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ExAC Section 3 > Building Construction Illustrated > Flashcards

Building Construction Illustrated Flashcards

1
Q

what is a soil profile

A

a drawing used to depict the succession of layers or strata called horizons of the soil. can consist of superimposed layers which contain a mix of soil types.

(1.12 soils)

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2
Q

what is a subsurface investigation

A

the analysis and testing of soil disclosed by excavation of a test pit up to 10’ (3m) deep, or by deeper test borings in order to understand the structure of the soil, its shear resistance and compressive strength, its water content and permeability, and the expected extent and rate of consolidation under loading.

(1.12 soils)

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3
Q

what is the allowable bearing capacity of a soil

A

the maximum unit pressure a foundation is permitted to impose vertically or laterally on the soil mass

(1.13 soil mechanics)

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4
Q

what is the Standard Penetration Test

A

measures the density of granular soils and the consistency of some clays at the bottom of a borehole, recording the number of blows required by a hammer to advance a standard soil sampler

(1.13 soil mechanics)

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5
Q

what are the types of soils?

A
  1. coarse-grained soils (granular soil, require confining force for their shear resistance, relatively shallow angle of repose, low % of void spaces and more stable)
  2. clay soils (cohesive soil, retain strength when unconfined, unstable because they shrink/swell with changes in moisture content)

(1.13 soil mechanics)

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6
Q

what does the shearing strength of a soil mean

A

measure of its ability to resist displacement when an external force is applied, due largely to the combined effects of cohesion and internal friction

(1.13 soil mechanics)

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7
Q

principal mechanical means of protecting an embankment against erosion

A
  1. rip rap
  2. cribbing
  3. bin wall
  4. gabions

(1.34 slope protection)

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8
Q

natural means of protecting an embankment against erosion

A

soil binders

(1.34 slope protection)

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9
Q

how can a retaining wall fail and ways to prevent

A
  1. overturning (resisting moment must counter overturning moment)
  2. horizontal sliding (weight of the wall x coefficient of friction of soil must counter lateral thrust on the wall; passive pressure; key)
  3. excessive settling (vertical force must not exceed bearing capacity)

(1.35 retaining walls)

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10
Q

types of reinforced concrete retaining walls

A
  1. gravity wall
  2. t-type cantilevered wall
  3. counterfort wall
  4. l-type cantilevered wall

(1.36 retaining walls)

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11
Q

materials used for low retaining walls

A
  1. timber wall (with deadman for anchor and gravel drain)
  2. brick veneer wall (with concrete footing at frostline)
  3. dry stone wall (with granular subbase, mortared stone walls extend below frostline)

(1.37 retaining walls)

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12
Q

layers of paving

A
  1. pavement (receives traffic wear)
  2. base (foundation of aggregate, transfers load, prevents capillary action)
  3. subgrade (carries load, sloped to drain)

(1.38 paving)

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13
Q

types of pavement

A

flexible and rigid

(1.38 paving)

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14
Q

what are the two types of loads a building must be able to support

A
  1. static (dead, live, occupancy, snow, rain, settlement, impact)
  2. dynamic (wind and earthquake)

(2.10 loads on buildings)

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15
Q

building must be designed to resist wind-induced…

A

sliding, overturning, uplift

(2.11 wind loads)

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16
Q

which is more critical in structural design: horizontal or vertical loads

A

horizontal (vertical load-carrying elements usually have considerable reserve for resisting additional vertical loads)

(2.12 earthquake loads)

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17
Q

what is base shear?

A

minimum design value for the total lateral seismic force on a structure assumed to act in any horizontal direction (dead load x coefficients)

(2.12 earthquake loads)

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18
Q

what is design wind pressure?

A

minimum design value for the equivalent static pressure on the exterior surfaces

(2.11 wind loads)

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19
Q

describe different ways forces are related

A
  1. collinear forces (acting along a straight line)
  2. concurrent forces (lines of action intersection at a common point)
  3. nonconcurrent forces (lines of action that don’t intersect)

(2.13 structural forces)

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20
Q

define moment

A

tendency of a force to produce a rotation of a body

(2.13 structural forces)

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21
Q

define couple

A

force system of two equal, parallel forces acting in opposite directions and tending to produce rotation but not translation

(2.13 structural forces)

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22
Q

what needs to happen for a rigid body to be in equilibrium?

A

forces and moments equal zero (translational and rotational equilibrium)

(2.14 structural equilibrium)

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23
Q

how would a short, thick column fail vs a long slender column?

A

short, thick would fail by crushing, long and slender would fail by buckling

(2.15 columns)

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24
Q

what are the means to resist buckling?

