Define possible interventions and strategies

Estimation of financial needs and condition of infrastructure assets

Hamed Mehranfar

Yushu An

2024-03-25

What type of interventions are we talking about?

Maintenance interventions

• All activities that help to ensure that an object provides the level of service for which it was constructed.
  • Routine maintenance interventions
  • Rehabilitation interventions
  • Renovation interventions

Development interventions

• All activities that help to ensure that an object provides a new level of service.
  • Adaptation interventions
  • Transformation interventions
  • Expansion interventions

Routine maintenance: Relatively small interventions that help prevent the occurrence of inadequate LOS due to deterioration. They are normally included in intervention strategies to be executed at regular time intervals.

Rehabilitation: Relatively large interventions that help prevent the occurrence of an inadequate LOS due to deterioration. They are normally included in intervention strategies to be executed when the item reaches a specific state.

Renovation: Relatively large interventions that help prevent the occurrence of an adequate LOS due to deterioration, by restoring the item to a new or like new state. They are normally included in intervention strategies to be executed when the item reaches a specific state.

Intervention strategies and intervention programs

Intervention strategies

• Include all interventions to be executed on an item taking into consideration of all possible conditions of the item
• Are developed without consideration of other sub-items, items or super-items

Intervention programs

• Include the interventions to be executed on items taking into consideration the specific conditions of the items
• Are developed with or without consideration of the other sub-items, items, or super-items

• The interventions on an item include all interventions on the sub-items of the item.
• The conditions of the item include the conditions of the sub-items of the item.

Intervention strategies example

Bridge type	CS1	CS2	CS3	CS4	CS5
Reinforced concrete	Do nothing	Do nothing	Do nothing	Rehabilitation	Replacement
Pre-stressed concrete	Do nothing	Do nothing	Do nothing	Rehabilitation	Replacement
Masonry	Do nothing	Do nothing	Do nothing	Rehabilitation	Replacement
Composite	Do nothing	Do nothing	Rehabilitation	Renewal	Replacement
Metal	Do nothing	Do nothing	Rehabilitation	Renewal	Replacement

Introduction – Which processes do you want to consider?

Intervention	Description of activities
Do nothing	-
Rehabilitation	- Replacement of waterproofing - Restoration of parts of drainage system - Improvement or replacement of construction joints - Repair of the reinforced concrete - Renewal of any finishing
Renewal	- Strengthening of one or more structural elements - Renewal of the drainage system
Replacement	- Replacement of part or all of the structure

Activities can affect only the future (e.g., waterproofing layer, application of a corrosion inhibitor which builds a protective layer on the reinforcement) Activities can affect the present and future (e.g., repair by adding new concrete layer)

Interventions in relation to condition state

CS	General description	General description of damage	Values of damage indicators
1	Good	None/Insignificant	Concrete elements: Small superficial cracks, no indication of corrosion, no or few humid zones Bearings: No indication of corrosion or damage
2	Acceptable	Minor	Concrete elements: Small cracks due to the corrosion of the reinforcement, some rust spots, some humid zones but no leaching of the concrete Bearings: Some indication of corrosion or damage
3	Damaged	Significant	Concrete elements: Some calcium deposits along concrete cracks, some spalling of concrete with less than 10% of reinforcement exposed, insignificant loss of cross section area of the reinforcement, humid zones with leaching of the concrete Bearings: Medium amount of corrosion and damage
4	Poor	Extensive	Concrete elements: Significant calcium deposits along concrete cracks, spalling of concrete with less than 25% of exposed reinforcement, occurrence of pitting corrosion, large humid zones with leaching of concrete Bearings: Significant corrosion, including corroded support plates and anchoring connections
5	Alarming	Safety is endangered	Concrete elements: Extensive spalling of concrete with more than 25% of exposed reinforcement, significant loss of cross sectional area of the reinforcement, advanced pitting corrosion occurring, large humid zones with leaching of concrete Bearings: Advanced corrosion, seized bearings, anchoring connections heavily deteriorated

Activities can affect only the future (e.g., waterproofing layer, application of a corrosion inhibitor which builds a protective layer on the reinforcement) Activities can affect the present and future (e.g., repair by adding new concrete layer)

Connect interventions and states to service

CS	Intervention	Effectiveness vectors					Maintenance costs	Travel time costs	Accident costs
		1	2	3	4	5	\(mu/m^2\)	\(mu/m^2\)	\(mu/m^2\)
1	Do nothing	Same as the deterioration trans. probs.					0	0	0
2	Do nothing	Same as the deterioration trans. probs.					10	0	0
3	Do nothing	Same as the deterioration trans. probs.					50	0	0
	Rehabilitation	0.8	0.2	0	0	0	500	1’000	40
	Replacement	1	0	0	0	0	3’500	3’000	10
4	Do nothing	Same as the deterioration trans. probs.					100	100	50
	Rehabilitation	0.75	0.25	0	0	0	550	1’100	45
	Replacement	1	0	0	0	0	3’500	3’000	10
5	Do nothing	Same as the deterioration trans. probs.					500	500	100
	Rehabilitation	0.6	0.4	0	0	0	750	1500	75
	Replacement	1	0	0	0	0	3’500	3’000	10

How to evaluate possible maintenance intervention strategies

flowchart TB
    step1[<font size=2>Step 1: Estimate the state of each object at t=0]
    step2[<font size=2>Step 2: Determine the maintenance intervention strategy]
    step3[<font size=2>Step 3: Determine the steady state probabilities]
    step4[<font size=2>Step 4: Determine the costs associated with the steady state]
    step5[<font size=2>Step 5: Generate the view of condition and costs over time]
    step6[<font size=2>Step 6: Repeat steps 2-5 for all strategies]
    step7[<font size=2>Step 7: Compare results with goals and constraints]

    step1 --> step2
    step2 --> step3
    step3 --> step4
    step4 --> step5
    step5 --> step6
    step6 --> step7

Next steps

• Today:
  • Determine at least two possible interventions
  • Estimate intervention cost

• Next step:
  • Determine optimal intervention strategy (if there is enough time)
  • Mid-term presentation practice

Thank you for your attention!

Questions?

Hamed Mehranfar
Doctoral student
hmehranfar@ethz.ch

ETH Zürich
Institute of Construction and Infrastructure Management (IBI)
Chair of Infrastructure Management
HIL G 32.2, Stefano-Franscini-Platz 5
8093 Zürich

www.ibi.ethz.ch