A Comparison of Design, Construction and Dynamic Performance of Timber Floors in the UK and Finland - STSM of COST Action E55 - Host: Dr. Tomi Toratti Host Institution: - Technical Research Centre of Finland Visiting Scientist: Jan Weckendorf Home Institution: - Napier University Edinburgh Proposer: Dr. Binsheng Zhang Duration: 05 - 29 October 2007
Contents of presentation • Background • Objectives of STSM • Undertaken research • Conclusions
Background of research on floor vibration Lightweight flooring structures easily get excited and start to vibrate: • Occupants may get annoyed by excessive floor vibrations; • Current design rules do not satisfactorily control floor vibrations; • Design rules are not fully harmonised within EU.
Main research background as basis for STSM • VTT: - rating of vibration performance - classification of flooring structures - modification of design criteria • Napier University: - parametric studies on timber floor design - determination of the effects of (non-)structural modifications - prediction of floor performance by FE-method
Objectives of STSM in line with those of COST Action E55 Improving the understanding with respect to: • Serviceability • Design criteria • Construction details
Design criteria Serviceability Limit States (SLS) in Eurocode 5 Country Low-frequency floor High-frequency floor Condition Guidance Condition Guidance 1) Limiting unit point load deflection w * UK (based f 1 ≤ 8 Hz N/A f 1 > 8 Hz 2) Limiting unit impulse on EC5) velocity response v Limiting unit point f 1 ≥ 9 Hz FI (NA) f 1 < 9 Hz N/A load deflection δ * Formula not provided in EC5
Design criteria Country Fundamental Point load Velocity frequency deflection response " For a rectangular floor [...], simply supported along all four edges [...] " (EC5-1-1): UK π ( EI ) f = l 1 2 2 m l EC5 FI (NA)
Design criteria Country Fundamental Point load Velocity frequency deflection response " For a rectangular floor [...], simply supported along all four edges [...] " (EC5-1-1): UK π ( EI ) f = l 1 2 2 m l EC5 for 2-side supported floors: π ( EI ) f = l 1 2 2 m l FI (NA)
Design criteria Country Fundamental Point load Velocity frequency deflection response " For a rectangular floor [...], simply supported along all four edges [...] " (EC5-1-1): UK π ( EI ) f = l 1 2 2 m l EC5 for 2-side supported floors: π ( EI ) f = l 1 2 2 m l FI (NA) for 4-side supported floors: ⎡ ⎤ 2 4 π ( EI ) ( EI ) ⎛ l ⎞ ⎛ l ⎞ f = ⋅ 1 + 2 ⋅ ⎜ ⎟ + ⎜ ⎟ ⋅ b l ⎢ ⎥ 1 2 2 m b b ( EI ) l ⎝ ⎠ ⎝ ⎠ ⎢ ⎥ ⎣ ⎦ l
Design criteria Country Fundamental Point load Velocity frequency deflection response " For a rectangular floor [...], simply supported along all four edges [...] " 3 k 1000 L k (EC5-1-1): dist eq amp w = UK 48 ( EI ) π ( EI ) joist f = l 1 2 2 m l UK NA EC5 for 2-side supported floors: π ( EI ) f = l ⎧ F 2 l 1 2 2 m l ⎪ FI (NA) ⎪ 42 ⋅ k ⋅ ( EI ) δ = min δ � � ⎨ l 3 F l ⎪ for 4-side supported floors: ⎪ ⋅ s ⋅ EI 48 ( ) ⎩ l ⎡ ⎤ 2 4 π ( EI ) ( EI ) ⎛ l ⎞ ⎛ l ⎞ f = ⋅ 1 + 2 ⋅ ⎜ ⎟ + ⎜ ⎟ ⋅ b l ⎢ ⎥ 1 2 2 m b b ( EI ) l ⎝ ⎠ ⎝ ⎠ ⎢ ⎥ ⎣ ⎦ l
Design criteria Country Fundamental Point load Velocity frequency deflection response " For a rectangular floor [...], simply supported along all four edges [...] " ( ) 3 k 1000 L k 4 0 . 4 + 0 . 6 n (EC5-1-1): v = 40 dist eq amp w = UK m L B + 200 48 ( EI ) π ( EI ) joist f = l 1 2 2 m l UK NA EC5 EC5 for 2-side supported floors: π ( EI ) f = l ⎧ F 2 l 1 2 2 m l ⎪ FI (NA) ⎪ 42 ⋅ k ⋅ ( EI ) δ = min δ � � ⎨ l N/A 3 F l ⎪ for 4-side supported floors: ⎪ ⋅ s ⋅ EI 48 ( ) ⎩ l ⎡ ⎤ 2 4 π ( EI ) ( EI ) ⎛ l ⎞ ⎛ l ⎞ f = ⋅ 1 + 2 ⋅ ⎜ ⎟ + ⎜ ⎟ ⋅ b l ⎢ ⎥ 1 2 2 m b b ( EI ) l ⎝ ⎠ ⎝ ⎠ ⎢ ⎥ ⎣ ⎦ l
Design limits and thresholds Country Fundamental Point load deflection Velocity frequency response 1.8 mm/kN for l ≤ 4000 mm UK f 1 > 8 Hz 16500/ l 1.1 mm/kN for l > 4000 mm ⎧ ( EI ) 4 b ⎪ ⎪ mm/kN for l ≤ 6000 mm ( EI ) 0 . 5 × min ⎨ l b ⎪ FI f 1 ≥ 9 Hz ⎪ ⎩ l 0.5 mm/kN for l > 6000 mm An additional 0.5 mm deflection can be allowed in case of floating and raised floors
