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BDCS CHING > STRUCTURES > Flashcards

STRUCTURES Flashcards

1
Q

What is the slenderness ratio?

A

L/r where L is the effective length and r is the radius of gyration

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2
Q

What does effective length depend on?

A

If the ends, or one of the ends, is fixed, or pinned.

Where k is the effective length factor:

Both ends fixed: k=0.5
One end pinned one and fixed: k=0.7
Both ends pinned: k=1.0
One and free, one and fixed: k=2.0

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3
Q

What is the span limit of planks?

A

About 15 feet

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4
Q

What is the span limit of joists?

A

About 20 feet

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5
Q

What is the span limit of laminated beams?

A

About 80 feet

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6
Q

What is the span limit of open web joists?

A

About 90 feet

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7
Q

Relatively short, fit columns are subject to failure by _____. Long, slender columns are subject to failure by _____.

A

Crushing, buckling

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8
Q

What is a horizontal diaphragm?

A

A rigid floor structure acting as a flat, deep beam, transferring lateral loads to vertical sheer walls, brace frames etc.

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9
Q

Describe the problem of a reentrant corner

A

An L-shaped plan configuration which tends to produce differential motions between different portions of the structure, resulting in local stress concentrations at the corner.

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10
Q

What are three ways to avoid problems from reentrant corners?

A

Seismic joints or splayed corners… Or stronger connections at the corner

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11
Q

What is a discontinuous diaphragm?

A

A diaphragm with a large cut out or open area, or a stiffness significantly less than that of the story above

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12
Q

What is a tuned mass damper?

A

A heavy mass mounted on rollers and attached to the upper portion of a tall building with spring damping mechanisms… The weight will have an internal tendency to remain at rest and thus counteracting and dissipating any building movements

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13
Q

What is base isolation?

A

Isolating the base of a building from the ground with damping mechanisms to allow the superstructure to float as a rigid body and alter the natural vibration of the structure so that it is different from that of the ground, thus preventing destructive resonances from occurring.

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14
Q

For bending to be illuminated throughout an arch…

A

The line of thrust must coincide with the arch axis

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15
Q

What are guy cables?

A

They absorb the horizontal component of thrust in a suspension structure, transferring the force to a ground foundation

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16
Q

If a wood joist is being slotted into a concrete or masonry wall, it needs ___” minimum air space on the tops, sides, and ends of wood beams. Why?

A

1/2”… Unless you’re using pressure-treated wood, you don’t want the beams to receive moisture

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17
Q

What is the effective depth of a concrete footing?

A

The distance between the top of the footing and the steel reinforcing bars

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18
Q

Uphill polls have shorter unsupported heights but require _______ in order to provide the necessary rigidity for the structure… About how much?

A

Deeper embedment… 5 feet to 8 feet

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19
Q

________, ________, or _______ improves the bearing for beams and provides better contact with ground poles.

A

Notching (sometimes referred to as dapping), spiked grid connector, gusset

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20
Q

Rule of thumb for estimating the depth of a concrete beam

A

Span/16

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21
Q

Two ways concrete slabs can carry from ____ to ____ spans… But two-way waffle slabs can carry from ___ to ____.

A

From 15 to 40 feet… From 24 to 54 feet… Or even longer with posttensioning

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22
Q

Rule of thumb for estimating the beam thickness of a one-way concrete slab… And suitable spans would be between ___ and __.

A

Span/30… Between 6 feet and 18 feet

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23
Q

Rule of thumb for estimating the thickness of a two way flat plate… Good for spends between ____ and ____. And for a two way flat slab?

A

Flat plate: Span/33… For spans between 12 feet and 24 feet

Flat slab: span/36… For spans between 20 feet and 40 feet

24
Q

What is the difference between a two way flat plate and a two-way flat slab?

A

The flat slab is thickened at its column supports to increase its sheer strength and moment resisting capacity

25
Q

What do you do to the voids in hollow core units at the ends in order to tie into concrete or masonry support?

A

Grout the ends of voids

26
Q

What are plate girders?

