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ARE 5.0 - Programming & Analysis > Selection of Structural Systems > Flashcards

Selection of Structural Systems Flashcards

1
Q

What is the typical spacing of wood joists? Typical maximum span?

A

Spacing: 12 in, 16 in, and 24 in OC

Span: 20 ft > 25 ft

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2
Q

What is the most common use of solid wood beam structural system? What is its typical max span?

A

Planks and beams framing = members of 4 in or 6 in nominal width span between girders or bearing walls at spacing of 4 ft, 6 ft, or 8 ft

Span = 10 ft > 20 ft

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3
Q

What are the advantages of glu-lam construction?
What are standard widths?
Spans?

A

Advantages =
Appearance: often are left exposed as part of architectural/structural expression
Shape: can be manufactured in tapered and curved beams and arches

Widths = 3 1/8”, 5 1/8”, 6 3/4”, and 8 3/4”

Spans = 15 ft < 60 ft

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4
Q

What is the main advantages of a lightweight I-joist (TJI)? When is it typically used?

A

Advantages:
Allows longer spans with a joist system because it is stronger and stiffer than standard wood.

Used in residential and light commercial construction

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5
Q

What is LVL?
What is it primarily used for?
What is its primary advantage?

A

Individual layers of thin veneer glued together.

Primarily used for:

  • Headers over large openings
  • Singly or built-up for beams

Advantages:
- Has higher modulus of elasticity than standard wood joist, so its allowable stress in bending is about twice that of a Douglas-fir joist.

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6
Q

When are wood trusses most often used?

What is its main advantage?

A

Typically used for residential and light commercial construction

Advantage = allow easy passage of mechanical ductwork through truss

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7
Q

What are typ spans of wood trusses?

Typ depths? Typ spacing?

A

Typical spans = 20 ft > 40 ft
Typical depths = 12 in > 36 in
Common spacing = 24 in on center

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8
Q

What is a box beam? When is it used?

A

Plywood panels are glued and nailed to solid wood members, typ 2x4

Uncommon but most often used where depth of member is not critical and other types of manufactured beams cannot be brought to the site

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9
Q

What is a stressed-skin panel? What type of assemblies can it be used for?

A

A type of wood construction where plywood is glued and nailed to both sides of solid 2x’s. Uncommon due to lack of availability and difficulty in on-site fabrication

Used for floor, roof or wall construction

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10
Q

What are 4 advantages of steel construction?

A
  1. High strength
  2. Availability
  3. Ability to adapt to a wide variety of structural conditions
  4. Ductility (able to tolerate some deformation and return to its original shape before breaking)
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11
Q

What type of construction is steel best suited for?

A

multi-floor construction due to strength and structural continuity

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12
Q

What are the two most common steel structural systems?

A
  1. beam-and-girder system

2. open-web steel joist system

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13
Q

What is the beam and girder steel structural system? What is the typical:

  • beam span?
  • beam spacing?
A

Larger girders span between vertical supports, and smaller beams are framed into them.

Typical beam span = 25 ft > 40 ft
Typical beam spacing = 8 ft > 10 ft on center

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14
Q

What is the open-web steel joist system?

What is the typical span? Long span? Deep long span?
What is the typical depth? Long depth? Deep long depth?

A

Open-web steel joists span between beams or bearing walls.

Standard open-web joist span = 60 ft
Standard depth = 8 in > 30 in

Long-span joist = 96 ft
Long-span depth = 18 in > 72 in

Deep long-span = 144 ft

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15
Q

What are 4 advantages of the open-web steel joist system? 1 disadvantage?

A
  1. Efficient structural members
  2. Well-suited for low-rise construction where overall depth of floor/ceiling is not critical
  3. Span long distances
  4. Mech/elec pipes and ducts can easily run through joists

Disadvantage:
1. Combustible construction

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16
Q

What are the two primary types of concrete structural systems?

A
  1. cast-in-place

2. precast

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17
Q

What are the advantages/disadvantages of cast-in-place construction? Of precast?

A 
1. Cast-in-place
Cons: 
- Require formwork
- Take longer to build than precast
Pros: 
- Can conform to almost unlimited variety of shapes, sizes, design intentions, and structural requirements
  1. Precast
    Pros:
    - Quality control is better since made in a factory
    - Erection proceeds quicker
    Cons:
    - More limited in variety of shapes, sizes, design intentions, and structural requirements than cast-in-place
    - Typically prestressed but can also be post-stressed. Sometimes mild reinforcing steel is used
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18
Q

What are two classifications of cast-in-place structural systems?

A
  1. one-way systems = slabs and beams are designed to transfer loads in one direction only (slab → beam → girder)
  2. two-way systems = transfer loads in 2 directions, all designed for use in rectangular bars where distance between columns is the same in both directions
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19
Q

What are 2 types of one-way cast-in-place structural systems?

A
  1. Beam-and-girder system = most common one-way system
  2. Concrete joist system = concrete members spaced 12 in or 36 in apart, running in one direction that frame into larger beams.
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20
Q

What is the typical span of a beam-and-girder cast-in-place structural system? What are 3 advantages of this system?

A

15 ft > 30 ft

  1. easy to form
  2. allows penetrations and openings in the slab
  3. most economical option for most applications
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21
Q

What is the typical span of a concrete joist cast-in-place structural system? What are 3 advantages of this system?

A

Typical spans = 20 ft > 30 ft
Typical depths = 12 in > 24 in

Easy to form
Good for light or medium loads where moderation distances must be spanned

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22
Q

What are 3 types of two-way cast-in-place concrete systems?

A
  1. Flat plate
  2. Flat slab
  3. Waffle slab
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23
Q

What is a flat plate concrete system?
Max span?
Typical thickness?
When it is most useful?

A

The simplest type of two-way system where a slab spans in both directions directly into columns.
Loads increase near columns but slab thickness is not increased or reinforced at columns so this system is limited to light loads and shorts spans.

Max span = 25 ft
Slab thickness = 6 in > 12 in

Useful when floor-to-floor height must be kept to a min or an uncluttered underfloor appearance is desired

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24
Q

What is a flat slab concrete system?

What is its max span?

A

A type of two-way system similar to a flat plate, except that drop panels are provided at columns to provide longer spans and accommodate heavier loads.

Max span = 30 ft

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25
Q

What is a waffle slab concrete system?

Is it precast or cast-in-place?

A

A type of precast two-way system that provides support for heavier loads at even longer spans.

Typ span = 40 ft

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26
Q

What are the most common precast forms? Why?

A

Single tee and double tee are popular forms because they provide both structure and floor or roof decking, and are easy/fast to erect.
- a 2” topping slab can be placed over the tees to provide uniform flooring and/or increased strength

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27
Q

When is post-tensioning used instead of pre-tensioning?

A

Pre tensioning is more common in prefab, but post tensioning is useful when high strength is required and it may be too difficult to transport precast members to job site.

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28
Q

what kind of assembly is masonry typically used?

A

Bearing walls

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29
Q

What are 7 advantages of masonry? 1 disadvantage?

A

Advantages:

  1. High compressive strength
  2. Design flexibility
  3. Attractive appearance
  4. Resistance to weather
  5. Fire resistance
  6. Sound insulation
  7. Thermal mass

Disadvantages:
1. weak tension and bending

30
Q

What are 3 types of masonry construction?

A
  1. Single-wythe
  2. Double-wythe
  3. Cavity
31
Q

How are single wythe walls reinforcerd?

A

Although there are no requirements for reinforcement or grouting, they are typically only reinforced vertically but not horizontally.

32
Q

How are double wythe walls reinforcerd?

A

May be either grouted and reinforced or ungrouted

33
Q

How are double wythe walls reinforcerd?

