Structural Systems (Are)

Front 1

FORCE

Back 1

Push or pull on an object, including magnitude, direction and point of application

Front 2

COLINEAR FORCES

Back 2

Vectors lie along the same straight line

Front 3

CONCURRENT FORCES

Back 3

Lines of action meeting at a common point

Front 4

NONCONCURRENT FORCES

Back 4

Lines of action meeting at a common point

Front 5

COPLANAR FORCES

Back 5

Lines of action lie all within the same plane

Front 6

STRUCTURAL FORCES

Back 6

Any combination of forces

Front 7

LOAD (P)

Back 7

A force applied to a body (external force)

Front 8

STRESS (F)

Back 8

The resistance of a body to a load (internal force)

Front 9

UNIT STRESS

Back 9

Stress / unit of area at the section measured in psi or ksi (kips / square inch)

Front 10

ALLOWABLE STRESS

Back 10

Maximum permissible unit stress

Front 11

FACTOR OF SAFETY

Back 11

Ratio of ultimate strength of material to it's working stress

Front 12

STRAIN

Back 12

The deformation of a material caused by exterior loads

Front 13

SHEAR

Back 13

A strain produced by pressure in the structure when its layers are laterally shifted in relation to each other

Front 14

MOMENT

Back 14

The tendency of a force to cause rotation about a given point or axis

Front 15

MODULUS OF ELASTICITY

Back 15

A material's resistance to non permanent (or elastic) deformation

Front 16

REACTION

Back 16

The force acting at the supports of a beam that holds it in equilibrium

Front 17

ECCENTRIC LOAD

Back 17

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

Front 18

TRUSS

Back 18

Framework consisting of rafters, posts, and struts

Front 19

MOMENT OF INERTIA

Back 19

The measure of an object's resistance to changes to it's rotation

Front 20

SECTION MODULUS

Back 20

The ratio of a cross section's second moment of area to the distance of the extreme compressive fibre from the neutral axis

Front 21

DEFLECTION

Back 21

The displacement of a structural element under a load

Front 22

HOOK'S LAW

Back 22

Unit Stress is proportional to unit strain up to the elastic limit

Front 23

YIELD POINT

Back 23

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

Front 24

COMPOSITE STRUCTURAL MEMBER

Back 24

More than one material working together (eg: reinforced concrete, box beam, flitch beam)

Front 25

RESILIENCE

Back 25

Ability of material to absorb energy while undergoing elastic range stresses

Front 26

DUCTILITY

Back 26

Ability of a material to absorb energy prior to fracture

Front 27

Stress (f)

Back 27

Total Force (P) / Area (A)

Front 28

F (Force)

Back 28

Mass (M) x Acceleration (a)

Front 29

Force (F) (on a retaining wall)

Back 29

soil pressure (w) x height of wall (h)2 / 2

Front 30

Moment (M)

Back 30

Force (P) x distance (d)

Front 31

Moment (M) (uniform load)

Back 31

uniform load (w) x length (L)2 / 8

Front 32

Section Modulus (S)

Back 32

base (b) x diameter (d)2 / 6

Front 33

Section Modulus (S)

Back 33

Moment (M) / Bending Stress (Fb)

Front 34

Section Modulus (S)

Back 34

Moment of Inertia (I) / given constant (c)

Front 35

Moment of Inertia (I)

Back 35

base (b) x depth (d)3 / 12

Front 36

Deflection (e) (shortening of column or elongation of a horizontal member)

Back 36

Force (P) x Length (L) / Area of cross section (A) x Modulus of elasticity (E)

Front 37

Deflection (∆) (of a beam)

Back 37

5 x weight (w) x original length (L)4 / 384 x modulus of Elasticity (E) x Moment of Inertia (I)

Front 38

Thermal Change (∆) (shortening or elongation due to temperature change))

Back 38

Coefficient of Thermal Linear Expansion (e) x original length (L) x temperature change (∆t)

Front 39

Slenderness Ration (SR) (steel column)

Back 39

End condition (k) x unbraced length in inches (L) / radius of gyration (r)

Front 40

Radius of gyration (r)

Back 40

sqrt (moment of intertia) (I) / Area

Front 41

Slenderness Ration (SR) (wood column)

Back 41

end condition (k) x Length (L) / cross section width of rectangle (b)

Front 42

Ultimate strength of steel

Back 42

58,000-80,000 psi

Front 43

Ultimate Strength of Concrete

Back 43

3,000-6,000 psi

Front 44

Ultimate strength of Wood

Back 44

2,000-8,000 psi

Front 45

Vertical Forces

Back 45

Dead / Live Loads, Static / Dynamic, Concentrated / Distributed. Mostly caused by gravity

