3.4. Asset Representation

This section discusses the translation of asset descriptions into representations of structures suitable for simulation within the workflow, consistent with the HAZUS description of building classes and associated attributes, which becomes the default data schema. Thus, the description of assets below is organized according to the HAZUS conventions for classifying buildings and organizing damage and loss data according to attributes associated with those building classes.

The following discussion will reference a number of rulesets initially developed for the Atlantic County, NJ testbed to enable various assignments of these HAZUS building classes and corresponding attributes. Details of these rulesets are available to users in one of two forms:

  1. Ruleset definition tables (PDFs) curated in DesignSafe that include additional documentation justifying the proposed rule, with provenance information for any sources engaged in that rule’s development.

  2. Scripts (in Python) that implement the ruleset’s logic for this testbed. Users wishing to execute the testbed in its current form are recommended to download the Python rulesets from DesignSafe. Users wishing to adapt the rulesets to potentially change the way attributes are assigned to buildings are encouraged to access the Python implementation of the rulesets in GitHub.

Both of these repositories also include additional documentation (PDFs) justifying the proposed rule, with provenance information for any sources engaged in that rule’s development. Note that all of the rulesets introduced herein are tiered, initiating by assigning all assets a default value for their building classification or a given attribute based on the primary rule. This ensures that every asset receives a HAZUS building class and related attribute assignments, regardless of data sparsity. The sections below detail the ruleset development, closing with a table linking the relevant PDFs from DesignSafe and Python scripts from GitHub.

3.4.1. Building Classifications

HAZUS classifies buildings based on a more nuanced interpretation of Occupancy Class (see building inventory field OccupancyClass) based on other attributes of relevance for a given hazard type.

HAZUS groups buildings into five main types by primary building material/construction mode for projecting wind losses. Given the focus of this testbed on residential wood construction, the only relevant HAZUS classes are Wood Single Family (WSF) homes and Wood, Multi-Unit/Hotel/Model (WMUH). These HAZUS building classifications are listed in Table 3.4.1.1, and the corresponding rulesets (PDFs and Python scripts) are cross-referenced later in Table 3.4.1.2.

Table 3.4.1.1 HAZUS building classification for wind loss assessment.

BuildingDescription

HazusClass-W

OccupancyClass

Wood, Single-Family Homes 1 story

WSF1

RES1

Wood, Single-Family Homes 2+ stories

WSF2

RES1

Wood, Multi-Unit/Hotel/Motel 1 story

WMUH1

RES3, COM1

Wood, Multi-Unit/Hotel/Motel 2 stories

WMUH2

RES3, COM1

Wood, Multi-Unit/Hotel/Motel 3+ stories

WMUH3

RES3, COM1
Table 3.4.1.2 Additional details for rulesets assigning HAZUS building class

Ruleset Name

Ruleset Definition Table

Python script

Building Class Rulesets - Wind

HAZUS Building Class Rulesets - Wind.pdf

WindClassRulesets

3.4.2. Building Attributes

Within each of these building classes, e.g., wood single-family homes 1-2+ stories, the HAZUS Hurricane Technical Manual ([FEMA21]) further differentiates buildings based on asset attributes and the hazard type (e.g., wind vs. flood) for the purpose of loss estimation. These attributes define key features of the load path and components (e.g., roof shape, secondary water resistance, roof deck attachment, roof-wall connection, shutters, garage), and the number of attributes necessary to describe a given building varies.

As these attributes are beyond what is typically encompassed in a building inventory, a library of rulesets to infer the HAZUS-required attributes was developed and implemented for the Atlantic County, NJ testbed, based upon the fields available in the building inventory, legacy building codes in New Jersey, local construction practices/norms, surveys capturing owner-driven mitigation actions (e.g., [Javeline19]) and market/industry data. Where possible, the rulesets are time-evolving, considering the age of construction to determine the governing code edition and availability of specific mitigation measures in the market. Though reliant on engineering judgment and historical data availability, each rule provides detailed notes cross-referencing the various documents and practices that governed that era of construction and thus informed the ruleset formation. In cases where engineering judgment was required, rules were assigned based on what was understood to be the most common construction practice. In cases where that was not clear, the ruleset assigned the most vulnerable configuration for a more conservative approach to loss estimation.

The rulesets from the Atlantic County, NJ testbed are applied here, without modification, as the purpose herein is solely to demonstrate the workflow. It is acknowledged that, while also grounded in the International Residential Code and International Building Code, Louisiana has a different regulatory framework and code eras that would require adaptation of the rulesets. Such adaptations are encouraged as part of the community’s use and adaptation of this workflow in its research.

Table 3.4.2.1 Building attributes for wind loss assessment for WSF and WMUH.

