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[SEAOC] Expansion Joints and Shear Walls Additional Information

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     Sorry, I haven't told enough of the story.
     
     The building is a steel braced frame in the long direction (4,000+ 
     feet) and the walls I described (fire wall / shear wall) in the short 
     direction (80+ feet). I think that this type of structure is preferred 
     because the stiffness of the shear walls will be less prone to 
     transfer deflections along the length of the building from transverse 
     seismic loads.  I believe that because of the rigidity of the shear 
     walls possible whipping action at the ends of the structure will be 
     prevented.
     
     The detail I discussed in the previous memo would be installed to 
     allow expansion in the longitudinal direction.  I also believe that by 
     using this detail I can prevent accumulation of loads at the end of 
     the structure.  A close analysis of later load on the walls will yield 
     the required deflection to be designed into the connection of the roof 
     diaphragm to the shear wall.
     
     I agree with you, Martin, that the best earthquake design is a well 
     connected building with robust connections to hold everything 
     together. But, what do you do about the thermal deflections in a 
     building this long?  I believe that the interaction of this structure 
     poses an interesting scenario.  It resembles a tunnel, but does not 
     have the characteristic rigidity of a tunnel nor the natural dampening 
     provided by the soil.  And to make things worse, the temperature 
     gradient is much higher than if it was insulated by soil.
     
     So, what do you think of the value of the so called "breakaway beam" 
     detail now?  Could it contribute in a positive way to the seismic 
     performance of the building as well as the thermal expansion and 
     contraction?
     
     Scott Horn
     BSRI
     scott.horn(--nospam--at)srs.gov

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