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Structural Systems > Jenny's Notes > Flashcards

Jenny's Notes Flashcards

1
Q

Define “Factor of Safety”

A

The ratio of the ultimate strength of material to its working stress.

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2
Q

Define “Eccentric Load”

A

A load imposed on a structural member at some point other than the centroid of the section.

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3
Q

What is the equation for Stress (f)

A

Stress (f) = Total Force (P) / Area (A)

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4
Q

Define “Yield Point”

A

The amount of stress that causes a material to deform without additional load added

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5
Q

What is the ultimate strength (psi) of steel, concrete, and wood ?

A 
Steel = 58,000 - 80,000 psi
Concrete = 3,000 - 6,000 psi
Wood = 2,000 - 8,000 psi
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6
Q

What is the equation for Slenderness Ratio (Loading Capacity) of a steel column?

A 
Slenderness Ratio (SR) = end condition (k) * unbraced length in inches (L) / radius of gyration (r) 
SR= kL/r
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7
Q

Shear force acts parallel to area _________ force

A

resisting

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8
Q

For an object to be in equilibrium it must….

A

1) Have no unbalanced force acting on it

2) Have no unbalanced moment acting on it

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9
Q

What are the 3 most important types of stress in building design and construction?

A

1) Tension
2) Compression
3) Shear

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10
Q

Define “Deconstructive Agents” and give examples

A

They reduce capacity of structural elements

1) Fire
2) Chemical corrosion
3) Erosion (wind/water)
4) Insects/Plants/Animals

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11
Q

What are the three general steps in structural design?

A

1) Determine the loads (compute)
2) Calculate the stresses (analyze)
3) Dimension and proportion the members and detail the connections (design)

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12
Q

Two forces equal in magnitude, but opposite in direction, and acting at same distance from each other form a ______.

A

Couple

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13
Q

If a force causes a clockwise rotation, then the moment is 1)__________. If a force causes a counter-clockwise rotation, then the moment is 2)________.

A

1) Positive

2) Negative

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14
Q

Define “Gage Line”

A

Standard dimension from corner edge of an angle to the centerline of bolt holes. (this depends on the size of the angle)

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15
Q

Define “Seismic Design Category”

A

The classification assigned to a structure based on its occupancy category and the severity of the design earthquake ground motion at the site

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16
Q

What is a “Site Class,” name the 8 types

A

Classification assigned to a site based on the types of soils present and their engineering properties

a: hard rock
b: rock
c: dense soil
d: stiff soil
e: soft soil
f: varies
g: varies with multiple characteristics

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17
Q

How does concrete get its strength?

A

By curing through a chemical reaction between water and cement, not drying

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18
Q

What are the typical grades for manufactured rebar?

A

40, 60, 75 (60 being the most common)

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19
Q

What is the minimum distance rebar should be placed from exposed face of concrete in the following situations…

  • Slabs and Walls
  • Beams and Columns
  • Exposed to weather or contact with soil
  • Concrete poured directly on soil
A
  • Slabs and Walls= 3/4” from face of concrete
  • Beams and Columns = 1 1/2” from face of concrete
  • Exposed to weather or contact with soil= 1 1/2” from face of concrete
  • Concrete poured directly on soil= 3” from face of concrete
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20
Q

What is the equation for Strain

A

Strain (E) = Deflection (e) / Original Length (L)

E = e/L

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21
Q

Charpy V-Notch Test

A
  • A ductility test where a piece of material has a v-notch cut into the top
  • Tests how much energy it takes to make the notch go through the whole piece
  • if it breaks quickly = not much energy/brittle
  • if it breaks slowly = takes a lot of energy/ductile
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22
Q

Shear

A

Two members sliding past each other

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23
Q

Calculate stress

A

f=P/A

stress(f) = force (P) / area (A)

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24
Q

Define “center of gravity” and “centroid”

A

Center of Gravity = the point at which the mass of a member is concentrated

Centroid = The actual point at the center of gravity that measurements are taken

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25
Q

Post-tensioned Concrete

A

Steel tendons are laid out in desired direction and concrete is poured on top. when concrete is cured, tendons are tensioned and force is transferred to the concrete through end anchorages

26
Q

Flat panel system

A

Basically a two-way slab with no supporting beams, only columns. Reinforced slab spans in both direction directly into columns at 25’ with 6”-12” thickness

  • Typically used for light loads, short spans, when floor-floor height must be minimized, or simple underside of slab appearance is required.
  • has low shear capacity
27
Q

Waffle Slab System

A

Ribs formed with reusable prefab metal/fiberglass forms and span up to 40’
-provides largest spans of conventional concrete systems.

28
Q

Selecting a structural system is based on 1)___________, 2)__________, 3)__________.

A

1) Economy
2) Span
3) Shape

29
Q

What is the typical construction weight per floor :

1) Timber
2) Steel
3) Concrete/Masonry
4) Light loads / Pneumatic

A

1) Timber = 7-10 lbs/sf typical construction weight/floor
2) Steel = 15-20 lbs/sf typical construction weight/floor
3) Concrete/Masonry = 150-200 lbs/sf typical construction weight/floor
4) Light loads / Pneumatic = lightest system, but must deal with wind

30
Q

Dowel Type fasteners

A

(nails, screws, bolts) that transmit lateral loads via bearing stresses between the fastener and members of the connection OR that transfer withdrawal loads parallel to the fasteners axis via friction or bearing to the connection materials

31
Q

Bearing Type Fasteners

A

(shear plates) that transmit lateral loads only by shear forces via bearing on the connected materials

32
Q

Hangers

A

combination of dowel and bearing type fasteners that support one structural member and are connected to another member by a combination of dowel and bearing action

33
Q

Plate Girder

A

assembly of steel plates, or plates and angles, fastened together for form an integral member

34
Q

Underpinning

A

The process of strengthening and stabilizing the foundation on an existing building

35
Q

Shoring

A

supporting a structure in order to prevent collapse so that construction can proceed ( e.g. support beans and floors of building while a column/wall is removed, shoring in trenches for worker safety in excavation

36
Q

Nails

A
  • are the weakest connection, and the most common. they should be fastened lateral in side grain where the holding power is the greatest
  • are identified by penny size (d)
  • box nails : 6d - 40 d, smallest diameter
  • wire nails : 6d-60d, medium diameter
  • wire spikes: 10d–8.5” with 3/8” diameter, largest diameter
37
Q

What are the 5 types of foundation footings?

