GL28c
Combined glulam: bending 28 MPa, E0,mean 12 500 MPa, ρk 390 kg/m³.
Combined glulam: stronger lamellas in the outer zones, weaker ones inside. Same bending strength as the homogeneous class, lower tension and compression.
All values
- Mechanical 13
- Design values 14
- Physical 2
- Moisture and transport 1
- Thermal 1
- Fire 2
- Chemical and durability not yet
Mechanical
Elastic
Modulus of elasticity parallel to grain E0,mean
Mean value, for deformation calculations.
| Condition | Value | Evidence |
|---|---|---|
| 12 500MPa | Confirmed |
Shear modulus Gmean
Mean value, for deformation calculations.
| Condition | Value | Evidence |
|---|---|---|
| 650MPa | Confirmed |
Modulus of elasticity, 5th percentile E0,05
Parallel to grain. Used for stability (buckling, lateral torsional buckling).
| Condition | Value | Evidence |
|---|---|---|
| 10 400MPacharacteristic | Corroborated |
Modulus of elasticity perpendicular to grain E90,mean
Mean value, for deformations across the grain.
| Condition | Value | Evidence |
|---|---|---|
| 300MPa | Confirmed |
Modulus perpendicular to grain, 5th percentile E90,05
Characteristic value across the grain.
| Condition | Value | Evidence |
|---|---|---|
| 250MPacharacteristic | Corroborated |
Shear modulus, 5th percentile G05
Characteristic shear modulus, for stability checks.
| Condition | Value | Evidence |
|---|---|---|
| 540MPacharacteristic | Corroborated |
Strength
Bending strength fm,k
Characteristic bending strength.
| Condition | Value | Evidence |
|---|---|---|
| 28MPacharacteristic | Confirmed |
Tension parallel to grain ft,0,k
Characteristic tensile strength along the grain.
| Condition | Value | Evidence |
|---|---|---|
| 19.5MPacharacteristic | Confirmed |
Compression parallel to grain fc,0,k
Characteristic compressive strength along the grain.
| Condition | Value | Evidence |
|---|---|---|
| 24MPacharacteristic | Confirmed |
Shear strength fv,k
Characteristic shear strength.
| Condition | Value | Evidence |
|---|---|---|
| 3.5MPacharacteristic | Corroborated |
Tension perpendicular to grain ft,90,k
Characteristic tensile strength across the grain; small, so details avoid it.
| Condition | Value | Evidence |
|---|---|---|
| 0.5MPacharacteristic | Confirmed |
Compression perpendicular to grain fc,90,k
Characteristic compressive strength across the grain: governs bearing at supports.
| Condition | Value | Evidence |
|---|---|---|
| 2.5MPacharacteristic | Corroborated |
Rolling shear strength fr,k
Shear in the plane across the grain (fibres rolling over each other).
| Condition | Value | Evidence |
|---|---|---|
| 1.2MPacharacteristic | Corroborated |
Design values
Modification factor for load duration and moisture kmod
Multiplies characteristic strength: fd = kmod · fk / γM. Wood is weaker under long-lasting loads and when wet.
| Condition | Value | Evidence |
|---|---|---|
| 0.6 | Single source | |
| 0.5 | Single source | |
| 0.7 | Single source | |
| 0.55 | Single source | |
| 0.8 | Single source | |
| 0.65 | Single source | |
| 0.9 | Single source | |
| 0.7 | Single source | |
| 1.1 | Single source | |
| 0.9 | Single source |
Deformation factor (creep) kdef
Final deformation = instantaneous × (1 + ψ2 · kdef) for quasi-permanent loads.
| Condition | Value | Evidence |
|---|---|---|
| 0.6 | Single source | |
| 0.8 | Single source | |
| 2 | Single source |
Partial factor for the material γM
Recommended value; each country may set its own in the National Annex (a Nationally Determined Parameter).
| Condition | Value | Evidence |
|---|---|---|
| 1.25 | Single source |
Physical
Characteristic density ρk
5th-percentile density.
| Condition | Value | Evidence |
|---|---|---|
| 390kg/m³characteristic | Confirmed |
Mean density ρmean
Mean density.
| Condition | Value | Evidence |
|---|---|---|
| 420kg/m³ | Corroborated |
Moisture and transport
Swelling and shrinkage across the grain αu,90
Change in cross-section dimension per 1 % change in moisture content.
| Condition | Value | Evidence |
|---|---|---|
| 0.24% per % moisture | Single source |
Thermal
Thermal conductivity λ
Heat flow through 1 m of material per kelvin of temperature difference.
| Condition | Value | Evidence |
|---|---|---|
| 0.13W/(m·K) | Single source |
Fire
One-dimensional charring rate β0
Charring depth per minute of standard fire exposure on one face.
| Condition | Value | Evidence |
|---|---|---|
| 0.65mm/min | Single source |
Notional charring rate βn
Includes the effect of corner rounding and fissures; used with the reduced cross-section method.
| Condition | Value | Evidence |
|---|---|---|
| 0.7mm/min | Corroborated |
Sources here are public pages that reproduce EN 14080:2013. For design and acceptance, the standard edition named in your specification and the CE marking and Declaration of Performance of the delivered product take precedence. Design factors are recommended values; your National Annex may set others.