Some form of structure to provide lateral stability to the rafters is required, whether it is herringbone bracing or blocking with SmartJoist panels. There is not a requirement to have rigid blocking for the transfer of heavy point loads through the roof.
Yes, provided that the nailing is carried out in such a fashion that each adjacent nail is slightly skewed so that they do not go into the LVL flanges of the SmartJoist in a perfectly straight line. (See page 11 of the SmartJoist Design Guide)
View these small holes as one large hole. Group the holes so that one large circular or rectangular hole encompasses the individual small holes, and use the dimensions of this large hole for checking the holes charts or by analysis using SmartFrame.
It depends on whether the blocking carries vertical load. If so, do NOT cut any holes larger than 40mm, or use cripples (squash blocks) if a larger hole is unavoidable. If not, such as in roof blocking for stability only, then larger holes may be cut.
This varies from application to application, but the best advice would be to use SmartFrame Software. Cut as few holes as possible. One large hole for several wires and/or pipes is usually preferable to several smaller holes.
Yes. The only limitation is the 450mm spacing between holes.
Shear determines the allowable hole size and shear is carried mainly by the web. This is why larger holes must be placed closer to mid-span, where shear is typically lowest.
Concentrated or Point loads such as wall and roof loads are not allowed directly over a hole.
For square or rectangular holes, Yes. There are two reasons: Firstly, the sharp corners of a rectangular hole create stress concentrations that lead to cracks developing at these points, typically at opposite corners. Secondly, a square hole of the same dimension as a circular hole, requires the removal of more web. To visualise this, draw a 150mm square. Then draw a 150mm circle within the square. You can see the difference. In mathematical terms, a 150mm square has an area of 22,500 square mm, while a 150mm circle has an area just slightly more than 17,671 square mm. The result is 21% less web removed for the circular hole.
Round holes do not need to be centered within the web. Simply Maintain a 6mm minimum clearance from the flange. This will allow you to add the required slope for drain lines.
In most cases, NO.
Generally, YES. Subject to the normal structural requirements of joists. There are specific models within SmartFrame to deal with this situation.
NO!, they have been designed to be supported by their bottom flange with a minimum of 30mm bearing. A comprehensive range of joist hangers are available to support the joists in most situations, otherwise use a piece of unequal angle as shown in detail F27 of the SmartJoist Design Guide.
Generally NO. If you consider the I-Joist like a truss, or better still, like a ladder, the top and bottom flanges representing the stringers and the web representing the rounds, would you stand on a ladder which had some of the outside stringers removed? The SmartJoist design guide, however, allows the limited notching of the flanges at supports subject to the strict criteria shown under the heading “Limited End Notching At Supports”.
The web of SmartJoists can be notched under certain circumstance when connecting to a steel beam. This must be done strictly as per detail F18 of the SmartJoist Design Guide.
For more detailed information on this matter, contact the SmartData Customer HelpLine on 1300 668 690.
The SmartFrame engineered products are kiln dried timber products of durability class 4 wood fibre. This means that they can be exposed to the elements for short periods of time (up to 3 months), typically during the normal construction period of a dwelling without any ill effects. If there is any reason to store them for extended periods they should be either stored inside or under a water proof cover, up off the ground on bearers or gluts. The OSB web of the SmartJoist is specifically manufactured with a wax additive which repels water very effectively, so is less effected by water than the thin veneers of any LVL material.
In most cases, NO. Midspan joist blocking has been included within the AS1684 codes for several reasons, namely:
- A measure to control warping and twisting of solid green timber joists
- To prevent joist rollover during construction and to maintain position
- An attempt to control adverse floor dynamics issues
With the advent of engineered timber products, most of these requirements which are related to green timber joists are no longer necessary. The introduction of sophisticated computer analysis software such as SmartFrame, gives engineers a powerful tool to better understand the complex issues of floor dynamics. Consequently, joists designed with the SmartFrame system have been analysed to ensure that their dynamic response falls within the guidelines of the AS1684-1999 Residential timber-framed construction Code. Notwithstanding the above, the “About Floor Performance” page within all the SmartFrame Design Guides gives an expanded discussion on the above topic and outlines some measures to ‘improve’ the floor dynamic performance above the code minimum recommendations.
Detail F3 gives the basic requirements for using SmartRim.
There are three (3) methods of blocking SmartJoists detailed within the SmartJoist Design Guide.
- Detail F1: SmartJoist blocking panels – SmartJoist panels of the same size as the SmartJoist floor joists cut to fit between the joists, nailed as per #1 of “General Notes For The Installation of SmartJoists” within the SmartJoist Design Guide.
- Detail F2: SmartJoist rim Joist – SmartJoist panels of the same size as the SmartJoist floor joists run on top of the joist support, with the SmartJoists butting into it. (Note: The SmartJoists require at least 30mm bearing length, so this method is only suitable where there is sufficient width of the support to accommodate the 30mm bearing length and the width of the SmartJoist rim joist.)
- Detail F3: SmartRim of the same depth as the SmartJoist and run on top of the joist support, with the SmartJoists butting into it. This is to be nailed as per #2 of “General Notes For The Installation of SmartJoists” within the SmartJoist Design Guide.
The minimum end bearing for the SmartJoist is 30mm if the SmartJoist is fully loaded. If there is a special requirement for a lesser end bearing length, contact the SmartData Customer HelpLine at email@example.com or 1300 668 690. The bearing length over an internal support is usually less critical, however, if very heavily loaded, joists are to be supported upon a very narrow internal support beam (less than 45mm width), further advice should be sought from the SmartData Customer HelpLine.
The end bearing length is the distance that the member extends past the face of the support on the support structure. For a simple experiment, take a ruler and place one end of it off the edge of the desk with only 50mm of it left supported. As this ruler sits onto the desk for 50mm of its length, you would describe it as having a 50mm end bearing length.
End blocking is the addition of timber bracing panels to the end of joists at their supports to provide 3 very important functions:
- Provide Lateral (horizontal) stability from wind and other horizontal (Racking) loads
- Provide additional vertical load capacity for the ends of the joists from point loads above
- Maintain the stability and accurate position of the joists during construction
It is of vital importance that the building designer understands the difference between ‘during construction blocking’ and ‘joist end blocking’ as a vital component of the overall lateral stability of the structure. Some engineered product design manuals do not make this distinction clear, with many users only specifying the minimal blocking of joists on exterior load bearing walls as necessary to provide ‘during construction’ blocking. They are unfortunately assuming in error that this level of blocking of the joists has also been designed to provide the necessary lateral stability of the whole structure. WRONG; the requirements for ‘during construction ‘ blocking (1 block every 1.8m etc) DOES NOT necessarily mean you have satisfied the requirements for racking loads (Lateral stability).
If you do the sums and work out how many blocks are actually needed to provide all the requirements of vertical load transfer and racking loads, you find that most, if not all, of the ends need to be blocked anyway. The simple SmartFrame recommendation is to block all the ends of joists onto exterior load bearing walls, and THUS satisfy ALL the requirements in one go.
The user is required to correctly identify the member’s intended use within any structure, and then select the required spans, spacing, load widths and any other loading requirements requested within the model. All models within SmartFrame replicate the standard models as contained within AS1684-1999.