BIM planning

 

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The need for a standardized practice for exchanging digital building information Working with building information models differs significantly from working with traditional paper and 2D CAD systems - they rely on highly structured data and protocols. As BIM is increasingly used in collaborative working methods (integrated practice), a much more formalized and standardized approach to data exchange is required. The schedules, which are the subject of this report, have been selected as an area for standardization practice by a group of NATSPEC subscribers and representatives of the construction industry. Schedules represent the most used method of representing and exchanging the (non-graphical) informational content of digital models - it comes from the Australian NATSPEC document published in 2010. Below are the most important fragments of it:

Cited Document

The guidelines are part of the development of industry-wide formal standards for the exchange of digital building information. This development process can be characterized by the following stages:

1. Analysis of existing practices.

2. Formulation of abstract principles (theories) underlying existing good practice.

3. Formulating principles of operation.

4. Developing formal standards of practice.

Listing properties - definitions and required values: (door example) Identification; Door number; Room number; Room name; Location; Door set; Number of wings; Operation; Fire resistance level (FRL); Door leaf; Leaf height (mm); Leaf width (mm); Leaf thickness (mm); Wing structure; Leaf material; Meeting profile details; Leaf undercut; Preview panel; Glazing material; Vent; Door frame; Overall frame depth (mm); Frame material; Frame section; Door fittings; Hinge type; Guide for sliding or folding doors; Type of lock or latch; Description of the operation of the lock or latch; Arrangement of keys; Handles, holders, plates; The door closer; Door bolts (top and bottom); Door seals; Door stopper; Digging plate; Marking; Comments;

Problems with describing the dimensions of objects in the text When dimensions are described in text without the object being visible to the reader, there is considerable potential for confusion due to the ambiguity of the terms. This is the challenge of describing dimensions in schedules, specifications, or any other written document. When planning items from different sources, it is important to use a common set of descriptors so that the dimension orientation is not confused with another. Schemes for describing dimensions The changes in the meaning of dimension descriptors, such as length, width, depth and height, can be explained with the different conceptual schemas used, depending on the type of object (form, etc.), its context and its viewer relationship. For the purposes of this document, two schemas can be distinguished: - Based on aspect ratio - Based on orientation Schematics based on proportion In a proportion based schema, descriptors are assigned according to the aspect ratio of the form. The aspect ratio or aspect ratio of a two-dimensional shape is the ratio of its longer dimension to its shorter dimension. It can also be applied to any pair of dimensions with a three-dimensional shape. Length is usually assigned to the largest dimension, and width and depth to the two intermediate dimensions. The ambiguity of width and depth is greater than that of other terms due to the many ways in which they are used. Thickness is generally the distance between two parallel faces of an object when that distance is the shortest in relation to the other dimensions of the object. It is typically used for linear and flat forms regardless of orientation. Orientation-based schemas In orientation-based schemas, descriptors are assigned according to the orientation of the object relative to a hypothetical reference plane. Typically this plane is nominally horizontal, corresponding to a horizontal piece of ground or floor. However, in some cases, the descriptors can be applied to a vertical plane such as a wall or the underside of a horizontal plane such as a ceiling. Height describes the perpendicular distance above the reference plane. The width is usually assigned to the side-to-side dimension of the object. Depth is more ambiguous because it can be assigned to the vertical dimension or front to back of an object. Note: Width is considered equivalent to width for the purposes of this document and is not used. Reference Frames for an Orientation-Based Scheme You can use a number of reference frames to define orientation in an orientation-based schema: Cartesian coordinate system. A conceptual system in which any point (and distance between points) is defined by reference to three mutually perpendiculars no intersecting planes. The intersections of planes are called the X, Y, Z axes. Conceptual planes are not associated with any real reference points by default, but in CAD and BIM applications the Z axis is the vertical axis and the plane defined by the X and Y axis intersection as the horizontal plane - the X axis from left to right in relation to the viewer, and the Y axis from the viewer (or up the page / screen). Geographical. The direction in the horizontal plane is determined by reference to the North point and other cardinal points: east, south and west. The horizontal plane is assumed to be perpendicular to a line drawn between a point on the earth's surface and its center. The vertical is assumed to be perpendicular to the horizontal plane. Viewer oriented. The direction is described with reference to a standing person - the spine is nominally vertical. In this document, the direction descriptors in the horizontal plane are from the anatomy field: front to front, lateral to each side, and top to top.

