Concrete Saddle Modelling Capability
The new reinforcement option in LimitState:RING 3.0 opens up many new possibilities, including the capability to model the effects of a reinforced concrete 'saddle', cast over the arch barrel to increase load carrying capacity.
PDF application note 
Example files
To demonstrate the capability, the predicted failure mechanisms for multi-ring brickwork arch bridges tested by the Transport Research Laboratory (TRL) in the UK which were (a) unstrengthened, and (b) reinforced with a saddle are shown below:
Critical failure mechanisms for unstrengthened (a) and saddle reinforced (b) TRL arch bridges, as modelled by LimitState:RING (click to enlarge)
It was found that the corresponding predicted load carrying capacities matched the experimental capacities reasonably well, as indicated in the table below (which also lists a bridge containing near-surface reinforcement for comparative purposes):
| Bridge Details | TRL Collapse Load (kN) | RING 3.0 Collapse Load (kN) | RING 3.0 / TRL |
| Multi-ring (debonded) | 200 | 198 | 98% |
| Multi-ring (debonded) & Reinforcement | 320 | 325 | 101% |
| Multi-ring (mortared) & Saddle | 701 | 549 | 78% |
Single and multi-span bridges containing reinforced concrete saddles can be modelled, obviating the need to resort to highly simplistic 'rules of thumb' to model the anticipated effects of saddles on load carrying capacity.