Front 46

Horizontal Forces

Back 46

Lateral forces

Front 47

Internal Forces

Back 47

Movements when resisted, shrinkage, humidity, thermal changes, fabrication errors, prestressing

Front 48

Deconstructive Agents

Back 48

Fire, chemical corrosion, erosion, insects / plants / animals

Front 49

Tension

Back 49

Most efficient

Primary deformation - elongation (e)

Failure mode- tearing

Front 50

Compression

Back 50

Primary deformation- shortening

Failure mode - crushing (strength related), buckling (stiffness related)

Front 51

Shear

Back 51

Primary deformation- change in angle

Failure mode- torsion

Front 52

Stiffness

Back 52

resist deformation

Elastic response is temporary / inelastic is permanent

Front 53

Resolving forces

Back 53

Replace one force with two or more that will produce the same effect on a body as the original force

Front 54

Charpy V-notch test

Back 54

Ductility test where a piece of material has a v-notch cut into the top and tests how much energy it takes to make the notch go through the whole piece (if it breaks quickly, it's brittle, if not, ductile)

Front 55

St. Venant's Principle for Direct Stress

Back 55

The stresses and strains in a body at points that are sufficiently remote from the points of application of load depends only on the static resultant of the loads and not on the distribution of the loads.

IF: -loaded thing is straight, load applied axially, cross-section is constant, loaded member is a single material, material is homogenous, elastic range stresses only, loading must be pure tension compression or shear

Front 56

How to solve a direct stress problem

Back 56

1. Determine whether to use f=P/A, P=AF(allowable) or A=P/F(allowable)

2. Figure out cross-section

3. Figureo ut the stress

4. Allowable stress- 22,000 psi steel

900 psi concrete bearing

1,150 psi wood parallel to grain

Front 57

How to solve a Direct Shear problem

Back 57

1. Determine whether to use f=P/A, P=AF(allowable) or A=P/F(allowable)

2. Find the area of the bolts (A=(# bolts) x (pie x r2)

3. Find allowable stress- A x Fallowable

Front 58

Resultants

Back 58

Calculate using pythagorus & SohCahToa

Front 59

Elastic Limit

Back 59

Beyond which strain and stress are no longer proportional

Front 60

Yield Point

Back 60

Material continues to deform with little or no load applied- point of no return, will rupture at ultimate strength

Front 61

Modulus of Elasticity

Back 61

Resistance to reaching ultimate strength, typically listed in building code

Front 62

Howe Truss (bridge)

Back 62

Flat on top

Right side up triangle in the middle

No right side up triangle at the end

Front 63

Pratt Truss (bridge)

Back 63

Flat top

Upside down triangle in the middle

Front 64

Warren truss (bridge)

Back 64

Flat top

Right side up triangle in the middle

Right side up triangles continue

Front 65

Parker Truss

Back 65

Connections form an arch

Front 66

K truss (bridge)

Back 66

K at the beginning

Front 67

Baltimore truss (bridge)

Back 67

Triangles within triangles at the ends

Open (except one line) upside down triangle in the middle

Front 68

Warren truss (roof)

Back 68

Rectangle with open triangles inside

Front 69

Howe truss (roof)

Back 69

Triangle with open triangle in the middle

OR

Triangle with diamond in the middle

Front 70

King Post truss (roof)

Back 70

Super simple triangle with one post in the middle

Front 71

Pratt truss (roof)

Back 71

Triangle with right side up triangle in the middle with a post through it

Front 72

Trusses in general

Back 72

Depth- span rations of 1:10 through 1:20

Spans: 40'-200'

Spacing: 10'-40'

(Residential / light commercial: 2x4s or 2x6 members at 24" o.c.)

Front 73

Trusses- compression / tension

Back 73

Compression in top chord

Tension in bottom chords

Front 74

Rigid Frames

Back 74

Horizontal & Vertical members work together. Only resist loads in tension- instability due to wind must be stabilized or stiffened with heavy infill material

Front 75

Air Supported Structures

Back 75

Resists loads in tension only - held in place with constant air pressure that is greater than the outside air pressure

Front 76

What type of structure?

Building with Irregular form & Simple roof framing, frabricated onsite

Back 76

Sitecast concrete with any slab system (no beams / ribs) OR

Light Gauge Steel Framing OR

Masonry with concrete slab / wood light floor framing

Front 77

What type of structure?