Design limits and thresholds Country Fundamental Point load deflection Velocity frequency response 1.8 mm/kN v ≤ b ( f 1 ζ - 1) for l ≤ 4000 mm UK f 1 > 8 Hz where ζ = 0.02 16500/ l 1.1 mm/kN for l > 4000 mm (EC5: ζ = 0.01) ⎧ ( EI ) 4 b ⎪ ⎪ mm/kN for l ≤ 6000 mm ( EI ) 0 . 5 × min ⎨ l b ⎪ FI f 1 ≥ 9 Hz N/A ⎪ ⎩ l 0.5 mm/kN for l > 6000 mm An additional 0.5 mm deflection can be allowed in case of floating and raised floors
Summary of design criteria • British design criteria - based on EC5 - deflection criterion defined in UK NA - damping ratio doubled in UK NA • Finnish design criteria - EC5 criteria revised by adopting own NDPs - assessment based on deflection and frequency only - frequency threshold 12% above the EC5 threshold
Test floors The Finnish test floor (6.0 m x 4.3 m) • Laminated Veneer Lumber (LVL) joists (600 mm spacing) • LVL blocking • Tension bar • Glue and screws • Concrete screed on top of mineral wool isolation layer • Four-side supported
Test floors The British test floor (3.5 m x 2.44 m) • I-joists (400 mm spacing) • Screws • Particleboard deck • Two-side supported
Summary of differences in common construction practices Material Finnish floors British floors Joist types LVL/Solid timber joists I-joists Fasteners Glue and screws Screws mainly Deck Plywood + Wood based panels (sometimes) concrete mainly screed
Investigation of design criteria • Finnish flooring structure at two design stages - without concrete screed and isolation layer - completed (with concrete screed) • British flooring structure (completed)
Investigation of design criteria Assessing floor performance using Finnish and British rules • Fundamental frequency calculated twice, without and with partial/full composite action • Other parameters calculated under consideration of composite action • Results (columns) presented in blue regarding the Finnish criteria and in violet regarding the British criteria
Investigation of design criteria Finnish flooring structure at the two design stages Fundamental frequency 30 30 Design to Finnish NA Design to Finnish NA 28 28 Design to EC5 incl. UK NA Design to EC5 incl. UK NA 26 26 24 f 1, meas = 24.00 Hz 24 22 22 Frequency f 1 [Hz] Frequency f 1 [Hz] 20 20 18 18 16 16 14 14 f 1, meas = 12.00 Hz 12 12 10 10 FI NA FI NA 8 EC5 threshold 8 EC5 threshold 6 6 4 4 2 2 20.68 20.63 28.30 25.88 10.81 8.77 13.41 10.87 0 0 no composite action full composite action no composite action full composite action Without concrete screed With concrete screed
Investigation of design criteria Finnish flooring structure at the two design stages Fundamental frequency 30 30 Design to Finnish NA Design to Finnish NA 28 28 Design to EC5 incl. UK NA Design to EC5 incl. UK NA 26 26 24 f 1, meas = 24.00 Hz 24 22 22 Frequency f 1 [Hz] Frequency f 1 [Hz] 20 20 18 18 16 16 14 14 f 1, meas = 12.00 Hz 12 12 10 10 FI NA FI NA 8 EC5 threshold 8 EC5 threshold 6 6 4 4 2 2 20.68 20.63 28.30 25.88 10.81 8.77 13.41 10.87 0 0 no composite action full composite action no composite action full composite action Without concrete screed With concrete screed
Investigation of design criteria Finnish flooring structure at the two design stages Fundamental frequency 30 30 Design to Finnish NA Design to Finnish NA 28 28 Design to EC5 incl. UK NA Design to EC5 incl. UK NA 26 26 24 f 1, meas = 24.00 Hz 24 22 22 Frequency f 1 [Hz] Frequency f 1 [Hz] 20 20 18 18 16 16 14 14 f 1, meas = 12.00 Hz 12 12 10 10 FI NA FI NA 8 EC5 threshold 8 EC5 threshold 6 6 4 4 2 2 20.68 20.63 28.30 25.88 10.81 8.77 13.41 10.87 0 0 no composite action full composite action no composite action full composite action Without concrete screed With concrete screed
Investigation of design criteria Finnish flooring structure at the two design stages Fundamental frequency 30 30 Design to Finnish NA Design to Finnish NA 28 28 Design to EC5 incl. UK NA Design to EC5 incl. UK NA 26 26 24 f 1, meas = 24.00 Hz 24 22 22 Frequency f 1 [Hz] Frequency f 1 [Hz] 20 20 18 18 16 16 14 14 f 1, meas = 12.00 Hz 12 12 10 10 FI NA FI NA 8 EC5 threshold 8 EC5 threshold 6 6 4 4 2 2 20.68 20.63 28.30 25.88 10.81 8.77 13.41 10.87 0 0 no composite action full composite action no composite action full composite action Without concrete screed With concrete screed
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