Rod Elongation Calculator

Rod elongation is a critical consideration in the design of threaded rod systems carrying uplift loads from roof to wall anchorage or shearwall overturning. This quick easy calculator assists the designer in determining elongation given a demand load and rod properties. Click here for more information and code requirements regarding rod elongation.

Elongation Calculator Design

Tension Load

Demand Load:  lbs. ?
Input the design ASD tension force.

Rod Properties

Rod Diameter:  ?
Select the desired or specifed rod diameter and steel grade (H.S. represents high strenth steel). The rod options presented are only those that have allowable loads which exceed the demand load.
Length of Rod: ft – in  ?
Rod length is the measured distance between the rod restraints. For the graphic shown this distance is from the top of concrete to the bottom of the nut at the top of the run.

Calculation Results

Rod elongation = PL/(Ae×E)
P =
L =
Ae = which is the rod effective net area from AISC.
E =
For overturning restraint systems, the total elongation should not exceed the local jurisdictions limits. If no such limits exist it is recommended the values not exceed 0.200" per floor unless wall specific drift calculations are performed.
For uplift restraint systems, per AC-391 Section the total elongation shall not exceed 0.18".

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