I have an HSS in a polygon shape which has a stitch bolted piece of reinforcement (channel) being added (built-up section). The section has an axial load but it is very small in magnitude when compared to the moment. Chapter F13 of AISC 13th Edition refers me to E6 and D4 for bolt spacing. Both of those sections refer me to Chapter J3.5. J3.5 instructs me to limit my bolt spacing for plate-plate and shape-plate sections but says nothing about shape-shape built-up sections. My understanding of the bolt spacing requirement is that it is there to ensure that the plate will not buckle between the bolts and the section will remain fully composite. If I use Chapter F13 for my nominal bending moment and limit my maximum stress to the maximum stress allowed by Chapter E, would that hold true to the intent of Chapter J3.5?
Some engineering firms are treating sections between the stitch bolts in the above mentioned problem as though they are fixed at one end (K=0.8). To achieve this K value, wouldn't we have to increase the lu to allow for a moment arm at one end (moment not possible without a moment arm)? The assumption is that the reinforcement will try to deflect in an S shape and the polygon surface keeps it from forming the S.
Thanks in advance for your input.
Some engineering firms are treating sections between the stitch bolts in the above mentioned problem as though they are fixed at one end (K=0.8). To achieve this K value, wouldn't we have to increase the lu to allow for a moment arm at one end (moment not possible without a moment arm)? The assumption is that the reinforcement will try to deflect in an S shape and the polygon surface keeps it from forming the S.
Thanks in advance for your input.