Double tapered, curved, or pitched-cambered beams

This refers to glulam or LVL beams of a rectangular cross-section whose geometry changes symmetrically along its axis. These can be double tapered, curved, or pitched cambered beams.

The design is checked for bending about the y-y axis, taking into account the effect of local bending, shear, and tensile (perpendicularly to the grain) stresses at the apex, according to Clause 6.4.3.

All references to EN 1995-1-1:2004+A2:2014 unless otherwise stated.

Cross-sectional Inputs tab

Timber strength class

The timber strength class of the cross-section. This design case supports only glulam and LVL classes.

Beam type

The user can selected between double tapered, curved, and pitched cambered beams.

Beam span $l$

The span of the beam, in $mm$.

Width $b$

The width of the cross-section, in $mm$.

Depth $h$

The depth of the cross-section, in $mm$.

Depth $h_{ap}$

The depth of the cross-section at the apex, in $mm$.

Factor $k_{vol}$

The volume factor $k_{vol}$ is required for Kerto-Q LVL where all veneers are not parallel to the beam axis.

Angle of the taper $α_{ap}$

The angle of the taper in the apex zone for a double-tapered or pitched-cambered beam, in degrees.

Angle $β$

The angle of a curved beam in the middle of the apex zone, in degrees.

Inner radius of curvature $r_{in}$

This is the radius of curvature of the beam, measured to the centre of gravity of the beam, in $mm$.

Lamination thickness $t$

The lamination thickness, in $mm$.

Area reduction

The area reduction $ΔA$ refers to reductions in the nominal cross-section size that have to be taken into account in the calculation of the member strength (e.g. holes from fasteners) according to Subclause 5.2(2).

It should be given as a percentage of the total nominal area of the cross-section.

Section modulus reduction

The section modulus reduction $ΔW$ refers to reductions in the nominal cross-sectional modulus that are to be taken into account in the calculation of the member strength (e.g. holes from fasteners) according to Subclause 5.2(2).

It should be given as a percentage of the total nominal section modulus of the cross-section.

Contribution of cross-section size on the determination of member strength properties

Includes factors $k_h$ for the calculation of the member strength in solid timber, glulam and LVL, according to Clauses 3.2, 3.3, and 3.4.

In the case of an LVL member under tension, the member length is also required.

Contribution of the load distribution system in the member strength properties

Includes factor $k_{sys}$ for the calculation of the member strength, according to Clause 6.6, for a member that functions as part of a continuous load distribution system.

Note that Subclause 6.6(3) states that the strength verification for a continuous load distribution system should be carried out assuming short-term load duration.

Loading Inputs tab

Design bending moment $M_{ap,d}$

The design bending moment about the y-y axis in the apex zone, in $kNm$.

Design shear force $F_{V,d}$

The design shear force in the apex zone, in $kN$.

Load duration class

The Load Duration Class, as defined in Clause 2.3.1.2.

Service class

The Service Class, taking into account the temperature and relative humidity of the environment, as described in Clause 2.3.1.3.

$k_{mod}$

Factor $k_{mod}$ taking into account the effect of the duration of the loads and the moisture content, according to Clause 3.1.3.

Fire Design tab

Active

Selects if this cross-section will also be designed against fire.

Cross-section surface

Defines if the cross-section surface is unprotected (exposed to fire on all sides) or is protected (on all sides).

Time of fire exposure t

The time of the exposure of the cross-section to fire, in minutes.

Time $t_{ch}$

The time of exposure of a protected cross-section to fire until it starts to char, in minutes.

Time $t_f$

The time of exposure of a protected cross-section to fire until the protection fails completely, in minutes.

Note that this is can be longer (but not shorter) than $t_ch$.

Factor $k_2$

Factor $k_2$ defines the charring rate of a protected cross-section between the time it starts to char and the time the protection fails completely.

It is required when $t_{ch}$ has a different value to $t_f$.

Theoretical charring rate $β_n$

The theoretical charring rate of the timber, in mm per minute.

It is required for plywood where the relevant standards do not provide a default value.