It is likely that none of this will need to be updated, as the default load magnitudes and rafter spacing are all pulled directly from the Project Defaults. The calculation is pre-filled with the roof loads, snow loads, and wind loads, an example of which is shown on the right. For the purpose of bearing calculations, the supports are assumed to be eclusively on the rafter, not any of the ties. Eaves & Rafter Supports: The length of the eave, equal to the distance between the edge of the rafter and the wall, as well as the bearing length of the wall, are set in one table.Note that, if there are two ties, it does not matter which tie is the "first" or "second", as long as it remains consistent throughout Depth of First/Second Tie: The depth of the collar and/or rafter tie from the roof ridge to the tie.If both are present, then select "Two", otherwise select "One". Number of Ties Present: This refers to collar ties or rafter ties.Note that this module does NOT design the ridge strap itself it is simply assumed that the ridge strap is of sufficient strength to keep the rafters connected at the ridge under any uplift conditions. Ridge Strap Present?: A ridge strap is a metal strap which runs over the top of the roof and connects rafters on either side of the rafter.Roof Pitch: The rise over run pitch of the roof, given in the form of "x:12".This is the horizontal plan length, which will only equal the total rafter length if the roof pitch is zero (flat). Usually, this will be half the width of the roof, from eave to ridge. Rafter Plan Length: The horizontal length of a single rafter. #Roof rafter ties update#The diagram, an example of which is shown to the right, will update dynamically as each of the inputs are set. The first step in using the calculator is to input the overall geometry. Ridge straps are not designed in this module, but may be added to control the uplift separation. However, a ridge strap has no effect upon gravity load scenario of the walls being pushed outward. However, a tie in any position will help in both scenarios.Īlternatively instead of a collar tie, a ridge strap can also be used to keep the rafters from separating at the ridge. A tie located in the bottom third of the roof, usually called a "rafter tie" (and which may also serve a dual purpose as a ceiling joist), is most efficient in preventing the walls from splaying outwards under downward loading.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |