IfcMaterialLayerSet
IfcMaterialLayerSet
实体定义
IfcMaterialLayerSet是一个名称，通过该名称，由多个材料层构成的元素的材料是已知的，并且可以通过该名称来表达各个层的相对定位。
“材质层集基准”（MlsBase）描述了放置材质层所沿的假想轴。
如果将IfcMaterialLayerSet直接指定给元素或元素类型，则各层将根据其在MaterialLayers列表中的位置进行堆叠，而不提供有关如何在空间上将材质层信息与元素或元素类别的形状表示关联的信息。
如果通过IfcMaterialLayerSetUsage将IfcMaterialLayoutSet指定给元素，则MlsBase将沿着元素的参考轴或参考平面定位。IfcMaterialLayerSetUsage支持从参考轴或平面到MlsBase的偏移，它结合了图层和偏移。子类型IfcMaterialLayerWithOffsets支持图元边缘的偏移。正LayerSetDirection（MlsDirection）描述了单个材质层的堆叠方向。IfcMaterialLayer的堆叠没有间隙。材质层集中的间隙本身表示为层。
示例：空心砖墙将建模为IfcMaterialLayerSet，由三个IfcMaterialLayer组成：砖、空心墙和砖。气隙由IfcMaterialLayer处的IsVentilated标志标识。
IFC1.0中的新实体
IFC4 修改子类型来自IfcMaterialDefinition，属性Description已添加到属性列表的末尾。
属性使用定义
如图所示，每个IfcMaterialLayerSet隐含地定义了一个材料层集基线（MlsBase），第一个IfcMaterialLayer的起点与该基线对齐。层组的总厚度根据各个层的厚度计算，第一层从MlsBase开始，随后的层放置在前一层的顶部（没有间隙或重叠）。
Attribute inheritance
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcMaterialDefinition | |||||
| AssociatedTo | IfcRelAssociatesMaterial @RelatingMaterial |
S[0:?] | Use of the IfcMaterialDefinition subtypes within the material association of an element occurrence or element type. The association is established by the IfcRelAssociatesMaterial relationship. | X | |
| HasExternalReferences | IfcExternalReferenceRelationship @RelatedResourceObjects |
S[0:?] | Reference to external references, e.g. library, classification, or document information, that are associated to the material. | X | |
| HasProperties | IfcMaterialProperties @Material |
S[0:?] | Material properties assigned to instances of subtypes of IfcMaterialDefinition. | X | |
| IfcMaterialLayerSet | |||||
| 1 | MaterialLayers | IfcMaterialLayer | L[1:?] | Identification of the IfcMaterialLayer’s from which the IfcMaterialLayerSet is composed. | X |
| 2 | LayerSetName | IfcLabel | [0:1] | The name by which the IfcMaterialLayerSet is known. | X |
| 3 | Description | IfcText | [0:1] | Definition of the IfcMaterialLayerSet in descriptive terms. | X |
| TotalThickness :=IfcMlsTotalThickness(SELF) |
IfcLengthMeasure | [1:1] | Total thickness of the material layer set is derived from the function IfcMlsTotalThickness. | X | |
EXPRESS Specification
ENTITY IfcMaterialLayerSet
SUBTYPE OF (IfcMaterialDefinition);
MaterialLayers : LIST [1:?] OF IfcMaterialLayer;
LayerSetName : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
DERIVE
TotalThickness : IfcLengthMeasure := IfcMlsTotalThickness(SELF);
END_ENTITY;
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