Tensile Forces in Sag Rods

[EV11]

I am looking for some guidance on how to determine the tensile loads carried by sag rods in structural steel buildings.

The situation that I’m dealing with is common - a frame in a structural steel building with horizontal wall girts spanning from column to column to support the weight of the wall assembly and resist wind loads. Because it is a long span (32 feet), I want to add sag rods at mid-span of the frame. The girts can withstand the vertical wall loads, but there will be quite a bit of vertical deflection and the sag rods will help with that. Could someone share their approach for determining the loads carried by the sag rods in this situation? I had thought of assuming that the rods carry a certain percentage of the wall’s weight, but I’m unsure whether this is a good approach.

Thank you.

 

[JedClampett]

The way I've always done sag rods is they carry the gravity loads (not some of it) and the girts carry the wind loads. Why refine it?

 

[MotorCity]

What does the detail at the bottom of the wall assembly look like? Is the bottom of the wall supported by a slab or curb? If so, just design the girts for wind. If the bottom of the wall is not supported, the girts will need to carry the weight of the wall in addition to wind.

 

[JedClampett]

The sag rods hang from a support beam. The girts do not take the wall weight if the sag rods are properly designed. You need to get a steel detailing/design book.