CH 3 Flashcards
(33 cards)
General concept of forces stresses and loads
pg 66
Forces within a structural support system that resist applied loads are referred to as reactions(R)
When a structural support system can support a load equal to or greater than the applied load (L), equilibrium exists
Loss of equilibrium results in
pg 66
partial or total collapse
when a building disintegrates into a pile of debris on the ground equilibrium is reestablished
Additional forces added to structure that will increase the load that must be supported by the buildings supports and the soil are:
(3)
pg 67
vibration
-natural (wind, seismic)
- building related (ventilation system motors)
- external (traffic/trains)
Temperature (external members vs internal members)
Shrinkage (wood shrinks over time)
Types of Stresses
(3)
pg 68
Tension
compression
shear
types of unique stresses
(3)
pg 69
axial load
eccentric load
torsional load
(picture of 69)
axial load
pg 69
load applied to center of a cross section of a member and perpendicular to that cross section
can be either tensile of compressive.
creates uniform stresses across cross section of material
eccentric load
pg 69
load perpendicular to the cross section of the structural member but does not pass through the center of the cross section.
creates stresses that vary across the cross section and may be both tensile and compressive
torsional load
pg 69
load applied off center from the cross section of structural component and at an angle to or in the same plane as the cross section
produces a twisting effect that creates shear stresses
many types of live loads are also
pg 71
static
Water Loads
pg 73
water load from fire fighting can be dynamic as fire flow or static as accumulated water
dynamic load of a stream discharging 250 gallons per minute may impact target zone with 2,080 pounds of water per minute
dewatering can be necessary because 3 inches of water can add:
pg 73
static load of 21 pounds per square foot
Effects of wind
(8)
pg 73
wind speed
direction
direct pressure (straight line winds applied to a surface) THIS IS THE PRIMARY CONSIDERATION DURING CONSTRUCTION
drag (wind flowing around a surface
negative pressure (suction effect)
rocking (sway back and forth)
vibration
clean off (dislodge or move objects off of a surface)
Beams definition
pg 79
structural member that carries loads perpendicular to its longitudinal dimension
primary design consideration is their ability to resist being deformed from applied loads
support systems for beams
pg 79
Simply supported- both ends and free to rotate
restrained beams- fixed at both ends cannot rotate (more fire resistance than simple)
cantilever- supported at one end. vertical load as well as bending stress
overhanging beams- similar to cantilever but with more support
continuous beams- spans several vertical support
Locations of stresses on I beam
pg 80
top flange- compressive
bottom flange- tensile
web- shear
Columns definition
pg 80
designed to support axial load
stresses created are primarily compressive
long columns fail by buckling, squat columns fail by crushing, medium ones fail by either
Trusses definition
pg 82
Framed structural units made up of a group of triangles in one plane
True truss definition
pg 82
made up of only straight members
anatomy of a truss
pg 82
top and bottom members called chords
middle section is web or diagonals
types of trusses
(see picture)
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pg 82
name of trusses used in floor construction
pg 83
truss joists
wood or metal
bar joists definition
pg 83
lightweight steel trusses used in floor and roof construction in fire resistive and non combustible construction
connectors used in steel trusses
(3)
pg 83
steel gusset plates
rivets
welds
connectors used in wood trusses
(5)
pg 83
pins or bolts
gusset plates
structural adhesives
brackets
metal straps
