Benefits

Technology

Benefits

Flexibility and Power

• Analyse single or multi-span bridges, with no fixed upper limit on the allowable number of spans
• Automatically identify the critical failure mode even if:
  • only a single span is involved
  • sliding is involved
  • modelling multi-ring arch bridges
• Multiple load case facility
• Automatic detection of 'passive' pressures allows deep and multi-span arch problems involving passive pressures to be analysed without difficulty
• Facility to model the presence of arch backing material

Ease of Use

• Undo / redo
• Interaction with the model
• Easy to use wizard system
• Explorers
• Property editor
• 3D graphical output
• Automatic generation of reports
• Comprehensive library of standard road and rail vehicles

Specify Local Properties

• User-definable arch and backfill profiles
• User-definable individual block weights, masonry strength, mortar loss etc.

Previous Track Record

LimitState:RING is the product of over 17 years research effort.

• 'ring' was originally developed as an academic research tool in 1992, with results published in papers in The Structural Engineer and elsewhere
• The first public versions of 'ring' were developed in association with Network Rail
• LimitState:RING 2.0 was developed for worldwide use in association with the International Union of Railways (UIC)

Technology

LimitState:RING idealizes a masonry arch structure as an assemblage of rigid blocks and uses computational limit analysis methods to analyse the collapse state only. Although limit analysis, or ‘plastic’/ ‘mechanism’ analysis techniques were originally developed for steel components and structures, it has since been shown that these can be applied to masonry gravity structures, such as piers and arches. To help understand why limit analysis theory is applicable, compare and contrast the response of a steel column with uniform plastic cross-section and a weakly mortared masonry pier, both subject to a horizontal load F, as shown below

It can be deduced that:

1. Whilst the tensile and compressive strength of the steel column endow it with a finite plastic moment of resistance, Mp, the absence of tensile strength means that the masonry pier does not possess a comparable (i.e. strength derived) moment capacity;
2. however, the thickness and self weight of the pier mean that there is some resistance against overturning and the masonry pier could conceptually be considered as possessing a moment capacity, albeit one that varies with height (equal in magnitude to the normal force at a given cross-section multiplied by half the pier thickness);
3. furthermore, provided pier displacements do not become large, the resistance of the masonry pier against overturning at a given cross-section will remain broadly constant;
4. hence the response of the pier can be considered ‘ductile’, an important requirement in order for limit analysis theory to be applicable.

This is clearly a very simple example. In arch bridges of rather more complex geometry LimitState:RING 2.0 uses rigorous mathematical programming techniques to identify the most critical of numerous possible failure modes (e.g. see this small selection of masonry arch failure modes). Further details of the underlying theory are provided in the Theory and Modelling Guide.