Irregular column grid, without beams or joists in floor or roof

Back 77

Site Cast concrete 2 way flat plate OR

Metal space frame

Front 78

What type of structure?

Exposed structure with fire / heat resistance

Back 78

All concrete systems (without ribs)

Heavy timber frame

Front 79

What type of structure?

Minimum floor thickness or minimal total building height

Back 79

Prestressed concrete slabs

Site cast concrete 2 way flat slab

Posttensioned 1 way slab

Front 80

What type of structure?

Minimum area occupied by columns and / or bearing walls with a long span system

Back 80

Heavy wood trusses

Glulam wood beams

Glulam wood arches

Steel frame

Steel trusses

Open web structural joists

Waffle slab

Single or double tee concrete

Front 81

What type of structure?

Changes in use over time with short span or one way systems that can be easily modified

Back 81

Light gauge / conventional steel frame

Wood systems (may include masonry)

Site cast 1 way concrete slab

Precast concrete slab

Front 82

What type of structure?

Exposure to Adverse weather - no reliance on on-site chemical processes

Back 82

Steel

Wood

Precast Concrete

Front 83

What type of structure?

Minimal off-site fabrication time

Back 83

Sitecast concrete

Light gauge steel framing

Platform framing

Masonry

Front 84

What type of structure?

Minimal on-site erection time

Back 84

Single story rigid steel frame

Steel frame with hinged connections

Precast concrete

Heavy timber frame

Front 85

What type of structure?

1-2 stories with minimal construction time

Back 85

Any steel

Heavy timber frame

Platform frame

Front 86

What type of structure?

4-20 stories with minimal construction time

Back 86

Precast concrete

Conventional steel frame

Front 87

What type of structure?

30+ stories with minimal construction time

Back 87

Steel frame

Sometime site / precast concrete

Front 88

What type of structure?

Minimal diagonal bracing or shear walls with rigid joints

Back 88

Site cast concrete

Single frame with welded connections

Single story rigid steel frame

Front 89

What type of structure?

Minimal dead load on foundation

Back 89

Any steel

Any wood

Front 90

What type of structure?

Minimal structural distress dueto unstable foundation

Back 90

Steel frame with bolted connections

Heavy timber frame

Precast concrete system

Platform framing

Front 91

What type of structure?

Concealed Spaces for MEP with no added height tot he building

Back 91

Truss

Open web joists

Light gauge steel framing

Platform framing

Front 92

Weight of typical structural materials?

Back 92

Timber- 7-10lbs/sf

Steel - 15-20 lbs/sf

Concrete masonry - 150-200 lbs/sf

Front 93

Cost implications:

Precast concrete

Back 93

-Can be expensive but it is competitive if there are a number of pieces that are the same size / shape

Front 94

Cost implications:

Cast in place concrete

Back 94

Most expensive and slowest but good for irregular shapes and fireproofing / durability

(slip-forming can help save on cost)

Front 95

Cost implications:

Steel

Back 95

More economical than concrete

Faster than concrete

Durable, needs fireproofing

Front 96

Cost implications:

Pre-engineered metal

Back 96

Least expensive way to quickly enclose a large area but not very flexible, 20-30 year life span

Front 97

Cost implications:

Wood

Back 97

Smaller commercial or residential

Economical up to 3 stories

Inexpensive for non-fire resistive construction

Front 98

Dowel type fasteners

Back 98

Nails, screws, bolts

Front 99

Bearing type fasteners

Back 99

Shear Plates- transmit lateral loads only by shear forces via bearing on the connected materials

Front 100

Hangers

Back 100

Combination of dowel & bearing type fasteners, connecting / supporting members

Front 101

Plate girder

Back 101

Assembly of steel plates or plates and angles

Front 102

Underpinning

Back 102

Strengthening and stabilizing the foundation of an existing building

Front 103

Shoring

Back 103

Supporting a structure to prevent collapse during construction

Front 104

Counterforts

Back 104

Reinforced concrete webs act as diagonal braces

Front 105

Critical net section

Back 105

Section where most wood has been removed

Front 106

End distance

Back 106

Distance measured parallel to the grain from the center of connector to square cut end of member

Front 107

Edge distance

Back 107

Distance from edge of member to center of connector closest to it

Front 108

Earth pressure on a wall (P)

Back 108

30 lb / ft3 x height of wall

Front 109

Strap / Cantilever Footing

Back 109

Combined footing for far-apart columns

Front 110

Mat foundations

Back 110

Very expensive- one continuous foundation

Front 111

Pile foundations

Back 111

Deeper where soil is unsuitable to get to better soil

Front 112

Belled Caissons

Back 112

Like very deep spread footings

Front 113

Friction Pile

Back 113

In softer soil- friction transmits load between pile and soil

Front 114

Socketed Caisson

Back 114

Hole drilled deep into strata, bearing capacity from end bearing & frictional forces

Front 115

End Bearing Piles

Back 115

Driven until tip meets firm resistance from strata. 2-3x cost of spread footings.

