Wind produces horizontal (racking) loads on buildings that must be transmitted through the structure to the foundation. In a conventionally constructed house these loads are transmitted to the ground by a complex interaction between the roof, floor, wall and the ceiling frames. This interaction requires each of the frames to be connected appropriately, creating a continuous link to enable load transfer.
The connection between the truss bottom chords (ceiling frame) and non-loadbearing bracing walls is critical to preserving the continuous link. Although this connection has been often overlooked in the past, building surveyors are now increasingly becoming aware of its importance and has found its way into their frame check lists.
The Pryda Shear Connector (PSC) has been especially developed to facilitate the connection between the truss bottom chords and non-loadbearing internal bracing walls. A pair of PSC can be used as a direct substitute for a pair of nail fixed timber shear blocks as specified in Table 8.22 AS1684.2:2006 and AS1684.3:2006.
The effectiveness of more traditional timber shear blocks is reliant on how well they are fixed, which is seldom appreciated by carpenters on site. The fixing of shear blocks are often inconsistent or incorrect, which could result in the bracing panels being rendered useless. Also, fixing shear blocks too tightly against the truss bottom chord could hinder the free vertical movement of the truss, resulting in possible unevenness in the ceiling.
PSC has several advantages over the timber shear blocks and other alternative brackets. The advantages include:
· Can be installed with collated nails rather than hand driven nails only;
· More reliable as the alternative ‘short’ timber shear blocks are prone to splitting,
· No messing about having to hand drive nails into the corner holes of alternate brackets;
· Greater flexibility as they can be used with any truss bottom chord or ceiling joist thickness, including multi laminated trusses;
· Easy to fit, as they are not controlled by a specific timber thickness, and therefore oversized or swollen timbers can be handled without fuss;
· Long term performance is not affected should the nails have been overdriven;
For more information on Pryda’s Shear Connector, contact the Pryda Design office on 1800 810 741.