ceiling structures ceilbot-project introduction to ceiling structures history situation today...
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Ceiling structuresCEILBOT-PROJECT
INTRODUCTION TO CEILING STRUCTURES
• History• Situation today• Loading• Fastening• Vibrations and sound• Risks
Eelon Lappalainen
A.Aalto, Maison Carré, France
”A ceiling is an overhead interior surface that bounds ("ceils") the upper limit of a room.” Wikipedia
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History• Ceiling is quite new ”invention” in residential
buildings, started to become general after WW II
• Ceilings were used before WW II usually in castle’s and churches
• Before 19th century ceilings were mostly made of timber or masonry
• During 19th century cast iron, steel and concrete were also used in ceilings
– Ceiling made of cast and wrought iron: 1780 - 1900
– Ceilings made of concrete: 1850 -– Ceilings made of steel: 1880 -
• Typical for ceilings is diversity of different structures and support systems
• Old ceilings were designed mainly to support it’s own weight -> adding more load will usually cause problems (big deflection, cracking, even collapse)
• Design methods and quality of materials varies a lot
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Benedectine Abbey of Einsiedeln, Switzerland
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Situation today• Pre-fab pre-stressed slabs (etc. hollow
core slab) are commonly used• In residential buildings ceiling is
normally in washrooms and hallways (installations are hidden behind ceiling)
• In office buildings ceiling is usually in large areas and hide’s structures and installations (main installation routes are in hallways and vertical shafts)
• Small family houses, day-cares, ware-houses and even some industrial buildings timber structures and ceiling is used
• Fire regulations strongly defines materials what is allowed to use in certain buildings
• Modern ceiling usually hangs from load bearing structure by fasteners
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Installations inside the ceiling
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Loading• Basic loads are given in design codes
(Eurocode, ACI, DIN, RakMK)• Dead load• Live load (1,5…10kN/m2)• Ceiling load (~0,2…1kN/m2)• Dead load, live load and ceiling loads
for are in horizontal structures mainly vertical loads
• Installations (HVAC, motors, robot etc.) causes three dimensional loads
• Three dimensional loads are usually handled separately in structural dimensioning
• For simple calculations dynamic loading can be expressed:
– static load x dynamic factor– displacements are limited
• Complex dynamic problems are usually calculated by FEM
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Fastening• Ceiling is fastened to load
bearing structure (slab, beam, truss)
• Fasteners and anchors should carry mainly vertical dead loads from ceiling and attached equipment (electric, HVAC)
• There are numerous different fastener types
• All fasteners and anchors which are strained dynamically, should be approved for such purpose
• Actions causing fatique will decrease strength
TIMBER
SCREW
HOLLOW CORE SLAB
LOCKING PART
FIXING DEVICE
COLD FORMED STEEL PROFILE
FIXING DEVICE
SCREW
NUT&BOLTANCHOR BOLT OR
CHEMICAL ANCHOR
CONCRETE SLAB
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Vibration and sound insulation• Walking 1,6…2,2Hz• Natural frequences are divided in two
classes:– Low frequency floor (f0<8Hz)
• Heavy, long span– High frequency floor (f0>8Hz)
• Light or mid-weight• Resonance should be avoided by
tuning• Passive damping (fixing points)• Active damping (etc. robot equipped
with sensors, regulators and actuators) • Structure-borne (impacts) and airborne
sounds should be avoided • Impact sound level L´n,w<53dB
(residential buildings in Finland)• Sound reduction index (airborne) R
´w>55dB (residential buildings in Finland)
• Robot fixing points and railing systems should be insulated from structure
Free oscillation Free oscillation, damping
Forced oscillation Forced oscillation,
damping
steady-state
steady-state
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Vibration sources and isolation
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Risks
• Overloading and wrong material choises could be fatal and may cause serious damages and even loss of life’s
• Fixing type must be safe and inspected properly
• All fixings should be designed so that they are easy to check and maintain
• Design boundaries should be clear; who is designing and what -> responsibilities
Collapsed spa ceiling in Kuopio, Finland
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Sources• RT 84-10916, Alakatot ja sisäkattoverhoukset• RT 83-10902, Välipohjarakenteita• Betoni Suomessa 1860-1960, Betoniyhdistys ry• Tutkintaselostus B 4/2003 Y, Kylpylän alakaton romahtaminen
Kuopiossa 4.9.2003, Onnettomuustutkintakeskus• Terasrakenneyhdistys.fi//Esdep• wikipedia.org• SFS-EN 1991-1-1• Fastening Technology Manual, Hilti Corporation, 2004• Lattioiden värähtelysuunnittelu, VTT Rakennus- ja
yhdyskuntatekniikka• KSU-3010 Mekaaniset värähtelyt, Luentomoniste, Machine
Dynamics Lab, Tampere University of Technology• Teräsrunkoisten välipohjien värähtelyjen hallinta, VTT
Rakennustekniikka