Ceiling structures CEILBOT-PROJECT MID-TERM REPORT, CEILING STRUCTURES A.Aalto, Maison Carré, France Eelon Lappalainen
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 A ceiling is an overhead interior surface that bounds ("ceils") the upper limit of a room. Wikipedia
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, warehouses 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 Situation today
Installations inside the ceiling
Wall material limits the methods for robot route and/or new openings Reinforced concrete Masonry Timber Steel profiles Wall could have several functionalities Load bearing Stiffening wall (wind, earthquake, eccentricity) Fire wall (30 240 min) Partition wall Acoustic wall Walls
Door frame and openings
Sports hall environment Open space demand -> Long spans -> larger deformations Structural geometry (main structure) Trusses Arches Frames Domes Cable structures Airdome / balloon structure Division in main structure and secondary structure Ceiling or/and installations can be suspended from both Secondary structures usually beams, trusses, slabs, steel sheeting Materials Steel Timber (Glue Laminated, Laminated Veneer Lumber) Reinforced concrete (with or without tendons) Cables (high strength steel) System movements (deflection, creep, moisture and temperature deformations) must be noticed for designing installations (etc. Robot railings)
Some sports halls Sports hall in Joensuu Sports hall in Oulu
Basic loads are given in design codes (Eurocode, ACI, DIN, RakMK) Dead load Live load (1,5 10kN/m2) Ceiling weight (~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 Some cases (depends on load type and structure) dynamic loading can be expressed: static load x dynamic factor displacements are limited Complex dynamic problems are usually calculated by FEM Loading
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 allowable stress level TIMBER SCREW COLD FORMED STEEL PROFILE SCREW FIXING DEVICE NUT&BOLT HOLLOW CORE SLAB LOCKING PART FIXING DEVICE CONCRETE SLAB ANCHOR BOLT, CHEMICAL ANCHOR
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 Forced oscillation Free oscillation, damping steady-state steady-state Forced oscillation, damping
Vibration sources and isolation
Risks Overloading and wrong material choises could be fatal and may cause serious damages and even loss of life s Fastener type must be safe and inspected properly All fastenings 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
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