsC. Special StructuresD. Investigation and Testing
Record Drawings1.Studying the record layout,structural framing plans and structuraldetails.2.Checking if any unusual detailingthat may cause abnormal structuralbehaviour during demolition.
Survey items• The structural materials used;• The original structural system employed;• The method of construction;• Condition of structural elements;• The structural conditions of adjoiningstructures;• The presence of continuous structures thatmay be truncated by the demolition
Special Structures• The correctness of structural informationavailable;• Any unconventional structural elements;• The possibilities of structural modification toenable efficient demolition traffic duringdemolition;• Any limitation on shoring and othertemporary supports.
If no structural details are available, thestructural survey shall include:1. Site measurement;2. Field testing;3. Expose some key structural elements
Demolition Plans• The construction and condition of the buildingto be demolished, including sections showingslopes and ground supported by it, and allaffected buildings, structures, streets, land andservices• The existing nature of the site and surrounds(including an accurate survey plan with groundlevel contours and sections showing slopes andground supported by the building to bedemolished) and all necessary removal of ground
Demolition Plans (cont.)• The sequence, equipment and procedures for thedemolition works• The support to be provided to the building to bedemolished and any slopes and ground supported by itand all affected buildings, structures, streets, land andservices at each stage of the demolition works• All precautionary measures for the protection of thepublic including dust screens, catch fans, hoardings andcovered walkways• The support to be provided to all affected buildings,structures, streets, land and services at each stage ofthe demolition works
Methods of Demolition• Top-down manual• Top-down machines• Mechanical by hydraulic crusher withlong boom arm• Wrecking ball• Implosion• Others: non-explosive demolitionagent; saw-cutting; cutting and lifting;mechanical demolition; thermallance and water jet
Special Structures• Precast concrete structures• Prestressed concrete structures• Statically determinate structures• Composite structures and steel structures• Cladding walls• Hanging structures• Oil storage facilities• Marine structures• Underground structures• Structures supporting ground or sitting on slopes
Comparing Top-down manual and Top-down machines methods• Manual: by jack (or pneumatic) hammers andoxy-acetylene torch• Machines: by percussive breaker, hydrauliccrusher and excavator arm• Similar Sequence: cantilevered slabs andprojected elements – roof – cantilever beams –secondary beams – main beams – nonloadbearing walls – columns and load bearingwalls.• Machines support and lifting: temporary rampconstruction