RING - Support & FAQ

Version history:

RING 1.1      RING 1.5

Support to users:

RING 1.5 has now been replaced by LimitState:RING 3.0, which is a fully supported commercial product. It is not possible to offer free technical support to users of RING 1.x. However, reports of bugs and constructive comments and suggestions are essential in order for the software to be improved in the future, and are most welcome. Please direct these to: m.gilbert@sheffield.ac.uk, with 'RING-COMMENTS' as the subject. 

 

FAQ

Q1. What is the 'failure load factor' ?


Q2. When I specify end abutment blocks, I seem to get a very low predicted load factor. Why?

 

Q3. Is RING being constantly updated?


Q4. Has RING been validated against full-scale test results?


Q5. How does a multi-span analysis work using RING? Does it involve manually balancing thrusts from adjacent arches, as with ArchieM?

 

Q6. How does RING deal with transverse distribution of the load through the fill?

 

Q7. I am modelling a multi-ring brick arch bridge. I get very different answers depending on whether I define each ring separately or simply specify an overall barrel thickness. Why?


Q8. I am modelling a multi-ring brick arch bridge. I am not sure if ring separation (delamination) is present. What assumption should I make when using RING?

 

Q9. The more bricks I specify per ring, the lower the failure load factor. Why?

 

 

Q1. What is the 'failure load factor' ?

A. For whatever live load is specified, RING will determine the multiplier, which when applied to this load, leads to collapse. This multiplier is termed the 'failure load factor'. e.g. if a 1kN single axle load is specified and RING indicates a computed failure load factor of, say, 154, this means that the load which would cause collapse is 154kN. Alternatively if a 10kN single axle load was specified in the previous case the failure load factor computed would be 15.4 (15.4x10=154kN). 


Q2. When I specify end abutment blocks, I seem to get a very low predicted load factor. Why?

A. If an end abutment is specified then often RING will predict a sliding failure just below the skewback at the top of the abutment. In reality when soil is present behind an abutment such a failure mode would be resisted by horizontal soil pressures. Currently in RING the abutment option is really meant for situations when a beam and arch span are adjacent to one another, when the possibility of the above failure mode is real (though it is possible in RING to manually specify pressures acting on blocks below the skewback, this can be a laborious exercise).


Q3. Is RING being constantly updated?

A. Yes. At present the core of RING is being completely rewritten using the programming language C++. RING 2.0 is scheduled to be posted later in 2005.


Q4. Has RING been validated against full-scale test results?

A. Yes. RING was originally developed as a means of interpreting the results from full-scale laboratory tests, and reasonably good correlation was found. Interested users are referred to the reference list at the back of the RING manual.


Q5. How does a multi-span analysis work using RING? Does it involve manually balancing thrusts from adjacent arches, as with ArchieM?

A. RING uses rigorous optimisation techniques to find the critical collapse load factor, which can be found when the yield, mechanism and equilibrium conditions of plastic analysis are all simultaneously satisfied. In ArchieM by balancing thrusts from adjacent spans the user is basically attempting to carry out this process manually (the yield condition being deemed to be violated when the line of thrust lies outside the thickness of the pier).


Q6. How does RING deal with transverse distribution of the load through the fill?

A. RING is a 2D analysis program. Hence the user must make appropriate assumptions about the amount of transverse distribution which will occur (unfortunately this is an area which would benefit from more research).


Q7. I am modelling a multi-ring brick arch bridge. I get very different answers depending on whether I define each ring separately or simply specify an overall barrel thickness. Why?

A. Defining each ring separately sets up a series of separate rings which can interact with each other via interfaces which the user may specify to be frictional. Such a configuration is usually significantly weaker than a single barrel of thickness equal to the sum of all the rings - hence a lower predicted capacity will result.


Q8. I am modelling a multi-ring brick arch bridge. I am not sure if ring separation (delamination) is present. What assumption should I make when using RING?

A. This is a difficult question. Basically it depends on your judgement of the strength of the bond at the joint between rings. If this is low, or non-existent (as it certainly is in many cases) then you should treat the barrel as a series of separate rings, interacting via frictional interfaces.  Also you should remember that the square scaling law for stresses in gravity structures means that a large bridge needs to have a greater inter-ring bond strength to avoid ring separation than a geometrically similar small bridge. Remember that the effect of your assumption on carrying capacity can be dramatic and it will normally be prudent to experiment with differing levels of ring separation (e.g. separating bottom ring only, or partial separation in crown region only for example).
 

Q9. The more bricks I specify per ring, the lower the failure load factor. Why?

A. Relative rotations (hinges) and sliding movements between blocks are a necessary feature of failure mechanisms. In RING these can only occur at the interfaces between bricks/block units. Thus the fewer units that are specified, the less options the optimiser has open to it when trying to find the minimum load factor. In practice when the number of units exceeds say 40 or 50, changes in the computed load factor as a result of adding further units will generally be small.
 

 

Future enhancements:

Feedback on the enhancement(s) you  most want to see in the next version of RING are most welcome. Enhancements currently being considered are: 

  • Including a 'gross displacement mechanism analysis' option (this option is already available in the research version of RING and is potentially useful for dealing with soil-structure interaction problems. In such problems stabilizing horizontal soil pressures are only mobilized with large arch displacements, but conversely these gross arch displacements adversely affect carrying capacity). 
  • Including backing/spandrel masonry as discrete blocks (this option is already available in the research version of RING) 

 

Copyright © 2007, CLADU, The University of Sheffield.

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