1. Managing Railway Bridges Bryant Le Professor John Andrews

2. >100 years old Bridge Asset Railway bridges is a major railway asset group 35,000 bridges 50% of the population more than 100 years old Bridge management and maintenance planning is a difficult task

3. Aims and Objectives Develop a management tool Maintenance strategy (repair and renew) can be investigated and optimised Longer term objective to minimise the whole life costs.

4. Current bridge system Structure condition marking index (SCMI) Bridge condition is often rated in term of condition score from 0-100 Problems Data not available with the rating system started in 2000, only 60% of bridges were inspected by 2006 Large inspection interval (6 years) Asset contains only one set of score Concern from the ORR (Office of Rail Regulation) about the accuracy of the scores

5. Degradation study Study historical work done data Analyse the time of the component requiring a certain type of repair Distribution fitting As New Component life As new conditionGood conditionPoor conditionVery poor condition Needs minor repair Needs major repair Needs replacement β1, η 1β3, η 3 t (year) β2, η 2 Weibull distribution

6. Degradation study Weibull Fitting (Weibull 2p RRXY)Number of data Bridge componentMaterialConditionInterventionBetaEta (year)Mean (year) CompleteCensored GIRDERMetal GoodMinor Repair 1.7123.3920.863772 PoorMajor Repair 0.8744.2747.491235 Very Poor*Replacement* 1.14149.63142.7731 DECK Metal GoodMinor Repair 1.26510.289.541667 PoorMajor Repair 1.03820.0019.711058 Very PoorReplacement 1.00928.4728.361472 Concrete GoodMinor Repair 1.08219.0918.5237 Poor*Major Repair* 1.00026.67 04 Very PoorReplacement 0.97634.2634.63210 Timber GoodMinor Repair 1.3123.993.68125 PoorMajor Repair 1.3717.136.5256 Very PoorReplacement 1.5016.125.522740 BEARINGMetal GoodMinor Repair 0.83814.9416.411239 PoorMajor Repair 2.12914.4312.78510 Very Poor*Replacement* 1.00021.92 12 ABUTMENTMasonry Good*Minor Repair* 1.00051.94 19 Poor*Major Repair* 1.000100.87 12 Very Poor*Replacement* 1.000150.00 00 The bridge is considered in term of principal elements: –girder, –deck, –bearing, –abutment Weibull distribution is best fitted Increasing failure rates

7. Bridge models Widely adopted Easy and fast to construct and run Consider opportunistic maintenance, servicing, environment, repair delay. Constant deterioration rates Model size increases exponentially for more complex problem Markov modelPetri-Net model Non-constant deterioration rates Models coating of metal element Interventions is not effective after a certain no. of times carried out Model size is manageable Possession schedule is taken into account when carry our repair

8. Model outputs The expected maintenance cost Bridge future condition profile

9. Model comparison Markov model Petri-Net model

10. Model comparison

11. Maintenance Strategy Optimisation Multi-objective Genetic Algorithm Optimisation Find optimum maintenance strategy gives: –Best condition profile –Lowest WLCC cost Model inputs (variables ) –Repair strategy –Scheduling of maintenance (delay repair) –Inspection, servicing interval –Possession schedule

12. Optimisation Results Optimised maintenance strategies

13. Thank you for your time