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Structures > Final Exam Study Guide > Flashcards

Final Exam Study Guide Flashcards

1
Q

What is a force that tends to cause a rotation or twist about a point?

A

Moment

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2
Q

What is a moment?

A

a force that tends to cause a rotation or twist about a point

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3
Q

Moment Equation is M= ? * ?

A

M=F*(perp dist to origin)

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4
Q

What are the units of a moment?

A

Force times distance

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5
Q

Name 2 examples of a moment unit

A

kip-ft, kip-in, lb-ft, lb-in

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6
Q

What is the difference between a dead and a superimposed dead load?

A

dead– only the structural weight
superimposed– all permanent loads (flooring, roofing, permanent equipment, MEP)

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7
Q

Name some types of superimposed dead loads

A

flooring, roofing, permanent equipment, MEP

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8
Q

Name some types of dead loads

A

this is me being silly & tricky,,, it’s just the self-weight

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9
Q

What is the load on a structure that is temporary or transient?

A

Live load

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10
Q

What is a live load?

A

A load on a structure that is transient or temporart

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11
Q

What are some examples of live loads?

A

People, vehicles, partitions, furniture, moveable equipment, snow

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12
Q

What are the units of inertia?

A

(unit of length)^4

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13
Q

What is a mathematical expression that describes the relative location of material in a cross section?

A

Moment of Inertia

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14
Q

What is a moment of inertia?

A

Relative location of material in a cross-section. It resists bending stress and deflection

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15
Q

What is another name for moment of inertia?

A

Second moment

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16
Q

What is moment of inertia a measure of?

A

Cross-sectional stiffness

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17
Q

How would one find the Moment of Inertia of Hollow Shapes?

A

If the centroids of two shapes coincide, you may subtract the moment of inertia of the void from the moment of inertia of the overall body. THIS IS CALLED THE NEGATIVE AREA METHOD

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18
Q

What is the manner in which loads travel throughout the structure?

A

Load Path

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19
Q

What is a Load Path

A

the manner in which loads travel throughout the structure

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20
Q

What concept considers the area that a member must support as being halfway between the adjacent similar members?

A

Tributary area

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21
Q

What is tributary area?

A

concept that the area that a member must support as being halfway between the adjacent similar members

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22
Q

Beams are classified based on ____

A

support conditions

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23
Q

What is a simply supported beam?

A

2 supports, 1 on each end

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24
Q

What is a continuous supported beam?

A

3 or more supports

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25
Q

What is a cantilever beam

A

1 end supported rigidly

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26
Q

What is an overhang beam?

A

2 supports but 1 or both are not located at the end

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27
Q

What is a propped beam??

A

2 supports, 1 end is fixed

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28
Q

What is a restrained or fixed beam

A

both supports are fixed, allowing no rotation

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29
Q

What is the mathematical relationship between nominal and actual dimensioning?

A

1 nominal inch=3/4 actual inch
2-6 n”= -.5” actual
8+” n= -3/4” actual

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30
Q

What concept is represented by the equation I/C, where I is the moment of inertia and c is the distance from the centroidal axis to the extreme fiber

A

section modulus S

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31
Q

What is the variable S?

A

Section modulus, a ratio that can be standardized for materials of given size/makeup & found in tables

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32
Q

What is the equation for section modulus S?

A

I/C
Where C is the distance from the centroidal axis to the extreme fiber
and I is the moment of inertia
This equation is not usually used for standard shapes bc S is in tables

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33
Q

What is the variable fb?

A

fb is the bending stress at the extreme fiber, top or bottom

34
Q

What is the formula for bending stress or flexure?

A

fb= Mc/I or M/S since S=I/C
M is the bending moment in the beam, usually Mmax and found through the shear & moment diagrams
S is the section modulus, found in a table

35
Q

What equation could be used to determine the required section modulus when designing a wood beam?

A

Sreq=M/Fb
where Fb is the allowable bending stress
M is the maximum bending moment in the beam (shear&stressgraphs)

36
Q

What is a load in which the resultant concentrat4ed load passes through the centroids of all resisting sections

A

Axial load

37
Q

What is a load in which the loads are applied transversely to the longitudinal axis of the member.

A

Flexural or bending load

38
Q

What is an axial load?

A

a load in which the resultant concentrated load passes through the centroids of all resisting sections

39
Q

What is a flexural load?

A

load in which the loads are applied transversely to the longitudinal axis of the member. also known as bending load

40
Q

Stress flexural

A
41
Q

What is the quantity of force that acts on a unit of area

A

stress

42
Q

What is normal or axial stress

A

force per unit area. Stress acts perp. to the cross-section

43
Q

What is the average value of the axial stress?

A

f = σ = P / A
where P is axial force
and A is perp. resisting area

44
Q

What is shear stress?

A

quantity of tangential force acting over an area parallel to the direction of the applied load. Acts parallel or tangential to the cross-section

45
Q

What is the formula for shear stress?f

A

fv = τ = V / A
Where V is shearing force
A is cross-sectional area parallel to load direction

46
Q

What type of stress is the primary concern when designing beams?

