developments to the RING masonry arch bridge analysis software

1. developments to the RING masonry arch bridge analysis software intro • what is RING? • >5000 downloads from www.shef.ac.uk/ring • recent & current developments sponsored by Network Rail & UIC

2. the presentation… 1992 developments to RING: (i) recent (ii) current (iii) future... 2003/4 2004/5 2005+

3. (i)recent developments • speedup for multi-ring problems (in RING 1.5) • obtained by switching to a joint equilibrium formulation

4. Shear force, s Shear force, s j j m j = tan j j Normal force, n Normal force, n (i) recent developments [cont.] • RING originally treated friction as associative; i.e. dilatancy accompanies sliding • new version will provide option to model non-associative friction (more conservative)

5. essence of non-associative friction algorithm: • involves solving a series of LP sub-problems with successively modified failure surfaces • sub-problem governed by a Mohr-Coulomb failure surface with an effective cohesion intercept • a negative angle of friction is also initially specified • parameters are updated at each iteration by referring to the real problem, with the angle of friction also being successively relaxed towards zero Shear force Algorithm failure surface Problem failure surface Normal force

6. non-associative example • new algorithm applicable to large problems • cpu time  20 that for associative friction problems • often larger reductions in load factor for walls than arches…

7. (ii)current developments: • complete rewrite of program underway… • better documentation • incl. manual focussed on railway bridges (for UIC) • better user-interface: • possible to change local, block level, properties • no limits on numbers of spans, blocks etc. • greater interactivity • provision of load library • gross displacement analysis feature

8. (iii) future developments: • key priorities: • soil-structure interaction • reinforcement synthesis • presence of RC slabs (d) full 3D modelling

9. (a) soil-structure interaction • currently influence of backfill (if present) modelled indirectly: • the form of the passive pressure distribution is specified in advance of an analysis Dispersion of applied load Passive fill pressures

10. (a) soil-structure interaction [cont.] • but RING quite often identifies non-standard failure modes… • …here soil pressures may not be as initially specified [in practice likely to be greater resistance]

11. Load • another non-standard failure mode (Konjic bridge, Bosnia)

12. (b) reinforcement synthesis • what if bridge found to be under-strength? • limit analysis & limit design synthesis problems are closely linked • design synthesis could perhaps be used to automatically identify: • soil reinforcement • even truss reinforcement e.g. ‘arch’ at Seville Expo(!)

13. RING has recently been enhanced, making it much faster for some problems RING is now being rewritten & will be enhanced & extended in the future downloadable from: www.shef.ac.uk/ring conclusions developments to the RING masonry arch bridge analysis software