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3. Laminated Timber Curved Beams

CURVED BEAMS

The flexibility of Glulam beams allows for the designers creative

imagination to be realised. Factory made members can be formed

into any practical shape and any desired size.

It is important to bear in mind that best economics are achieved

by using maximum radius thus permitting thicker laminates (see

table).

CRANKED BEAMS

These beams follow the roof pitch on their top edge while the

bottom forms a radius curve. Cranked beams taper from the

tangent point to a minimum end depth to provide maximum

economy. They may be simply supported on timber or concrete

posts.

CONTINUOUS CURVES

Beams curved throughout their length provide consistent shapes

for dome roofs and other complex forms. Elliptical or regular

curvatures can be achieved. Connection details can be included

making for simple on site assembly.

COMPLEX CURVES.

Beams that move from straight line into a curved section or from

one radius to another, even reverse curves can be easily catered

for in glulam beams. The thickness of the laminates will be

governed by the tightest curvature. These members enable

unique shapes to be formed that would not be possible in other

materials.

INVERSE CURVES

Upward curving beams provide a popular variation and can bemade to form inverted arches. These beams can taper through

their length to cater for highly stressed areas. Care should be

exercised in requesting a continuous lamination on the

undersurface if this is required for appearance.

Lamin

atedTimberCurvedBeams

3

14m span reverse curve beams

Cranked roof beams Elliptical curved beams

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Laminated Timber Curved Beams

FEATURES

Aesthetics - Curved members in natural wood provide a

structural system that would otherwise require camouflaging or

disguising. Staining Glulam beams can bring added contrast to

highlight the chosen ceiling form.

Pre-Fitting - Glulam members can be pre-fitted in factory so that

once on site the members and their connecting brackets need only

to be assembled. Complex angles, raking joints and circular

compression ring fittings are all able to be supplied and pre-

assembled saving valuable on-site labour and craneage costs.

Ease of Installation - Light, dry, timber beams arrive on site

ready for speedy installation. Glulam members are confidently

handled by carpenters and sub contractors. They require no

specialist erection techniques.

Fire Resistance - For superior fire resistance ratings of Glulam

beams see Data Sheet 1 - Laminated Timber General.

Table: Minimum Radius of Curvature

Net thickness Member with Member with

of laminations constant curvature tangent ends

Thickness (mm) Radii (mm) Radii (mm)

10 1400 1200

13 2200 1800

16 3000 2300

19 3800 2800

45 12000 9700

Nothing contained in this material shall be construed as a

warranty or otherwise as to the accuracy or safety of the

information provided. Specific design work should be carried out

by qualified engineers.

SPECIFICATION

For specification see details on Data Sheet 1 - Laminated Timber

General.

Dimensions - Notching or cutting and drilling especially to edges

and surfaces will reduce the design strength. Advice should be

sought before cutting into beams.

PRELIMINARY DESIGN PROCEDURE FOR CRANKED

OR CURVED BEAMS

Cranked or curved beams are adaptable to a variety of roof

pitches. Curvature, degree of taper and ratio of rise to span

influence the economics of design of these members. For

preliminary planning and estimating purposes the following

general design procedure may be used to select sections for

cranked or curved beams. This procedure should be used for

preliminary design purposes only. In all cases, the data is subject

to specific design requirements of local building codes or special

conditions. A complete design check should be made in

accordance with NZS 3603.

1. Determine minimum end depth (de) based on allowable shear

stress rather than using centreline depth (dc) and roof pitch.

2. Estimate centreline depth (dc) to be 1.15 times the depth

required for a constant cross section beam designed to carry

the same load.

3. Analyse the trial section for allowable bending stress and

interaction stress.

4. Using depths verified in step 3 and the known roof slope, lay

out the beam to scale. Scribe in the radius (R) of the soffit using

a minimum radius as shown in table.

5. Scale the centreline depth (dc) and compute the approximate

radial tension stress using the formula:

frt = 3M where R = radius of curvature of

2bdcR neutral axis at centreline.

Design information for structural laminated timber is fully

contained in NZS 3603 Chapter 8.

Quality Control - McIntosh Timber Laminates are licensed

manufacturers under AS/NZS 1328 Licence No.2061. We also hold

Licence No.2354 under finger jointing code AS/NZS1491. Regular

in-factory quality control is carried out in conformance with these

Standards and also as required by the NZ Timber Certification

Board. Conformance to AITC, BS and AS Standards are achieved.

MCINTOSH TIMBER LAMINATES SERVICE

1. Free cost estimates on all types of Glulam.

2. Experienced advice on suitability of Glulam design options,

sizing and connections to meet clients particular need.

3. Full engineering design and drawing facilities can be provided if

required.

4. Complete building packages including design, manufacture,

supply of all connections and components, and installation

supervision is available.

5. Close liaison and client satisfaction are high priorities in

McIntosh Timber Laminates personal service.

McIntosh Timber Laminates Limited

9 Bostock Place, East Tamaki. PO Box 14 604, Panmure, Auckland, New Zealand.

Telephone: 64-9-273 2888 Facsimile: 64-9-273 2880

email: sales@mcintosh.co.nz

website: www.mcintosh.co.nz

AS/NZS 1491

LIC. No. 2354

AS/NZS 1328

LIC. No. 2061