EBF's IBC 2003

[TPNY]

What is the difference between the eccentrically braced frame moment-resisting, and non-moment resisting per Table 1617.6.2 (2.A and 2.B)?
(Which is the frame with the inverted V-shape and which is the V-shape?)

 

[Taro]

Doesn't have anything to do with the braces being in a V-shape or inverted V. It is just whether the beam-to-column connections are moment-resisting or not.

 

[TPNY]

But the beam-column connection is more critical with the V-shape than the inverted v-shape because the beam-column connection forms a plastic hinge for "failure" or energy absorption, or hatever it's considered. This is not so for the inverted v-shape because the plastic link is on the center of the beam. Does it make sense to allow both of these types of lateral bracing systems the same R-value?

 

[Taro]

Whether the braces are in a V-shape or inverted does not necessarily dictate the location of the link segment. Either one could have the link in the middle of the beam or adjacent to the column. If a link is not adjacent to a column, the beam-column connection is not required to be moment-resisting. However, moment connections add more redundancy and robustness to the system.

 

[TPNY]

Interesting... the AISC seismic section part 1 commentary defines the links for each type of EBF. Are they not always correct about the function of each piece of the frame? ...maybe there is an exception?

So, then what is the difference between the dual EBF and moment frame and the regular EBF frame? The IBC also defines two types of EBF frame in each case: moment resisting and non-moment resisting.

 

[Taro]

The figures in the AISC commentary are just some possible frame configurations. They are not the only acceptable configurations.

A dual EBF/moment frame system has SEPARATE moment frames that are designed to resist 25% of the total building base shear.

The only distinction between the two types of EBFs is whether or not the beams outside of the special link segment have moment connections.