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SCT1c- 1 & 2 Slide 1
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Structural Collapse Technician Training
Module : 1c
Structural Engineering Systems
Part 1- Materials, Basic Structural Sys & Bldg Characteristics
Feb0824Jun11
SCT1c- 1 & 2 Slide 2
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Terminal Objectives
The Student shall understand the essential materials and components of structures, and how they behave when subjected to normal and extreme loading
The Student will understand how Building are classified by Engineers and what are their Common Characteristics
SCT1c- 1 & 2 Slide 3
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Key Learning Points
Brittle vs. Ductile Materials Vertical & Lateral Loading Systems Framed and Un-Framed Structures Redundancy Building Characteristics
The Student will become familiar with the following Basic Engineering Concepts
SCT1c- 1 & 2 Slide 4
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Force Type: TensionForce Type: Tension
SCT1c- 1 & 2 Slide 5
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Force Type: CompressionForce Type: Compression
SCT1c- 1 & 2 Slide 6
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Force Type: BendingForce Type: Bending
tension
compression
shear shear
Bending is Combinationof Tension, Compression, & Shear
SCT1c- 1 & 2 Slide 7
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Force Type: ShearForce Type: Shear
Shear Causes Diagonal Tension
Racked Shearwall
ends get stretched
SCT1c- 1 & 2 Slide 8
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Material Properties Brittle vs Ductile
Wood Steel Reinforced Concrete
C.I.P. or P.C.Rebar or Prestressed Cable
Reinforced Masonry Unreinforced Masonry
SCT1c- 1 & 2 Slide 9
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Vertical Load Systems Concept of gravity load path Loads must be transferred
from Source to Ground Top down approach
Plumbing system analogy Framed & Un-Framed Connections are particularly
vulnerable
SCT1c- 1 & 2 Slide 10
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Concrete Floor SystemsConcrete Floor Systems
Most of the reinforcing steel is concentratedin and over Beams and over Columns
SCT1c- 1 & 2 Slide 11
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Lateral Load Resisting Systems
Concept of load paths Pushover analogy
Connections are particularly vulnerable
SystemsBox BuildingsMoment Frames
(MUST BE DUCTILE )Diagonally Braced Frames
SCT1c- 1 & 2 Slide 12
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Load
Lateral Load Path Concept - Box Building
Basic Components Roof/Floor – Laterally
supports Walls Walls – Keeps System
from RackingBest to have walls on all
Four SidesWalls may have
Openings
SCT1c- 1 & 2 Slide 13
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Lateral Load Path ConceptMoment FrameBasic Components Roof/Floor – Laterally
supports Walls/Frames Moment Frames –
Keep System from RackingNeed Moment Frames
in N-S & E-W directionsBest to have many
Load
SCT1c- 1 & 2 Slide 14
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Load
Lateral Load Path ConceptDiagonal Braced FrameBasic Components Roof/Floor – Laterally
supports Walls/Frames Diag Braced Frames –
Keep System from RackingNeed Diag Br. Frames
in N-S & E-W directionsMay have combo of Mo.