A

need to reduce slenderness ratio by shortening effective length or maximizing the radius of gyration of cross section

(2.15 columns)

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25
Q

define effective length of a column

A

distance between inflection points in a column subject to buckling (use coefficient to adjust based on end conditions)

(2.15 columns)

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26
Q

define kern area

A

central area of any horizontal section of a column or wall within which the resultant of all compressive loads must pass if only compressive stresses are to be present in the section. a compressive load applied beyond this area will cause tensile stresses

(2.15 columns)

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27
Q

describe the types of beam end conditions

A
  1. simple beam (supports on both ends, ends free to rotate and having no moment resistance)
  2. cantilever (one fixed end)
  3. overhanging beam (simple beam extending beyond one of its supports)
  4. double overhanging beam (simple beam extending beyond both supports)
  5. fixed-end beam (both ends restrained against translation and rotation, transfers bending stresses and increases rigidity, reduces max deflection)
  6. suspended span (simple beam supported by overhangs of 2 adjoining spans with pinned construction joints at points of zero moment)
  7. continuous beam (extends over more than 2 supports, greater rigidity, smaller moments)

(2.17 beam spans)

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28
Q

how do you create a rigid frame?

A

joints connecting the columns and beams are capable of resisting both forces and moments. used for lateral bracing of simply supported beam

(2.19 frames & walls)

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29
Q

what are the types of rigid frames?

A
  1. fixed frame (fixed joints, more resistant to deflection than hinged, more sensitive to support settlements and thermal expansion/contraction)
  2. hinged frame (pin joints, allows frame to rotate as a unit, flex slightly)
  3. 3-hinged frame (2 rigid sections connected to each other and its supports with pin joints, more sensitive to deflection, least affected by support settlements and thermal stresses)

(2.19 frames & walls)

30
Q

how can you make sure a system acts in two-ways?

A

square shape (more rectangular the more it acts as one-way)

(2.20 plate structures)

31
Q

what type of construction should you use to achieve 30m span?

A

precast tees or timber trusses (both one-way)

(2.23 structural spans)

32
Q

what are the basic mechanisms for ensuring lateral stability?

A
  1. rigid frame (least efficient)
  2. shear wall
  3. braced frame (timber or steel with diagonal members, knee bracing/k-brace/cross bracing/cable bracing - one cable in tension, the other would buckle)

(2.26 lateral stability)

33
Q

what are the types of tube structures?

A
  1. framed tube (closely spaced perimeter columns)
  2. perforated shell tube (perimeter shear walls, >30% openings)
  3. braced tube (diagonal braces)
  4. trussed tube (trussed wall frames of columns tied together by diagonal/cross bracing)
  5. latticed tube (perimeter frames of closely spaced diagonals with no vertical columns)
  6. bundled tubes (assembly of narrow tubes tied directly to each other, modular)
  7. tube-in-tube (inner braced core added to the perimeter tube)

(2.28 high-rise structures)

34
Q

describe types of damping mechanisms

A
  1. tuned mass damper (heavy mass mounted on rollers, attached to upper portion with spring damping mechanisms)
  2. base isolation (isolated from ground, superstructure floats as a rigid body to alter natural period of vibration so it’s different from ground)
  3. internal damping (damping that naturally occurs as a building undergoes plastic or elastic deformation)

(2.28 high-rise structures)

35
Q

what is a diagrid?

A

triangulated framework of diagonal members connected at specially jointed nodes, capable of resisting lateral forces and gravity loads. exterior framework reduces internal supports, flexible interior layouts. 60-70° optimal angle

(2.29 diagrids)

36
Q

list the principle loads on a foundation

A
  • dead and live loads
  • wind-induced sliding, overturning, uplift
  • earthquake
  • pressure from soil mass and groundwater
  • thrust from arched or tensile structures

(3.02 foundation systems)

37
Q

methods to reduce settlement

A
  • properly designed foundation that distributes loads so that any settlement is minimal and uniformly distributed
  • not exceeding bearing capacity of soil

(3.03 foundation systems)

38
Q

main categories of foundation systems

A
  1. shallow foundations: transfer building loads directly to supporting soil by vertical pressure
  2. deep foundations: transfer building loads to bearing stratum of rock or dense sands/gravels well below superstructure (used when soil is unstable)

(3.03 foundation systems)

39
Q

what things should you consider when selecting/designing type of foundation system

A
  • pattern, magnitude of building loads
  • subsurface groundwater conditions
  • topography
  • impact on adjacent properties
  • building code requirements
  • construction method and risk

(3.05 types of foundation systems)

40
Q

what is underpinning

A

process of rebuilding or strengthening the foundation of an existing building or extending it when a new excavation in adjoining property is deeper than the existing foundation

methods of temporary support: needle beams and intermittent pits

(3.06 underpinning)

41
Q

when do you need excavation support systems?

