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RE: Seismic Joint + ETABS

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From: "Reza Dashti Asl" <rezadashti(--nospam--at)hotmail.com>

To: seaint(--nospam--at)seaint.org

Subject: RE: Seismic Joint + ETABS

 

Jim,

 

So if the seismic force applies at an angle to the seismic joint, then these

straps have to transfer the component of the load parallel to the wall

(without excessive deflection or deformation) across the joint and at the

same time move freely (perpendicular to the joint) without resisting the

other component and deflect as required. Would you please elaborate? Are we

talking about concrete shearwalls and considerable shear loads?

 

Thanks,

Reza Dashti P.Eng

Vancouver, BC

 

>From: "Jim Getaz" <jgetaz(--nospam--at)shockeyprecast.com>

 

>We have also designed straps that carry horizontal load across a seismic

>joint to a shearwall on the other side, rather than having back-to-back

>shearwalls.

 

            Reza,

                        I work in SDC B, and sometimes A, which I assume is much less than Vancouver.

                        Rather than build concrete shear walls on each side of a seismic joint, we have built one on one side. We reach across that joint with straps (threaded rod or bar) that are nearly parallel to the joint, so they are rarely as short as 2’, but usually at least 3’-4’ across a 2”-3” joint. They have flexible anchorages on their ends. So we assume they carry axial load across the joint (mostly parallel), but rotation at the ends occurs before any appreciable restraint perpendicular to the joint does.

                        Is this a valid scheme? We have not had any earthquakes of a design magnitude in the years that we have been doing this. Since we usually leave those for you all on the west coast, we may never know. :-)

            Jim Getaz

            Winchester, Virginia