Chap 3 Flashcards
structural design
Direction of forces from loads acting on interior of structural members is expressed as ?
Stress
Forces within structural supports systems that resist applied loads are referred to as
reaction R
Any effect that a structure must be designed to resist like gravity, wind , earthquakes ..
load
any interaction that may change the motion of an object
force
condition of balance that exists when a structural system is capable of supporting the applied load
EQUILBRUIM p. 66
A REACTION W/IN a structural component that opposes a vertical load is what kind of moment ?
bending Moment
Most common load imposed on a structure ?
gravity
Sources of vibration can include
Natural ( wind) , building related ( vent system ) external ( traffic )
what changes external to building may cause peripheral structural members to expand and contract
Temperature pg.67
Pulls material apart referred to as tensile stress
Tension
squeeze the material is referred to as
compression streee
slides one plane of material past an adjacent plane
shear
what forces often can be visually identified and evaluated
external forces
what forces must be calculated
Interior forces p. 68
load applied to CENTER of cross section of a member and perpendicular to that cross section.. it can be either tinsel or compressive and create uniform stresses across across section of the material
axial load
loads perpendicular to the cross section of the structural members , But which does not pass THROUGHT THE CENTER of the cross section..
Creates stresses that Every across cross-section and maybe both tensile and compressive
eccentric loads
loads applied OFF CENTER from the cross section of the structural compentent And at an angle to or in the same plane as the cross-section produces a twisting effect that creates sheer stress IN A material
Torsional load
Point at which materials Ceases
to perform
failure point
Ratio of failure points of materials to maximum design stress; indicates the strength of a structure beyond the expected or actual loads is a factor of ?
factor of Safety
p. 69
’’’ types can meet multiple categories that are based on factors such as :
Change over time
load application velocity
weight distribution
Load
a load that is fixed in its location
Weight of a structure, structural member, building component and any other feature permanently attached to the building that are consistent and immobile
dead load
loads that is not fixed or permanent…
Items within a building that are not movable, but are not included as a permanent part of the structure
Force placed upon a structure by the addition of people, objects, or whether
Live load
loads that are steady or applied gradually
static load p. 70
’’’’ LOADS that involve motion.. also known as shock loading
May include impact from:
Wind
Moving vehicle
Earthquake
Vibrations
Falling objects
Emergency or maintenance work
dynamic loads
For dynamic loads to stop moving, the surface it impacts must absorb the ?
absorb the kinetic energy
Dynamic loads may cause ‘’’’ FAILURE
structural failure
Rain and snow are
Live loads
ponding is
water accumulation. 72
Energy possessed by moving objects because of motion
kinetic
air pressure less than that of the surrounding atmosphere
negative pressure
water at a depth of
3 inches adds a static load of
21 pounds per sq ft.
Straight line winds apply forces to a surface is ?
direct pressure
wind flowing around the objects may catch what ‘’ along building surface?
drag
wind may produce a suction effect on the downwind side of the building resulting in outward pressure
negative pressure
wind may cause the building to sway in back and fourth
rocking
Wind passing over a surface , such as a roof, may shake it is
vibration
wind may dislodge or move objects from a building surface
clean off. 73
Egineers must also account for complex factors such as:
BH
ST
AUD
Building height , surrounding terrain and adjacent urban development
common locations where walls may be insufficiently ‘’ include:
construction sites, demo sites , fire damaged buildings
braced
materials used in beams:
S
W
RC
steal , wood, reinforced concrete
what is supported beneath both ends and free to rotate ‘’’ BEAMS
simply supported beams
What beams are rigidly supported at each end, under fire condition, originally supported beam may restrain its fire bearing ability longer than a simply supported beam.
restrained beam
supported at one end , must be able to support a vertical load in addition to resisting being stresses is what beam ?
cantilever beam ( often to support balconies)
Similar to cantilever beams but with additional support
overhanging beams p.79
i beam is composed of
flange (top /bottom) and web( middle)
center horizontal line of a web is known as
neutral axis
stresses created within a column are
compressive
materials used in columns:
W
S
CI
C
M
wood, steel , cast iron, concrete and masonry
what are not primarily designed to withstand bending stresses
column
tall, thin columns fail by ? / short squat column fail by ?
bucking / crushing
arches produce what forces at ends
inclined forces that there end supports p.80
materials used in arches:
M
S
C
LW
masonry , steel , concrete and laminated wood
if what is removed of an arch it comes unstable
end supports p.81
cables used to support loads over distance will have what type of shape ?
