FAQ


This area gives you the answers to some of the more common questions about ring2.0. However, for logged in users, there is also an area where you can ask specific questions of the limitstate team.

 

For new ring users

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

  3. Is ring2.0 being constantly updated?

  4. Has ring2.0 been validated against full-scale test results?

  5. How does a multi-span analysis work using ring 2.0? Does it involve manually balancing thrusts from adjacent arches?

  6. How does ring2.0 deal with transverse distribution of the load through the fill?

  7. 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?

  8. 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 ring2.0?

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

  10. Can I model 'slender' piers using ring2.0?

  11. Do I need to apply global factors of the type used in the MEXE method to the computed ring2.0 load factor (e.g. profile factor, material factor, condition factor etc.)?

For users upgrading from ring1.5

  2. Can I import my ring1.x files into ring2.0?

  3. I am happy with ring1.5, so why should I upgrade?

For new ring users

Q1. What is the 'failure load factor' ?

For whatever live load is specified, ring2.0 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 ring2.0 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?

If an end abutment is specified then often ring2.0will 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 ring2.0 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 ring2.0 to manually specify pressures acting on blocks below the skewback, this can be a laborious exercise).

Q3. Is ring2.0 being constantly updated?

Yes. limitstate will be regularly updating the software during 2007 and beyond.

Q4. Has ring2.0 been validated against full-scale test results?

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 ring2.0 manual.

Q5. How does a multi-span analysis work using ring2.0? Does it involve manually balancing thrusts from adjacent arches?

ring2.0 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 other software, 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 ring2.0 deal with transverse distribution of the load through the fill?

ring2.0, unlike previous versions, allows load to be distributed transversely. This is used to compute the effective bridge width (when the auto-width calculation is enabled).

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?

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 ring2.0?

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?

Relative rotations (hinges) and sliding movements between blocks are a necessary feature of failure mechanisms. 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.

Q10. Can I model 'slender' piers using ring2.0?

Yes, ring2.0 can model piers of any height/width. Some codes of practice distinguish between 'stocky' and 'slender' piers in multispan masonry arch bridges, with bridges containing piers that are deemed 'slender' requiring a full multispan analysis. However, the distinction is somewhat artificial as in some cases the critical failure mode in a bridges comprising 'stocky' piers will actually involve more than one span (indicating that a single span analysis will be non-conservative). The key thing is that ring2.0 will identify the critical failure mode, whether this involves one, two or even more spans.

Q11. Do I need to apply global factors of the type used in the MEXE method to the computed ring2.0 load factor (e.g. profile factor, material factor, condition factor etc.)?

Generally speaking the answer is 'no' as ring2.0 directly takes account of e.g:

  1. the actual profile of the arch;
  2. the actual masonry strength specified;
  3. the effects of defects such as ring separation and mortar loss.

However, as ring2.0 is a 2D modelling program the global effective width should be reduced e.g. if longitudinal cracks are present.

For users upgrading from ring1.5

Q1. Why isn't ring2.0 free for commercial use?

There are three main reasons:

  1. ring1.x was unsupported software which deterred some potential commercial users from using it.

  2. To produce a modern high quality software application is very time consuming and a dedicated development team was required to incorporate the features users have requested.

  3. The generation of revenue from the product is essential for sustainability, enabling its ongoing availability with a programme of continuous improvement.

For academic users wishing to use ring2.0 for educational or research purposes, please click here .

Q2. Can I import my ring1.x files into ring2.0?

Yes (the upgrade wizard will warn you in the event that your old file has properties which are not compatible with ring2.0).

Q3. I am happy with ring1.5, so why should I upgrade?

See all these reasons!

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