Standard V-1 Derivation of Vulnerability Functions

Transcription

1 Derivation of Vulnerability Functions

2 A. Development of the vulnerability functions is to be based on a combination of the following: (1) historical data, (2) tests, (3) structural calculations, (4) expert opinion, or (5) site inspections. Any development of the vulnerability functions based on structural calculations or expert opinion shall be supported by tests, site inspections, or historical data. The development of the vulnerabilities is based on a component approach. The determination of external damage to buildings is based on structural calculations, tests, and Monte Carlo simulations. The wind loads and strength of the building components in the simulations are based on laboratory and in-situ tests, manufacturer s data, expert opinion based on site inspections of actual damage post-hurricane, and code and standards. The internal and content damage are extrapolated from the external damage based upon expert opinion, and confirmed using historical claims data and site inspections of areas impacted by recent hurricanes.

3 B. The method of derivation of the vulnerability functions shall be theoretically sound. The method used in the derivation is based on extrapolating the results of Monte Carlo simulations of physical exterior damage, through simple equations based on engineering judgment, expert opinions, and claims data. Uncertainties at each stage are accounted by distributing the damage according to reasonable probability distributions and validated with claims data.

4 C. Any modification factors/functions to the vulnerability functions or structural characteristics and their corresponding effects shall be clearly defined and be theoretically sound. The Monte Carlo component models take into account many variations in structural characteristics and the result clearly filters through the cost estimation model. There are also different and clearly defined costing considerations applied to each structural type. These adjustments come directly from resources developed exclusively for defining repair costs to structures and therefore are theoretically sound.

5 D. Construction type and construction characteristics shall be used in the derivation and application of vulnerability functions. A detailed exposure study was carried out to define the most prevalent construction types and characteristics in the Florida residential building stock, for different regions of the State. s of varying combinations of the above characteristics (e.g. wood frame, gable end, no window shutters) were created for four different regions in Florida, where the region dictates the square footage footprint of the model

6 E. In the derivation and application of vulnerability functions, assumptions concerning building code revisions and building code enforcement shall be reasonable and be theoretically sound. The structural models include options that allow the representation of building code revisions. In addition to the various models that reflect construction type, region of Florida, and era of construction (weak, medium or strong construction), each model has numerous additional strength features that can be adjusted before simulations are conducted in order to represent various combinations of mitigation features.

7 F. Vulnerability functions shall be separately derived for building structures, mobile homes, appurtenant structures, contents, and additional living expenses. This requirement is fully met. The building structures, mobile homes and appurtenant structures are independently derived. The contents and additional living expenses are separate vulnerabilities, which are functions of (receiving input from) the results of structure vulnerability simulations.

8 G. The minimum wind speed that generates damage shall be reasonable. The minimum one-minute average sustained wind speed at which some damage is observed is 38 mph (3 second gust 50 mph) for appurtenant structures. Site-built and manufactured homes have a very small probability of some very minor damage at 42 mph (3 second gust 55 mph). This probability becomes more significant at 46 mph (3 second gust 60 mph) and increases from there. Simulations are run for a series of 3- second gusts from 50 mph to 250 mph.

9 Part A Form V1 Wind Speed (mph ) 3 Sec Gust Wind Estimated Damage/ Subject Exposure % % % % % % % % % % % % %

10 Part A Form V1 Form V-1 Damage ratio 60% 50% 40% 30% 20% 10% Total damage 0% Wind speed mph (3 sec gust actual terrain)

11 Part B Form V1 Construction Type Estimated Damage/ Subject Exposure Wood Frame 3.41% Masonry 2.66% Mobile Home 7.99%

12 Discussion Reference structures of V-1 are the weak masonry and frame types, and the pre94 tied down MH type of the Florida Hurricane Loss The reported damage in part A is the total damage for all 3 types of building combined, including contents. The reported damage is consistent with the vulnerability matrices used in the computations