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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