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Fastener information is entered for deflection calculations only, it has no impact on hold-down capacity.
Horizontal Fasteners (slippage)
This group pertains to the horizontal fasteners connecting hold-down bracket or strap to the wall end studs. This group is not active when full assembly displacement is specified (combined elongation and slippage), as the fastener information is not needed in this case.
Bolts
Bolts are used to attach bracket or strap to wall stud. Slippage is determined by formula in NDS 10.3.6, = 270,000 x D^1.5, where D is bolt diameter, plus bolt hole tolerance as input in the Hold-down Settings.
Bolts are assumed to extend through the stud (i.e. not lag bolts).
Nails
Common wire nails are used to attach bracket or strap to wall stud. Slippage is determined by SDPWS Table C4.2.2D, using the values for wood structural panels.If the force Vn on each nail is greater than the maximum allowed, then the program uses the slippage over-ride value in this dialog instead of the calculated value. A warning note in the Hold-down Displacement table indicates when this occurs.
Diameter
Shank diameter of bolt or nail – can select from list or enter custom size.
Number
Number of fasteners connecting one bracket or strap to wall end stud on upper and/or lower level.
Vertical Bolt ( add’l elongation)
This group pertains to bolted, threaded rod or anchor bolt attaching the brackets to each other or one bracket to the foundation or some other anchoring mechanism.
Used to calculate elongation when not included in published displacement, or the additional elongation for that portion of an anchor bolt in excess of the maximum bolt length for published displacement.
Elongation is calculated by the formula PL/AE, where P is the strength-level uplift force, L is the bolt length as input in the Structure dialog for each building level minus the maximum bolt length for given displacement that is input here, A is the cross-sectional bolt area, and E is the steel modulus = 2.9 x 10^7 psi
No/with anchor bolt
These radio buttons allow you to indicate that the connection does not have an anchor bolt, disabling the other controls and causing the program to dispense with anchor bolt calculations.
No anchor bolt
Steel strap or plate is attached to upper and lower studs using nails or bolts. Does not include a vertical anchor bolt, so published elongation or displacement value is the only source of elongation.
With anchor bolt
Hold-down assembly contains either one or two steel brackets attached to each other or to the foundation with a threaded and bolted steel rod or anchor bolt. The bracket(s) are attached to the upper and lower wall studs with vertical bolts.Elongation/displacement and manufacturer's anchor bolt length entered are for one bracket; these values are doubled in Shearwalls when two brackets are specified in the Wall or Opening input views. The capacity is the same regardless of whether one or two brackets is used.
Diameter
Shank diameter of anchor bolt, used in tensile strength and elongation calculation, – can select from list or enter custom size. Used to calculate cross sectional area A in the formula PL/AE for anchor bolt elongation
Max Length for Given Elongation
The length of anchor rod the manufacturer used in tests to determine the displacement or elongation when bolt elongation is included. It is usually found in a note in the product literature or evaluation reports.\nIt is subtracted from the hold-down bolt length input in the Structure dialog to get L in the formula PL/AE for anchor bolt elongation. When anchor bolt elongation is not included in the published displacement or elongation, then this value is set to zero and the program calculates the elongation or the entire bolt length.