General arrangement drawings (GA’s) present the overall composition of a structure such as a floor plan, elevation. or section through the building, depending on its complexity this may require a number of different drawings. Enlarged views or details may also be required to provide additional detailed information such as specific complex connections or assemblies.
As a minimum, they should show the relationships between the main elements with key dimensions – they should also indicate all individual Part / Assembly numbers and any relevant notation and symbols. It’s important that these are consistent with industry standards so that their precise meaning is clear and can be understood. Additionally, plan views should always show the numbered grid reference lines, while elevations and sections should clearly indicate levels.
Another useful feature is the Bill of Quantities - which is usually placed at the top-right of the drawing sheet.
General arrangement drawings may include references to additional information such as specifications and detail drawings, however they should not duplicate information included elsewhere as this can become contradictory and may cause confusion.
General arrangement drawings are likely to be prepared at each stage of development of a building design, showing the overall relationship between the main elements and key dimensions. The level of detail will increase as the project progresses and they may need to be supplemented by more detailed drawings, showing specific elements and assemblies. On very simple projects these may be included on the general arrangement drawings themselves, but generally, separate drawings will be required.
The scale at which drawings are prepared should reflect the level of detail of the information they are required to convey. Different line thicknesses can be used to provide greater clarity for certain elements. They may be drawn to scale by hand, or prepared using Computer Aided Design (CAD) software. However, increasingly, Building Information Modelling (BIM) is being used to create 3 dimensional representations of buildings and their components.
BS EN ISO 7519:1997 Technical drawings. Construction drawings. General principles of presentation for general arrangement and assembly drawings establishes the general principles of presentation to be applied to construction drawings for general arrangement and assembly. This standard compliments the ISO 128 series on technical drawings.
Preparing Arrangement Drawings using Parabuild
Fortunately, as the structural detailer all the heavy lifting is done automatically. Once the Settings have been addressed the general arrangement drawings are automatically produced at the click of a button from the 2D Sheets Manager.
Click on the Generate button and select Add new Plan Views - here you can create a new general arrangement view based on a grid, a level, an ISO view or the current 3D view.
The new view will be drawn on a new 2D sheet if no sheet is currently active.
- Position number (or Part number) : This is the number assigned to a single part. This can be a single plate, profile or structure object.
- Assembly number (or Mark number) : This is the number assigned to a group of parts.
These parts are typically welded together in the workshop. An assembly can contain any combination of any number of plates, profiles and structures. However, the main of the assembly always needs to be a profile.
It is possible that the assembly group contains just 1 part when it is not welded.
While assigning numbers to parts, Parabuild will look up the entire drawing and assign the same number to identical parts. This will reduce the number of shop drawings and CNC files that would need to be produced, which simplifies the fabrication in the workshop.
The tolerance for the matching of identical parts can be found in the Global Settings Here you can also change the default settings for the Prefix and Suffix
Manually Edit the Drawing
Parabuild has a full range of Dimension Commands derived from the regular CAD properties. In some cases, these tools are not the most efficient, especially for drawing Chain, Ordinate and Oblique dimensions, where it can often take too many steps to draw. For this reason, some commands were added to Parabuild to intercept these shortcomings.
These commands will however draw standard CAD dimensions, so you can still use the properties and dimension styles on the dimensions drawn by Parabuild.
Adjust Text and Labels
Often it's necessary to manually edit parts of the drawing - usually to make things clearer and easier to read.
To move text and labels, indicate the text or label to be moved with the left mouse button, and holding the text grips, relocate it.
To change the appearance of the object (The grid line notation in this case) double click the item and modify its Properties. Do not modify the Values!