Frames and Diag Brace
SCT1c- 1 & 2 Slide 15
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Redundancy Multi - Elements
(at least 2 in every line of resistance)Box BuildingsDiagonal Braced Frames
Majority of ConnectionsMoment Frames
Dual Systems Collapse Preventers
SCT1c- 1 & 2 Slide 16
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Tension Structure RedundancyTension Structure Redundancy
Suspension Bridge
Partly Collapsed Building
Catenary
Catenary
SCT1c- 1 & 2 Slide 17
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Truss Hazards – No Redundancy High forces in top & bottom members
Tension in bottom chords Collapse in Fire - 5 to 10 minutes
Light Steel and 2x Wood especially dangerousLow volume – High surface area
Gang-nail Plates & Glue Joints
SCT1c- 1 & 2 Slide 18
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Building CharacteristicsBuilding Types - ATC-20 W1 Dwellings & small wood buildings W2 Wood bldg over 5000sf & 3+ story S1 Steel moment resisting frames S2 Braced steel frames S3 Light metal buildings S4 Steel frames w/C I P conc walls
SCT1c- 1 & 2 Slide 19
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Building types - ATC-20 C1 Concrete moment resisting frames C2 Concrete shear wall buildings C3/S5 Conc/steel frame w/urm infill walls TU/PC1 Tilt-up concrete wall building PC2 Precast concrete frame buildings RM Reinforced masonry buildings URM Unreinforced masonry building Mobile Homes & Manufactured Units
SCT1c- 1 & 2 Slide 20
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Problem Buildings W 1 & 2 1 to 3 story houses & 2 to 4 story
Apartments (especially pre 1970) S1 Frames w/brittle welded conns S2 Frames where column capacity is
less than capacity of diag braces
S3 Light structure vulnerable to Wind C1/C3 Pre 1971 bldgs (espec pre 1941) PC2/TU Factory built precast & tilt-up wall URM 1 to 8 story (most 3 story & less) +
steel & conc frames w/URM infill Mobile Homes & Manufactured Units Others Irregular - soft story, open front
SCT1c- 1 & 2 Slide 21
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Wood Houses W1
Moment Frame
Platform framed w/ Skin (sheathing)& Bones (2x framing)
Some sort of roof trussis common
Brick chimneysare hazards
SCT1c- 1 & 2 Slide 22
National Urban Search & Rescue Response System
Structural Collapse Technician Training
W 1 & 2 Type Characteristics Bearing Wall System
Light Frame (2X wood framing or light gage steel framing) Un-Framed System
Typical Occupancies Residential, light commercial – up to 4 stories
Key Performance AspectsMany walls create redundant structures w/
significant overstrength, generally ductile failure modes, depending on sheathing type.
CombinationsMay be built above R/C parking garageFrequently used for interior partitions in
residential and commercial masonry structure
SCT1c- 1 & 2 Slide 23
National Urban Search & Rescue Response System
Structural Collapse Technician Training Wood Houses Under Construction
In California
In Texas
Moment Frame
SCT1c- 1 & 2 Slide 24
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Wood Houses under Construction After 50mph wind
In California
In Texas(Lateral load Sys ?)
SCT1c- 1 & 2 Slide 25
National Urban Search & Rescue Response System
Structural Collapse Technician Training
SCA-RS2 - 25
Hurricane Rita Storm Surge Damage(Grand Chenier, on Louisiana CoastMany houses with
fiberboard sheathingwere swept away
One house remained, Plywood Sheathing(under brick veneer)
SCT1c- 1 & 2 Slide 26
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Wood Frame Apartments W-2Those w/ wood framed, soft 1st story are most vulnerable
SCT1c- 1 & 2 Slide 27
National Urban Search & Rescue Response System
Structural Collapse Technician Training
3 Story Wood Apartments
(also 4 story)
Over Conc Parking
Over Weak 1st Story Parking
SCT1c- 1 & 2 Slide 28
National Urban Search & Rescue Response System
Structural Collapse Technician Training Mobile Homes & Manufactured Units Mobile Homes in large neighborhoods
Units remain mobile w/ wheels attachedUsually supported on jack standsCompact interior spacesUsually have utility connectionsMay contain propane tanks
Portable ClassroomsInterconnected units, each with one open sideUsually supported on temporary foundationLarger interior spaces, semi-permanentBetter structure usually with moment frame supporting
open side
SCT1c- 1 & 2 Slide 29
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Mobile Homes/Mfr’d Units- CharacteristicsStructural Systems
Very light, metal covered walls on steel base frameSupported on jack stands or temporary foundations
Typical Occupancies Residential, classroom, office
Key Performance AspectsPerformance of box structure is dependent on connection to base (25ga. Straps w/ staples = poor 16ga. w/ screws = better)
Base frame needs adequate connection to groundAwnings, etc are very vulnerable
CombinationsMore than one unit may be interconnected to form larger space
SCT1c- 1 & 2 Slide 30
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Portable Classrooms – Seismic design Low profile, near ground w/tiedownSteel moment frame each unit at 8ft o.c. Thicker walls/roof
SCT1c- 1 & 2 Slide 31
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Temporary Office – for 30 years? 8ft wide units make
16ft x 40 ft space Jack stands may
eventually rust-out
SCT1c- 1 & 2 Slide 32
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Steel Moment Frame S1
Most common floor:Conc fill on metal deck
Exterior walls systems:Precast Concrete or GFRCMasonry Infill or over metal studsWindow-wall Systems
SCT1c- 1 & 2 Slide 33
National Urban Search & Rescue Response System
Structural Collapse Technician Training
S1 Type Characteristics Frame System
Heavy Structural Steel (hot rolled sections) Typical Occupancies
Office & Commercial, Industrial, Highway bridges2 to 100 stories
Key Performance AspectsNormally well-engineered; Members very ductile.