A

May be either grouted and reinforced or ungrouted

34
Q

How is horizontal reinforcement accomplished in lasting walls?

What are 4 characteristics of horizontal reinforcement for masonry walls?

A

Joints must be reinforced horizontally at regular intervals (typ 16” OC)

  1. Strengthen the wall
  2. Control shrinkage and cracks
  3. Tie multi-wythe walls together
  4. Anchor veneer to structural wall
35
Q

How is vertical reinforcement accomplished in masonry walls?

A

Vertical reinforcement is accomplished with standard reinforcing bars sized and spaced according to structural requirements of the wall
Typically horizontal bars are tied to the vertical bars, with entire assembly being set in a grouted cavity space

36
Q

For masonry walls, what 3 important properties does wall thickness determine?

A
  1. Slenderness ratio = (wall’s unsupported height) / (thickness) = indicates wall’s ability to resist buckling under compressive strength
  2. Flexural strength = important to resist lateral forces
  3. Fire-resistance rating
37
Q

What is the Slenderness ratio?

A

= (wall’s unsupported height) / (thickness)

Aka it indicates a masonry wall’s ability to resist buckling under compressive strength

38
Q

What is Composite construction?

A

Any structural system consisting of 2 or more materials designed to act together to resist loads while using the best characteristic of each material

39
Q

What are 4 types of composite construction? Which is the most common?

A
  1. Reinforced concrete = the most common
  2. Steel beam with composite steel and concrete deck
  3. Steel beam with concrete slab
  4. Open web steel joists with wood chords
40
Q

In steel/concrete composite construction, how are loads transferee between concrete and steel to make it act as one unit?

A

headed stud anchors transfer load between concrete and steel to make it act as one unit

41
Q

What are 3important considerations when determining how to attach the exterior, nonstructural envelope to the structural frame ?

A
  1. How will the weight of the envelope itself be supported?
  2. How will exterior loads (primarily wind) be transferred to the structural frame without damaging the facing?
  3. How will expansion and contraction be allowed due to temperature changes and slight movement of the structural frame?
42
Q 
How are expansion and contraction allowed in:
Masonry?
Steel?
Concrete?
Wood?
A

Materials with low coefficient of expansion (like masonry) require expansion joints at regular intervals
Steel does not often have expansion issues
Wood and concrete will have expansion issues, need to detail connections accordingly

43
Q

What are 9 types of complex structural systems?

A
  1. Trusses
  2. Arches
  3. Rigid frames
  4. Space frames
  5. Folded plate
  6. Thin-shelled structure
  7. Stressed skin structure
  8. Suspension structure
  9. Inflatable structure
44
Q

What loads to trusses resist?

A

Primarily tension/compression structures, but some bending is present

45
Q

Arches may have which 2 types of supports?
What is the difference between the 2?
Which is most common?

A

Hinged or fixed.

Hinged arch = resurrects horizontal and vertical movement at its two ends

Fixed arch = restricts the horizontal, vertical or rotational movement at its two ends, so a fixed arch is an indeterminate structure.

Most arches are hinged since it allows the arch to remain flexible and avoids developing high bending stress under live loading, temperature changes, and foundation settlement

46
Q

What is a three-hinged arch?

A

Three-hinged arch: An arch may have a third hinge at its apex to make it statically determinate (as opposed to statically indeterminate)

47
Q

What is funicular shape?

A

Funicular shape = the shape of an arch to resist the loads only in compression (think: Gaudi’s hanging strings turned upside down to form the arch’s shape)

48
Q

What shape does a hinged arch need to be to support a uniform load?

A

A parabola

49
Q

What is thrust?
How does it relate to arch height?
How can it be resisted?

A

the forces that cause the arch to spread out.

Thrust = 1 / (arch height), so as arch height decreases, thrust increases

It can be resisted with tie rods that hold the two lower portions of the arch together or a foundation that prevents spreading.

50
Q

What is the typical span of wood, concrete, and steel arches?