Front 116

Cantilever wall (retaining wall)

Back 116

Resists force by the weight of the structure and weight of the soil on the heel of the base slab. KEY projects from bottom to increase resistance to sliding

Front 117

Counterfort walls

Back 117

Like cantilever, but spaced at distances approximately half the wall height

Front 118

Gravity walls

Back 118

Resist forces by own weight- non-reinforced concrete

Front 119

Wood connections

Back 119

Designed for 10 year loading PLUS

-Permanent loading beyond 10 years = +0.9

-Snow loading (2 month duration)= +1.15

-7 day duration = +1.25

-Wind or earthquake = +1.6

-Impact Loads= +2.0

Front 120

Nail sizes

Back 120

Penny sizes:

-2d=1", 6d=2", 10d=3", 20d=4", 40d=5", 60d=6"

-Box nails- 6d to 40d (smallest diameter)

-Wire nails: 6d-60d, medium diameter

-Wire spikes- 10d - 8.5" with 3/8" diameter (largest)

Front 121

Screws

Back 121

-Best when used laterally in side grain, no withdrawl from end grain

Front 122

Lag screws / bolts

Back 122

With heads, Diameter, 1/4" - 1 1/4", Lengths, 1"-12"

Front 123

Split Ring Connectors

Back 123

-Transmit loads between two pieces of wood by placement in precut grooves

Front 124

Shear plates

Back 124

Flat plates with flange extending from the face of the plate with a hold in the middle where a bolt is placed to hold two members. Good for connections that must be disassembled. Used for two pieces of woodor one piece of wood and a steel plate

Front 125

Steel bolt connection types

Back 125

Bearing Type - resists shear loads on bolts through friction

Slip Critical- When any slippage cannot happen

Note: connection's shear failure is parallel to the load

Front 126

Welding Connections

Back 126

-Best for moment connections

-Often used with bolting as members have to be held in place until welding is finished

-Single plate can be welded to a column and connected with beams

-Used over bolts because gross section of member can be used instead of net section

-More efficient construction

Front 127

Electrical Arc Welding Process

Back 127

-Normal way of welding- one electrode from power source attached to steel member while other is the welding rod

Front 128

Symbols for welding

Back 128

-Symbol above the weld is on the opposite side of the leader

-Symbol below the weld means the weld is on the same side

Front 129

Types of Welds

Back 129

-Lap, Butt, Tee-- most common

-Plug / Slot - holes cut in one side and area is filled with weld

Front 130

Throat

Back 130

-Distance from the corner of the connection tot he hypotenuse of the weld

Front 131

Concrete Connection Types

Back 131

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

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

Front 132

Coefficient of Thermal Expansion

Back 132

Ratio of unit strain to temperature change, a constant

Front 133

Fatigue

Back 133

Progressive damage that occurs when a material is subject to cyclic loading

Front 134

Creep

Back 134

Tendency of a material to move slowly or deform permanently under stress

Front 135

Moisture content

Back 135

Weight of water in a wood as a fraction of the weight in oven-dry wood

Front 136

Hydration

Back 136

Chemical hardening of concrete

Front 137

Abrams Law

Back 137

Compressive strength of concrete is inversely proportional to ratio of water to cement

Front 138

Laitance

Back 138

An accumulation of fine particles on the surface of fresh concrete due to the upward movement of water. Occurs when there's too much water in the mixture

Front 139

Wood with regards to moisture

Back 139

-Ideally moisture content should be equal to prevailing humidity at which it was installed

-Dry lumber max moisture content= 19%

-Kiln dry lumber max moisture content = 15%

Front 140

Structural Lumber Grading

Back 140

-Structural Light Framing: 2"-4" thick & 2'-4" wide, No.1, No.2 & No. 3

-Light framing: 2"-4" thick, 2"-4" wide, construction, standard and utility

-Stud- 2"-4" thick & 2"-6" wide

-Decking- Select & Commercial

Structural Joists and Planks: 2"-4" thick & 5"+ width, structural, No.1, No.2 & No.3

