Structural Drafting

Structural Symbols and Conventions

General

Structural drafting principles are based on time tested practices based on standards set forth by The American Standards Institute (ANSI), The American Institute of Steel Construction (AISC), and the U.S. National CAD Standard. Structural drawing technique refers to a style or quality of a drawing imparted by the individual drafter to the work. It is characterized by crisp black line work, lettering, consistency, and uniformity. Structural drawings should reflect the rigid line control of a mechanically produced drawing. The development of good detail drawings is a real engineering accomplishment and art. Students should develop a stylized drawing technique that conforms to the rigid conventions of line drafting with added variations of artistic techniques to produce a very individualized finished drawing.

General

The original concepts of a framework of a structure is shown on the architect's and engineer's design drawings. These design drawings are interpreted and translated into detail drawings to give complete instructions for the fabrication and assembly of the various structural components. Through the shop drawings the draftsman must convey in a technical language all information required for the shop to fabricate the structural members. To be able to accurately prepare the required drawing the draftsman must have a thorough knowledge of the latest engineering specifications, be familiar with the techniques of shop fabrication and field erection, and be knowledgeable and skilled in the techniques of structural drafting. Therefore it is imperative that the structural drafter develop good drawing techniques.

Lettering

Lettering heights will be in accordance with the recommendations of the ANSI Standards. General lettering and dimensioning use 3/32".

Drawing Numbers

All drawings will be numbered using the standard designation for structural drawings. All drawing are numbered consecutively with a letter "S" preceding the number (S-1, S-2, S-3, etc.). Drawing number should receive the greatest emphasis and have a height greater then 1/4”.

Drawing Scales

The standard unit of structural measurement is "FEET". The scale is always noted as FEET and INCHES. such as 1/8" = 1' -0" or 1/4" = 1' - 0". The word SCALE is always written to identify what is being read, for example: SCALE: 1/8" = 1' -0".

Any scale specified on an "Architect's Scale" can be used on structural drawings. Generally plan views and elevations are drawing using a scale of 1/8" = 1' -0" or 1/4" = 1' - 0". Connection details use scales of 1" = 1' - 0", 1 1/2" = 1' -0" or 3" = 1' - 0" for smaller details. Shop drawings use a scale of 1" = 1' - 0" for beams 21" or less and a scale of 3/4" - 1'- 0" for beams greater than 21".

When a drawing sheet contains details drawn using different scales the notation SCALE: AS NOTED is used in the title block. When a detail or drawing is not made to any scale the notation N.T.S. is used to indicate that the drawing is NOT TO SCALE.

Titles

All entities on a drawing must have a title whether it is a plan view, elevation, section, detail, note column, symbols legend, etc. Titles are lettered large enough catch the viewers eye. Generally the lettering is between 1/4" and 3/8" high. To accent the titles even more they are underlined. Underlining can consist of a single line, a double line, or a combination of thick and thin lines. The underlining can be centered with the lettering, be flush, or be broken as shown when using circle call‑outs. A few examples of titles and underlining are shown below.

Section Marks

Section marks are used to indicate where sections are being taken or cut. Structural drafting practices are very similar to that used in engineering drawing. Because of the complexity of structural drawings cutting plane lines are generally omitted and only the arrow indicating the direction of sight of the section view is shown.

The section call‑out consists of a 1/2" diameter circle, an arrow indication the direction of sight, and two numbers. The upper number/letter indicates the name of the section on the sheet and the lower number refers to the sheet where the section view is drawn.

B

S-5

Name of the section view

Sheet reference

Section Marks

The lettering in the section call‑out circle is always horizontal regardless of the direction of the arrow. The arrow is a 45 degree line, tangent to the circle. S-5

B B

S-5

Section Marks

The arrow can be left open or colored in. The short line segments extending from the circle represent the cutting plane line. They can be single lines, double lines, or alternating thick and thin lines to conform to the overall drawing style.

B

S-5

S-5

B

S-5

B

S-5

B

S-5

B B

S-5

North ArrowsThe purpose of a north arrow in structural drawings is to reference the structural components as they relate to the orientation of the building.

North arrows are drafted with drawing tools, never drawn freehand. Lettering will always have guidelines no matter how simple the letters. The north arrow itself should be drawn with a minimal amount of time, therefore it should be simple in design.

The circle for the north arrow should be 1" diameter. Color can also be used to enhance the north arrow by shading in the arrow itself or shading the area surrounding the arrow.

A few typical north arrows are shown below.

Title BlocksTitle blocks are a very important part of the overall drawing. They contain information not given directly on the drawing with dimensions or notes. Title blocks for structural drawings are prepared according to the specifications set forth by the company. The following information is generally provided in the title block:

Title of the project/name of the drawing

Name and address of the client.

Name and address of the structural company.

Date of the completion of the drawing package.

Scale of the drawing.

Drawing Number.

Structural engineer's professional stamp.

COMPANYADDRESS

DRAWING TITLEDR. BY.