A

Spread footing, wall footing , column footing, combined footing, strap/cantilevered footing

38
Q

What are the 3 types of retaining walls?

A

Cantilever Wall, Counterfort walls, gravity walls

* they fail as a whole by overturning or sliding

39
Q

Define “Pile Foundations”

A

They are used when soiled is unsuitable for spread footings, and are driven into soil by transmitting loads through soil to a more secure bearing farther below

40
Q

Mat Foundation

A

Are very expensive, used only when the strata is weak. They act as one continuous foundation

41
Q

Friction Pile

A

Driven into soft soil. It transmits the load between pile and soil. Bearing capacity is limited by whichever is weaker (soil or pile)

42
Q

Socketed Caissons

A

like Belled Caissons, but the hole is drilled deep into the strata. Bearing capacity comes from end baring and frictional forces.

43
Q

What are the 2 Concrete connection types?

A

Rebar Dowels: reinforcing for the purpose of tying two pours of concrete together instead of transmitting loads

Shear connections: steel concrete tied together so forces are transmitted from one to the other via connectors that are welded to the top of beams

44
Q

Describe the 5 types of cement

A

Type 1: standard cement used for general construction
Type 2: modified cement where heat of hydration needs to be controlled
Type 3: high early strength cement where quick set is required
Type 4: low heat cement for very slow setting , used to avoid damage caused by heat
Type 5: sulfate resisting cement, where exposed to water or soil with high alkaline content

45
Q

Admixtures

A

chemicals and/or misc. materials added to the mixture to speed up hydration, improve workability, add color (either dye or colored stone)

46
Q

Concrete Materials

A

made up of aggregate, cement, and water (and sometimes admixtures)

47
Q

What are the 8 types of soil and describe

A

Gravel: well drained and able to bear loads (+2mm)
Sand: well drained and can serve as foundation when graded (0.5-2 mm)
Silt: stable when dry, swells when frozen, do not use when wet (.002-.05mm)
clay: must be removed, too stiff when dry and too plastic when wet <.002mm)
Alluvium: soil, sand or mud deposited by flowing water
Humus: soft dark soil containing decomposed organic matter, poor bearing capacity
Loam : rich soil containing equal parts of sand, silt, and clay

48
Q

Bearing Capacity

A

the max pressure a foundation soil can take with harmful settlement …
Bedrock = 10,000 psf
Well graded gravel/sand = 3,000-12,000psf
Compacted sand/fill = 2,000-3,000psf
Silt/clay = 1,000-4,000psf

49
Q

Borings

A

locations depend on nature of the building and should be 20’ past firm strata

  • open warehouses: one in each corner and one in the middle
  • large structures : 50’-0” spacing
  • uniform conditions : 100’ - 500’ spacing
50
Q

Slump Test

A

measures the workability of fresh concrete/the consistency of the concrete in that specific batch and done on the jobsite

  • concrete is poured in a cone mode that is 12” tall with 8” diameter at base and 4” diameter at top
  • the mold is removed and the concrete is allowed to slump naturally
  • the amount of slump is measured, the less slump the better the quality
51
Q

Life Safety Code

A

consensus standard widely adopted (but not legal code) that addresses construction, protection, and occupancy feature necessary to minimize danger to life from, including smoking, fumes, or panic

52
Q

Fire Code

A

set standards established and enforced for fire prevention and safety incase of fire. Addresses fire prevention and building construction features/ratings.

53
Q

Base Isolation

A

a method whereby a building superstructure is detached from its foundation in order to change the characteristics of earthquake forces transmitted to the building

54
Q

Bracketed Duration

A

the time between the first and last peaks of motion that exceeds ta threshold acceleration value of 0.05g

55
Q

Drift

A

the vertical deflection of a building or structure caused by lateral forces

56
Q

Equation for Base Shear

A

Base shear = seismic response coefficient * effective seismic weight of building

57
Q

What are the seismic design categories per IBC

A 
A = building in regions with little probability of earthquake 
B= ordinary occupancy that could experience shacking 
C= structures of ordinary occupancy that experience strong shaking or important structures that experience medium shaking 
E= Ordinary building close to a fault line 
F= Important building close to a fault line
58
Q

T/F The epicenter or and earthquake occurs on the surface directly above the focus point or fault rupture

A

True

59
Q

The most common cause of earthquake damage is ground shaking, name the three ways a building is effected

A
  • Internal forces
  • period/resonance
  • torsion
60
Q

Define Modulus of Elasticity and provide its equation

A

A materials resistance to non permanent (or elastic) deformation

Modulus of Elasticity = Stress / Strain

61
Q

Define Moment of Inertia and provide its equation

A

(occurs about the centroid Axis)
Measure of an objects resistance to changes to its rotation

Moment of Inertia = Base x Depth ^3 / 12

Structural Systems (16 decks)

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