Front 141

Allowable stresses for structural steel

Back 141

Expressed as a % of the minimum yield point - A36 steel = yield point of 36ski

Front 142

Concrete types

Back 142

Type 1: standard cement, 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 IV: low heat for slow setting, used to avoid heat damage

Type V: Sulfate resisting cement, where exposed to water or soil with high alkaline

Front 143

Minimum water to cement ration

Back 143

.35-.40 by weight

Front 144

Aggregates

Back 144

-Account for 70-75% of total concrete volume

-No larger than 3/4 x's the smallest distance between bar

-No larger than 1/5 xs the smallest dimension of form or 1/3 depth of slab

Front 145

Concrete weights

Back 145

-Standard concrete: 150 lb/ ft3

-Lightweight structural concrete: 80-120 lb/ft3

-Non-structural insulating concrete: 50-80 lb/ft3

Front 146

Concrete strength

Back 146

Note: cures after 28 days

-Typical strength range: 2,000 psi- 4,000 psi

-Most common: 3,000 psi

-Higher strength: 12,000 psi

Front 147

ACCELERATORS

Back 147

Speed up hydration of cement

Front 148

Plasticizers

Back 148

Reduce the amount of water required while maintaining consistency

Front 149

Retarders

Back 149

Slow down setting time to reduce heat of hydration

Front 150

Fly Ash

Back 150

Waste material from coal fired power plants, increases strength, decreases permeability, reduces temperature rise, improves workability

Front 151

Rebar

Back 151

Used as a tensioning device in concrete / masonry

Front 152

Rebar sizing

Back 152

-Rebar ID number based on diameter: #3=3/8", #8= 1 and so on...

Front 153

Rebar grade

Back 153

Equal to minimum strength of the bar in KSI

60 rebar = min. yield strength of 60 ksi (40, 60, 75 most common

Front 154

Rebar distance from edge

Back 154

-Slabs & walls: 3/4" from face of concrete

-Beams and columns: 1 1/2" from face of concrete

-Exposed to weather or in contact with soil: 1 1/2" from face of concrete (2" if larger than no.5)

-Concrete poured directly on soil: 3" from face of concrete

Front 155

Maximum "drop" for concrete

Back 155

5'-0" (too much can cause segregation)

Front 156

Wood construction Requirements

Back 156

-Bottom of joists must be 18" above exposed ground

-Bottom of wood girders must be 12" above ground

-End of wood girders must have 1/2" air space when entering masonry / concrete (unless treated)

-Under floor areas (crawl spaces) must be ventilated with openings having a net area of not less than 1sf per 150 sf

Front 157

Steel Construction Requirements

Back 157

-Horizontal framing members should be designed for deflection criteria and ponding requirements

-Trusses longer than 80'-0" can be cambered for the dead load deflection

Front 158

Concrete Construction Requirements

Back 158

-Construction loads cannot be supported or any shoring removed until concrete has sufficient strength to safely support its weight and loads placed on it

-There are limitations on amount and placement of conduits and other pipes embedded in concrete

-Aluminum conduits cannot be embedded unless effectively coated to prevent aluminum - concrete or steel / aluminum reactions

-Pipes with carrying fluid or gasses must be pressure tested

Front 159

Water Load

Back 159

-Equals unit weight of fluid in pounds per cubic foot multiplied by depth

-Weighs approximately 62 lb/ft3

Front 160

Gravel

Back 160

Well drained / able to bear loads (+2mm)

Front 161

Sand

Back 161

Well drained and can serve as foundation when graded (0.5-2mm)

Front 162

Silt

Back 162

Stable when dry, swells when frozen, do not use when wet (.002-.05mm)

Front 163

Clay

Back 163

Must be removed, too stiff when dry and too plastic when wet (.002mm)

Front 164

Levels of soil

Back 164

A- Topsoil

B- Minerals

C- Partially weathered / fractured rock

D- Bedrock

Front 165

Alluvium

Back 165

Soil, sand or mud deposited by flowing water

Front 166

Humus

Back 166

Soft dark soil containing decomposed organic matter, poor bearing capacity

Front 167

Loam

Back 167

Rich soil containing equal parts of sand, silt & clay

Front 168

Potential land problems

Back 168

-Water table- within 6'

-Rock- need to use explosives

-Soil is soft clay, waterbearing sand or silt- deeper foundations or drive piles / or remove poor soil