Overall performance dependent upon connections – welds may be brittle.
PC or URM, Ext wall panels usually perform badly Combinations
Precast or CIP concrete floors w/ or w/o metal deck Masonry, precast or metal curtain walls +URM infill
SCT1c- 1 & 2 Slide 34
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Moment Frame Under Construction
New, Improved Joints
SCT1c- 1 & 2 Slide 35
National Urban Search & Rescue Response System
Structural Collapse Technician Training Steel Frame w/URM
Being repaired following
Loma Prieta EQ
SCT1c- 1 & 2 Slide 36
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Steel Diag. Braced Frame S2
Same Floor and Exterior Wall Systems as S1 Bldgs
SCT1c- 1 & 2 Slide 37
National Urban Search & Rescue Response System
Structural Collapse Technician Training
S2 Type Characteristics Frame System
Heavy Structural Steel (hot rolled sections) Typical Occupancies
Office & Commercial, Industrial, 2 to 30 stories
Key Performance AspectsNormally well-engineered; Members very ductile.
Overall performance dependent upon connections and proper proportioning of column strength
CombinationsPrecast or CIP concrete floors w/ or w/o metal deck Masonry, precast or metal curtain wallsExterior precast walls may perform badly
SCT1c- 1 & 2 Slide 38
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Steel Diag. Braced Frame S-2
5 Story Office Bldg
2 Story Retail Over Conc Parking
SCT1c- 1 & 2 Slide 39
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Light Metal Building S3Roof Systems:Metal deck on steel purlins with Steel Trusses or Frames
Wall Systems:Metal sheathing on steel framing orMasonry Infill or on metal studs
SCT1c- 1 & 2 Slide 40
National Urban Search & Rescue Response System
Structural Collapse Technician Training
S3 Type Characteristics Frame System
Light-gage Steel (pre-fab metal buildings) Typical Occupancies
Office, Industrial & Commercial Low-rise up to 3 stories Most industrial/commercial are single story
Key Performance AspectsHighly engineered Little redundancy or overstrength; very flexible
CombinationsMay have wood or light gage metal interior
partitions and mezzanine Masonry, precast, tilt-up or metal int./ext. walls
SCT1c- 1 & 2 Slide 41
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Typical 1-story S3 building
Hurricane Iniki
Typical Connections
SCT1c- 1 & 2 Slide 42
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Concrete Moment Frames C1
PC WallsURM Infill
Concrete floor systems
SCT1c- 1 & 2 Slide 43
National Urban Search & Rescue Response System
Structural Collapse Technician Training
C1 Type Characteristics Frame System
Heavy Floor Structure - CIP Non-ductile Reinf ConcCIP Ductile Reinf. Conc., CA & WA post 1980
Typical Occupancies Office & Commercial, Highway bridges 2 to 30 stories
Key Performance AspectsNon-ductile = brittle failure modes when loaded
beyond capacity; Cracking generally means significant loss of strength
Ductile = robust structural system can absorb considerable energy and sustain considerable cracking w/o loss of integrity
CombinationsVarious types of infill & partitions = C3 Type
SCT1c- 1 & 2 Slide 44
National Urban Search & Rescue Response System
Structural Collapse Technician Training
C1 w/ Brick InfillMexico City
C1 w/ Clay Tile Infill = C3 Santa Monica Sea Castle
SCT1c- 1 & 2 Slide 45
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Concrete Shearwall Bldgs C2
Wood or concrete roof systems