A

I-beams built up from plates and/or angles welded or riveted together

27
Q

What are box girders?

A

Like a plate girder, but with two pieces of web separated from each other to create a hollow shape Ibeam

28
Q

What are castellated beans?

A

When the web of the wide flange section is divided with the lengthwise zigzag cut… And two sides are welded back together so that there are hexagon hollows

29
Q

What is the difference between form decking, composite decking, and cellular decking?

A

Composite decking has embossed rib patterns to adhere to the concrete. Cellular decking is welded onto a flat steel sheet, forming a series of spaces or raceways for electrical and communications wiring.

30
Q

Where do you use web stiffeners?

A

concentrated loads

31
Q

Tell me the span ranges for wood joists

A

2X6: up to 10 feet
2X8: 8 feet to 12 feet
2X10:10 feet 14 feet
2X12:12 feet 18 feet

… Span/16

32
Q

What is the maximum diameter of a hole cut into a wood joist?

A

1/3 the joist depth

33
Q

What is the maximum depth of a notch in the top or bottom part of a wood joist?

A

1/6 joist depth

34
Q

What is a rim joist?

A

Perpendicular to the joists, it’s at the perimeter

35
Q

If you are lapping or splicing wood joists over a beam, how far do you have to lap minimum? If you are splicing, what is the minimum bearing?

A

4 inches of lap, one and a half inches minimum bearing with a splice

36
Q

How far can a wood joists cantilever without being engineered?

A

24”

37
Q

What is the difference between a box beam, a flitch beam, a spaced beam, I do regular build up being?

A

Box beam: made by going to a more plywood/OSB to a timber above and below (hollow within)… Can spend up to 90 feet

Flitch beam: Timber set on edge and bolted side-by-side to steel plates

Spaced beam: blocked and securely nailed at frequent intervals, too deep timbers are spaced apart

Built up beam: equal in strength to the some of the strengths of the individual pieces if none of the laminations are spliced

38
Q

What is the difference between parallel strand lumber and laminated veneer lumber?

A

PSL is a structural member made by bonding long, narrow wood strands together under heat and pressure with a waterproof adhesive.

LVL is a structural lumber made by bonding layers of wood veneers together under heat and pressure using a waterproof adhesive.

39
Q

Best place to splice wood beams

A

Point of zero moment

40
Q

Whenever possible, very the required steel reinforcement rather then…

A

Column size

41
Q

Wells more than 10 inches thick require reinforcement in…

A

Two layers

42
Q

What do yolks do for concrete columns?

A

They clamp the form work together for square or rectangular columns

43
Q

In concrete formwork, what are spreaders?

A

They keep the two faces of plywood sheathing away from each other

44
Q

What are composite precast panels?

A

Rigid foam insulation core with two wythes of concrete on either side… Up to 24 foot high

45
Q

The tallest wall surface?

A

Precast ribbed panels as walls. They are up to 48 feet high.

46
Q

What is MSNOK?

A

Masonry types in declining order of strength and weatherability

47
Q

The cavities within a double wythe wall should be between ___” and ___”.

A

2” - 4.5”

48
Q

What is a jack arch?

A

A horizontal soffit with voussoirs radiating from a Centerpoint below… I.E.it is a rectangular opening

49
Q

Minimum lintel bearing

A

6”: steel angle lintels

8”: concrete masonry and precast concrete lintels

50
Q

Masonry corbels are permitted only in solid walls at least __” thick.

A

12”

51
Q

Tooled joints

A

Concave and V

52
Q

Troweled joints

A

Striking off excess mortar with a trowel

Flush joint, struck joint, whether to joint… Most effective for shedding water

53
Q

Glass block has a maximum width of __’ and a maximum height of __‘… For a total area of not more than __ sf.

A

25’, 20’, 144’

54
Q

Light gauge steel studs are usually ________ to allow piping, wiring, and briefing to pass through.

A

Pre-punched

55
Q

What is the maximum unsupported height of 2X4 platform framing? 2X6?

A

14’… 20’

BDCS CHING (4 decks)

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