Objective: Support decision making when designing monitoring schemes

Transcription

1 TRIMM is supported by funding from the 7 th Framework Programme Call: SST Theme: Advanced and cost effective road infrastructure construction. management and maintenance Wim Courage TNO

2 Objective: Develop SCBA model to assess life cycle costs and benefits of different maintenance scenarios - especially scenarios with different or without monitoring systems Support decision making when designing monitoring schemes

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4 EUSL Availability Safety Environment Actions Do nothing Remixing Renewal Condition Rutting Skid Resistance Longitudinal Evenness

5 s Action related Condition related Penalty denoted Actions Do nothing Remixing Renewal Condition EUSL Availability Safety Environment Rutting Skid Resistance Longitudinal Evenness denoted... denoted.. Δ..Δ denoted.. Δ..Δ

6 ,,,,, EUSL Condition Action

7 SIMPLE EXAMPLE what can/will happen (see figure) when we have: Repetitive decision periods decision at beginning of period e.g. each year 2 Actions a repair ā do nothing 2 States (conditions) 1 good 2 bad Degradation Transition probabilities p ij probability to change from state i to state j within a period

8 SIMPLE EXAMPLE what implications would this have Each branch will be associated with costs: s of actions direct costs unavailability costs s of exploitation each state/condition represents a risk (costs) with respect to: unavailability safety

9 SIMPLE EXAMPLE Planning/decisions Noting the repetitive character of the branches. we get, s condition at beginning of period s condition at end of period s a condition as a result of the action discount for future costs transition probability after action a to move from state s a to s cost associated with a node from the tree, costs risk of exploitation costs of implementing an action a Which enables cost optimisation and maintenance scenarios

10 Markov Decision Proces (MDP),,, s condition at beginning of period s condition at end of period s a condition as a result of the action discount for future costs transition probability after action a to move from state s a to s cost associated with a node from the tree, costs risk of exploitation costs of implementing an action a, _...,,,,,,,,,,, Planned strategy of actions

11 Net present Value 1 Year Action State before Action State after Action Monitorin g Maint. EUSL Total 1 DN DN DN DN DN DN R DN DN DN Planned strategy of actions

12 Transition Matrices: States s where.. with

13 Measurements: Year Class Year 1 Class n ij is the number of transitions from state i to state j within a given time period and n i is the total number of elements in state i before the transition

14 Example: State s of bridge is monitored Conservative upper bound is used for safety measures: When s u exceeds the value of 3.30, heavy traffic is forced to take the alternative route, at a cost of 730 /year. When s u exceeds the value of 4.85, all traffic is forced to take the alternative route, which costs 3650 /year as a result of travel time los Description value unit AADT passenger cars 4000 #/day AADT trucks and lorries 1000 #/day distance main route 10 km distance alternative route 30 km unit prize for TTL 10 Euro/h Traffic speed V 100 km/h Period 1 Year Horizon 25 Year discount rate λ Criterion 1 for f u Criterion 2 for f u Action cost Initial state 1 - State after action 1 -

15 Example: 2 Monitoring systems: E Reference system 50 initial cost 2 annual cost Alternative system 100 initial cost 4 annual cost

16 Example: E Reference system 50 initial cost 2 annual cost Alternative system 100 initial cost 4 annual cost

17 Example: Year Action State before Action Reference scenario State after Action Monit. Maint. TTL Total 1 DN DN DN DN DN DN R DN DN DN DN DN DN R DN DN DN DN Reference DN 2 system DN R initial cost DN DN annual 2 0cost DN DN Year Action State before Action Alternative scenario State after Action Monit. Maint. TTL Total 1 DN DN DN DN DN DN DN DN DN R DN DN DN DN DN DN DN DN Alternative DN 3 system R DN initial 4 cost DN annual cost 23 DN DN DN

18 CBA: method based on Markov Decision process for maintenance planning SCBA: Extensions with respect to direct and indirect costs (social costs) Monitoring data: condition values and transitions (degradations) NPV s for comparing added value of monitoring systems Feasible method, although laborious Connecting: data information condition performance decisions actions Added value + : operational maintenance planning Further need of performance models