Concrete floor sys
CIP concrete walls
SCT1c- 1 & 2 Slide 46
National Urban Search & Rescue Response System
Structural Collapse Technician Training
C2 Type Characteristics Frame & Bearing Wall System
Heavy Wall Structure - Reinforced Concrete Shearwalls
Typical Occupancies Residential, commercial, institutional and industrial
1 to 20 stories
Key Performance AspectsExcellent quake, windstorm, blast & fire resistanceSpecial wall edge reinforcing provides ductility and
improved ability to resist unanticipated loads Combinations
Structure may contain non-structural, non-ductile elements; Curtain walls & URM partitions
SCT1c- 1 & 2 Slide 47
National Urban Search & Rescue Response System
Structural Collapse Technician Training Concrete Shearwall Bldgs C2 12-story, Alaska EQ
NASA Ames
SCT1c- 1 & 2 Slide 48
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Precast Concrete Bldgs PC2PC roof, floor, & walls
May have concrete topping on floor
May have concrete walls
SCT1c- 1 & 2 Slide 49
National Urban Search & Rescue Response System
Structural Collapse Technician Training
PC2 Type Characteristics Frame System – (Residential Bearing Wall Sys)
Precast Concrete columns, beams & slabsMay have CIP floor fill in CA & WAResidential usually have PC bearing walls
Typical Occupancies ( 1 to 12 stories) Parking Garages, Office, Residential, & Commercial
Key Performance AspectsMay have highly engineered prestressed systems –
especially Parking Garages. Brittle connections with little reserve strengthBearing wall systems are highly redundant – better
performance Combinations (see TU for other walls)
Precast panels used for floors and roofs of masonry and steel frame structures.
SCT1c- 1 & 2 Slide 50
National Urban Search & Rescue Response System
Structural Collapse Technician Training
PC-2 Armenia Apartments
Parking Garages(Common in U.S.)
SCT1c- 1 & 2 Slide 51
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Post Tensioned Lift Slab Bldg(see Manual for comment)
SCT1c- 1 & 2 Slide 52
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Tilt-Up Wall Buildings TUTrusses on older buildingsGlulam Beams since 1960
Plywood roof sheathing on 4x purlins or 2x joist
Concrete walls are usually cast on site: mostly 6” thick
May have metal deckroof on steel joistin some areas
SCT1c- 1 & 2 Slide 53
National Urban Search & Rescue Response System
Structural Collapse Technician Training
TU Type Characteristics Interior Frame & Exterior Bearing Wall System
Modern low-rise, most single story but up to 4 stories.Long span roof (50ft+) and floors (25ft+).
Typical Occupancies Office, commercial, light industrial and institutional
Key Performance AspectsRobust wall panels dependent upon diaphragms for
out-of-plane support. Wall/diaphragm connection vulnerable – Retrofit in CA
Combinations
Light frame or steel joist diaphragmsLt wt. concrete floor fill in multi story buildings
SCT1c- 1 & 2 Slide 54
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Light Roof 24’x60’ Bays
Heavy Walls
Tilt Up
1 Story Lt. Industrial
Most Common
SCT1c- 1 & 2 Slide 55
National Urban Search & Rescue Response System
Structural Collapse Technician Training
TU 2 Story Office
Large TU – Home Supply StoresFramed Steel Roof & Lots of Storage Racks
SCT1c- 1 & 2 Slide 56
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Types of URM Buildings Brick bearing wall buildings -
URM exterior walls w or w/o URM veneer Wood floors & interior wood walls.
