huangyhg

masonry parapet detail question
we have a parapet wall of 8" masonry. the top of the wall was a u-block bond beam. we have been asked if the vertical steel needs to be hooked into the bond beam. our opinion is no, but we cant find any code reference one way or the other. we are using fbc2001 in a 130 mph hurricane zone.
any thoughts on hooking the vertical bars into the bond beam?
thanks.
as long as the unreinforced cmu can resist the wind load on the top 8" of the wall (and i have to believe it can), you should be ok.
daveatkins
whenever i have vertical reinforcing in any exterior masonry wall, i always specify the vertical bar to extend a minimum of 4" straight, without a hook, into the bond beam at the top of the wall. this is not a problem for the masons to punch a hole throught the bottom of the block. this will make the bond beam part of the structural cantilever of the wall to aid in the resistance of lateral loads.
i see no reason to hook the rebar. my only thought is, if i am understanding this correctly, the hook would only prevent the bond beam from lifting away from the rest of the wall. and with forces that great, i believe you are dealing with tornado-like conditions.
the top hook is usually a designers option. i know several that do and several that don't. the masonry design manual published by the masonry institute is a good guideline and it does not require a hook. your area may have a local code requirement for such.
thanks all for the super quick responses. it seems that we generally agree that hooking would not be required, unless you have some very large uplift load on the bond beam.
in this case, my uplift would be something like 85 psf worst case. so on an 8" wall, with say a total width of 12" (architectural capping etc) i would have maybe 85 plf of uplift. i have #6 bars @ 32" o.c. extending up into bond beam. if i have 4" embed depth into beam, i would have an allowable tension capacity of about 3600 lb per #6 bar (4" / ld * 60 * 0.44). so i guess i have lots of capacity to resist the bond beam from lifting off the wall.
thanks again everyone.
does a 4" embeddment actually develope the rebar adequately?

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