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50 Cards in this Set
- Front
- Back
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Wood Structural Systems
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Oldest and most common. Typically a one way system where load is transmitted thru members in one direction.
JOIST: Span between beams or bearing walls. Spacing = 12" or 16" o.c. Span = 20' - 25' BRIDGING: Used to support bottom edge of joist. Top is held in place by sheathing. Spacing = Max. interval of 8' PLANK-AND-BEAM FRAMING: Members of 4" or 6" nominal width span between girders or bearing walls. Solid or laminated wood decking span between beams with underside of decking being finished ceiling. Spacing = 4', 6', or 8' Span = 10' - 20' GLUE LAMINATED CONSTRUCTION (GLU-LAM): Made from individual pieces of lumber 3/4" or 1-1/2" thick. Standard Widths = 3-1/8", 5-1/8", 6-3/4", 8-3/4" Spans = 15' - 60' Advantages = Appearance and can be tapered or curved (arches) LIGHT WEIGHT I-SHAPED JOISTS: Solid top & bottom chord with plywood or OSB web. Used for residential and light commercial. Efficient structural shape because manufactured in factory. Eliminates warping, splitting, checks, and other common defects. Higher modulus of elasticity than standard wood joist and allowable stress in bending is 2x that of douglas fir joists. TRUSS: Made of standard wood members connected with metal plates. Advantages include easy passage of mechanical ductwork. Spans = 24' - 40' Depths = 12" - 36" Spacing = 24" o.c. BOX BEAM: Plywood panels glued and nailed to solid members. Typically 2x4 framing. STRESSED SKIN PANELS: Plywood glued and nailed to solid 2" nominal thickness lumber for floors, roofs, or walls. |
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Steel Structural Systems
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Most commonly used structural material because of high strength, availability, ability to adapt to variety of conditions, ductile. Suited for multi-floor construction because of strength and structural continuity.
BEAM-AND-GIRDER SYSTEM: Large members span between vertical supports and smaller beams are framed into those girders. Girders span shorter distances while beams span the longer distances. Girder spans = 25' - 40' Beam spans = 8' - 10' OPEN WEB STEEL JOIST: Span between beams or bearing walls. Standard Open Web Joists: Span = 60'; Unit Depth = 8" - 30" in increments of 2" Long Span Joists: Span = 96'; Depth = 18" - 72"; Floor Joist Spacing = 2' - 4'; Roof Joist Spacing = 4' - 6' Deep Long-Span Joists: Span = 144' |
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Composite Construction
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- Two or more materials designed to act together to resist loads.
- Reinforced concrete construction is most typical. - Concrete and steel beams with headed stud anchors used to transfer load between them making the two materials act as one unit. - Composite open web joists provide a nailable surface for floor and ceiling while using high strength-to-weight ration of steel for web members |
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FORCE
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A push or pull exerted on an object. The description of a given force includes its magnitude, direction, and point of application. A force applied to a body is called an external force or a load. The resistance of the body to the load is called an internal force or a stress.
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FORCE - LINE OF ACTION
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The line of action of a force is a line parallel to and in line with the force.
If the lines of action of several forces pass through a common point, the forces are called concurrent. If the lines of action do not pass through a common point, the forces are non-concurrent. |
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RESULTANT
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One force that will produce the same effect on a body as two or more forces.
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EQUILIBRANT
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A force equal in magnitude to the resultant, but opposite in direction and on the same line of action as the resultant.
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RESOLVING FORCES
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In the analysis of structure, it is sometimes convenient to repolace one force with two or more forces that will produce the same effect on a body as the original force. These forces are called components of the original, and the procedure is called resolving forces.
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MOMENT
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The tendency of a force to cause rotation about a given point or axis.
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MOMENT ARM &
AXIS OF ROTATION |
The point around which rotation occurs is called the center of moment or axis of rotation. The distance, called the moment arm or lever arm, is measured in a direction perpendicular to the line of action of the force.
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COUPLE
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Two forces equal in magnitude, but opposite in direction, and acting at some distance from each other.
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EQUILIBRIUM
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For an object to be in equilibrium, it must have no unbalanced force acting on it, or it would move.
It must also have not unbalanced moment acting on it, or it would rotate. The three conditions of equilibrium may be stated as follows: 1) The summation of all the horizontal forces actin on the body must equal zero. 2) The summation of all the vertical forces acting on the body must equal zero. 3) The summation of all the moments action on the body must equal zero. |
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CENTROID
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The centroid of an area is equivalent to the center of gravity of the area.
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STRAIN
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The deformation, or change in size, of a body caused by external loads. Tensile loads stretch a body, while compressive loads shorten it.
