8. CONCLUSIONS

The following general conclusions can be drawn from the results of the two load tests, on the bridge in its unstrengthened condition and after being Archtec strengthened, and from predictions of their behaviour using numerical simulations.

1. Based on strain measurements, the Archtec anchors used to strengthen the bridge are stressed under working loads and are contributing to the bridge’s stiffness.
    
2. Archtec strengthening reduces tensile intrados macro strains and, therefore, reduces the likelihood of loosening masonry under cyclic live loads.
    
3. Direct instrumentation of cracks and intrados macro strain measurements have demonstrated that Archtec anchors positioned across transverse cracks reduce cyclic opening and closing under repeated live loads. The main benefit of this behaviour would be the reduction in load cycle derived hysteretic damage; opening and closing of cracks under traversing traffic. Reducing this type of damage will almost certainly be beneficial to the bridge service life.
    
4. Predictions of strain and displacement made with DE numerical simulations agree well with measured values, both masonry and anchors. Results are conservative because of skew behaviour, transverse load distribution and spandrel wall stiffening.
    
5. It has been demonstrated that Archtec strengthening can be designed not only for the ultimate limit state(4) (strength) but also for the serviceability limit state (deflections, strains and stress ranges).

In summary, the two principal objectives of the tests;

• to validate the use of the ELFEN DE analytical method to predict serviceability behaviour in un-strengthened and strengthened arches, and,
   
• to demonstrate that the retrofitted anchors contribute to the structural behaviour under service loads and that the effects are beneficial and measurable, have been achieved.

9. REFERENCES

1. Gifford and Partners. October 2003, Proposed Monitoring of Pop Bottle Bridge
    
2. Gibb Ltd for Rail Property Ltd. March 2001. 00/01 BE4 Assessment Programme – Assessment and Inspection Report.
    
3. Gifford and Partners. March 2002. Pop Bottle Bridge – Arch Barrel Special Assessment. Report number B1660a/214/R01.
    
4. Gifford and Partners. August 2003. Archtec – Verification of Structural Analysis. Report number B1660A/V10/R02 Revision C dated 6 April 2004.