Benefit-cost ratio calculator
This calculator computes a loss curve considering the original properties of an asset, and another loss curve considering the behaviour of the asset after retrofitting. The average annual loss is combined with the expected life expectancy of the building and retrofit cost to compute a ratio that reflects whether is worth or not to perform retrofitting.
Blueprint information
- Status:
- Complete
- Approver:
- John Tarter
- Priority:
- Not
- Drafter:
- None
- Direction:
- Approved
- Assignee:
- Anton Gritsay
- Definition:
- Approved
- Series goal:
- None
- Implementation:
-
Implemented
- Milestone target:
-
0.4.6
- Started by
- John Tarter
- Completed by
- John Tarter
Related branches
Related bugs
Sprints
Whiteboard
This is an update from Vitor relating to this calculator
The addition of this calculation
- BCR = (EALo - EALr)(1-
Firstly, this calculator uses the probabilistic event-based or the classical psha-based risk calculators (the latter is recommended) to compute two loss curves: one considering the original properties of the asset and a second one with considering the behavior of the asset after retrofitting. These curves needs to be computing assuming a time span for a year. The difference in the properties of the two assets is taken into account by indicating two different vulnerability curves (original and retrofitted).
When these two curves have been computed, the expected annual loss (EAL) for each curve needs to be computed. A function that computes this parameter have been already coded in OpenQuake, but it is not being currently used.
After computing these two values (original and retrofitted EAL), the following formula needs to be applied:
BCR = (EALo - EALr)(1-
Where:
- BCR - Benefit cost ratio
- EALo - Expected annual loss for original asset
- EALr - Expected annual loss for retrofitted asset
- r - Interest rate
- t - Life expectancy of the asset
- C - Retrofitting cost
Notice that it was assumed that the exposure model xml schema supports a retrofitting cost and a life expectancy per asset and that an interest rate can be inserted in the config file.