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STRESS
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An internal resistance to an external force.
Measured in pounds or kips. Three common kinds of stress concerning building design are: tension, compression, and shear. |
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UNIT STRESS
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The stress per unit of area of the section and is measured in pounds or kips per square inch.
In every case, the unit stress (f) is equal to the load (P) divided by the cross-sectional area (A). |
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STATICAL MOMENT OF AN AREA
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The statical moment of an area with respect to an axis is defined as the area multiplied by the perpendicular distance from the centroid of the area to the axis.
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TOTAL STRAIN
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The total elongation or shortening of a body.
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UNIT STRAIN
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The total strain divided by the original length.
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MATERIAL STRENGTH
(STEEL, CONCRETE, WOOD) |
Steel: 58,000 to 80,000 psi.
Concrete: 3,000 to 6,000 psi in compression. Higher strengths are possible to achieve. Wood: 2,000 to 8,000 psi. |
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WORKING STRESS
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The maximum permissible unit stress. Also called allowable stress.
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THERMAL EXPANSION
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The ration of unit strain to temperature change is called the coefficient of thermal expansion and is constant for a given material.
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SAFETY FACTOR
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The term factor of safety is often used to denote the ration of the ultimate strength of a material to its working stress.
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MODULUS OF ELASTICITY
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A materials resistance to deformation is determined by its modulus of elasticity.
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YIELD POINT
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The unit stress at which the material continues to deform with no increase in load.
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HOOKS LAW
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States that up to the elastic limit, unit stress is in direct proportion to unit strain.
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HOOKS LAW
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States that up to the elastic limit, unit stress is in direct proportion to unit strain.
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FREE BODY DIAGRAM
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After cutting a free body diagram of a structure, if the calculated internal forces are negative, then the internal forces act in the opposite direction from the assumed.
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CENTER OF GRAVITY
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If a load acts through a body's center of gravity, then the body has no tendency to rotate, and tends to translate in the direction of the applied force.
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BEAM
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A member that supports loads perpendicular to its longitudinal axis.
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SIMPLE BEAM
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A beam that rests on a support at each end and whose ends are free to rotate.
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CANTILEVER BEAM
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A beam that is supported at one end onle and which is restrained against rotation at the end.
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OVERHANGING BEAM
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A beam that rests on two or more supports and has one or both ends projecting beyond the support.
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FIXED END BEAM
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A beam that is restrained (fixed) against rotation at its ends. Some beams are fixed at one end and simply supported at the other.
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REACTIONS
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The forces acting at the supports that hold the beam in equilibrium.
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CONCENTRATED LOAD,
DISTRIBUTED LOAD, UNIFORM LOAD |
Concentrated Load: load acts at one point on the beam.
Distributed Load: load acts over a length of the beam. Uniform load: load per unit of length of the beam is constant. |
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STATICALLY DETERMINATE BEAMS
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Simple beams, cantilever beams, and overhanging beams that rest on two supports are statically determinate.
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INDETERMINATE BEAMS
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Beams whose reactions cannot be found from the equations of equillibrium only, and require additional equations, are called statically indeterminate. Continuous and fixed end beams are statically indeterminate.
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POINT OF INFLECTION
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The point where the moment changes from positive to negative.
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BEARING WALL
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A wall that supports vertical load in addition to its own weight.
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NON-BEARING WALL
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A wall that supports no vertical load other than its own weight.
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SHEAR WALL
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A wall designed to resist lateral forces parallel to itself.
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RETAINING WALL
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A wall that resists the lateral displacement of soil and other materials.
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PROCTOR TEST
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A soil test used to determine the soild optimum moisture content and density.
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HYDROSTATIC PRESSURE
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Lateral and upward pressure caused by the water in the soil.
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DEAD LOAD
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The vertical load due to the weight of all permanent structural and non-structural components of a building, such as walls, floors, roofs, and fixed service equipment.
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LIVE LOAD
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The load superimposed y the use and occupancy of the building, not including the wind load, earthquake load, or dead load. It includes the weight of people, furniture, supplies, etc. that are supported by the buildings structure.
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THIN SHELL STRUCTURE
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A structure with a curved surface that supports load by compression, shear, or tension in its own plane, but which is too thin to resist any bending stresses.
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GLUE LAMINATED BEAMS
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The wood species is generally Douglas Fir or Southern Pine.
They are more dimensionally stable than sawn timber beams. They are stronger than conventional sawm timbers. |
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HYPERBOLIC PARABOLOID
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Can be formed by a series of straight lines.
Is a very stiff structure. Is economical in the use of material. Is curved downward in one direction and upward in the other. |