Attribute

Description

Format

HazusClassW

Hazus building classes as defined for wind hazards

CHOICES: WSF1, WSF2, WMUH1, WMUH2, WMUH3

HazardProneRegions

Defines Hazard Prone Regions (HPR) for the purposes of Hazus wind vulnerability assignments for WSF1-2

Choices: yes, no

WindBorneDebris

Defines Wind Borne Debris (WBD) for the purposes of Hazus wind vulnerability assignments for WSF1-2

Choices: yes, no

SecondaryWaterResistance

Defines Secondary Water Resistance (SWR) for the purposes of Hazus wind vulnerability assignments for WSF1-2, WMUH1-3

Choices: yes, no

RoofCover

Defines roof cover for the purposes of Hazus wind vulnerability assignments for WMUH1-3

Choices: N/A, BUR, SPM

RoofQuality

Defines roof cover quality for the purposes of Hazus wind vulnerability assignments for WMUH1-3

Choices: N/A, poor, good

RoofDeckAttachmentW

Defines Roof Deck Attachment (RDA) for wood for the purposes of Hazus wind vulnerability assignments for WSF1-2, WMUH1-3

Choices: A, B, C, D

RoofToWallConnection

Defines Roof to Wall Connection (R2WC) for the purposes of Hazus wind vulnerability assignments for WSF1-2, WMUH1-3

Choices: strap, toe-nail

Shutters

Defines use of window opening protection for the purposes of Hazus wind vulnerability assignments for WSF1-2, WMUH1-3

Choices: yes, no

AugmentedGarage

Defines presence of attached garage for the purposes of Hazus wind vulnerability assignments for WSF1-2

Choices: none, SFBC 1994, standard, weak

Note that the rulesets for assigning wind loss attributes call upon two meta-variables relevant to wind losses for any building: “Hazard Prone Region” and “Wind Borne Debris,” which are assigned based on the design wind speed at the asset location (building inventory field DWSII) and the flood zone (building inventory field FloodZone). The rules used to assign these meta-variables are provided in Table 3.4.2.2. Also note that the roof shape (building inventory field RoofShape), derived from aerial imagery, and terrain roughness (building inventory field Terrain), derived from Land Use Land Cover data, are also attributes required by the HAZUS wind loss model. As these were already assigned in the Atlantic County, NJ testbed Asset Representation, they are not discussed again herein.

Table 3.4.2.2 Additional details for rulesets for meta-variables in wind loss attribute assignment in HAZUS

Ruleset Name

Ruleset Definition Table

Python script

Attribute Assignment - Wind (Meta-Variable)

Hazus Building Attribute Rulesets - Wind - Meta-Variables.pdf

WindMetaVarRulesets

The following sections summarize the rulesets used for wind loss attribute assignments for WSF and WMUH in this testbed. See the Atlantic County, NJ testbed Asset Representation, the source of these rulesets, for additional rulesets guiding attribute assignments for other building classes and hazards.

Wind Loss Attributes for Wood Buildings

The wind loss model in HAZUS classifies wooden buildings into five building classes:

  1. two for single-family homes (WSF1 and WSF2), and

  2. three for multi-unit homes (WMUH1, WMUH2, and WMUH3).

The required attributes for wind loss modeling, the possible entries (values, terms) that can be assigned for those attributes, and the basis for the ruleset developed to make that assignment are summarized in Table 3.4.2.3 and Table 3.4.2.4. Note that these rulesets were developed for Atlantic County, NJ to reflect the likely attributes based on the year of construction and the code editions and construction norms at that time. They are applied in this testbed for demonstration purposes only. The corresponding time-evolving rulesets (PDFs and Python scripts) are cross-referenced in Table 3.4.2.5.

Table 3.4.2.3 Additional HAZUS attributes assigned for wood single-family (WSF) homes: wind losses.

Attribute

Valid Entries

Basis

secondary water resistance (SWR)

yes | no

Codes/standards/human subjects data

roof deck attachment

6d @ 6”/12” | 8d @ 6”/12”| 6d/8d mix @ 6”/6” | 8d @ 6”/6”

Codes/standards

roof-wall connection

strap | toe-nail

Codes/standards

shutters

yes | no

Codes/standards/human subjects data

garage

shuttered houses = garage II (SFBC 1994, none) | unshuttered house = garage I (none, weak, standard)

Trends/norms
Table 3.4.2.4 Additional HAZUS attributes assigned for wood multi-unit home (WMUH): wind losses.

Attribute

Valid Entries

Basis

secondary water resistance (SWR)

yes | no

Codes/standards

roof cover

N/A | BUR | SPM

Trends/norms

roof quality

N/A | poor | good

Trends/norms

roof deck attachment

6d @ 6”/12” | 8d @ 6”/12” | 6d/8d mix @ 6”/6” | 8D @ 6”/6”

Codes/standards

roof-wall connection

strap | toe-nail

Codes/standards

shutters

yes | no

Codes/standards/human subjects data
Table 3.4.2.5 Additional details for rulesets assigning wind loss attributes for wood buildings

Ruleset Name

Ruleset Definition Table

Python script

HAZUS Building Attribute Rulesets - Wind (WSF1-2)

Hazus Building Attribute Rulesets - Wind - WSF1-2.pdf

WindWSFRulesets

HAZUS Building Attribute Rulesets - Wind (WMUH1-3)

