mnchamber
Structural
- Mar 14, 2016
- 3
The existing building is a 1979 tilt-up concrete warehouse will a wood-framed roof. The roof consists of 6-3/4" glulam beams at 40 feet spacing with TJL and TJ-50's between. The glulams vary in depth from 24" to 39". The maximum span of the glulams is 48 ft. My client wants to remove a post: this will create an 80 ft span. For the 80 ft span, the new beam is a W40x211 steel beam. My client wants to trim the glulam to leave the top 6" remaining, and then attach the new steel beam to the bottom of that remaining 6" of glulam beam....like a nailer.
My concern is lateral torsion buckling. I can connect the steel beam to the 6" of remaining glulam using vertical steel plates on top of the top flange and through-bolts. However, I am concerned that the connection of the glulam to the TJL and TJ-50 joists will not be strong enough to prevent buckling of the beam. I have reviewed Appendix 6 of the AISC 360 for Lateral Torsion Buckling: it only covers "Nodal Bracing" and "Relative Bracing" for LTB, but not "continuous bracing". I have also reviewed Yura's "Fundamentals of Beam Bracing" and cannot find an answer.
I would like to be able to calculate a force for the connection of the glulam to the TJL / roof sheathing. Please let me know if you have an equation or reference.
Thank you!
Here is a sketch of my proposed connection of the steel beam to the 'nailer'....but it is the connection of the existing TJL to the nailer that I am concerned about.
My concern is lateral torsion buckling. I can connect the steel beam to the 6" of remaining glulam using vertical steel plates on top of the top flange and through-bolts. However, I am concerned that the connection of the glulam to the TJL and TJ-50 joists will not be strong enough to prevent buckling of the beam. I have reviewed Appendix 6 of the AISC 360 for Lateral Torsion Buckling: it only covers "Nodal Bracing" and "Relative Bracing" for LTB, but not "continuous bracing". I have also reviewed Yura's "Fundamentals of Beam Bracing" and cannot find an answer.
I would like to be able to calculate a force for the connection of the glulam to the TJL / roof sheathing. Please let me know if you have an equation or reference.
Thank you!
Here is a sketch of my proposed connection of the steel beam to the 'nailer'....but it is the connection of the existing TJL to the nailer that I am concerned about.