## Robot Structural Analysis

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# Re: Crack width calculation for reinforced concrete

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gn wrote:

I have ran the reinforcement design in robot, but would like to extract the design data from robot and use it to produce a detailed crack width calculation, I will complete this on a excel sheet we use in the office.

My intension is to use the various functions in the Robot addon, spreadsheet calculator (SC) to take the relavent data from my robot model and use it in this spread sheet.

I recommend ordinary Excell + Robot API

What I was looking at doing was trying to extract things like reinforcemnt diameters, fyk for steel etc directly from the robot model and into my crack width spreadsheet so that when the design was completed on Robot it could be cross checked and a detailed design calc could be produced also. Do you have a copy of the SDK for robot so make it easier for us to extract the relavent data.

SDK installation on your DVD. If not, SDK in unpacked version here:

http://www.megaupload.com/?d=XM699PPN

I note there has been a request for a "RC slab deflections in Robot according to BS 8110" but according to EC 2 could you provide that as I wish to update our system here to EC 2 and that would help in the transition.

In different way: code paragraphs, formulas, tables

not implemented in RC EC2 design:

2.5 Design assisted by testing

2.7 Requirements for fastenings

3.1.5 Stress-strain relation for non-linear structural analysis

3.1.9 Confined concrete

3.2.6 Fatigue

3.3 Prestressing steel

3.4 Prestressing devices

5.6 Plastic analysis

5.7 Non-linear analysis

5.8.3 Simplified criteria for second order effects

5.8.6 General method

5.9 Lateral instability of slender beams

5.10 Prestressed members and structures

6.2.5 Shear at the interface between concretes cast at different times

6.3.3 Warping torsion

6.5 Design with strut and tie models

6.7 Partially loaded areas

8.7.3 Lap length

8.7.4 Transverse reinforcement in the lap zone

8.9 Bundled bars

8.10 Prestressing tendons

9.6 Walls

9.7 Deep beams

9.8.1 Pile caps

9.9 Regions with discontinuity in geometry or action

9.10 Tying systems

10. Additional rules for precast concrete elements and structures

11. Lightweight aggregated concrete structures

12. Plain and lightly reinforced concrete structures

Annexes:

F (Informative) Reinforcement expressions for in-plane stress conditions

G.2 (Informative) Soil structure interaction

H (Informative) Global second order effects in structures

I (Informative) Analysis of flat slabs and shear walls

J (Informative) Examples of regions with discontinuity in geometry or action

Limitations:

- theoretical RC calculations :

calculation model of concrete - no choice, always a rectangle

calculation model of steel - no choice, always perfectly elastic-plastic (flat plastic branch)

• provided reinforcement for slabs

Punching - forces applied within the penetration zone not considered, except for concentrated forces aplied on the same node as the support (by analogy to other standards)

Punching - only for the dimensioning of ULS (by analogy to other standards)

Punching - dimensioning is carried out for only one combination, this occurs for which the largest axial force, although in the calculation comes to interaction with the bending moments (similarly to other standards)

Punching - dimensioning slabs or columns with heads - lack of double bar-critical circuits (by analogy to other standards)

[9.10] Systems binding and wreaths-

**Rafal Gaweda**

# Re: Crack width calculation for reinforced concrete

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**I have few questions:**

** **

**IN CALCULATION NOTE FOR RC BEAM, WHAT IS WHAT:**

**2.5.5 Deflection and cracking**

wt(QP) Total due to quasi-permanent combination** - LONGTERM DEFLECTION IN t=∞ ?**

Dwt(QP) Deflection increment from the quasi-permanent load combination after erecting a structure. - **INSTANT DEFLECTION IN t=0 ?**

wk - width of perpendicular cracks - **WHICH CRACKS, LONGTERM (t=∞) OR SHORTTERM (t=0)?**

** **

**Which code combination does it uses for crack width calculation? SLS - QP?**

# Re: Crack width calculation for reinforced concrete

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Ad1 Yes,„Long term deflection (t=inf) due to quasi-permanent combination”

Ad2 Deflection as described :

**EN 1992-1-1:2004 7.4.1**

(5) Deflections that could damage adjacent parts of the structure should be limited. __For the__

** deflection after construction**, span/500 is normally an appropriate limit

__for quasi-permanent__** loads**. Other limits may be considered, depending on the sensitivity of adjacent parts.

(Long term deflection increase depends on QPR loads after building errection)

Ad3 long term cracks:

**EN 1992-1-1:2004 ****7.3.1**

(5) A limiting calculated crack width, *w*max

(…)

it may be assumed that limiting the calculated

crack widths to the values of wmax given in Table 7.1N, under the ** quasi-permanent** combination of loads,

**Rafal Gaweda**

# Re: Crack width calculation for reinforced concrete

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Thank you Rafal. I just wanted to be sure.

Still, it's to bad that we cannot control what's Robot doing, it would be nice that we can check what value Robot uses in each variable, either that or good verification manual so we don't have to ask this kind of questions. This way, we have to 'trust' Robot uses right values and right formulaes.

I have manually calculated an example of T-beam, and results are different from those Robot gives me:**ROBOT:**

{

wt(QP)=23,70mm

Dwt(QP)=15,33mm

wk=0,25mm

}**Manual:**

{

wt(QP)=27,9mm

Dwt(QP)=19,0mm

wk=0,22mm

}

As you can see, differences are from 13% to 24%.

I already wrote on other forum thread that I can't find verification manual for v2014.

# Re: Crack width calculation for reinforced concrete

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File please + scan of your manual calcs please.

**Rafal Gaweda**

# Re: Crack width calculation for reinforced concrete

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I've sent you private message.

# Re: Crack width calculation for reinforced concrete

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Mirko,

First part of answer - cracks (basing on model and documents you sent me):

In fact rebars are loacated 2mm beloww the level you assumed:

but it does not give significant difference.

According to your book example explanations, our understanding of Slovenian language + googletranslate...

we see this

we understood that c is calulated as d - 1/2*rebar_diam - transversal_rebar_diam

so it is cover to transversal rebar

But according to EC2 7.11

so this difference gives srmax 209mm instead of 190mm and thus 0.25mm cracks instead of 0.22mm.

**Rafal Gaweda**

# Re: Crack width calculation for reinforced concrete

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hi,

Which version of MS Office do you guys use? I have tried with 2007, but without any luck. Do I have to enable or disable something to get spread sheet working.

# Re: Crack width calculation for reinforced concrete

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..it's Croatian language, not Slovenian. They are similar but very different.

*we understood that c is calulated as d - 1/2*rebar_diam - transversal_rebar_diam*

*so it is cover to transversal rebar*

**That's correct.**

** **

*But according to EC2 7.11....*

Yes, I've cheked in my Croatian version of EC2, that correct too. I didn't pay attention to it before.

Usually, when we calculate reinforced concrete, and someone says cover "c", we all assume that's distance from face of concrete to the first reinforcement bar.

This may be an error. I will check this with the author of the book.

Thank you very much Rafal !

Hope to see the rest of it soon.

** **

# Re: Crack width calculation for reinforced concrete

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If you are referring to *Robot extension Spreadsheet caculator* then it is assumed that you must enable macros to make it work.

Look here:

http://grok.lsu.edu/article.aspx?articleid=6144

I didn't use those spreadsheets much, though.