URM infill - in concrete or steel frames. Infill is brick, hollow clay tile, hollow CMU
CMU - Hollow conc block bearing wall . May have bond beams at floor & roofTie Beam/Tie Col is currently used in Florida May also have vertical bars at edges of openings
SCT1c- 1 & 2 Slide 57
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Types of URM Buildings UR or Under-reinforced Brick cavity walls.
Insulation layer between masonry layers May be used as infill or as bearing walls with
bond beams. Masonry veneer on wood/steel studs
Anchorage is all important due to interaction of brittle wall covering on flexible structure.
Native stone, adobe, mud, etc. bearing wall buildings.
SCT1c- 1 & 2 Slide 58
National Urban Search & Rescue Response System
Structural Collapse Technician Training
URM Bearing Wall BldgStraight or diag.1x roof sheathingWood roof
trusses
Heavy timber floor systems in older buildings
SCT1c- 1 & 2 Slide 59
National Urban Search & Rescue Response System
Structural Collapse Technician Training
URM Type Characteristics Bearing Wall System
Heavy Wall Structure Unreinforced Masonry (includes unreinforced brick & CMU low-rise bldgs)
Older “red brick” with bond/header courses Lack of strap anchors & ties (except Retrofit in CA)
Typical Occupancies (1 to 8 Stories) Residential, commercial, and industrial
Key Performance AspectsBrittle with little capacity to resist unanticipated
loads. Numerous interior walls may prevent floor collapse
CombinationsHeavy timber, light frame or steel joist diaphragms,
with concrete floor fill in multi story buildings.
SCT1c- 1 & 2 Slide 60
National Urban Search & Rescue Response System
Structural Collapse Technician Training
URMShould be
Retrofit if in CA
Brick Bearing Wall Bldg
CMU-Tie Beam/Tie ColCMUCurrently Built in FL
SCT1c- 1 & 2 Slide 61
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Review Key Learning Points
Brittle vs. Ductile Materials Vertical & Lateral Loading Systems Framed and Un-Framed Structures Redundancy Building Characteristics
The Student should be familiar with the following Basic Engineering Concepts
SCT1c- 1 & 2 Slide 62
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Structural Collapse Technician Training
Module : 1c
Structural Engineering Systems
Part 2- Causes of Collapse
Feb08
SCT1c- 1 & 2 Slide 63
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Terminal Objectives The Student shall understand the Extreme
Environmental and Man caused Forces and how they Effect Structures.Also how they may effect US&R Operations
Those Forces are:Earthquake – Motion that accelerates structureWind BlastFire
SCT1c- 1 & 2 Slide 64
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Earthquake Basics Extent of damage is determined by
Type of shaking that occurs at site Coupled with the structures response
Magnitude (energy release)Mag. 8 releases about 30 times as much energy
at Mag. 7 Determines POTENTIAL number of effected
structures Aftershocks
Earthquakes are unique type of disasterJust keeps on giving
SCT1c- 1 & 2 Slide 65
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Aftershocks Smaller quakes that occur on same fault as
original quake. Minor fault adjustments
Occur after most quakes regardless of size of original shock
On average largest is 1.2M less than originalSome have been almost as large as original.
(in range of M 6) Will occur during US&R Ops since are most
prevalent in first week.
