3. Direct Monetary Loss Estimation

The second objective of the project was to determine the monetary losses for MMI seismic events VI - XII. The steps involved in applying this methodology are; (1) determine the structural mean damage factors per building, (2) determine the non-structural mean damage factors per building, (3) estimate the dollar loss per building, and (4) model the spatial distribution of the results using a GIS.

3.1 Assessment of Structural Damage

Damage Probability Matrices (DPM’s)

The methodology applied in this analysis uses damage probability matrices that were developed for the BC 31 building prototypes. “These matrices were developed assuming that the buildings are very nearly regular in shape and they are founded on firm ground, designed to a code prior to 1990” (Onur, 2001). The DPM is used to determine the probability of being in a certain damage state given the MMI level of a seismic event. In other words, they are used to relate different levels of ground shaking intensities (MMI VI - XII) with the probability of being in specific damage states, which are defined as follows (Table 3.1.1.).

Table 3.1.1. The 7 Damage States used in Structural Damage Probability Matrices.

A damage factor (DF) range is associated with each damage state.  The damage factor is defined as the ratio of dollar loss to the replacement cost.

Mean Damage Factors (MDFs)

In order to estimate the total amount of structural damage expected per building, we used MDF’s for MMI events VI-XII which was provided in Tuna Onur’s thesis. The structural MDF is defined as a total measure of structure damage, representing the ratio of dollar loss to replacement cost given a MMI. This MDF is derived from all of the discrete damage states by adding up the product of the CDF’s and their corresponding probabilities for each MMI level.

A structural MDF value for each intensity level (MMI VI - XII) was assigned to each of the 31 prototypes included in the BC 31 Classification.  This allowed us to relate the values to our building inventory through prototype.  Structural damage per block has some of the highest expected damage values, which could be determined through three different methods of weighting; average MDF per block, average MDF per block weighted by footprint area and average MDF per block weighted by total area (Figure 3.1.1).  Footprint defines the perimeter of a building.  Total area is defined as subfloors plus stories multiplied by footprint area.  In this analysis, structures sustaining 60% structural damage or above are considered as right offs that require complete reconstruction (Ventura).  For full size structural MDF maps MMI VI - XII, refer to Appendix D.

Figure 3.1.1. Weighting Methods for Structural MDF

3.1 Assessment of Structural Damage

In order to estimate non-structural damage, DPM’s for non-structural damage were needed. The DPM’s used for this methodology were developed by Cook in 1999, and describe five damage states rather than seven. Damage states used in the DPM’s are defined for each type of non-structural component: displacement sensitive, acceleration sensitive and building contents.

Displacement Sensitive Components

The content of displacement sensitive components consists of “non-load-bearing partition walls, exterior wall panels, architectural finishes, veneer, cladding and penthouses” (Onur, 2001).  Damage to displacement sensitive components can be described in the following table in terms of damage states.

Table 3.2.1.  Damage States for Displacement Sensitive Components

Figure 3.2.1. Non-structural MDF per block for MMI VIII

Acceleration Sensitive Components & Building Contents

Acceleration sensitive components are described as “cantilever elements, parapets, mechanical and electrical equipment, suspended ceilings, elevators, tanks, pumps, piping systems, racks and cabinets” (Onur, 2001). Building contents describes the expected damage sustained to objects within a building such as bookcases, office equipment and furnishings and are also considered acceleration sensitive. The damage to these components is described in damage states in the following table.

Table 3.2.2. Damage States for Acceleration Sensitive Components

Non-Structural Mean Damage Factors (MDF’s)

Similar to structural damage estimation, these damage states are also associated with a range of DF’s and CDF’s. From the DPM’s, MDF’s can be calculated to express total non-structural damage. Three MDF tables for displacement, acceleration, and building contents containing values for all 31 prototypes and were linked to the building inventory to assess the non-structural impact on Vancouver’s downtown core for MMI VI-XII. The following is an example of the estimated non-structural damage for MMI VIII (Figure 3.2.1.). For full size non-structural MDF maps MMI VI - XII, refer to Appendix E.

3.3 Monetary Loss Estimation

Monetary loss is determined by the amount of structural and non-structural damage to each building. Non-structural damage has a larger impact than structural damage in terms of economic loss. 75% (37.5% acceleration sensitive and 37.5% displacement sensitive components) of the monetary value lost in an earthquake can be accounted for by non-structural damage. The structural damage component makes up the remaining 25%. Building contents are considered acceleration sensitive and are therefore included in the weighting of acceleration sensitive components, used to calculate monetary losses. The monetary loss for each building was determined by the amount of structural and non-structural damage multiplied by a replacement cost value per square foot of damaged structure.

The percentage of building damage was calculated based on the total area of the structure (sub floors + stories * footprint area). Queries were used to weigh structural and non-structural damage, calculate the dollar loss per building, and summarize the values per block to be displayed in a GIS (Appendix F). This was done by relating a replacement cost table, and all the MDF tables with the building inventory.

3.4 Results

The results of our calculation determined that Block 00389 sustained the highest potential for monetary losses within the entire study area. This block is of significant importance because it contains many hospital buildings associated with Vancouver General Hospital. The building with the highest potential for monetary losses was the Laural Pavillion VGH building, with an estimated value of $673,365 for a MMI VIII event, and $2,104,410 for the worst case scenario earthquake, MMI level XII. This building was prototype Concrete Frame with Concrete Walls High Rise (CFHR). The following is a general description of CFHR. “Concrete framed structure with concrete shear walls providing lateral resistance in one or both directions; greater than 8 stories in height. Roof and floors are reinforced concrete slabs and beams. Exterior walls are clad in marble or masonry veneer, steal/glazing panels, precast panels or extensive glazing. Shear walls are located interior (ie. around stair and elevation shafts) or peripherally” (Blanquera, 1999). This prototype has one of the higher replacement cost values, with $110 per square foot of damaged building. This building is expected to sustain 54% structural damage, as well as 21% displacement sensitive component damage and 3% acceleration sensitive component damage. The entire block had a total of $2,103,680 at MMI VIII, $3,171,860 for MMI IX and $4,147,740 for an MMI X event.

Aside from the block containing the Vancouver General Hospital, the building with the highest potential for monetary loss is the Hyatt Regency Hotel, located at 655 Burrard St. This building has 34 stories and has a large footprint of 2,800 square feet. This hotel was built in 1970. This building had a CFHR prototype, associated with the high MDF’s and replacement cost discussed above for VGH. This building is expected to sustain monetary losses ranging from $763,147 for a MMI VIII event to $2,384,998 for MMI XII.

The spatial distribution of the blocks experiencing the highest monetary losses is highly correlated with blocks that contain concrete as the prevalent material, generally in the northwestern portion of downtown. For an MMI XII event, 75 blocks expect monetary losses greater than one million dollars; out of these 75 blocks, 50% of them consist of concrete as the material type, 22% consist of masonry, and 22% consist of wood (Figure 3.4.1.). Also, the 75 blocks contain 632 buildings, 31% of them are high rises and 21% are medium rises. Most of the blocks experiencing low levels of monetary losses are from wood as the prevalent material type. This is because the potential for monetary losses in a small wood frame residential building is much lower than large concrete buildings.

Figure 3.4.1. Monetary Losses expected for MMI VI - XII