Technology Education Department
Technical Drawing Program
- A structural system refers to the type
of construction used to create the skeletal sturcture and exterior materials
of the building. The floors, walls, roofing, and support materials are
part of the structural system for a building.
- Several of the basic structural systems are structural
steel, reinforced concrete, precast concrete, laminated wood and curtain
wall systems.
- The structural steel
system uses panels, columns, beams, trusses and decking to enclose a building.
- The reinforced concrete system uses concrete
and steel rebars poured on site in wooden or steel forms along with masonry
products to enclose a building.
- The precast concrete system uses concrete
panels, columns, beams, trusses and decking manufactured at another location
to enclose a building.
- The laminated wood system uses plywood
or strand-oriented stress-skin panels, wood columns, beams and trusses
to enclose a building.
- The curtain wall system uses manufactured
wood, metal or glass panels in conjunction with structural steel or reinforced
concrete to enclose a building.
- The specifications for the construction
of a structural system are given in a structural
layout drawing, structural schedules
and structural detail drawings.
- The structural layout
drawing shows the structural components, the spacing of the components
and an identification label for each component.
- The structural schedules
are a part of the layout drawing and include the component identification
label, a description of the component and the quantity needed to build
the structure.
- There may be several pages of structural details
in a set of architectural drawings for a building as every aspect of the
constructions must be illustrated and labeled. The part names, materials,
sizes and locations are included along with a 1/2" to 3"=1'-0
scale drawing on a structural detail.
- Structural members are selected by the
load or weight
they must support; therefore, the architectural engineer must begin with
the roofing materials and work downward to the foundation to determine
the sizes of support members.
- There are two types of loads: live
load which includes people, furnishings, equipment, snow and rain;
and dead load which pertains to the weight
of the construction materials. Standarized live and dead loads can be found
in building code books for use in residential construction. Commercial
projects usually use actual weights of materials (Architectural Graphics
Standards) and manufacturers' load tables (Steel Joist Institute) to determine
sizes of materials.
- A typical small (5000 to 20,000 sq. ft.) one story, commercial building
will have a flat built-up roof consisting
of two to four layers of hot tar, saturated felt paper and gravel or a
one piece rubber membrane covering; over 1" to 6" of rigid
foam insulation that sits on 1.5" to 6" high corregated
steel decking; which is supported by 16" to 36" deep steel, open web, flat trusses; that are held up
by 8" to 24" high steel I- beams;
that are in turn supported by 4", 6", 8" or 10" round,
square or I shaped steel columns; and all
of which sit on concrete pilasters, piers and pads.
- The modular grid size of the building and the placement of window and
doors are important considerations in determining the location and size
of structural components such as trusses, beams and columns.
- Trusses are usually placed to span the
shortest measurement of a building and are classified as either end
(one at each end of the building) or interior
(all within the exterior walls of the building. End trusses usually hold
up less weight.
- Trusses are designated by a number, letter(s)
and a number: 16K2 - where the 16
is the DEPTH
of the truss in inches, the K, KCS, LH, DLH or SLH
is the SERIES for simple
to super longspans with uniform loads and the 1,
2, 3, 4, 5, etc. is the sequencial number
for ordering purposes.
- The total roof load (live and dead) in
pounds per square foot and the spacing between trusses
in feet and inches must be know to find the size
of a truss from standardized tables.
- Beams are usually placed along the longest
measurement of a building and classified as exterior
(sit on exterior walls of building) or interior
(set in the middle of building). Interior beams are usually used when interior
columns do not interfer use of the building.
- Beams are designated by a letter and two
numbers: W 12 x 22 - where the W,
M, S, C or MC is for the shape of the beam (W= I-Beam); the first
number 12 is the DEPTH of the beam in inches; and the second number
22 is the WEIGHT
of the beam per lineal foot.
- The total roof load (live and dead) in
pounds per square foot, the weight of the
truss per lineal foot, the number
of truss between the columns, the spacing
between the trusses and the
length of the trusses must be know to find the size
of a beam from standardized tables.
- Columns are placed at the corners (corner columns) of a building and at the points
where the modular grid intersects the long outer walls (exterior
wall columns). Additional columns may be placed in the center of
the end walls (end wall columns) and along
a central modular grid line for the length of the building (interior
columns).
- Columns are designated by a symbol, a
number and a second number: Ø4 x 10
- where the Ø4 is the DIAMETER
of the column in inches and the 10 is for
the LENGTH of the column.
- The total roof load (live and dead) in
pounds per square foot, the weight of the
truss per lineal foot, the number
of truss between the columns, the spacing
between the trusses, the
length of the trusses, the length of the beam,
the weight of the beam in pounds per lineal
foot, the height of the column and spacing
of the columns in feet and inches must be know to find the size of a column from standardized tables.
- A safety factor of 5 to 15 percent should
be considered at the end of each calculation but should avoid
duplicaton when calculating beams and columns.
- See the following pages for truss, beam and column
calculation procedures:
END Trusses
INTERIOR Trusses
EXTERIOR Beam
INTERIOR Beams
CORNER Columns
EXTERIOR Columns
END Columns
INTERIOR Columns
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