A 
Wood = 50 ft < 240 ft
Concrete = 20 ft < 320 ft
Steel = 50 ft < 500 ft
51
Q

What is a rigid frame?

A

Rigid frames are constructed so that vertical and horizontal members act as a single structural unit because the vertical/horizontal members are rigidly attached.

More efficient than a post and beam system (which does not as single structural unit)

52
Q

What are the 2 ways that a rigid frame can be connected to the ground?

A

Column attachment to ground may be hinged or rigid, the difference being that the rigid frame is stiffer and has greater thrust

53
Q

What is a gabled frame?

A

Gabled frame = a type of rigid frame in which the shape decreases bending stress in the inclined members and increases compression, making it a more efficient structure

54
Q

What is a space frame?

A

Space frame = structural system consisting of trusses in 2 directions rigidly connected at their intersections

55
Q

What is the most common type of space frame?

A

Triangulated space frame = bottom chord is offset from top chord by ½ bay, and each is connected by inclined web members

56
Q

Which type of space is a space frame most efficiently used for?

A

Very efficient for large rectangular areas because the two way action of components acts as a single, very stiff structure

57
Q

What is the max span of a space frame? Span to depth ratios?

A

Can span up to 350 ft

Span to depth ratios = 20:1 or 30:1

58
Q

What is an advantage of space frames during construction?

A

Members are lightweight and repetitive, so fabrication and erection time are minimized

59
Q

What is folded plate structure?

A

Loads are carried in two different directions, first transversely down the angled slabs, and then longitudinally across the slab ends that act like a girder spanning the vertical supports

60
Q

What material are folded plates typically constructed of?

What are typ longitudinal slabs (aka the span of the length of plates)?

A

Folded plates are typically constructed of reinforced concrete 3-6 in thick

Typ longitudinal spans = 30 ft > 100 ft

61
Q

What is a thin-shell structure?

A

Thin-shell structure = one with a curved surface that resists loads through tension, compression, and shear in the plane of the shell only (no bending, so extra thickness is not needed)

62
Q

What type of material are thin shell structures often made of?

What shapes do thin shell structure often take?

A

Material is almost always reinforced concrete 3 in > 6 in thick

Forms can be domes, parabolas, barrel vaults, etc

63
Q

Hyperbolic parabolas and domes are two common shapes of thin shelled structures. What are their slabs?

A

Dome = 40 ft > 200 ft

Hyperbolic parabola = 30 ft > 160 ft

64
Q

What are stressed-skin structures?

A

Stressed-skin structure = panels of sheathing attach on one or both sides of intermediate web members, acting like a series of I beams.

Connection between skin and interior web members must transfer all the horizontal stress

65
Q

What are stressed-skin panels typically made of?

Typical span?

A

Typically made of wood, but can be steel or composite

Typ span = 12 ft > 35 ft

66
Q

What is a suspension structure? Where is it most often used?

A

Similar to arches in that the loads they support must be resisted by both vertical reactions and horizontal thrust reactions, but the vertical is up and thrust is outward

Most often seen in bridges or in large stadiums with suspended roofs

67
Q

In suspension structures, horizontal reaction is dependent on…

A

Horizontal reaction is dependent on amount of sag in the cable

Shallow sag = high horizontal reactions
Deep sag = lower horizontal reactions

68
Q

What types of loads do suspension structures resist?

A

Can only resist loads with tension (no bending), so the shape of cable changes as load changes.

69
Q

Suspension structures can only resist loads with tension. What disadvantage does this create?

A

This means that suspension structures are inherently unstable in the wind, so they must be stabilized or stiffened with heavy infill materials, cables attached to the ground, or a second grid of cables either above or below the primary set

70
Q

Uniform horizontal loads on a suspension structure results in which shape?

Uniform loads on a suspension structure result in which shape? (Ex. its own load)

A

Parabola

Catenary curve

ARE 5.0 - Programming & Analysis (5 decks)

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