SCT1c- 1 & 2 Slide 66
National Urban Search & Rescue Response System
Structural Collapse Technician Training
How Many Aftershocks ? USGS - Rule of Thumb
For every single decrease in magnitude, get 10 fold increase in number
If original quake is M 71 or so aftershock in range of M 610 “ “ “ “ 5100 “ “ “ “ 41000 “ “ “ “ 3
Have fewer as time passesDay 2 = 1/2 as many as day 1Day 3 = 1/3 as many as day 1Day 4 = 1/4 as many as day 1, etc
SCT1c- 1 & 2 Slide 67
National Urban Search & Rescue Response System
Structural Collapse Technician Training
1989 Loma Prieta Aftershocks
Days after original shock
Mag
nit
ud
e
SCT1c- 1 & 2 Slide 68
National Urban Search & Rescue Response System
Structural Collapse Technician Training
World Map of E.Q Faults
.
San Andreas Fault TraceFault is 5 + km deep
SCT1c- 1 & 2 Slide 69
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Large Offset shown in Creek BedThis is due to creep over centuries, not one quake
Fault Trace
Creek Bed Offset
SCT1c- 1 & 2 Slide 70
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Earthquake Loading
Quake Motion Produces Forces in Buildings
Force = Mass x acceleration
SCT1c- 1 & 2 Slide 71
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Damage to Heavy, Weak URM
Damage to Heavy, Weak Buildings
SCT1c- 1 & 2 Slide 72
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Damaged to Under-Engineered Wood
Brick Veneer on old Wood Sheathing
Stucco w/o Good Sheathing
SCT1c- 1 & 2 Slide 73
National Urban Search & Rescue Response System
Structural Collapse Technician Training
KOBE Severe Damage due to Near Fault Effects
MEXICO CITY Harmonic, Far Field Effects
SCT1c- 1 & 2 Slide 74
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Quake Effects Bldg & Contents
SCT1c- 1 & 2 Slide 75
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Wind LoadingForce is proportionalTo speed squaredForce from 100mph = 4 times from 50mph
SCT1c- 1 & 2 Slide 76
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Hurricanes Winds 75 to 175mph + Missiles
Much Damage to Light Structures
SCT1c- 1 & 2 Slide 77
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Hurricane Storm SurgeForce of Moving Water
SCT1c- 1 & 2 Slide 78
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Tornado - winds to 250mph little warning
SCT1c- 1 & 2 Slide 79
National Urban Search & Rescue Response System
Structural Collapse Technician Training
OKC-1999 44 Dead 795 Injured3140 Destroyed Bldg
Mile Wide Path
SCT1c- 1 & 2 Slide 80
National Urban Search & Rescue Response System
Structural Collapse Technician Training
2001 Kansas Tornado Path of Destruction
Unbroken Window
SCT1c- 1 & 2 Slide 81
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Explosion Basics Explosion is chemical reaction involving:
Rapid expansion of Gas Liberation of HeatExplosion is defined as bursting of an enclosure
due to development of internal pressure High Explosive (Primary & Secondary)
Primary Explosives - detonate by simple ignition due to spark, flame, impact or friction
Secondary Explosives – are relatively insensitive to simple ignition and are detonated by shock from a Primary Explosive
Detonation results when a combustion zone (conversion of energy) proceeds at greater than the speed of sound (as high as 4miles/sec)
SCT1c- 1 & 2 Slide 82
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Explosion Basics Low Explosive (or Propellants)
Deflagration (rapid burning) results when a combustion zone proceeds from the ignition point at less than speed of soundBlack Powder, Rocket Fuel, Flammable Gas, Dust
If Low Explosives are confined they can Detonate
Detonations vs DeflagrationsDetonation pressures usually much higherDeflagration duration is normally longer If collapse is not initiated, effects of Detonation
can be more localized
SCT1c- 1 & 2 Slide 83
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Explosion Effects Rapid release of Energy
Sound (bang) and Heat and Light (Fireball) Shockwave (very high, but short duration pressures)
