Robot Beam Module - Openings Technical Clarification

[esuffk]

Helle all

I have noticed that the beam module within RSAP has the ability to model openings in the web of RC beams.  I am looking for clarification on the design process undertaken by ROBOT in order to do this as I was unaware of any clause in the British Code that will allow you to make a judgemnt on the reduced capacity at openings.  

As a cursory glance at the problem, I have undertaken a shear check based upon the reduced cross-section. i.e. calculating the shear stress applied based upon a reduced d across the openings, and utilised the full d value for the calculations of reinforcement ratio and vc value (for an upper bound Asv result) and the result is representative of the robot output.  The reinforcement has been specified by myself and is not the standard opening reinforcement for openings  (this is infact a post drilled opening required - I have doubled the spacing of the stirrups in the middle to simulate the cutting of a link)

I am struggling to believe that ROBOT is simply undertaking this heavily simplified calculation.

If anybody could shed some light on the situation, that would be very helpful. 

A few screen shots attached

Many Thanks,

Andrew 

[Artur.Kosakowski]

In general for openings considered in calculations the beam is replaced with the model as shown on the attached picture. After static calculations of such structure for the 'beams' above and below the opening have their reinforcement bars generated based on the obtained internal forces.

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[esuffk]

Many thanks for your reply.  

Does the model take account of the longitudinal shear transfer in bending? 

what would be the load path for shear from a concentrated point load over a large rectangular opening with a width greater than the required link spacing.  Would the cross section of the bottom 'beam' be fully effective in resisting the shear applied on the 'beam' above?

Many Thanks,

Andrew 

[Artur.Kosakowski]

Does the model take account of the longitudinal shear transfer in bending? 

No, it does not.

what would be the load path for shear from a concentrated point load over a large rectangular opening with a width greater than the required link spacing.  Would the cross section of the bottom 'beam' be fully effective in resisting the shear applied on the 'beam' above?

The force will be applied to a 'top' beam and such model calculated. For such model the shear force in the bottom beam will be none therefore the top one will be responsible for shear force transfer.

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