DATE SCALES-1

Title BlocksLettering should be simple and conform to the overall lettering style of the drawing. Lettering can be produced with templates, stencils, appliqué, lettering instruments, or simply freehand with guidelines.

The heights of the lettering should follow in accordance with their relative importance. The drawing number should receive the greatest emphasis and have a height greater than 1/4". The drawing name, title of the project, clients name, and the name of the structural company should follow with a letter height of 1/4". The addresses, the date, and the scale should have a letter height of 1/8". Incidental words like DATE and SCALE should receive the least emphasis and have a letter height of 1/16".

The lettering in the title block should be either centered or have a flush margin. Variations in the lettering heights adds an overall pleasing affect to the drawing and breaks up the monotony of a line drawing and the margins tie in with overall style of the drawing adding continuity and consistency to the drawing.

Revision Blocks

Revisions blocks always appear on a drawing to record any changes that are made after the drawing has been approved. Changes to the drawing are necessitated by changes in design, changes made by the customer, or changes due to errors in design. Changes are made by erasures directly on the original drawing. Additions are made by drawing directly onto the original. The revisions to the drawing are highlighted and marked and reverenced to the revision block.

NO. REVISIONS DATE BY

1

2

3

Bill of Materials

The bill of materials is a listing of all of the component parts of the steel framework, including all structural members, connections angles, and fasteners.

The bill of materials is included on all shop drawings and generally list all information for the items shown on that sheet.

NO. SHAPE

MATERIALLENGTH

FEET INCHES

REMARKSASSEMBLY

MARKS

1

2

3

4

5

6

7

8

9

10

General NotesNotes are classified as general notes and as local notes. Notes are lettered horizontally on a sheet and arranged in a systematic manner. Abbreviations in general notes should be avoided as much as possible. Proper grammar, sentence structure and punctuation are used in constructing a note.

Note columns are titled to make them distinguishable from other parts of the drawing. The lettering heights should be the same height as other titles on the sheet.

Each note is referenced with a number. Margins are used to align the note numbers and the notes. Use a minimum space of 1/2 inch between the number and the note. Spacing between notes should be such that each note is distinguished from the other notes. Remember, uniformity and consistency play an important role in the construction of the note column.

Sheet LayoutThe drawing paper need to be framed with a border line. A 1/2 inch border line is drawn around the paper. This line is a very thick line. The border line can be a single line or a double line and should conform to the overall style of the drawing.

Title blocks are added and placed along the bottom and/or the right side of the drawing paper.

A north arrow (if applicable) is placed in the upper left corner of the sheet.

In general all of the drawing area should be filled. The main drawing should be the dominate picture on the sheet with detail drawings and general notes related to the main drawing placed around it.

All drawings, details, and notes should be titled. Titles are placed beneath the picture.

TITLESCALE

TITLE BLOCK

SCALE

TITLE

NOTES

MAIN DRAWING

NORTH ARROW (IF APPLICABLE)

DETAIL

REVISION BLOCK

BILL OF MATERIALS

DETAIL

TITLESCALE SCALE

TITLE

DETAIL

Structural Drafting Line WorkLines used in structural drafting will conform to the recommended ANSI drafting standards. Visible Object lines are the most important lines on the drawing, therefore they are made thick and dense black (0.020). Border lines are made thicker than visible object lines to contrast strongly with all other lines on the drawing.

Hidden lines are dished lines with 1/8" dashes and 1/16" spaces. These lines are made dense black but thin (0.012).

Center lines are thin, dense black lines (0.010). There are two types of center lines used in structural drawing. The first type is the traditional long line-dash-long line center line. This type of line is used wherever possible. Sometimes the spacing requirements are to small to allow for the small dash in the center line. to avoid confusion in reading the drawing a thin, dense black solid line is used in place of the traditional center line.

Structural Drafting Line Work

Lines used for dimensioning, gage lines, crosshatching lines. match lines, and conventional break lines are drawn as thin, dense black lines (0.010).

The length of an arrowhead is the same dimension used for the height of lettering (3/32”). Arrowheads can be either open, closed, solid, or the traditional slash as shown.

In all cases, the style of arrowheads should not be mixed on a drawing. Consistency is the key to good drafting.

OPEN

CLOSED

SOLID

SLASH

Dimensioning

The style of dimensioning in structural drafting is the same style used in general architectural drawings.

The dimension line is a continuous, unbroken line with the dimension figure placed above the line.

Never place the dimension figure below the dimension line. The Aligned system is used as opposed to the unidirectional system of dimensioning.

Consistency and uniformity is the key to good dimensioning. In spacing the dimension lines, the first dimension line should be a minimum of 1/2" away from the object. All successive dimension lines should be spaced a minimum of 3/8" away from each other.

16'-0"

Fastener Representation

Fasteners are not drawn to actual shape or size., they are simply represented using basic symbols. Open circles or filled in circles using a minimum 3/32 diameter circle are generally used to represent fasteners.

Balloons

Balloons are used to identify rows of columns and beams on a plan view. Balloons are drawn using a 1/2" diameter circle with 1/4" lettering. A