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RE: Coupled Shear Walls

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Thanks Stan.

 

Actually, what I’m looking for is an analysis method for an existing URM masonry gable end wall with stacked openings [arched lintels, not steel]: a doorway at grade and a window above.  The spandrels, the masonry elements between the openings and above the window to the top of the wall, are seriously earthquake damaged with cracking patterns that indicate the spandrels cracked in shear and flexure as the piers each side deformed independently in flexure as cantilevers from the ground.  The piers each side are undamaged.

 

If analyzed by Appendix A of either the UCBC or the IEBC, the wall is O.K.; however, those codes do not address the spandrels between piers.

 

The analysis method needs to take into account that the vertical deformation of the vertical edge of the pier at one edge of the spandrels is due to tension in the adjacent pier, and in the opposite direction at the other edge where the deformation is due to compression in the adjacent pier, forcing one spandrel edge upward, one downward.  These deformations are incompatible with the un-deformed effectively horizontal and rectangular shapes of the spandrels.  The effect is magnified toward the top of the wall: spandrels high in the wall tend to get beat up more than spandrels low in the wall.

 

Reinforcing for the spandrels that couple shear walls is discussed in Section 21.7.7 of ACI 319-02 and illustrated in figure 21.7.7.  This ACI Section assumes that the design forces and moments have been determined; my question is about how to determine them.

 

Nels Roselund, SE

South San Gabriel, CA

njineer(--nospam--at)sbcglobal.net

 

 


From: sscholl2(--nospam--at)juno.com [mailto:sscholl2(--nospam--at)juno.com]
Sent: Friday, October 27, 2006 11:42 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Coupled Shear Walls

 

If I understand your question, I believe what is needed is to design each element (each of the shear walls in the same line) so that they each have approx. equal deflection. For example if a 4 ft. length wall is in line with a 10 ft. length wall, the 4 ft. wall might need plywood on both side with heavier nailing so that the deflection will equal the deflection of the 10 ft. long wall with plywood on only one side and with less nailing. And the hold downs will be different for each.

Stan Scholl, P.E.

Laguna Beach, CA