Transcript Engineering Graphics - Community College of Allegheny County

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.
Name of the section view
B
S-5
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.
B
B
S-5
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
B
B
B
B
S-5
S-5
S-5
S-5
S-5
B
S-5
North Arrows
The 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 Blocks
Title 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.
COMPANY
ADDRESS
DRAWING TITLE
DR. BY.
DAT E
SCALE
S-1
Title Blocks
Lettering 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.
3
2
1
NO.
REVISIONS
DATE
BY
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.
MATERIAL
NO.
1
2
3
4
5
6
The bill of materials is included
on all shop drawings and
generally list all information for
the items shown on that sheet.
7
8
9
10
LENGTH
SHAPE
FEET
INCHES
ASSEMBLY
MARKS
REMARKS
General Notes
Notes 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 Layout
The 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.
BILL OF MATERIALS
NORTH ARROW (IF APPLICABLE)
MAIN DRAWING
Title blocks are added and placed along the
bottom and/or the right side of the drawing
paper.
NOTES
TITLE
S C A LE
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.
DETAIL
DETAIL
DETAIL
TITLE BLOCK
TITLE
TITLE
TITLE
S C A LE
S C A LE
S C A LE
REVISION BLOCK
Structural Drafting Line Work
Lines 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.
OPEN
CLOSED
SOLID
SLASH
In all cases, the style of arrowheads should not be mixed on a
drawing. Consistency is the key to good drafting.
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.
16'-0"
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.
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