-Underground streams - avoid and be cautious of siting structure

-Cut & Fill- balance it, there shouldn't be more taken away than added or vice versa

Front 169

Soil Bearing capacity

Back 169

Bedrock- 10,000psf

Well graded gravel / sand- 3,000-12,000psf

Compacted sand / fill- 2,000-3,000psf

Silt / clay - 1,000-4,000psf

Front 170

Borings

Back 170

20' past firm strata. Large structures, 50' spacing. Uniform conditions, 100'-500' spacing

Front 171

Wash boring

Back 171

Drilling of a test hole to locate bedrock beneath very compact soil

Front 172

Auger boring

Back 172

Soil testing that uses an auger drill bit fastened to a rod to bring the soil to the surface. Limited depth / most efficint in sand / clay (bit is easily obstructed)

Front 173

Core Boring

Back 173

Intact cylindrical sample extracted. Reliable / expensive

Front 174

Test pit

Back 174

Excavation of an open pit that allows for a visual examination of the existing conditions as well as the ability to take intact samples for further testing. Can determine the depth of the water table.

Front 175

Slump test

Back 175

Measures workability of concrete. Concrete is poured in a cone mold that is 12" tall with 8" diameter at the bottom and 4" diameter at the top.

Good slump- 1", bad - 6".

Front 176

Cylinder test

Back 176

-Measures compressive strength in PSI of concrete, done in a lab

Front 177

Core cylinder test

Back 177

Same is cylinder test but in place (expensive)

Front 178

Kelly Ball test

Back 178

Half-spherical steel ball is dropped onto a slab of concrete to measure its consistency. The amount it penetrates into the concrete is measured and compared to the half values of the slump test.

Front 179

Impact Hammer test

Back 179

Spring loaded plunger snapped against a concrete surface and the rebound is measured

Front 180

NFPA 101

Back 180

Commonly used standard (widely adopted) for fire protection

Front 181

Reduced design load per SF of area

Back 181

=Design live load from table 1607.1 x

(.25+ 15*sqrt(live load element factor in table 1607.9) x tributary area in sf)

Front 182

Occupancy Categories of Building and other Structures

Back 182

-Category 1: buildings / structures that represent a low hazard to human life in the event of failure

-Category 2: other

Category 3: Substantial hazard: Schools, jails, anything with occupancy over 5,000, healthcare with more than 50 occupants but no surgery / ED)

-Category 4: Essential - hospitals, emergency structures, etc.

Front 183

Handrail / guard assemblies

Back 183

50 psl resistance

Front 184

Grab bars

Back 184

250 lbs in any direction

Front 185

Allowable stresses for Structural Steel

Back 185

-Tension on gross area: Ft=0.6*Fy

-Tension on net effect area: Ft=0.5Fu

-Shear on gross sections: Fv=0.4Fy

Front 186

Allowable concrete construction

Back 186

Average of 3 tests must be less than the specified strength given the PSI, no individual test can be 500 PSI below F'c.

Front 187

Fire stops

Back 187

10' intervals

-At interconnections between concealed vertical & horizontal spaces

-Fire stops required in concealed spaces in stairway construction

Front 188

Base isolation

Back 188

Superstructure detached from foundation to reduce transmission to building

Front 189

Base sheaar

Back 189

Shear force acting at the base of a structure

Front 190

Bracketed duration

Back 190

Time between first and last peaks of motion that exceeds a threshold acceleration value of 0.05g

Front 191

Velocity of seismic waves

Back 191

P-wave- 7,000-18,000mph

S-wave: 4,500-11,000mph

Front 192

Fundamental period

Back 192

Rate at which an object will move back and forth if given a horizontal push

Front 193

Period

Back 193

Time (in seconds) needed to complete one cycle of a seismic wave

Front 194

Frequency

Back 194

-Inverse of period or number of cycles that will occur in 1 second, measured in hertz

Front 195

Hertz

Back 195

1 hertz=1 cycle per second (measure of frequency)

Front 196

Structural Configuration

Back 196

Size, shape & arrangement of the vertical load carrying and lateral force resistance components

Front 197

Drift

Back 197

Vertical deflection caused by lateral forces

Front 198

Force (F)

Back 198

=Mass (M) x Acceleration (A)

Front 199

Base shear (V)

Back 199

Seismic response coefficient (Cs) * effective seismic weight of the building (W)

Front 200

Seismic response coefficient

Back 200

Design spectral response at a period of 1.0 sec (Sd1) = Seismic Response Coefficient (Cs) / Actual period of building (T) * (response modification coefficient (R) / Importance factor (I))

