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CON 243 Heavy Construction Equipment, Methods, and Materials Lecture 25 (Chap. 17) — CranesThe crane is the primary machine used for the vertical movement of construction materials.
MOBIL CRANES(CRAWLER or WHEEL MOUNT) TOWER CRANES Types of Cranes
Boom Mast Counter weight Rig Outriggers Mobil Crane Nomenclature
Counterweight jib Load jib Counterweight Trolley Tower Crane Nomenclature Cab Tower (mast)
Luffing jib Tower Crane configurations Saddle jib /hammerhead boom
Details of Tower Cranes http://www.towercrane.com/tower_cranes_Detail_Select.htm
SAFETY OSHA Crane fatality data: • Energized power lines 50% • Overturning 19% • Load dropped 14% • Boom collapsed 12% • Two-block 5%
Crane Accidents: • 61.0% Overturning
Counterweight C PayloadP Crane Geometry Tipping Moment TM= P x a Stabilizing Moment SM = C x b For stability: TM << SM SM is constant for a given position of the platform b a
L C Over the front (front lifting)
L C Over the rear (Rear lifting)
Over the side L C Over the side
Counterweight C PayloadP Crane Geometry Tipping Moment TM= P x a Stabilizing Moment SM = C x b TM = SM / safety_factor b a