Compression Flashcards

(61 cards)

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
Values of K can be determined with
Table C-A-7.1 in the commentary to AISC spec appendix 7
26
K is defined as___
Effective length factor
27
The effective length factor for FIXED-PINNED compression member is ____
.70
28
The effective length factor for FIXED-FIXED compression member is ____
.5
29
The use of the effective length KL in place of the actual length_________
in no way alters the relationship in the equations.
30
Steps to compute design compressive strength of a column
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
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.
200
32
Fy for A36 steel.
36 ksi
33
Fy for A572 steel.
50 ksi
34
Fy for A992 steel.
50 ksi
35
Fu for A36 steel.
58 to 80 ksi
36
Fu for A572 steel.
65 ksi
37
Fu for A992 steel.
65 ksi
38
Fa =.6* Fcr
Allowable stress ASD
39
Fa*Ag
Allowable strength ASD
40
Square structural tubes HSS are efficiant shapes for compression members becasue________
ry=rx
41
Limiting values of width to thickness ratios are given in______
AISC B4.1
42
For compression members shapes are classified as_____
1.Slender 2. Non slender
43
If a shape is slender, its strength limit state is_______
Local Buckling
44
The width to tickness ratio of a beam flange in relation ot its web is defined as _____
= λ=b/t = bf/2* tf
45
If λ is less than or equal to λr then the shape is_______
non slender
46
For beams a shape can be______
1. compact 2. non compact 4. slender
47
Steps to check for local stability
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
In the steel manual, shapes that are slender for compression are indicated with a _______
Footnote C
49
Define be
Reduced effective width of the element
50
Define t
t is the design thickness of the element
51
When h/t is bigger than the upper limit (#*sqrt(E/Fy) i.e. λ >λr then....
the larger dimension element is slender and the local buckling strength must be computed
52
When λ< λr*sqrt(Fy / Fcr) then what is true about be?
It is equal to b
53
When λ> λr*sqrt(Fy / Fcr) then what is true about be?
It must be computed using be= b(1 - c1*(sqrt(Fel / Fcr))*sqrt(Fel / Fcr)
54
Define c1
effective width imperfection adjustment factor from AISC Table E7.1
55
Define Fel
Elastic local buckling stress = (c2*(λr/λ))2*Fy
56
(c2*(λr/λ))2*Fy
Elastic buckling stress equation AISC equation E7-5
57
AISC Table 4-1A shows_____
Width to thickness ratios for compression members
58
AISC table 6-2 shows...
Available axial compression and bending strengths of all shapes that have a Fy of 50ksi
59
Design steps to select shape for compression using tables
1. Find the sum of the factored loads Pu 2. enter the table 6-2 with the Length
60
If the capacity with respect to x-axis buckling is desired enter the table with_______equation
Lc = Lcx/(rx/ry)
61
Define Pn
nominal strength in tension or compression