How much adjustability does a tie rod assembly provide?
When Portland Bolt calculates the length of the rods in a tie rod using the pin-to-pin length of the assembly, we assume that the rods will be threaded into the clevises the full length of the female threaded nut component (Dimension ‘N’ in the drawing below) plus an additional length equal to ½” or half the diameter, whichever is greater. Per the drawing below, our Tie Rod Calculator assumes the rods are threaded through the length of the N and B dimensions.
The rods can be tightened further into the clevis until they touch the gusset plate to which the clevis is pinned – an additional amount equal to Y, a measurement whose length depends upon how far past the pin the connection plate protrudes (Z).
How much an assembly can be slackened is open to speculation. According to AISC guidance for structural connections, the bolt should be assembled until at least flush with the nut. If the same interpretation were applied to tie rod assemblies then you could theoretically slacken a tie rod by the length beyond which they extend past the nut component of the clevis on each end, which is the B dimension (½” or .5W Diameter), meaning you could slacken the assembly by a total of 2B (1” or one diameter, whichever is greater).
The assembly gains a greater range of movement in both directions when a turnbuckle is employed in addition to clevises. When Portland Bolt calculates the length of the rods in a tie rod assembly using the pin-to-pin length, we assume that the rods thread into each end ¼ of the length of the turnbuckle take-up. This means you can tighten the assembly an additional amount equal to half the length of the take-up. Assuming we apply the AISC interpretation of the necessary amount of thread engagement between bolt and nut you could theoretically slacken the assembly an amount equal to half the length of the take-up.