Hi all,
For longer lift struts it seems that a moderate savings in strut size and weight could be had by adopting struts with end fixity greater than 1. Bruhn says that end fixity up to 1.5 is permissible in trusses with riveted joints (C4.11).
Using C=1.5 reduces the effective length of the column to 0.82 of the physical length. On a 91" column with a 7600 lb compressive load, this reduces the required tubing size from 2.25x.058" to 2.00x0.49". That saves 2.5 lbs per strut and reduces strut wetted area by 11%.
So what are the downsides to this approach? I see a possible increase in the complexity of fitting design, and the risk of parting ways structural tradition. I wonder how much effort is required to achieve stiffness equivalent to C=1.5.
Thoughts?
David
For longer lift struts it seems that a moderate savings in strut size and weight could be had by adopting struts with end fixity greater than 1. Bruhn says that end fixity up to 1.5 is permissible in trusses with riveted joints (C4.11).
Using C=1.5 reduces the effective length of the column to 0.82 of the physical length. On a 91" column with a 7600 lb compressive load, this reduces the required tubing size from 2.25x.058" to 2.00x0.49". That saves 2.5 lbs per strut and reduces strut wetted area by 11%.
So what are the downsides to this approach? I see a possible increase in the complexity of fitting design, and the risk of parting ways structural tradition. I wonder how much effort is required to achieve stiffness equivalent to C=1.5.
Thoughts?
David