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The orientation based schema adopts a viewer-centered frame of reference because of its flexibility. Cartesian or geographic references would have to be defined for each building, and descriptors for each (even identical) feature would differ depending on their orientation relative to the absolute frame of reference. In the case of a viewer-oriented reference, once the orientation of an object is defined based on how it is viewed, zoomed in or used, the descriptors remain constant and consistent no matter where it is installed or how geographically aligned. The relevance of this frame of reference is not all that surprising considering that the buildings are primarily intended for people.

Adopting a basic conceptual framework can help to formalize the order of titles (ie, Properties) in schedules, but a rigid application of such a framework may not always produce the best results - it should be relaxed by considering what will be most useful. Always apply test: What will be the effect of this setting on the user when the schedule is used for common, routine tasks? In a BIM environment, it is generally better to break the properties down into the smallest subdivisions than to combine them, e.g. putting the manufacturer's name and product description in separate columns is better than putting both in one. Because BIM schedules are database managed and have spreadsheet-like functionality, the data in each column can be sorted as required. Breaking down properties increases specificity when searching and sorting data. The larger and more complex the design, the more this rule applies.

Suggested approach to ordering schedule properties

1. Identifiers should be placed before subclass descriptions and subclass descriptions before properties.

2. Place alphanumeric codes or tags in front of the item title to make sorting and pointing easier.

3. Put a description of the subclass or sub-class of planned features in front of the properties. A subtype can be defined by a number of criteria including form, function, operation, and power source, e.g. sliding windows, side-hung windows, awnings, double sash windows. A subtype directly affects the following set of properties. Early subtype placement in the procurement allows properties to be tailored to the subtype rather than having to provide a more universal set of properties to accommodate a wider range of possibilities. This typically involves considering the range of possible subtypes that you may need and establishing a naming convention for them before implementing them. This consideration is likely to be required anyway at some point, regardless of where the subtype description is placed in the schedule order.

4. Place the properties that are normally predetermined in the design process in front of those that are defined later, eg door handling, before panel type and finish.

5. Put general properties before special properties.

6. Put the relevant properties before the detail properties.

7. Place the more common or frequently used class properties in front of the less common or rarely used class properties. This means that as items are scheduled, the entries appear more uniform on the left and become more varied as you shift to the right. This gradation helps you find similarities and differences between items.

8. Place the properties associated with the assembly as a whole in front of the properties of its components.

9. Place properties related to major or essential assembly components in front of auxiliary or optional components. Arrange the properties of each component sequentially.

10. Plan the assembly components in the overall order of assembly or placement, e.g. framing before lining, subfloor before fabrication. ending or consistently applying any other policy listed in Part B, 3 Ordering Information. Then list the properties associated with each component in the order recommended above.

Digital model organization

BIM applications organize the modeled objects according to their spatial relations and internal classification system. The basic concept of object-oriented programming, exemplified in modeling applications, is the belonging of objects to "classes." Each class shares several properties or parameters whose values ​​vary to form a wide variety of subtypes - making "families" or "libraries" of parametric objects. This has the advantage that many common building elements can be modeled as variants of several archetypes, rather than modeling each element from scratch. This means that BIM objects are already organized spatially and by a predefined classification system when the schedule is created from the modeling application - a door schedule is a report on all objects in the 'door' class in the model. Ordering schedule properties according to classification ordering rules fits well with how your modeling application is organized.

Sources:

[1] pixabay.com

[2] BIM Planning Guidelines NATSPEC Standardized Australian Digital Building Information Exchange Practice BIM.NATSPEC.ORG https://bim.natspec.org/images/NATSPEC_Documents/BIM_Scheduling_project_report_Dec_2010.pdf

[3] Figure 1 Spatial Reference Frames - BIM NATSPEC Planning Guidelines [2]