Staad Reinforced Concrete Str. 3 floors

[juvepower]

Hi i need some help. I'm currently designing a 3-storey reinforced concrete house in Staad.pro 2007. Problem is I worked as a design engineer for about one year and then as proj manager for 3 years. So now i'm a bit rusty with my designing. Can someone please look at my design and let me know what i'm doing wrong.

I need help with the following:
1. I know that i have to adjust some of the beams sizes but what about everything else? Is there a way to design the pad footings (individually) without inputting the dimensions for the footing and only the bearing capacity of the soil? Can I use fixed supports and design the footings by hand or will this affect the design significantly?
2. I can't remember if i need to release moments and when do i have to release moments.
3. Is there a way for staad to automatically adjust individual beam sizes that fail? I would normally create a beam spec and add it to all the beams in the structure. Will i have to adjust each beam individually and add each individual dimensions as a beam specification?

 

[jhardy1]

I think the only responsible answer to your questions is that you should hire a qualified structural engineer.

I'm not trying to fob you off; but seriously, if you (the designer) are not sure where you should or should not be modelling pins, this suggests you have a very limited understanding of structural behaviour, and the chance of getting a meaningful analysis and design is very small!

 

[juvepower]

Yes my understanding is limited "jhardy1" that's why i am on "

http://www.eng-tips.com"

Thanks for no help at all :S

Anyone care to give actual advice?

 

[jhardy1]

1. Yes, you can use Staad.Pro to size your beams, columns, and slabs(assuming you have the concrete design module installed). You can also use Staad.Foundation to interactively size and design the footings, if you have it installed. It is quite common practice to model foundations as pinned or fixed supports in Staad.Pro, and use the results to design your footings using other methods, if you don't have access to Staad.Foundation, but you (the design engineer) will need to satisfy yourself whether that analytical simplification is sufficient for design purposes, or whether you need to consider footing settlement effects etc. Yes, if you use fixed supports instead of pinned supports, it can significantly change the analysis results, and therefore change the design requirements. (E.g. using fixed supports will generate base moments in the columns; this will in turn require footings which can carry combined vertical load and overturning moment, rather than just vertical load.) The selection of an appropriate analytical simplification (e.g. pinned vs fixed bases) requires an understanding of structural and foundation behaviour - e.g. simple isolated pad footings subject to overturning effects may rotate too much to be able to act as a fixed base, whereas a stiff raft or grid beam foundation may have ample stiffness to work as fixed bases for all columns.

2. You have to release moments in your analytical model wherever the construction details cannot carry the bending moments whcih would be genertaed in a fixed connection - this depends upon the construction details you are using. We cannot give guidance on this issue based on the Staad.Pro model you uploaded.

3. Yes, Staad.Pro can be used to iteratively check beam and column sections, pick new complying sections, and re-run the analysis until all sections pass the design check - assuming you have the code design check module installed.

Hope this helps! If you need further assistance, please refer back to my first post for guidance.