Physical Materials

Introduction

Properly capturing the PhysicalMaterial of a PhysicalElement is of great importance for Quantity takeoffs and material estimating. Note that in BIS the concept of PhysicalMaterial is different from RenderMaterial. The former defines the matter of which physical objects are made while the latter captures the rendering properties of materials for display.

Physical Material class-hierarchy

Physical materials are modeled in BIS using an abstract subclass of DefinitionElement named PhysicalMaterial, which is defined in the BisCore schema. More specific subclasses of bis:PhysicalMaterial are defined in a separate core-layer PhysicalMaterial schema, covering the main physical materials used in infrastructure. It includes sealed subclasses such as Aggregate, Aluminum, Asphalt and Concrete. The list of physical materials included in the PhysicalMaterial schema may grow over time.

In some cases, especially while converting legacy data, the software may not know enough about a physical material to be able to classify it in terms of the classes offered by the PhysicalMaterial schema. The core-layer Generic schema includes a generic:PhysicalMaterial class for those cases.

The following class diagram depicts the PhysicalMaterial class hierarchy. See Class-diagram Conventions for details about the conventions used.

Physical Materials in Types and Elements

In BIS, the physical material of a physical object is primarily captured by its physical type. The bis:PhysicalType offers a PhysicalMaterial navigation property that can be used to refer to the applicable concrete instance of bis:PhysicalMaterial. That way, any bis:PhysicalElement referencing a given bis:PhysicalType shares the same instance of bis:PhysicalMaterial.

For cases in which a particular instance of bis:PhysicalElement is made of a different physical material than the one referenced by its bis:PhysicalType, the bis:PhysicalElement instance can override it via its own PhysicalMaterial navigation property.

The following class diagram depicts the relationships between PhysicalElement, PhysicalType and PhysicalMaterial. See Class-diagram Conventions for details about the conventions used.

Modeling perspectives other than Physical may have the need to capture Physical Material information. Each concrete implementation of such modeling perspective may choose to reference PhysicalMaterial instances in their own way. The following class-diagram shows an example from the StructuralAnalytical domain (alias sa). See Class-diagram Conventions for details about the conventions used.

Heterogeneous Assemblies

It is not uncommon to find physical assemblies composed of parts made of different materials. This use-case spans multiple disciplines, from composite walls and structural beams to rigid pavement structures. The approach in BIS explained above associates one and only one PhysicalMaterial instance for each PhysicalElement instance. Heterogeneous assemblies are, therefore, accommodated by associating PhysicalMaterial instances with the parts being assembled rather than the parent assembly.

The following instance-diagram shows an example of a composite beam as an heterogeneous assembly. See Instance-diagram Conventions for details about the conventions used.

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