curved shape
what are framed structural units made up of a group of triangles in one plane
trusses
Pic of all truss
p.82
Typical truss shapes span, but in modern construction may exceed
22-70ft/100
connectors used with steel
steel gusset, rivets and welds
connectors used with wood trusses:
P/B
GP
SA
B
MS
pins/bolts, gusset plates , structural adhesives , brackets and metal straps
top or bottom longitudinal members of a truss
chord
lightweight truss design noted by bow shape , or curve of top chord
bowstring truss
open web truss made of steel
bar joist
metal or wood plates used to connect / strengthen the joints of 2 or more separate components
gusset plates p.83
3 dimensional truss
space frames
what are commonly placed at exterior of a structure but they may also include internal walls
load bearing walls
common materials in bearing walls:
C
B
S
SW
CP
concrete block , brick, stone, soild wood and concrete panel p. 84
bearing walls structures use walls to support spanning elements including:
B
T
PCS
beams , trusses , precast concrete slabs
frame construction often referred to
wood frame
historically stud wall frame has been associated with what size wood studs
2x4 i
internal system of structural supports w/in a building
frame.85
what framing uses a series of vertical element ( posts ) to support horizontal elements ( beams that carry traverse loads
post and beams
structural load that exerts a force perpendicular to structural members IS A ‘’’ LOAD
transverse load
material used in rigid frame:
S
LW
RC
steal , laminate wood and reinforced concrete
what will be the last portion of assembly to fail under fire conditions
joist p. 86
broad top surface of a column or pilaster designed to spread the load held by a column
capital
concrete floor in which portions of the floor above each column is dropped below the bottom level of the rest of the slab
drop panel
Construction techniques using concrete slabs supported by concrete beams
slab and beam frame
what system consist of an enclosing, waterproof surface
surface systems
similar to fabric tents , but are permit structures
membrane structure
types of membrane frames:
C/M
T
S
cable and masts , tubular and solid.87
other types of materials used in membrane structures:
W
C
S
wood , concrete and steel
A ‘’’’ IS A rigid 3 dimensional structure having thin components Completely made of ‘’’’
shell structures, concrete p.88
The top flange of the beam carries ‘’ stresses
Compressive p. 80
The bottom flange of the beam carries ‘’ stresses, THE TOP CARRIES ‘’’
tensile p. 80
Compressive
Columns are structural members designed to support ‘’’’’’’ LOADS
Axial loads page 80
An arch is a curved structural member with primary “” stresses
Compressive interior p80
What are shell structures commonly made from?
Concrete
What structural member that carries loads perpendicular to its longitude dimension
Beams
Compressive and tensile stresses in a beam are known as what stresses
Bending stresses
How is stress measured?
Mass multiplied by force
Force exerted on the top cord of a truss is an example of ?
tension
What kind of stresses are created across the cross-section of a material by an axle load?
Uniform stresses
Many types of live loads are also
Static
A load that is applied at one point or over a relatively small area is known as what
A concentrated load
Water accumulation that has happened on large flat roofs is known by what?
Ponding
What kind of maps is provided in all model building codes
Topographical maps
A structural member that carries loads perpendicular to its longitude dimension is known as what
Beam
The primary design consideration of a beam and its ability to resist what from an applied load
Deformity
Archers produce “”” forces at their end, supports which the support must resist
Incline forces
To provide for minor adjustments, archers are sometimes designed with
Hinges
A true trust is only made up of what kind of members
Straight members
Space frames are well suited to support ‘’’’ distributed loads
Uniformly
What is an alternative material that can be used for studs?
Lite gauge metal
A rigid frame structural system is characterized by columns and beams reinforced to transmit the “”” stress through the joints
Bending
Historically, what type of construction system evolved from the use of tree trunks for framing it is still commonly associated with the wood beams and columns
Post and beam construction
How tall are rigid frame buildings?
One story
Materials used for beams would include all but
masonry
a load-bearing system constructed with a skeletal frame and REINFORCEMENT between a column and beam IS WHAT FRAME ?
what structural system is characterized by columns and beams reinforced to transmit the bending stresses through the joist… Often single-story and height with gabled roofs
rigid frame
The use or addition of structural supports to improve the ability of a structure to withstand forces imposed by loads is known as structural ‘’’
Structural stiffness.
What building material is notorious for having good compressive strength but poor tensile strength?
concrete
Forces of loads would not include ‘’’ content
Building content
A reaction within a structural component that opposes a vertical load is known as -
Bending movement
What is a cantilevered beam usually constructed to support?
Balcony
A system of structural elements that create a joint between a building and its base to minimize seismic force effects on the main structure is called A ‘’ ISOLATION -
Base isolation
Structural accommodation that allows building sections to move independently of each other are called ‘’ JOINTS
Expansion joints
he stress resulting from when two forces act on a body in opposite directions in parallel adjacent planes is known as -
Shear stress
Which of the following absorb resonant energy as a structure begins to move?
Damping mechanisms
he amount of stress at which a structural member bends from its original alignment is known as the -
bending moment
Horizontal structural members used to support a ceiling or floor are called -
Joists
Wide vertical parts of a beam between thick ridges at the top and bottom of a beam are called ‘’’’ ALSO KNOW AN DIAGONALS
Webs, also known as diagonals
The forces that resist the effect of an applied load are called -
Reaction
With the exception of mechanical equipment that produces vibrations, dead loads are generally’’’’
Static load
Many types of live loads are also
Static