Front 201

Seismic Design Category

Back 201

A=building in regions with little probability of earthquake

B=ordinary occupancy that could experience shaking

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

Front 202

FEMA 454-

Back 202

Designing for earthquakes

Front 203

Natural period for building

Back 203

.05-2 seconds ish

Front 204

Natural ground period

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0.4 - 1.5 seconds

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Basic characteristics of buildings help resist and dissipate the effects of seismically induced motion:

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-Damping

-Ductility

-Straight / stiffness

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Damping

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-Modifies dynamic behavior of building / repsonse to ground motion

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Ductility

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Property of certain materials (typically steel) to fail only after considerable inelastic (permanent) deformation occurs

-Requires special detailing of joints

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Deflection

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Measure of stiffness

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Relative rigidities of members

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-Once rigid horizontal tied to vertical resisting, elements deflect the same amount

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Progressive resistance systems

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Combine 2 or 3 systems that progress in load carrying capacity from rigidity to ductility at predetermined levels

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Building drift

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Distance a building moves in wind

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Wind pressure

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-Front wall (where wind hits): Positive pressure

-Rear & side walls: negative pressure

-Roof: uplift

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Exposure categories

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Exposure B: Rough terrain, urban, suburban & wooded areas

Exposure C: flat open terrain with scattered obstructions & areas adjacent to oceans in hurricane prone regions

Exposure D: Smoothest terrain, areas adjacent to large water surfaces outside hurricane- prone regions, mud flats, salt flats & unbroken ice

(Exposure D equals greater wind load)

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Max drift

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1/500 x height of building

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Light Wood Frame Construction

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-Nail roof sheathing along ends of the sheathing of intermediate roof framing

-Tie gable end walls back to the structure (one of the weakest connection points)

-Use seismic / hurricane framing anchor to attach roof framing to the exterior side of the wall to prevent uplift & shear stress failure

-Nail upper and lower story sheathing to common wood structural panel to provide lateral and uplift load continuity

-Continuously sheath all walls with wood structural panels

-Extend structural panel sheathing to lap the sill plate

-The connection of the wall sheathing to sill plate is where uplift forces are transferred to the plate and into the foundation through anchor bolts

-Anchor bolt spacing - 32"-48"

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Most reliable structural system

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Cast in place conceete

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Roof Systems

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IBC requires load resistance of roof assemblies to be tested by one of the methods listed in IBC Chapter 15

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Highest uplift

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At roof corners

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Windows / doors / skylights

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Must have sufficient strength to resist the positive and negative design wind pressure

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Main Wind Force Resisting System (MWFRS)

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Structural assembly that provides for the overall stability of the building and receives wind loads from more than one surface (eg shear walls, diaphragms, rigid frames, space structures)

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IBC Wind Design Data (1603.1.4)

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-Basic wind speed: 3 second gust in MPH

-Wind importance factor I

-Occupancy category

-Wind exposure

-Applicable internal pressure coefficient

-Components and cladding (design wind pressure in terms of psf to be used for the design of exterior components and cladding materials not specifically designed by the registered design professional)

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Wind Loads (Section 1609)

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-Decreases in wind loads will not be made of the effect of shielding by other structures

-In wind born debris regions, glazing in buildings will be impact resistant

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Calculating wind pressure on MWFRS

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-Determine average roof height (h)

-Determine exposure category

-Determine velocity pressure qz

-Determine wind pressure on windward wall

-Determine wind pressure on leeward wall

-Determine wind pressure on windward roof

-Determine wind pressure on leeward roof

-Determine wind pressure on gable end walls

-Draw "summary sketches" showing worst case loads

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Three separate loads

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-Vertical & lateral both ways

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chord

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Edge members of a diaphragm (joists, ledgers, truss elements, double top plates)

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Box-type structure

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Diaphragms & shear walls used in lateral design

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Wall Bracing

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Resists lateral loads under low load situations

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Blocked diaphragm

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-In light frame construction, all sheathing edges not occurring on a framing member are supported on and fastened to blocking. More nailing provides a greater number of fasteners able to transfer shear from one panel to another

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Diaphragm boundary

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Location where shear is transferred into or out of the diaphragm sheathing, either to a boundary element or to another force resisting element

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Diaphragm chord

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-A diaphragm boundary element perpendicular to the applied load that is assumed to take axial stresses due to the diaphragm moment

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DIAPHRAGM FLEXIBLE

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Flexible for the purpose of distribution of story shear & torsional mooment

