Background and context

1. CYCLIC LOAD CAPACITY AND ENDURANCE LIMIT OF MULTI-RING MASONRY ARCHESClive Melbourne, Adrienn Tomor Jinyan WangSchool of Computing, Science and Engineering, University of Salford

2. Background and context • 40% of all European bridges is masonry • 60% of masonry bridges are over 100 years old

3. Background and context • Due to the increasing traffic loading the life expectancy, capacity and fatigue performance of arch bridges needs to be better understood. • Most experimental work so far has been carried out under static loading. • Ring separation failure under cyclic loading is one of the main sources of concerns as it can significantly reduce the capacity of multiring brickwork arches.

4. 5m span arches • 3m span arches Test series

5. A series of 3m span arches (2 rings)

6. and a series of 5m span arches (3 rings) under static and cyclic loading.

7. Loading Dead load Live load Cyclic loading Static loading

8. TEST RESULTS

9. STATIC LOADING3M SPAN Four – hinge mechanism

10. STATIC LOADING5M SPAN Ring separation

11. TEST RESULTS

12. CYCLIC LOADING3M SPAN Ring separation

13. CYCLIC LOADING3M SPAN COLLAPSE: By hinging

14. CYCLIC LOADING5M SPAN Ring separation

16. Load (% of static load) 100 75 50 25 100,000 200,000 300,000 400,000 Number of cycles • Small increase in the load level can cause rapid failure. • Failure occurred within a relatively few number of cycles (400,000) once endurance limit was reached. • Endurance limit was reached around 37-57% of the static load capacity of fully bonded arches. • Typical failure mode was ring separation. 57% 37% Endurance limit (5m arch) Endurance limit (3m arch)

17. Load (% of static load) 100 75 50 25 Endurance limit (5m arch) 100,000 200,000 300,000 400,000 Endurance limit (3m arch) Number of cycles Mortar bond (%) 57% 37%

18. 100 75 50 25 100,000 200,000 300,000 400,000 50 25 50% 0% Mortar bond (%) Load (% of static load) Endurance limit (5m arch) Endurance limit (3m arch) Endurance limit Number of cycles

19. Interactive S-N CURVE Ring separation Number of cycles (Log) 4-hinge mechanism Stress (Log) 3M TEST DATA 3m test data H Slope (m) Number of cycles (Log) Load (Log) Interactive S-N curve An Interactive S-N (ISN) curve can be developed for each mode of failure for every arch. Endurance limit (E) can be expressed for each mode of failure from the Interactive S-N curve as a function of the load range (R), slope (m) and intersection (H): E = 10H R–m • As a practical tool an Interactive S-N (ISN) curve can be developed for each mode of failure for every arch.

20. Large-scale: • Arch sections • Small-scale: • Triplet tests Shear testing Shear capacity of the mortar-brick bond was also investigated

21. Triplet tests • Mortar bond in arches is rarely perfect (100%). • Shear capacity with various extent of mortar bond was tested • under static and cyclic loading.

22. Trendline for static tests Shear testing summary Shear testing summary • Exponential relationship between shear strength and the extent of mortar bond was indicated under static loading. • Significant reduction in the static shear capacity was observed for <90% bonded surface area. • Large-scale arch sections show significantly greater shear capacity compared to triplets. • Cyclic shear capacity seems to be significantly smaller than the static load capacity.

23. Conclusions • Cyclic load capacity of arches is significantly lower (up to 60%) than static load capacity. • Under cyclic loading multiring arches failed by ring separation at significantly lower loads than that associated with a four-hinge mechanism. • A model for an Interactive S-N curve for the various modes of failures was proposed for assessment of residual life and fatigue performance. • Shear capacity of the mortar bond showed strong relationship to the extent of mortar bond.

24. END

26. Finite elements analysis

27. FE analysis Longitudinal shear stresses DL + LL DL 1st crack

28. Finite elements analysis • Currently there is not enough data available for calibrating and modelling arches under cyclic loading. • Convenient for modelling arches as a continuum, but ring separation and other modes of failures need to be investigated specifically. • Under static loading FE showed that radial cracks can locally increase the longitudinal shear stresses that can cause ring separation at a significantly lower load associated with formation of hinges.