A

when sides of a deep excavation exceed the angle of repose for the soil

(3.07 excavation support systems)

42
Q

describe some methods for support systems for excavation

A
  • sheet piling
  • soldier piles or beams with lagging

the above is supported by:
- continuous horizontal wales braced by horizontal steel crossbracing
- diagonal steel rakers bearing on heel blocks or footings
- tiebacks secured to rock or soil anchors

  • slurry walls
  • dewatering (lowering water table or preventing excavation from filling with groundwater) by driving perforated tubes (wellpoints) and pumping water away

(3.07 excavation support systems)

43
Q

where are footings placed in shallow foundations?

A

below the frostline to minimize effects of ground heaving when groundwater freezes and expands in cold weather

(3.08 shallow foundations)

44
Q

what contact area is required for footings in shallow foundations

A

area to distribute load over an area of soil wide enough that allowable bearing capacity is not exceeded

contact area required = quotient of magnitude of forces transmitted and allowable bearing capacity of supporting soil mass

(3.08 shallow foundations)

45
Q

what are the most common forms of spread footings? what are some other types?

A

strip footings (continuous spread footings of foundation walls) and isolated footings (freestanding columns) are most common

other types:
- continuous footing (supports a row of columns)
- stepped footings (grade change)
- mat or raft foundation (single monolithic footing used when allowable bearing capacity of soil is low)
- floating foundation (zero settlement, amount excavated equals structure of same weight)

footings used when foundation abuts PL:
- cantilever or strap footing (column footing connected by a tie beam to another footing to balance asymmetrically imposed loads)
- combined footing

(3.09 spread footings)

46
Q

what are foundation walls designed to resist

A

lateral forces such as active earth pressure and anchors against wind and seismic forces. horizontal component transferred largely through soil friction on bottom of footings and development of passive soil pressure on sides of footings and foundation walls.

(3.10 foundation walls)

47
Q

is ventilation of crawl spaces necessary

A

yes

(3.11 foundation walls)

48
Q

at the foundation floor, what kind of barrier do you need?

A

vapour barrier to control ground moisture, waterproofing if required

(3.11, 3.14 foundation walls)

49
Q

what kinds of foundation walls don’t require formwork?

A

concrete masonry foundation walls
- fill cells in top course with grout, screen underneath
- running bond with Type M or S mortar
- 8” wall thickness
- vertical reinforcement in grouted cells and horizontal bond beams as required

(3.12 foundation walls)

50
Q

what kind of foundation wall requires formwork?

A

cast in place
- 8” wall thickness
- horizontal and vertical reinforcement as required

(3.12 foundation walls)

51
Q

when is a foundation wall dampproofed vs waterproofed?

A

dampproofing applied when subsoil conditions indicate hydrostatic pressure from groundwater table will not occur.
- bituminous or acrylic modified cement coating

waterproofing when subject to hydrostatic pressure from groundwater table.
- rubberized or polymer-modified asphalt
- butyl rubber

both should extend above grade by 6” down to top of footing. protect during backfilling with drainage mat, rigid extruded polystyrene insulation, or asphalt-impregnated fiberboard

(3.14 foundation walls)

52
Q

how is water diverted away from the foundation wall?

A

drainage mat or gravel backfill allows water to flow down to the footing drains. perforated pipe or drain tile (4”dia min.) whose bottom side of pipe is located below elevation of slab, drains water to a storm sewer, dry well, or natural outfall on site.

(3.14 foundation walls)

53
Q

how should you treat wood and metal used in foundation systems

A

wood should be pressure-treated with a preservative approved for ground contact use, metal fasteners should be stainless steel or hot-dipped zinc-coated steel

(3.15 foundation walls)

54
Q

how do you design a concrete slab on grade with low bearing capacity of soil?

A

must be designed as a mat or raft foundation

(3.18 concrete slabs on grade)

55
Q

what is the min slab thickness required for slab on grade?

A

4”

(3.18 concrete slabs on grade)

56
Q

what are the layers that make up a concrete slab on grade?

