## Robot Structural Analysis

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# Reinforcement percentage below required value due to seismic requirements

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I use EC8 for seismic design and I notice I keep getting the attached error message about unsufficient reinforcement percentage. I understand that it is as a requirement of a clause in the code asking for a certain percentage of reinforcement over the whole length of the beam. My question is does RSA have a setting which automatically checks for this in designing beams?

# Re: Reinforcement percentage below required value due to seismic requirements

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WIthout the access to the file I can't tell what in this particular case causes this warning to be displayed but in general the RC design modules try to arrange reinforcement in such a way that the minimal area of reinforcement requirement is fulfilled.

**Artur Kosakowski**

# Re: Reinforcement percentage below required value due to seismic requirements

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is there a way to see the reinforcement ratios of a section?

# Re: Reinforcement percentage below required value due to seismic requirements

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I'm not sure if I understand what you mean by "reinforcement ratio". Is it area of reinforcement / area of beam's cross section?

**Artur Kosakowski**

# Re: Reinforcement percentage below required value due to seismic requirements

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Exactly Artur, thanks for responding. It is usually symbolized with character " ρ " for longitudinal reinforcement and distinguished between ρ tensile and ρ compressive (or top - bottom).

Also an other thing. In the calculation note of a RC beam I see clearly theorical reinforcement ( 2.6 Theoretical results - detailed results) in terms of area (cm2) in various sections (abscissa) but for the provided reinforcement (always in calculation note part 2.7 Reinforcement) I only see number of bars and the diameter of the bars. It would much better seeing in the calculation note also the provided reinforcement in terms of area (as it happens in slabs for example) + the reinforcement ratio ρ . Ok there's the diagram with the provided Abr, works fine while using RSA but in the printed calculation note no values are written in the diagram...

# Re: Reinforcement percentage below required value due to seismic requirements

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It looks like this issue http://forums.autodesk.com/t5/Robot-Structural-Ana

Since you are investigating about the above issue (kope's post) please check also

1) EN 1998-1 5.4.3.1.2 **(5)P** about ρmin in tension zone (Asmin) seems to work but 5.4.3.1.2 **(4)** b about ρmax (Asmax) looks that is not covered from RSA

2) If I use moderate ductility class (DCM) and try to use 12mm diameter bars I get the error : The shape of longitudinal reinforcement is incorrect according to seismic requirements ( EN 1998-1:2004, 5.5.3.1.3 (5)P b ) . The limit of 14mm diameter bars is referred to high ductility class (DCH => EN1998 5.5...) and not to DCM where chapter 5.4 should be applied

3) there are also some limitations about max longitudinal diameter in EN 1998:2004 5.6.2.2 that also doesn't seem to be covered by RSA.

I'm trying to find something in help documentation about what RSA does and what not according to EN 1998-1 but not many things are wtitten about EC8 member's design . Is there a list like the one about EN 1992-1-1 ? ( something similar like this http://help.autodesk.com/view/RSAPRO/2015/ENU/?gui

P.S. a small notation about my previous post. Ratio of tension reinforcement ρ is defined as As/b*d where As is area o tension reinforcement, b is the width of the beam, and d is the effective height of the beam (= h-c where h is the geometrical height of the beam section and c the reinforcement cover)

# Re: Reinforcement percentage below required value due to seismic requirements

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*It looks like this issue http://forums.autodesk.com/t5/Robot-Structural-Ana lysis/Anchorage-Length-based-on-Eurocode-RC-Beams-... is the reason of the message "Reinforcement percentage below required value due to seismic requirements" (=> reduction of Abr at the beam edges => so Asmin from EN-1998 5.4.3.1.2 (5)P ).*

Asmin is compared with the total reinforcement area, not reduced due to the anchorage length (Abr), so I can't see any link to http://forums.autodesk.com/t5/Robot-Structural-Ana

*Since you are investigating about the above issue (kope's post) please check also*

*1) EN 1998-1 5.4.3.1.2 (5)P about ρmin in tension zone (Asmin) seems to work but 5.4.3.1.2 (4) b about ρmax (Asmax) looks that is not covered from RSA*

Both points: EN 1998-1 5.4.3.1.2 (5)P and 5.4.3.1.2 (4) b are implemented in Robot

*2) If I use moderate ductility class (DCM) and try to use 12mm diameter bars I get the error : The shape of longitudinal reinforcement is incorrect according to seismic requirements ( EN 1998-1:2004, 5.5.3.1.3 (5)P b ) . The limit of 14mm diameter bars is referred to high ductility class (DCH => EN1998 5.5...) and not to DCM where chapter 5.4 should be applied*

Under investigation.

*3) there are also some limitations about max longitudinal diameter in EN 1998:2004 5.6.2.2 that also doesn't seem to be covered by RSA.*

Currently EN 1998:2004 5.6.2.2 is not supported in RC Beam design module due to limitation in accessing values of forces in columns during the beam design process.

*P.S. a small notation about my previous post. Ratio of tension reinforcement ρ is defined as As/b*d where As is area o tension reinforcement, b is the width of the beam, and d is the effective height of the beam (= h-c where h is the geometrical height of the beam section and c the reinforcement cover)*

Yes

**Artur Kosakowski**