Example Final Product
The final product of a PBEE design is a structure whose performance meets the specified performance target. An example performance target is: the probability of repair costs exceeding half of its initial construction cost, over the building’s design life, is 10% or less. In general, performance targets are expressed in terms of probabilities of DVs exceeding specified thresholds. Possible DVs include:
Cost of repair (“Cost”)
Time of repair (“Downtime”)
Number of severe injuries or deaths due to structural damage (“Casualties”)
Whether or not a building will be deemed safe after damage (“Unsafe placards”)
Example Final Curve
A curve like this shows the probability that repair cost will exceed a certain threshold, and is one possible output from a PBEE analysis
Detailed Process
Define the IM as spectral acceleration at the fundamental period of the building
Obtain hazard curve for this IM, which comes from PSHA done by USGS
Use the hazard curve to pick 8-10 discrete ranges of intensity for the IM
Perform the simplified structural analysis as described in FEMA Project 58 for each intensity level to get the EDPs for the structure
Make a list of all the types and quantities of components in the building that are subject to damage in each direction, which is called the Performance Model
Separate components into groups that will perform similarly (e.g. all the third-floor partition walls in one direction), which is called performance groups
Develop collapse fragility function for the building using the FEMA Project 58 simplified method
Develop residual drift fragility function for the building using the FEMA Project 58 simplified method
Input the above information and basic project data (e.g., cost of construction, number of stories, etc.) into the PACT Tool
Run the Monte Carlo simulation to quantify the seismic risk
Decide if building meets target performance goals and revise design if necessary
Realization Process
This proess is repeated on the order of hundreds to thousands of times by the PACT tool in order to calculate the range of possible performance levels for a structural design
Figure below adapted from figure 2-4 of Volume I: Methodology (2018 Edition) released by FEMA as part of
Project 58 (see references)