A
  1. 4” slab (admixtures and additives)
    with welded wire fabric reinforcement (controls thermal stresses, shrinkage cracking, differential movement)
  2. 2” layer of sand
  3. 6-mil polyethylene moisture barrier
  4. 4” base course gravel or crushed stone
    stable, uniformly dense soil base

(3.18 concrete slabs on grade)

57
Q

list the types of joints for concrete slabs on grade

A
  • isolation joints (aka expansion joints, mvmt between slab and columns/walls)
  • construction joints (place for construction to stop and then continue, also serve as isolation/control joints, can be keyed/doweled to prevent diff. mvmt)
  • control joints (create lines of weakness for cracking along predetermined lines)

(3.19 concrete slabs on grade)

58
Q

types of control joints

A
  • sawn joint with joint filler
  • premolded or metal strip
  • keyed joint (use metal/plastic joint material to prevent bond or curing compound on one side)

(3.19 concrete slabs on grade)

59
Q

when can/should you thicken edge of slabs on grade?

A

in warm or temperate climates where little or no ground frost occurs. economical to thicken edges of slab to form integral footings for exterior walls

(3.20 concrete slabs on grade)

60
Q

what are pole foundations?

A

elevate timber structures above ground, require minimal excavation, preserve natural features and existing drainage patterns. useful on steep slopes and areas with periodic flooding

61
Q

in pole foundations, what factors affect embedment lengths?

A
  • slope of the site
  • subsurface soil conditions
  • pole spacing
  • unsupported height
  • seismic zone

(3.22 pole foundations)

62
Q

in pole foundations, what are the recommended embedment lengths?

A
  • 5’-8’ (1525 - 2440) for uphill poles (deeper to provide rigidity)
  • 4’-7’ (1220 - 2135) for downhill poles
  • 4’-5’ (1220 - 1525) for flat slopes

(3.22 pole foundations)

63
Q

what should you do when the necessary pole foundation embedment length isn’t possible?

A

add steel rod crossbracing with turnbuckles or shear walls to provide lateral stability

(3.22 pole foundations)

64
Q

in pole foundations, how are spaced beams connected to the poles? how are solid/built-up wood beams connected to poles?

A

spaced beams:
- notching
- spiked grid connector with single through-bolt (better loadbearing values than notching)

solid/built-up beams:
- gusset (when piers terminate at first floor, beams can bear on piers and secured with wood gussets or metal connectors)

(3.23 pole foundations)

65
Q

how are poles in pole foundations anchored/distribute their loads?

A
  • concrete footing
  • concrete necklace (for higher loads, increases contact area with soil)
  • bearing directly on rock
  • backfilling with concrete or soil-cement mixture (can reduce embedment length)

(3.23 pole foundations)

66
Q

what are the types of deep foundations?

A
  1. pile foundations
  2. caisson foundations

(3.24 deep foundations)

67
Q

what are pile foundations?

A

type of deep foundation, system of end-bearing or friction piles, pile caps, and tie beams for transferring building loads down to a suitable bearing stratum

end-bearing: depend on bearing resistance of soil or rock beneath their feet

friction piles: depend on frictional resistance of surrounding earth mass

(3.24 deep foundations)

68
Q

what are types of pile foundations?

A
  • timber piles (usually friction piles)
  • composite piles (2 materials)
  • H-piles (steel H-sections sometimes encased in concrete, can be welded together)
  • pipe piles (heavy steel pipes filled with concrete)
  • precast concrete piles
  • cast-in-place concrete piles (cased or uncased)
    > cased piles: driving steel pipe or casing into ground until it meets required resistance, then filling it with concrete
    > uncased piles: driving concrete plug into ground along with steel casing until it meets required resistance, then ramming concrete into place as casing is withdrawn
    » pedestal pile: uncased pile with enlarged foot to increase bearing area (foot formed by forcing concrete out at bottom of casing)
  • micropiles (high capacity, small diameter, drilled and grouted in-place, reinforced, used in urban areas, any ground condition with minimal vibration and disturbance)

(3.25 pile foundations)

69
Q

what are caisson foundations?

A

type of deep foundation, cast-in-place, plain, or reinforced concrete piers formed by filling large shaft with concrete

aka drilled piles or piers

boring often 2’6” (760) diameter
temporary casing during excavation
base of caisson may be enlarged into bell shape to increase bearing area and resist uplift from soil expansion

(3.26 caisson foundations)

70
Q

what are types of caisson foundations?

A
  1. socketed caissons: drilled into stratum of solid rock to gain additional frictional support
  2. rock caissons: socketed caissons that have a steel H-section core within a concrete-filled pipe casing

(3.26 caisson foundations)

71
Q

what factors influence the depth of a floor system?

A
  • size and proportion of structural bays it must span
  • strength of materials used

(4.02 floor systems)

72
Q
A

ExAC Section 3 (2 decks)

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