EN 1995-2 Timber Bridges - standard.no anlegg og eiendom/2018... · timber bridges 2. Protection...
Transcript of EN 1995-2 Timber Bridges - standard.no anlegg og eiendom/2018... · timber bridges 2. Protection...
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EN 1995-2 Timber Bridges
Oslo May 2. 2018
CEN TC250 SC5
WG6 (Convenor Kjell Arne Malo)
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Topics with Priority
• Issues not covered in EN 1995-1-1 Buildings
1. Fatigue loading and resistance
2. Prestressed laminated timber deckplates (stress-laminated)
3. Durability, Detailing and Water Management
4. Timber-Concrete Composites bridges
5. Pedestrian bridges and human induced vibrations
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1. Fatigue, resistance
-1 0 1 2 3 4 5 6 7 8
Log N
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
f ma
x
R=0.1
Multiple dowel
connection axially
loaded
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Effect of stress ratio (or mean stress)
Source Type of loading RA
(experimental)
A
(EN1995-2)
Malo et al
(2006)
Dowelled
connections (Nordic
Pine glulam)
0.1 0.066 0.079
-1 0.098 0.111
Malo et al (2006)
ത𝜎𝑚𝑎𝑥 ≈ 1 − 𝐴 ∙ log10𝑁
Introduction · European Standards · Fatigue lives of WBP/Connections · Deformation/Damage - Conclusions
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Stress range vs max stress
• Steel – stress range:
𝛾𝐹𝑓Δ𝜎𝐸,2 ≤Δ𝜎𝑐
𝛾𝑓
• Wood – max stress:
𝜎𝑑,𝑚𝑎𝑥 ≤ 𝑘𝑓𝑎𝑡 ∙𝑓𝑘
𝛾𝑀,𝑓𝑎𝑡
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Fatigue life – mean stress, stress ratio
• Stress and Strength based on stress range
• implies
– Strength independent of mean stress (or R)
𝜎𝑚𝑒𝑎𝑛 =1
2𝜎𝑚𝑎𝑥 + 𝜎𝑚𝑖𝑛 =
1
2𝜎𝑚𝑎𝑥 1 + 𝑅
𝑅 = Τ𝜎𝑚𝑖𝑛 𝜎𝑚𝑎𝑥
1
2 1mean
R
R
Δ𝜎 = 𝜎𝑚𝑎𝑥 − 𝜎𝑚𝑖𝑛
σa =1
2𝜎𝑚𝑎𝑥 − 𝜎𝑚𝑖𝑛 =
1
2𝜎𝑚𝑎𝑥 1 − 𝑅
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𝜅 =𝜎𝑑,𝑚𝑎𝑥 − 𝜎𝑑,𝑚𝑖𝑛
𝑓𝑘𝛾𝑀,𝑓𝑎𝑡
≤ 𝜅𝑙𝑖𝑚
Type of loading or joint Limit value of ratio κ
members in compression parallel or
perpendicular to grain0.60
members in bending or tension 0.20
members in shear 0.15
connections with dowels 0.40
connections with nails 0.10
other connections 0.15
𝜎𝑑,𝑚𝑎𝑥 ≤ 𝑘𝑓𝑎𝑡 ∙𝑓𝑘
𝛾𝑀,𝑓𝑎𝑡
𝑘𝑓𝑎𝑡 = 1 −1 − 𝑅
𝑎 ∙ 𝑏 − 𝑅∙ log10 𝑁
Type of loading or connections a b
Compression parallel or perpendicular to
grain2.0 9.0
Bending or tension 9.5 1.1
Shear 6.7 1.3
Connections with dowels (d ≤ 12 mm) 6.0 2.0
Connections with nails 6.9 1.2
Unlimited fatigue strength if:
Fatigue life assessment (S-logN):
𝐴 =1 − 𝑅
𝑎 ∙ 𝑏 − 𝑅Slope of S-logN line:
Fatigue verification according to EN 1995-2 (informative)
ത𝜎𝑚𝑎𝑥 = 1 − 𝐴 ∙ log10 𝑁
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“Cyclic” Fatigue,
wood is anisotropic material
• Different slopes
of S- logN curves
for different:
– fastener types
– stress situation
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WOOD
Slope of the fatigue curves: Depends on R
ത𝜎𝑚𝑎𝑥 ≈ 1 − 𝐴 ∙ log10 𝑁
𝐴 =1 − 𝑅
𝑎 ∙ 𝑏 − 𝑅
𝑅 = Τ𝜎𝑚𝑖𝑛 𝜎𝑚𝑎𝑥
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“Static” Fatigue
• Interaction ?
– Static fatigue
(strength
reduction with
duration of
load (DOL)
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Fatigue strength
• Interaction ?
– Static fatigue (DOL: Duration Of Load)
– Cyclic fatigue (Number of cycles)
• Models for interaction ?
– Linear like Miner Palmgren
– Nonlinear incremental damage model
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Fatigue and load models timber bridges
• Effect of mean stress and Load models in EN 1991-2?
• Load combination, cyclic and static fatigue?
• Mean stress or stress ratio?
• How to count and combine different stresses and
cycles?
– Rainflow or similar methods
– Miner Palmgren?
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2. Prestressed laminated timber
deckplates (stress-laminated)
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Stress laminated decks
• Functional requirements of systems
• Special effects:
– Prestressing and long term properties
– Friction
– Computations
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3. Durability, detailing and water
management
Timber Bridge buillt 1988
DEMOLISHED
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Trondheim, Norway
• Buillt 1861
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Durability and detailing
1. Water management on covered or non-covered
timber bridges
2. Protection and preventive measures for weather or
humidity exposed constructions
3. Ventilation measures for dehumidification of timber
bridges
4. Monitoring and maintenance of timber bridges
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Wooden bridge decks – edge details
• Stress-laminated timber decks
• Asphalt wearing surface on top
• Waterproof layer
• Edge details
• Ventilated panels along sides
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4. Timber Concrete Composite Bridges
• General rules in buildings (in-house)
• Add bridge specific parts
– Weather exposed structures (moisture, creep)
– Fatigue
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5. Pedestrian bridges and human
induced vibrations
• General Requirements in EN 1990
• General Pedestrian Load models in EN1991-2
• Guidelines for calculation of fundamental frequencies in
EN 1995-2 Timber Bridges
• Damping Properties in EN 1995-2 Timber Bridges