Shockwaves (Pressure Wave)Propagates, outward in all directions from source
and causes most of the damage to StructuresDiffracts, creates both amplifications & reductionsShort term nature (milliseconds) allows structures to
survive much higher than “Static Design” pressures Other Effects
High speed winds (sucking effect after wave passes) propels debris
High intensity, short duration ground shaking
SCT1c- 1 & 2 Slide 84
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Interior Explosion Loading
SCT1c- 1 & 2 Slide 85
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Interior Explosion
Light Frame
Interior Explosion Concrete
Frame
SCT1c- 1 & 2 Slide 86
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Interior Explosion - WTC, Flat Slabs
SCT1c- 1 & 2 Slide 87
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Exterior Explosion Loading
overpressure
overpressure
sphericalshockwave
reflectedpressure
stand-off
dragoverpressure
SCT1c- 1 & 2 Slide 88
National Urban Search & Rescue Response System
Structural Collapse Technician Training
SCT1c- 1 & 2 Slide 89
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Exterior Explosion LoadingA
B
C
Exterior walls,columns & windows
Roof & Floor slabs
Frame
Ground shock
SCT1c- 1 & 2 Slide 90
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Exterior Explosion Murrah Bldg
Crater & E Q
SCT1c- 1 & 2 Slide 91
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Fire Effects on Steel Structures Expansion
About 10” in 100ft from ambient to 1100 deg F Loss of flexural rigidity
Significant above 800 deg Both Yield Point & Stiffness are reducedDeflected Floor is Warning Sign
Significant loss of strength above 1000 deg Strength OK up to approx 700 deg Drops below Design Strength at 1100 deg At 1000 deg both Stiffness and Strength are 50%
SCT1c- 1 & 2 Slide 92
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Effects of Fire – Expansion(10 “ in 100 ft)
Can cause restrained connections to failCan destabilize columns
SCT1c- 1 & 2 Slide 93
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Effects of Fire – Loss of RigidityCatenary forces can cause connections to fail
and can destabilize columnsDeflected floor can warn of collapse
SCT1c- 1 & 2 Slide 94
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Heat Effects on Steel Strength
SCT1c- 1 & 2 Slide 95
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Effects of Fire – Strength Loss
Can lead to floor collapse and eventually collapse columns
SCT1c- 1 & 2 Slide 96
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Effects of Fire – Strength Loss Worst effects on Joist, Beams, & Girders
Heat Concentrates and is Trapped on Horizontal Surface
Less effect on ColumnsUsually have some Protective CoveringColumns are thicker membersHeat dissipates into Continuous Column
Sections in Floors, Above & Below
SCT1c- 1 & 2 Slide 97
National Urban Search & Rescue Response System
Structural Collapse Technician Training Building Code Fire Resistive I.D. Type 1 - Non-combustible Construction
4-hour Exterior WallsStructure has 2 & 3-hour Fire Protection
Type 2 - Non-combustible Construction May have 1-hour or Non-rated Protection
Type 3 - Non-combustible Exterior Walls 4-hour Exterior WallsMay have combustible Roof, Floor & Interior
Walls, w/ or w/o Fire Protection Type 4 - similar to Type 4
Lower Fire Protection Requirements Type 5 – Wood or Lt. Metal frame
May require 1 hour Exterior and Dividing Walls
SCT1c- 1 & 2 Slide 98
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Fire Effects on Steel Structures Type 1 –Fire Protected Steel Bldgs
Prior to 9/11 no Type 1, Steel Building had ever collapsed due to Fire
Some had burned for many hoursOne Meridian Plaza, Philadelphia, 1991, 19
hours (11 hours uncontrolled)Interstate Bank, L.A., 1988, 4 ½ hrsMGM Grand Las Vegas, 1981, 11 hrs
– Multi-Helicopter Rescue from Roof– Changed Fire Protection Requirement
