Reinforced Concrete Cover

[huffte]

It is likely that situations requiring differnt values of cover for the various members will arise.

Would it be possible to make the concrete cover a section-specific parameter as opposed to a project-specific parameter, as currently exists?

[Stelios_Antoniou]

Dear Huffte,
I am sorry to disappoint you, but this is how things have been until SStruct v.4 (if I remember well). We removed such feature after the requests of several users that preferred simplicity to more freedom. To be honest, personally I prefer how things are now (IMHO the effect of different cover thicknesses is negligible anyway), but this is an issue that requires too much discussion.

Seismosoft Developer

[Michele]

Hello, I am kinda new to Seismostruct. As soon as I've started to create my first models I've noticed the way Seismostruct deals with concrete cover. Here are my observations:
1) In new construction the concrete cover is determined by code regulations, and, if I remember correctly it depends in some ways to the bars diameters. Now, I might have a 50x50 cm column where I use a concrete cover of 50-60 mm and a 30x60 cm beam where the same cover might still be a good approximation of the real cover, or I might have a wall where the cover could be much less. So assuming just one concrete cover for all it's a little bit of a limitation.
2) In assessments this might be an even greater limitation because I might have beams of the type 60X24 cm. In this case there is clearly a problem with a general standard concrete cover.
3) The concrete cover to be used in design is usually referred to the distance from the concrete edge to the edge of the first transversal bar. As a matter of fact the cover is there to protect the steel from external agents. Of course longitudinal bars and transversal bars are different particularly if you consider different kind of elements (columns, beams, walls).
4) I don't know to which extend, but the capacity of a section depends also on the dimensions of the concrete cover and the concrete core. So, if I keep the same cover for all sections, and if there are sections very different in dimensions, smaller sections might be affected. If I average the cover all the sections are affected.
5) Honestly I do not know how much the concrete cover will affect the behavior in a non linear analysis (I am very new to this kind of analysis), but for sure it affects the capacity in standard calculations.
Having say that I believe that it would be a much better and logical to make the concrete cover a section-specific parameter. This is also more similar to what reality and code are.
Well, that's my opinion.

V/R
Michele De Lorenzi

[seismosoft]

Dear Michele,

Thank you very much for this thorough and constructive comment.

Whilst we can certainly see your point regarding the manner in which concrete cover changes from one element to another, we also question, as you pertinently do, if a more articulated and section-customised definition of rebar cover will really make a difference in the seismic assessment of existing structures?

Our feeling is that it won't, especially if one considers all the much larger uncertainties associated to such assessment exercises (from the level of seismic action to the mechanical properties of the materials).

In any case, we will certainly brainstorm on the feasibility and justification for introducing an alternative manner to define concrete cover that will still be relatively simple and pragmatic.

Thanks again,

Seismosoft Support

[salar]

Dear seismostruct team
I recommend to have a both Constant and Not constant cover definition for better define section properties.
Please see the image:
http://www.4shared.com/download/cyCTbTf ... ?lgfp=3000

[seismosoft]

Dear Salar,

Thank you for your suggestion. There is a big discussion on this issue and obviously there are advantages (more flexibility and better modelling, although the response differences are not big in typical cases) and disdvantages (increased complication, for instance your suggestion would lead to 8 new input parameters for the U-section) in it.

In any case the way you suggest to include different values of the cover is very clever and we will consider it in the future

SeismoSoft Support

[salar]

Dear seismostruct
Another way to have a constant cover for each section.
Please see the image:

http://www.4shared.com/download/9L0ZE9I ... ?lgfp=3000