All,
I would like your input on a project that I’m working on that I’m having a disagreement with one of my co-workers on. I’ve had this debate with others before, and it seems that everyone has a different understanding of what constitutes lateral support to a W section. I’m familiar with Appendix 6 of the AISC Spec, and the paper, "Fundamentals of Beam Bracing," by Joseph A. Yura, but I would like to hear from other structural engineers.
Here is my situation:
I’m designing an addition to an existing industrial building. The roof of this addition will be engineered wood roof trusses with a 4:12 pitch at 16” O.C. On one side of the addition, the trusses will bear on a W18X50 steel beam, which must span 40’ to meet the client’s needs/existing site conditions. I’ve attached a 2X8 sill plate to the top of the W18X50 beam so I can attach the trusses to the beam. I’m using a Simpson HGA10 to connect the truss to the sill plate, along with 4 toe nails. The 2X8 is attached to the steel beam with ½” bolts 2’ O.C., alternating/staggering the bolts on each side of the W section web.
A detail of this connection is attached for reference.
My design assumes that this connection provides lateral support to the W18X50 and its top flange every 2’. The maximum distance (Lc) for bracing a W18X50 without reducing the allowable bending stress is 6.7’. Without a perpendicular member providing support to this beam, the unbraced length would be 40’, and it’s just not practical to design a steel beam with an unbraced length of 40’.
I was taught that for lateral bracing to be effective, it must prevent both twisting and lateral deflection of the member's cross-section at lateral brace points. I think this detail accomplishes that.
I’ve used similar designs in the past based on the assumption that the wooden trusses attached to a sill plate that is attached to a W section provide this support. To calculate the force that this adds to the truss, I’ve calculated 5% of the compressive force in the top flange of the W section and provided it to the truss manufacturer to incorporate into their design.
My coworker thinks that this connection is not adequate to provide support to the W18X50. If I make that assumption and go with an unbraced length of 40’, then I need a W18X130. That 3,200# of extra steel for this one beam.
What do you say, is this connection adequate or not to provide support to this beam?
I would like your input on a project that I’m working on that I’m having a disagreement with one of my co-workers on. I’ve had this debate with others before, and it seems that everyone has a different understanding of what constitutes lateral support to a W section. I’m familiar with Appendix 6 of the AISC Spec, and the paper, "Fundamentals of Beam Bracing," by Joseph A. Yura, but I would like to hear from other structural engineers.
Here is my situation:
I’m designing an addition to an existing industrial building. The roof of this addition will be engineered wood roof trusses with a 4:12 pitch at 16” O.C. On one side of the addition, the trusses will bear on a W18X50 steel beam, which must span 40’ to meet the client’s needs/existing site conditions. I’ve attached a 2X8 sill plate to the top of the W18X50 beam so I can attach the trusses to the beam. I’m using a Simpson HGA10 to connect the truss to the sill plate, along with 4 toe nails. The 2X8 is attached to the steel beam with ½” bolts 2’ O.C., alternating/staggering the bolts on each side of the W section web.
A detail of this connection is attached for reference.
My design assumes that this connection provides lateral support to the W18X50 and its top flange every 2’. The maximum distance (Lc) for bracing a W18X50 without reducing the allowable bending stress is 6.7’. Without a perpendicular member providing support to this beam, the unbraced length would be 40’, and it’s just not practical to design a steel beam with an unbraced length of 40’.
I was taught that for lateral bracing to be effective, it must prevent both twisting and lateral deflection of the member's cross-section at lateral brace points. I think this detail accomplishes that.
I’ve used similar designs in the past based on the assumption that the wooden trusses attached to a sill plate that is attached to a W section provide this support. To calculate the force that this adds to the truss, I’ve calculated 5% of the compressive force in the top flange of the W section and provided it to the truss manufacturer to incorporate into their design.
My coworker thinks that this connection is not adequate to provide support to the W18X50. If I make that assumption and go with an unbraced length of 40’, then I need a W18X130. That 3,200# of extra steel for this one beam.
What do you say, is this connection adequate or not to provide support to this beam?
