Correct RC frame design workflows?

[haroon.ashraf]

Good morning all,

I have used Robot for steel design in the past which generally works very well, but when it comes to projects which have composite steel/concrete sections or concrete sections I usually take the results and design by hand (or using other design proformas).

I am aware that RC design functionality is built in to Robot, but having watched some dated videos and reading the help/tutorials, I am not clear at all at what the best way of using it really is. I've attached a simplistic concrete frame comprising RC columns, beams and slab with simple loading on it. 

Could someone please clarify what is the correct way to use the model to determine both ULS (flexure/shear) and SLS (crack width) steel reinforcement requirements for the various RC elements? All loadings and design are to the Eurocodes with UK NA.

In the past I would have taken max loadings for each element and designed using Tedds or other proformas, probably doing some more analysis/design for openings in the slab and any required beam strips within the slab.

Be interested to know what/how people use Robot for RC frame analysis/design!

Thanks

[haroon.ashraf]

bump

anyone got any ideas? or does no one use Robot for RC design

[Rafacascudo]

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[haroon.ashraf]

Thanks Rafa, very helpful for the procedures/workflows for designing RC slabs/beams/columns/walls etc.

I am in the process of building my model at the moment (previous structure was steel, so I am changing it all out for RC sections/properties etc), but I had a question related to the design of the slab and beams.

For my preliminary scheme design calculations I have sized the RC elements on the basis that the slab acts as a cladding i.e. load transfer only and assumed one way spanning between secondary beams which transfer the load to the primary frame beams, which is conservative as in reality the slab provides stiffness, diaphragm action and will take a portion of the loading in bending/shear.

In reality the primary beams will be detailed as T and "L" beams within the slabs [see attached screenshot for general gist]. I've read up on the process of how to model this with most suggestions being to NOT model in offsets of the beams to the slabs and model the beam sections as rectangular beams and then modify the stiffness of the beams in relation to the 'T' width as recommended by Artur here https://forums.autodesk.com/t5/robot-structural-analysis-forum/how-to-design-reinforcement-for-rc-t-....

I intend on modelling my slab (300 thick to accommodate several openings etc) in the same plane as the primary beam members which have no offsets applied. This will result in some 'double counting' of section so to speak as I will have a 300 thick slab overlapping with 300 deep section of beam which will lead to some inaccuracies. I have attached the real structure geometry screenshot as well to show what I am trying to model.

What is the best way of modelling this bearing in mind I intend on importing all of the results to the design module for ease of rebar calculations. 

Thanks

[Rafacascudo]

If this inaccuracy is related to self weight taken in account twice (portion of the slab and part of the beam) , then you could manually load slab or the beam with an equivalent load. I wouldn´t do it. Too much work for a very neglegible effect.

[haroon.ashraf]

Im not too concerned about the double count of section from a weight point of view but rather then overestimated stiffness poitn of view?

Or since the beams will be in the same plane as the slab, there is no need to manually increase the effective stiffness of the beams to account for the T-section width as this overestimate in stiffness will effectively give me a similar effect.

I will make some sensitivity assessments and see the outcome