LFRS In Open Pavilion Structures

[labeattie]

Hi,

I'm a new engineer designing some open pavilion structures. Does anyone know any good ways to create your lateral force resisting system in these buildings? One of the structures has steel columns, so I designed those as fixed base columns, using AISC DG 1 for eccentrically loaded base plates. I understand, though, that fixed-base columns are a controversial topic, as deflections can be larger than anticipated. Does this mean a second order analysis with a partially fixed connection is necessary? It doesn't seem feasible to me to create a conventional moment frame with steel columns and wood beams.

The second structure has wood columns. It has become quickly apparent to me that a fixed-base wood column is a near impossibility, without embedding the column in the soil and/or concrete (which can lead to rot problems). My initial solution was to use knee bracing, but gravity loads alone distribute a great deal of axial load to the knee braces, making regular simpson connections unusable. Quick research shows that knee braces are not very highly regarded anyways. I'm about to the point where I might replace these wood columns with HSS and design as described in the first building. Any ideas or advice would be greatly appreciated.

Thanks in advance,
LAB

 

[structSU10]

Attached is a paper that derived the baseplate fixity. it is based upon applied loads, so you have to iterate the solution by modifying the spring at the base in the model until convergence. It should be a good place to start. For knee bracing the wood frames, it is difficult to get standard connections to work for you, but I would think wood to wood it is probably your best bet. I don't think a custom connection will be all that problematic.

 

[labeattie]

Thank you. That reference was very nice to have on the base plates. And yeah the knee bracing seems to be pretty common practice, although often with connections that seem inadequate to me. I'll just beef mine up. I appreciate it.