Frequently Asked Questions
What information is required to conduct a screening (non-engineer) analysis?
Building Class (Steel Moment Frame, Concrete Moment Frame, Wood Frame, etc.), Location (Latitude-Longitude), Building Design Year, Number of Stories, and Evaluation Lifetime.
What is a Probable Maximum Loss (PML)?
The expected maximum percentage monetary loss (damage level) that will not be exceeded for 9 out of 10 similarly constructed buildings (exceeded by 10% of other similar buildings) at a given ground shaking level.
What is a Probable Loss (PL)?
A PL is the best prediction of loss because it includes the randomness associated with ground shaking and building damage. This is the actual loss that should be encountered on average over a certain return period. The PML tends to be a conservative estimate because it represents the 90% fractile. The PL curve, however, includes the entire distribution of loss variation.
- Who uses your products?
We have a number of clients representing both private and government enterprises. Our client list includes structural design engineers, due diligence engineers and retrofit engineers.
- How long does it take to be trained?
The program offers a tutorial to get you started. The process for executing an analysis is very straightforward and the online help system is remarkable. A substantial portion of the FEMA-310 document is included in the help system. In addition we are committed to helping you get started and make sure that you are comfortable with the program. Phone support is available to answer any questions or concerns you might have.
How can I get help on filling out the building characteristics worksheet?
Much of the FEMA-310 document exists within the help system. If you have a question about a particular building characteristic and how to evaluate it, just click the help and select the feature. A FEMA-310 description of the characteristic appears with guidance on how to evaluate it.
- Are your damage functions based on MMI?
Our damage functions are primarily composed of observation sources. We dont want to loose the wealth of information regarding MMI-based damages, yet we want to include some of the recent damages that can be correlated to instrumental observations. We have therefore developed our damage functions based on MMI and instrumental ground motions. We have assembled both insurance information as well as earthquake reconnaissance data. You can be assured that the damage functions include and reflect the best mix of available data.
- For the worst-case event ST-RISK™ calculates a certain PML. The
2% in 50-year loss is higher. How can this be?
Probabilistic ground motions and losses can exceed the worst-case scenario. The reason for this is due to inclusion of uncertainty in the ground motion attenuation equations and damageability function. For example, the hazard at a particular level may be driven by values of ground motion that are above the mean best predicted attenuation function. If we could reduce these uncertainties to zero then the probabilistic losses would never exceed the worst case event. However, unless we can obtain better data to narrow uncertainties in historical observations, we are not justified in reducing these uncertainties.
Where can I get typical retrofit costs?
The best estimate for typical retrofit costs come from owners and contractors with experience in specific types of retrofit. Without this information, the most readily available publications are FEMA-156: Typical Costs for Seismic Rehabilitation of Existing Buildings, Second Edition, Volume 1 and FEMA-157: Typical Costs for Seismic Rehabilitation of Existing Buildings, Second Edition, Volume 2. The information provided in these two documents will provide a good estimate of relative cost, but may not be applicable for certain types of structures in certain areas of the country. It is recommended to carefully use the values provided in these documents.
How can I email results to other people?
You can create a PDF of the results and email that file. To generate a PDF, install a PDF generating utility such as Win2PDF™, then "print" your results to the PDF. The utility shows up as an available printer, but instead of printing your results to paper, it generates a PDF which you can email.
What do the PML uncertainties represent?
It is important to understand that the PML uncertainties only reflect the uncertainties associated with evaluating the building properly. Two engineers will probably not characterize a building the same and some characterizations are very difficult to assess. The PML uncertainties only represent the uncertainties in characterization and do not reflect any uncertainties in the hazard or uncertainties in determining the correct PML.