australian reinforced masonry wall design

huangyhg

australian reinforced masonry wall design
i know there are a few oz folks who monitor this forum, so would value your opinion, or for that manner anyone else who knows.  as3700-1988 had a clause for reinforced walls in compression which allowed the use of .70 as the capacity reduction factor provided the wall reinforcement complied.  as3700-2001 seems to discount any beneficial affect of reinforcement unless the bars are restrained in each direction by ties, and therefore requires using .45 as the capacity reduction factor.  anyone know if that is the intent of as3700-2001?  was the interpretation of as3700-1988 wrong?  if so, there are a lot of unconservative walls around.  
i think that they have found that individual bars are liable to axial buckling.
the ties mean that it acts more like a concrete column and the individual buckling is restrained.
general view on this is that for 190mm walls or smaller it is extremely difficult (if not impossible) to get two layers of bars and the ties between.
as for previously constructed wall, hey it is not a perfect world. try working in the us where the masonry code has changed from allowing big bars with low stress to limiting the bar to small sizes (with higher stress). what works with the old code is a violation of the new code and vice versa. we can only move on and design better from now on.
csd
there is an as/nzs code forum
look up under engineering codes, standards & certifications.
csd
the issue is not whether you could count the wall bars as compression steel.  we didn't do that.  but the clause in the old code recognized the benefit of the bars (if you used .0015a) by allowing the use of the reinforced masonry capacity reduction factor rather than the crd for unreinforced masonry.
yes you must use 0.45 if you don't have ties, i.e. 99% of the time.
table 4.1 really should include this.
personally i think 0.45 is a bit harsh...
i agree, harsh but true. we all know that strength will be improved with reinforcement but the current code doesn't recognise that.