I am designing an open picnic shelter and I am having difficulty getting the lateral system to work. I live on the west coast where we have very high seismic loads. The client wants to use mortise and tenon pegged knee braces which I am OK with in principle. I have them in pairs where the brace on one side will be in tension and the brace on the other side will be in compression. I am really struggling to get the tension side brace to work by just using the pegs to take all the load.
My question is: would it be acceptable to design these braces as compression only members? In other words, design the brace on the compression side to take all the lateral load, and the brace on the opposite side takes no load. Theoretically, this would make all my problems go away. My concern with this is that in reality, the brace on the other side could end up taking some tension load which it's not designed for. The member itself will be fine, but the pegged connection might fail. In this case, is there a concern that it will not be able to take the compression load once the load reverses?
I downloaded TFEC's Design Guide for Timber Trusses in which it does say the following:
"Diagonal braces with pegged mortise-and-tenon connections are often used in pairs such that when one brace is loaded in tension, its
companion is loaded in compression. To avoid overestimating the stiffness of a pegged joint in tension, it is conservative to model all braces as
compression-only"
This would seem to endorse what I am proposing, but I just want to get some other opinions incase I am misinterpreting what the guide is saying. Thanks for any help.