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National Urban Search & Rescue Response System
Structural Collapse Technician Training
Fire Effects on Steel Structures Unprotected Steel Building problemsLong span, low rise truss and bar joist
structures had spectacular collapsesMcCormick Place, Chicago – 1967, $154mil
– 30ft clear height Exhibition Hall– Fuel from 2 story high exhibits
Cobo Hall, Detroit, 1960– Bar joist roof & walls became spaghetti
Commonly used in Gyms & ArenasHigh School to Professional
SCT1c- 1 & 2 Slide 100
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Collapse of WTC - 7 Fire started at about 1000hrs FDNY abandoned fire suppression by
1200hrs Sprinkler system ineffective due to break in
water mainDesign of most Fire Sprinkler Sys assumes
smaller fires – overwhelmed by large fires Collapsed at about 1720hrs
Collapse started near bottom of building Initiated by interior collapseBuilding imploded – stayed within its own
footprint
SCT1c- 1 & 2 Slide 101
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Collapse of WTC - 7 Collapse Observations
East Penthouse disappeared firstWest Penthouse disappeared next and then the
entire building went down w/kink in roof Potential Problems
WTC 7 built over Electrical Substation Used 3 Transfer Trusses at 5th to 7th Fl Level
6 locations of generators & 4- 275 gal fuel, “Day Tanks” - on 5th, 7th, 8th & 9th floorsSome Generators & Tanks were near Trans TrussesFuel from tanks or broken pipes MAY have contributed to
the fire – DISPUTED BY RECENT REPORT
SCT1c- 1 & 2 Slide 102
National Urban Search & Rescue Response System
Structural Collapse Technician Training
East West
From the Northwest
SCT1c- 1 & 2 Slide 103
National Urban Search & Rescue Response System
Structural Collapse Technician Training
WTC 1 & 2 Effect of Aircraft Impact Impact fractured about 1/2
columns on impact face Partial collapse of floors Debris penetrated bldg core
Damaged some core columns – Severity ??
Damaged stair shafts and elevators
Impact probably caused failure of some fireproofing
INITIATED FIRE
SCT1c- 1 & 2 Slide 104
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Collapse of WTC – 1 & 2 Redundancy permitted structure to
resist initial damageLoad re-distribution highly stressed
many elementsReduced lateral support for other
highly stressed elements Fire effects
Further increase stresses due to expansion
Caused failure of some connectionsWeakened highly stressed elements
Once collapse initiated, debris weight on lower floors caused progressive collapse
SCT1c- 1 & 2 Slide 105
National Urban Search & Rescue Response System
Structural Collapse Technician Training Fire Effects on Other Structures Type 3 Bldgs – Conc/Masonry walls, Wood Roof
Burnout of Wood roof/floors creates dangerous, unbraced heavy walls
Buildings with Light Wood Trusses have been a deadly, Sudden Collapse Problem – 2x members 34 Firefighters killed in 19 incidents - 1977 thru 1999
Bldg’s with Lt. Steel Trusses have collapsed suddenly Furniture Warehouse in 2007 – 9 Firefighters killed
Type 5 Bldgs – Wood Walls & Wood RoofMany have Attics w/Light Wood Framing (1x & 2x)Same Problem of Intense Attic Fires
Usually less Collapse Issue due to many wallsStill has Deadly Potential
SCT1c- 1 & 2 Slide 106
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Worcester Fire Dec99
Burnout caused 6 story unbraced walls
SCT1c- 1 & 2 Slide 107
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Refer to Manual for Following Damage by Floods Storm Surge & Tsunami Landslide, Mudslide, Debris Avalanche
Construction Bracing, Overload Vehicle Impact Loading
SCT1c- 1 & 2 Slide 108
National Urban Search & Rescue Response System
Structural Collapse Technician Training
Review Key Learning Points There are many Environmental and Man
caused Forces that Effect Structures. Each of these produce Unique Effects on the
various Types of Buildings Some, like Earthquakes (and possible Blast)
have Secondary Effects that must be planned for during US&R Response