Hazus Building Attribute Rulesets - Wind - WMUH1-3.pdf

WindWMUHRulesets

Taking the attribute Second Water Resistance (SWR) as an example, the SWR attribute is assigned by a series of time-evolving rules calling upon four fields in the building inventory: year built, roof shape, roof slope, and average temperature in January. Table 3.4.2.6 provides the detailed rules that map these four variables to the Second Water Resistance (SWR) attribute. This example demonstrates an instance where the attribute is assigned as a random variable, based on the fact that secondary water resistance is not required by code, though surveys of homeowners in hurricane-prone areas can be used to infer how many may have voluntarily adopted this mitigation practice. Practices around SWR, particularly for contemporary construction, are likely to be different in Louisiana, warranting further refinements to these rulesets by users.

Table 3.4.2.6 Ruleset for determining the Second Water Resistance attribute for WSF homes.

Time Period

YearBuilt > 2000

1983 < YearBuilt < 2000

YearBuilt <= 1983

Ruleset

Assign as a Random Variable (RV) IF RoofShape = Gable OR Hip, SWR = yes (RV = 60%) IF RoofShape = Gable OR Hip, SWR = no (RV = 40%)

IF RoofShape=Flat, SWR=yes ELSEIF RoofShape=(Gable or Hip) & RoofSlope <= 0.17, SWR=yes ELSEIF RoofShape=(Gable or Hip) & RoofSlope (> 0.17 & < 0.33) & AvgJanTemp=Below, SWR=yes ELSEIF RoofShape=(Gable or Hip) & RoofSlope (> 0.17 & < 0.33) & AvgJanTemp=Above, SWR=no ELSEIF RoofShape=(Gable or Hip) & RoofSlope >= 0.33, SWR=no

SWR = no

Note

Minimum drainage recommendations are in place in NJ (See below). However, SWR indicates a code-plus practice. Use homeowner compliance data from NC Coastal Homeowner Survey (2017) to capture potential human behavior (% of sealed roofs in NC dataset). Minimum Code Requirements: R903.4 Roof Drainage. Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point of the roof: R903.4.1 Secondary (Emergency Overflow) Drains or Scuppers: Where roof drains are required, secondary emergency overflow roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason.

This rule applies until 1984, for anything from 1983 or earlier, there is no information available so this rule will continue to be applied.

According to 903.2 in the 1995 CABO, for roofs with slopes between 2:12 and 4:12, an underlayment consisting of two layers of No. 15 felt must be applied. In severe climates (less than or equal to 25 degrees average in January), these two layers must be cemented together. According to 903.3 in the 1995 CABO, roofs with slopes greater than or equal to 4:12 shall have an underlayment of not less than one ply of No. 15 felt. Two layers of felt cemented together is considered to be secondary water resistance. This ruleset is for asphalt shingles. Almost all other roof types require underlayment of some sort, but the ruleset is based on asphalt shingles because it is most conservative.

According to table No. R-803.4 in 1992 CABO, for roofs with slopes between 2:12 and 4:12 in severe climates (less than or equal to 25 degrees average in January), one layer no 40 coated roofing or coated glass base sheet from the eves to 12 inches inside the exterior wall line is required. The rule used for asphalt shingles is assumed to apply to every roof because more specific requirements based on roofing type were not specified.

According to R-803.3 in the 1989 CABO, for roofs with slopes between 2:12 and 4:12, an underlayment consisting of two layers of No. 15 felt must be applied. In severe climates (less than or equal to 25 degrees average in January), these two layers must be cemented together. According to R803.2 in the 1989 CABO, roofs with slopes greater than or equal to 4:12 shall have an underlayment of not less than one ply of No. 15 felt. Two layers of felt cemented together is considered to be secondary water resistance. This ruleset is for asphalt shingles. Almost all other roof types require underlayment of some sort, but the ruleset is based on asphalt shingles because it is most conservative.

According to R-803.3 in 1986 CABO, for roofs with slopes between 2:12 and 4:12 in severe climates (less than or equal to 25 degrees average in January), one layer no 40 coated roofing or coated glass base sheet from the eves to 12 inches inside the exterior wall line is required. The rule used for asphalt shingles is assumed to apply to every roof because more specific requirements based on roofing type were not specified. According to R-803.1 and R-803.2 in 1983 CABO, for roofs with slopes between 2:12 and 4:12 in severe climates (less than or equal to 25 degrees average in January), two layers of Type 15 felt must be applied and cemented together from the eaves up the roof to overlie a point twenty four inches inside the interior of the building.

Default
Javeline19

Javeline, D., & Kijewski-Correa, T. (2019). Coastal homeowners in a changing climate. Climatic Change, 152(2), 259-274.

FEMA21

FEMA (2021), Hazus Hurricane Technical Manual. Hazus 4.2 Service Pack 3. Federal Emergency Management Agency, Washington D.C. https://www.fema.gov/sites/default/files/documents/fema_hazus-hurricane-technical-manual-4.2.3_0.pdf