Table 1: Bolton laboratory test results

Table 2: TRL field test results

Table 3: Sheffield laboratory test results

Table 4: Salford laboratory test results

Bolton laboratory tests (full-scale)

In Bolton, UK, in the early 1990's a number of 3m and 5m span masonry arch bridges were tested in the laboratory. A key advantage of these tests over field tests was that the internal constructional details and material properties were known.

RING was originally developed to assist with the interpretation of the results from these laboratory tests. In Table 1, sample LimitState:RING analysis results are presented alongside experimental test results (only bridges with detached spandrel walls are included since these behave in a two dimensional manner). It is clear from Table 1 that predictions are quite conservative when the default soil angle of friction is used (Column A), but become much more realistic when the measured value is used (Column B).

TRL field tests (full-scale)

Also in the late 1980’s and early 1990’s, the Transport and Road Research Laboratory (TRRL, now TRL) carried out a series of load tests to collapse on redundant arch bridges. Most bridges failed in four hinge mechanisms, although some of the bridges were reported as failing by ‘three hinge snap through’ or in ‘compression’ (material failure). It was likely that many of the bridges tested were restrained considerably by their attached spandrel walls and/or masonry backing.

In 2001 TRL were commissioned to independently validate RING 1.1 and other available masonry arch bridge analysis software. As part of the validation process it was decided that the programs would be used to predict the carrying capacities of 5 of the field bridges load tested more than a decade previously. Details taken from the TRL report relating to RING for 4 of the bridges are provided in Table 2.

It is evident that agreement between the RING predictions and the full-scale test results was found to be good. Based on this evidence Network Rail have confirmed that RING is a suitable program for use to assess masonry arch bridges on the UK rail network.

Sheffield laboratory tests (small-scale)

A series of small-scale tests were performed at the University of Sheffield to confirm the relative importance of passive restraint effects (i.e. as parts of the arch barrel remote from the load sway into the fill) and live load dispersion effects (i.e. as the live load spreads through the fill).

Experimental and LimitState:RING 2.0 results are summarised in Table 3. It is evident that the LimitState:RING 2.0 predictions are remarkably good (all within 10% of the experimental results), verifying that the simplified LimitState:RING 2.0 soil model is capable of capturing the key effects of backfill.

Salford laboratory tests (full-scale)

To better establish the nature of the soil-arch interaction which takes place, a series of bridges were recently tested at the University of Salford, UK. Experimental and analysis results are provided in Table 4, where it is clear that, when the measured soil strength parameters are used (B), LimitState:RING 2.0 provides a very accurate prediction of the load carrying capacity.

For further information see:

LimitState:RING Theory and Modelling Guide.