Following the provisions of AISC 342-22 and referencing ASCE 41-17 where needed, I am trying to develop force-deformation relations for a modern RBS connection properly designed and detailed per AISC 341. The curve should be Type 1 in AISC 342 Fig. C1.1 (below) or ASCE 41 Fig. 7-4 since the connection has highly ductile behavior. I have several questions.
- The chord rotation at yield determined by AISC 342 Eq. C2-2 does not seem appropriate since the hinge is formed at a non-trivial distance from the column face. Should I modify the equation by including the shear amplification in the determination of MCE? For example, MCE = Mpe,RBS + VRBS*Sh?
- Following from question #1, should I also include shear amplification when determining the yield strength, Qy?
- Looking at charts from cyclic tests on RBS connections, the post-elastic slope seems much steeper than the 0.03 value recommended in AISC 342 Section C2.4a.1.b. Have there been any studies suggesting a larger value specific for RBS connections?
- Neither AISC 342 nor ASCE 41 provide much guidance on determining the slope between Points C and D. A steep slope (e.g., 10:1) is conservative, but it can cause analysis errors and does not seem reasonable for a connection that exhibits gradual strength degradation behavior. Is this left entirely to engineering judgment? Could I justify a 1.5:1 slope for an RBS connection? How about 1:1 instead?
#ASCE41#Seismic------------------------------
Matthew Bosch-Willett P.E., S.E., M.ASCE
DIRECTOR OF STRUCTURAL ENGINEERING
Walnut Creek CA
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