A

flexural or bending stress

47
Q

What is the formula for bending stress

A

σb = M * c / I
where σb is bending stress
M is bending moment
c is distance from centroid to extreme top & bottom fibers
I is moment of inertia

48
Q

Is bending stress for unsymmetrical cross-sections determined by the the smaller or larger of the distances from the centroid line to the extreme top/bottom?

A

larger of the 2. distance c.

49
Q

What is the sign convention for compression & tension?

A

compression is (-)
tension is (+)

50
Q

What is strain?

A

deformation per unit length. results from stress or temperature change.

51
Q

What is the symbol δ

A

deformation

52
Q

What is the symbol ε

A

normal STRAIN

53
Q

symbol γ?

A

shear strain

54
Q

What is normal/axial strain?

A

deformation per unit length resultant from a normal load.

55
Q

What is the formula for normal strain?

A

ε =δ/L
Where ε is strain
δ is the change in length
L is the original length

56
Q

What is the modulus of elasticity

A

Also called young’s modulus
Measure of the material stiffness or how much stress it will take to cause a unit strain (contraction or elongaiton)

57
Q

What is the equation for modulus of elasticity?

A

Hookes Law: E =σ/ε
modulus = stress / strain

58
Q

What is shear strain?

A

deformation due to shear stress, which is stress acting parallel to the cross section, results in changes to shape but not volume. represented by γ

59
Q

What is the formula for shear strain?

A

γ = δs/L = tanφ
where γ is shear strain
δ is shear deformation (distance one point of original side moves)
L is original length
φ is angle that the original side moves

60
Q

What is bending strain?

A

deformation per unit length due to bending stress

61
Q

What is the difference between ductile and brittle materials?

A

Ductile materials have molecular bonds that reform after exceeding the elastic limit that will result in permanent deformaiton while still remaining in one piece without a significant loss in strength.
Brittle materials when the elastic loimit is exceeded are unable to reform , causing cracks or seperation of material

62
Q

Give examples of ductile materials

A

low-carbon steel, aluminum, copper, gold

63
Q

give examples of brittle materials

A

cast iron, high-carbon steel, ceramics

64
Q

What is lumber grading?

A

Lumber is graded according to its quality, strength, and appearance, with trained inspectors using standardized criteria such as knots, grain patterns, and defects to assign a grade. This classification ensures that lumber meets industry standards and facilitates its appropriate use in construction and manufacturing.

65
Q

Do grades of lumber go up or down from 1 to 3?

A

1 is best quality, 3 is cheapest. select structural is highest. below 3 is stud, then construction.

66
Q

What is allowable stress?

A

Stress that a member can hold. Allowable stress divided by failujre stress provides the factor of safety.

67
Q

Section modulus rectangle?

A

S = bh^2/6

68
Q

How is stiffness of material evaluated?

A

Young’s modulus or the modulus of elasticity, which is the slope of the straight-line portion of a stress-strain daigram.
E = f/ε
where f is stress and ε is strain

69
Q

What is ultimate strength?

A

absolute highest stress magnitude on a stress-strain graph

70
Q

A structural system that distributes loads to supports through a alinear arrangement of various-sized members in patterns of planar triangles

A

truss

71
Q

What is a truss?

A

a structure that consists of members assembled such that they resist loads axially only

72
Q

Truss members are connected by ____

A

smooth pins @ their joints

73
Q

all loading is applied ____ of a truss

A

at the joints

74
Q

since members are ____, their weight is ____ compared to joint loads.

A

slender, negligioble

75
Q

What are the only forces oln truss members?

A

compression & tension

76
Q

What is a zero force member?

A

An unloaded joint where 3 members frame together. if 2 members are in a straight line, then the 3rd is zero force.

77
Q

What is deflection?

A

A stiffness requirement representing a change in vertical position of a beam due to the applied loads.

78
Q

What is the equation to find actual deflection on a simple span with a uniform load?

A

deltamax=5wL^4/384EI
where delta is deflection
w is the applied loads
E is the elastic modulus
I is the moment of inertia

79
Q

What is the shortcut formula form Maximum moment of a simply supported beam?

A

`wL^2/8
where w is the total load (dead+live)
L is the length of the beam

80
Q

What is the shortcut for Vmax of a simply supported beam?

A

wL/2
where w is the total load on the beam
L is the length of the beam

81
Q

What is the shortcut for cross-sectional area required of a simpy supported beam?

A

Areq=1.5Vmax/Fv
Where Vmax is the maximum shear on the loaded beam (found by wL/2)
Fv is the maximum shearing stress, may be given in the problem.

82
Q

What is the formula for allowable deflection of a simply supported beam?

A

deltaallowable(DL+LL) = L/240
where L is the length of the beam
deltaallowable (LL) = L/360
***dont forget to multiply L by 12 if it is in feet and not inches

Structures (4 decks)

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