Questions and discussion for this lecture live here. Fire away by hitting Reply below
I have three questions regarding the calculations of moment capacity for the doubly reinforced rectangular sections.
- In the singly reinforced section there was a check for the ratio of z/d and limit it to 0.95. Does it apply also to doubly reinforced sections?
- Is it acceptable to not subtract the area of concrete where compression steel is placed?
- The max area of steel of 0.04 is defined for both compression and tension steel or just tension steel?
Thank you in advance,
- This limit wouldn’t be relevant for a doubly reinforced section since we would only ever have such a section (i.e. provide compression steel) if the compression block was fully utilised - as such we would expect
zto be relatively far from the limiting max value of
0.95dthat applies to singly reinforced sections.
- Yes this is acceptable - the influence of double counting this area is negligible - especially by comparison to other potential sources of inaccuracy.
- This limit applied to for all longitudinal steel - so yea, tension and compression.