What experience have you had specifying Simpson Strong-Tie Special Moment Frames?
I assist a number of custom home builders, architects, and residential designers here in the upper Midwest (Seismic Category A, 115 mph wind). I'm in a large metro area with a building/plan review department that is very thorough. Many of these homes have tall wall foyers and/or great rooms, balloon-framed with LSL studs, up to 20ft tall in some cases. These tall walls exceed the prescriptive wall bracing methods allowed in the IRC. Sometimes the truss/lumber supplier will engineer the LSL stud framing, connections, etc., but not the overall wall bracing design. I am usually able to evaluate those exterior wall segments as engineered shear walls and make something work from SPDWS Table 4.3A, and some tension holdowns.
Attached is a sketch of my latest assignment where I don't see a solution with wood framing, I think a steel frame is required. The 14ft tall great room projects outward from the other exterior walls, with just ~16" wall segments at the corners. Often times I will consider the lateral wind loads to transfer thru to other wall segments, but those walls are only 10ft, and the mean roof height here is significant.
I downloaded/installed the Simpson Strong Frame Selector software, and after tinkering, I quickly found a one-story SMF assembly that will work here...much easier than if I designed it with hand calcs, yuck! The program provides a detailed report for permit submittal, etc. I am curious what experience other engineers have had with these frame products, especially with residential masons and carpenters who probably want nothing to do with steel. Obviously the anchor embedment into the foundation walls for these moment frames is critical and in my experience there typically isn't that level of coordination between trades in residential construction. On multiple occasions I have sized a tension holdown and anchor rod that does not get cast in the foundation wall pour. These custom homes keep getting bigger with more windows. Does it seem outrageous for a situation like this to require a moment frame to resist wind loads?
Any input is appreciated.
-Troy
I assist a number of custom home builders, architects, and residential designers here in the upper Midwest (Seismic Category A, 115 mph wind). I'm in a large metro area with a building/plan review department that is very thorough. Many of these homes have tall wall foyers and/or great rooms, balloon-framed with LSL studs, up to 20ft tall in some cases. These tall walls exceed the prescriptive wall bracing methods allowed in the IRC. Sometimes the truss/lumber supplier will engineer the LSL stud framing, connections, etc., but not the overall wall bracing design. I am usually able to evaluate those exterior wall segments as engineered shear walls and make something work from SPDWS Table 4.3A, and some tension holdowns.
Attached is a sketch of my latest assignment where I don't see a solution with wood framing, I think a steel frame is required. The 14ft tall great room projects outward from the other exterior walls, with just ~16" wall segments at the corners. Often times I will consider the lateral wind loads to transfer thru to other wall segments, but those walls are only 10ft, and the mean roof height here is significant.
I downloaded/installed the Simpson Strong Frame Selector software, and after tinkering, I quickly found a one-story SMF assembly that will work here...much easier than if I designed it with hand calcs, yuck! The program provides a detailed report for permit submittal, etc. I am curious what experience other engineers have had with these frame products, especially with residential masons and carpenters who probably want nothing to do with steel. Obviously the anchor embedment into the foundation walls for these moment frames is critical and in my experience there typically isn't that level of coordination between trades in residential construction. On multiple occasions I have sized a tension holdown and anchor rod that does not get cast in the foundation wall pour. These custom homes keep getting bigger with more windows. Does it seem outrageous for a situation like this to require a moment frame to resist wind loads?
Any input is appreciated.
-Troy