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Rigid diaphragm

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Rigid for the purpose of distribution of story shear and torsional moment when the lateral deformation of the diaphragm is less than or equal to 2xs the average story drift

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Unblocked diaphragm

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Diaphragm in which only 4'-0" wide panel ends occur over and are nailed to common framing

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Shear Wall Segment

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Portion of the shear wall that runs from the diaphragm above to the diaphragm / foundation below (occur between openings)

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Base shear

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Reaction at the base of a wall / structure due to an applied lateral load

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Drag strut

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Distributes diaphragm shear from one shear resisting element to another, served by the double top plate

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Perforated shear wall

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Shear wall with openings, slightly lower capacity than full height shear wall segment

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Panel

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Section of a floor, wall or roof comprised between the supporting frame of two adjacent rows of columns and girders or column bands of floor or roof construction

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Braced Frame

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Vertical truss system that provides resistance to lateral forces and provides stability for the structural system

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Rigid frame

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Load resisting skeleton constructed with straight or curved members interconnected by mostly rigid connection which resists movements induced at the joints of it's members. Members can take bending moment, shear, and axial loads

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Drag strut max force

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Diaphragm design shear in the direction of the shear wall x distance between shear wall segments

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Shear wall characteristics

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-More base shear anchor bolts in the bottom plate

-Hold down anchors at each end

-Tighter than normal nailing of the shearing / siding

-Thicker than normal sheathing / siding

-Different framing grades / species / sizes

-Limits on the placement (shear walls on upper floors must be placed directly over shear walls below)

-Special fastening at the top to make sure the load transfers from the diaphragm into the wall

-Double studs at the ends

-Tension ties (hold downs) maintain continuity of chords between each end of the shear wall and between chords of stacked shear walls

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Wall bracing

Back 243

-Used when building is designed using prescriptive requirements

-Must be laced at prescribed location throughout structure

-Low load

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Blocked diaphragms

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-When all four panel edges are on top of and are nailed to common framing

-Higher shear capacity, rigidity, stiffness

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Unblocked diaphragms

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-4'-0" wide panels on top of and nailed to common framing. Most common.

-Fewer nails.

-Loads are low enough that added blocking is not required

-Continuous ridge vents more feasible

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Level of acceleration that can create damage

Back 246

.1g. .5g accelration is high.

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Light or heavy better for earthquake?

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Light.

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Natural periods of structures

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Filing cabinet- .05 seconds

1 story building - .1 seconds

10-20 stories- 1-2 seconds

Period =approximately # stories/10

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Ground vibration

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.4-1.5 seconds typically in US

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How to avoid resonance

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Try to make periods different such as short stiff building on soft soil (long period)

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Base isolation

Back 251

Shifts base isolation towards the long period of the spectrum where the response is reduced

Front 252

Stiffness of column

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Cubic relationship. If a column is 2xs the length, the shorter is 8xs stiffer

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Preventing roofing from detaching in high wind scenarios

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1. Follow general recommendations given in the 4th edition NRCA Steep Roofing Manual.

2. 6 nails per shingle. (when within 3000 ft of salt water, specify hot dip galvanized or stainless steel nails)

3. In lieu of the eave detail from the manual, s pecify starter strip be nailed 1-2.5" from the eave edge of the starter strip. (closer better).

4. Specify tabbing rakes, ridges & hips. Nails penetrate the underside of sheathing or at least 3/4" into wood plank decks.

5. At eaves and rakes, shingles should overhang 1/4" (manual - 1/4"-3/4")

6. Bond-strength data from manufacturers should be used.

7. Nail pull-through resistance data should be used

8. Fiberglass-reinforced asphalt shingles or organic-reinforced shingles

9. Minimize water damage- 2 plies of underlayment

10. Reroofing projects- specify tear-off rather than re-cover

11. Re-roofing- inspect sheathing

12. Professional contractor

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Tile roof practices in wind

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1. High wind areas- nail on or tie-wire attachment methods

2. Nail-on, tie-wire, loose laid systems- determine uplift loads and tile resistance in accordance with SBC

3. Specify hurricane clips designed for screw-attachment of the deck

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Min. roof decks for wind resistance

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22 gauge steel, 19/32 plywood (more in hurricane prone regions)

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Roof deck considerations for wind resistance

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-Reinforced sheets in hurricane prone regions

-Barbed plates for membrane attachment

-Special consideration to fasteners in excess of 4"

-"Bar-over" systems in high wind areas

-Air retarder in high wind areas