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Steel Design > Compression > Flashcards

Compression Flashcards

1
Q

Pcr

A

The load that is just large enough to maintain the defelcted shape when the load is removed.

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2
Q

Critical Buckling load equation for elastic member

A

Pcr = (π2)EI / L2

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3
Q

Types of Failure for axially loaded columns

A
  1. Flexural Buckling
  2. Local Buckling
  3. Torsion Buckling
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4
Q

A columns tendency to buckle is measured by its __________

A

Slenderness ratio = L/rmin

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5
Q

Elastic Critical buckling stress equation.

A

FCR = PCR / A = π2*E / (L/r)2

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6
Q

Critical Buckling load equation for inelastic buckling

A

Pcr = (π2)EtI / L2

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7
Q

Fcr

A

Critical Compressive or bending stress used to determine nominal strength

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8
Q

Nominal Compressive strength based on the limit state of buckling AISC Equation E3-1

A

Pn = Fcr*Ag

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9
Q

Pu <= Φc*Pn

A

Nominal Compressive strength LRFD AISC Equation E3-1

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10
Q

Pu means

A

Sum of factored loads LRFD

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11
Q

Φc means

A

LRFD Resistance factor for compression = .90

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12
Q

Define Φc *Pn

A

Design compressive strength LRFD

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13
Q

Pa <= Pn/ Ωc

A

Allowable Compressive strength ASD AISC Equation E3-1

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14
Q

Pa means

A

applied axial service load= required strength ASD

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15
Q

Ωc means

A

ASD Safety factor for compression = 1.67

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16
Q

Pn/ Ωc

A

Allowable compressive strength

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17
Q

Fe <= Pe/ A = π2*E/ (Lc/r)2

A

Euler buckling stress AISC EQUATION E3-4

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18
Q

Lc & KL means

A

Effective Length of compression member

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19
Q

Fcr=.877*Fe

A

Critical stress for elastic columns

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20
Q

Fcr=(.658(Fy/Fe))*Fy is the equation for

A

Critical stress for elastic columns

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21
Q

Fa means

A

Allowable axial compressive stress

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22
Q

When Lc/r is less than or equal to 4.71sqrt(E/Fy)

A

Use AISC equation 3-2,

Fcr=(.658(Fy/Fe))*Fy

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23
Q

When Lc/r is greater than 4.71sqrt(E/Fy)

A

Use AISC equation E3-3, Fcr=.877*Fe

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24
Q

The critical buckling load is a function of…

A

the modulus of elasticity, and not the yield stress or ultimate tensile strength

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25
Q

Values of K can be determined with

A

Table C-A-7.1 in the commentary to AISC spec appendix 7

26
Q

K is defined as___

A

Effective length factor

27
Q

The effective length factor for FIXED-PINNED compression member is ____

A

.70

28
Q

The effective length factor for FIXED-FIXED compression member is ____

A

.5

29
Q

The use of the effective length KL in place of the actual length_________

A

in no way alters the relationship in the equations.

30
Q

Steps to compute design compressive strength of a column

A
  1. calculate effective length
  2. Calculate maximum slenderness ration L/r compare to limit of 200 if over choose another shape
    3.Compare L/r
31
Q

The upper limit for the slenderness ratio L/r is _______ becasue members that are any more slender will have little strength and not be economical.

A

200

32
Q

Fy for A36 steel.

A

36 ksi

33
Q

Fy for A572 steel.

A

50 ksi

34
Q

Fy for A992 steel.

A

50 ksi

35
Q

Fu for A36 steel.

A

58 to 80 ksi

36
Q

Fu for A572 steel.

A

65 ksi

37
Q

Fu for A992 steel.

A

65 ksi

38
Q

Fa =.6* Fcr

A

Allowable stress ASD

39
Q

Fa*Ag

A

Allowable strength ASD

40
Q

Square structural tubes HSS are efficiant shapes for compression members becasue________

A

ry=rx

41
Q

Limiting values of width to thickness ratios are given in______

A

AISC B4.1

42
Q

For compression members shapes are classified as_____

A

1.Slender
2. Non slender

43
Q

If a shape is slender, its strength limit state is_______

A

Local Buckling

44
Q

The width to tickness ratio of a beam flange in relation ot its web is defined as _____

A

= λ=b/t = bf/2* tf

45
Q

If λ is less than or equal to λr then the shape is_______

A

non slender

46
Q

For beams a shape can be______

A
  1. compact
  2. non compact
  3. slender
47
Q

Steps to check for local stability

A
  1. calculate width to thickness bf/2* tf
  2. Calculate upper compression limit λr from AISC B4.1
  3. Calculate height to thickness
  4. if the height and width to thickness is less than or equal to the upper limit its OK
48
Q

In the steel manual, shapes that are slender for compression are indicated with a _______

A

Footnote C

49
Q

Define be

A

Reduced effective width of the element

50
Q

Define t

A

t is the design thickness of the element

51
Q

When h/t is bigger than the upper limit (#*sqrt(E/Fy) i.e. λ >λr then….

A

the larger dimension element is slender and the local buckling strength must be computed

52
Q

When λ< λr*sqrt(Fy / Fcr) then what is true about be?

A

It is equal to b

53
Q

When λ> λr*sqrt(Fy / Fcr) then what is true about be?

A

It must be computed using be= b(1 - c1(sqrt(Fel / Fcr))sqrt(Fel / Fcr)

54
Q

Define c1

A

effective width imperfection adjustment factor from AISC Table E7.1

55
Q

Define Fel

A

Elastic local buckling stress = (c2(λr/λ))2Fy

56
Q

(c2(λr/λ))2Fy

A

Elastic buckling stress equation AISC equation E7-5

57
Q

AISC Table 4-1A shows_____

A

Width to thickness ratios for compression members

58
Q

AISC table 6-2 shows…

A

Available axial compression and bending strengths of all shapes that have a Fy of 50ksi

59
Q

Design steps to select shape for compression using tables

A
  1. Find the sum of the factored loads Pu
  2. enter the table 6-2 with the Length
60
Q

If the capacity with respect to x-axis buckling is desired enter the table with_______equation

A

Lc = Lcx/(rx/ry)

61
Q

Define Pn

A

nominal strength in tension or compression

Steel Design (4 decks)

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