Effects that can only be achieved by the versatility of Glulam are available using TimberLab’s Curved Knee Portals. These members represent the ‘top of the line’ in portal construction. Their laminations run continuously from base to pinned apex and give a clean sweeping appearance.
Benefits / Features
Appearance – No external plates or gussets clutter the continuity and beauty of the natural timber grain. The natural warmth and softness produced will add to the pleasant atmosphere of any building. Colour staining of portals to contrast with sarking or ceiling further highlights appearance advantages.
Variety of shape -An extensive variety of shape and pitch is possible using curved Glulam portals. Tapering of column and rafter sections allows shaping to take advantage of lesser stressed areas at base and apex. Clerestory roof section and eave cantilevers may all be catered for in TimberLab’s Curved Knee Portals.
Knee Curve – Radius of curvatures sets the lamination thickness requirement and therefore influences costs. The thinner the laminate, the greater the cost. For minimum radii of curvature, see table.
Simplicity – All base and apex fittings can be pre-fitted in our factory. On-site assembly simply means fixing of pre-fitted members, lowering portal halves into position and securing apex joint.
Reverse Curve – An elegant “swan neck” sweep is provided with this style of portal. The continuous laminations are curved in two directions. This most attractive portal has been used in churches and halls.
Open Knee – This style allows the curved knee section to follow a parallel form through the curve. Many school halls and swimming pools feature this type of portal.
Solid Knee – The gap left between the curved knee section in the open knee portal and the upper wall and roof line is eliminated in this style. The shape of this portal follows the wall and roof profile on the top side, while giving a sweeping curve on the inside.
Site Assembly – Members arrive on site in the form of half portals; with the use of a mobile scaffold to support the apex. Erection is quickly achieved by lifting the half portals into position onto holding down bolts and aligning the simple bolted apex joint. An average of 6 to 10 portals can be fully erected in a working day. Each frame can be temporarily braced longitudinally so that a secure structure is available for cladding and roofing.
With the convenience of nailing directly to the timber frames, no specialist labour is required.
Table - Minimum Radius of Curvature
|Lamination Thickness (mm)||Member with Constant - Radius (mm)||Member with Tangent ends - Radius (mm)|
Indicative Span Tables
|Span (m)||Spacing (m)||
Light Roof & Ceiling
LL=0.25kPa Tangent Depth
Heavy Roof & Ceiling
LL=0.25kPa Tangent Depth
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. Design information for structural laminated timber is fully contained in NZS 3603, chapter 8.