New "Ply to Ply Connection" Feature Coming in OnLine Plus Version 29
- by Moe Ghaedi -
The upcoming OnLine Plus version 29 will provide the designer with more flexibility in choosing preferred fasteners for ply to ply connection of multi-ply trusses.
Designers will be able to select from choices of 10d, 16d common, or gun nails, and a variety of screws from USP, Simpson, or FastenMaster, and 1/2” Dia. ASTM A-307 bolts as their preferred choice of fasteners for connecting multiple truss plies together. This enhancement also gives the designer the option of using different fasteners for top chord, bottom chords, and webs to maximize efficiency and cost control. For instance, screws can be selected for bottom chord, nails for the webs, and bolts for the top chord. To avoid confusion and provide for easy application and verification of the fastener schedule, the software limits nails to one size for the entire truss. The preferred choice of fasteners can be made at the master level and adjusted as needed at the job level, and finally made truss specific at the truss level if so desired.
Nails versus Screws and Bolts
Large magnitudes of uniform loads can sometimes be difficult to transfer to all plies of the truss depending on the type of fasteners used. This is especially true in cases where nails are used to connect three or more plies with high magnitude loads, since a higher percentage of the load needs to be transferred to the outer plies. In such cases, the OnLine Plus software will automatically alert the designer if the ply to ply connection is inadequate. If ply to ply connection is inadequate using nails, use of screws or bolts are recommended to transfer the load equally to all plies.
Nailing the plies together requires that nails be installed as each layer or ply is applied. This could increase the chance of inadvertently spacing the nails closer in the inner plies than the nailing schedule is called for, thus increasing the risk of damage to the lumber. Also, from the quality assurance perspective, it is difficult to verify the proper nailing since nails in the inner plies cannot be seen.
Screws are inserted from the loaded face of truss and as such their specified spacing can easily be maintained, reducing chances of damage to the lumber. Also, the quality assurance personnel can easily verify proper screw placement.
In most cases, nails are sufficient and most economical to properly transfer loads to all plies of the truss. Screws or bolts can be used as good alternatives if proper load transfer cannot be achieved with nails.
Enhanced Ply to Ply Connection Tool
To choose the enhanced ply to ply connection option, the designer will edit the master level or the job level by going to the Structure àPlies and Ply Connector àSelect Ply Connector from TableàYes.
Once this setting is done at the Master or the Job level, further deviations from selected choices of the fasteners can be made very easily at the Truss level by clicking on the “Change Multi Ply Connection Type” icon found at the bottom of the icon toolbar.
When USP or other screws are selected, proper lengths of screws are automatically selected depending on the number of plies in the truss.
Choosing this option gives the designer more control of selecting the preferred fasteners based on specific design criteria, inventory, availability, and the end user’s specific choice.This enhancement makes the truss design drawings even easier to review and comprehend as it reports the fastener schedule for the selected choices only and removes any redundant and unnecessary references to other fasteners.
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