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Structural Collapse Technician Training

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1 Structural Collapse Technician Training
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Structural Collapse Technician Training Module : 1c Structural Engineering Systems Part 1- Materials, Basic Structural Sys & Bldg Characteristics Changes to 2009 SCT01c ver3 Now there are now 5 Parts. The number of slides has been reduced from abt 500 to 300 Part 1 Basic Struct Sys & Bldg Characteristics Part 2 Causes of Collapse Part 3 Collapse Patterns Part 4 Hazard Assessment w/ optional Case Study Part 5 US&R Strategy & Size-up (Change Triage to Rapid Recon The new sequence is intended to save time and reduce some of the duplicate discussion of Collapse Patterns during the description of Bldgs and the Collapse Pattern Section. Hopefully, you will like this improvement Many slides have been combined and some have been added or changed for more contemporary incidents 24Jun11 Feb08 Apr09

2 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 This section (first 20 slides) should be a review of Basic Engineering Concepts. Inform class that they are expected to study the student manual. Most Firefighters have had classes in structures, but need a “Memorable” Review. Collapse of Burning Buildings by Vincent Dunn is a text book that many will have studied Use as many visual aids as possible. Very Important Better to use word “FORCE” than stress , don’t get wrapped-up in needless use of precise engineering terms Encourage questions by class members Remember to repeat all questions, especially in large classes Apr09

3 Key Learning Points Brittle vs. Ductile Materials
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Key Learning Points The Student will become familiar with the following Basic Engineering Concepts Brittle vs. Ductile Materials Vertical & Lateral Loading Systems Framed and Un-Framed Structures Redundancy Building Characteristics Emphasize that there are the most important concepts of this section You will cover Brittle vs Ductile in the next several slides The Vert Loading Sys slide also has the Framed vs Unframed bullet – see that Note page Redundancy is covered on a later slide, but you should point out the Redundant structures throughout the entire slide presentation Apr09

4 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Force Type: Tension Force that PULLS on an object & stretches it. Explain ELASTIC Behavior (use big rubber band - so back of classroom can see it ) Explain DUCTILE Behavior (use plastic tubing or something else that you can stretch) Define YIELDING = Ductile Behavior Steel NECKS DOWN when it YIELDS Apr09

5 Force Type: Compression
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Force Type: Compression Force that PUSHES on an object & shortens it. Explain that CRUSHING can occur or that BUCKLING (bowing) can occur Show Example of Buckling – Use wood dowel or Foam Plastic packing material bar-like piece Crushing can give warning (Structural Fuse) Buckling produces sudden failure - avoid Wood systems can be proportioned so that slow noisy crushing of cross grain wood fibers can be seen & heard as the system YIELDS Discussed later in Shoring Basics Apr09

6 Bending is Combination of Tension, Compression, & Shear
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Force Type: Bending tension compression shear Review simple bending - compression at top & tension at bottom. Occurs in most Beams, Slabs, Joist Since concrete has no tension strength, add rebar to take tension. Concrete cracks in order for the rebar to take tension - gives us warning system. (Structural Fuse) Stable, hairline cracks are to be expected, Larger cracks over 1/8” usually indicate significant degradation of concrete beams or slabs Use same plastic/foam bar w/parallel vertical lines on it to demonstrate tension at bottom, compression at top Bending is Combination of Tension, Compression, & Shear Apr09

7 Shear Causes Diagonal Tension
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Force Type: Shear ends get stretched Shear Causes Diagonal Tension Review Beam, Punching, and Wall Shear Define Racking. Use concept that in shear element at upper right, the change from square to parallelogram causes the upper-left and lower-right corners to move away, thereby stretching the middle on the diagonal (producing diagonal tension cracks in concrete) You can use a foam sheet with diagonal cut in it to demonstrate Punching Shear cracks can usually only be observed from the top of the slab, since the diagonal tension crack ends at the face of the column in the compression zone. Least important topic on this page Racked Shearwall Apr09

8 Material Properties Brittle vs Ductile
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Material Properties Brittle vs Ductile Wood Steel Reinforced Concrete C.I.P. or P.C. Rebar or Prestressed Cable Reinforced Masonry Unreinforced Masonry Discuss properties of each with emphasis on DUCTILE or BRITTLE Remember properly designed wood structures and FEMA shoring can give Ductile performance Demonstrate Brittle by breaking a pencil or small piece of wood Demo Ductile -bend a large paper clip or wire hanger Define C.I.P. vs. PC concrete and Pre-Tensioned vs Post Tensioned Apr09

9 Vertical Load Systems Concept of gravity load path
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Load system = all loads flow to ground – like plumbing Define Framed & Unframed – Framed = system w/ column/beam grid & longer spans Unframed = cellular sys w/ bearing walls & shorter spans Larger & progressive collapse more possible in Framed Sys. Unframed Sys w/lots of walls is more Redundant & collapse may only involve one room Mention that we will define buildings by their Lateral Load Systems, NEXT Apr09

10 Concrete Floor Systems
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Concrete Floor Systems Some of Concrete floor systems that we may encounter. Always want to cut thru where slab is thinnest & least rebar Emphasize StS can be big help in defining where to cut Most of the reinforcing steel is concentrated in and over Beams and over Columns Apr09

11 Lateral Load Resisting Systems
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Lateral Load Resisting Systems Concept of load paths Pushover analogy Connections are particularly vulnerable Systems Box Buildings Moment Frames (MUST BE DUCTILE ) Diagonally Braced Frames Define LATERAL LOADS = Forces from the side Introduce 3 Systems - Next Apr09

12 Lateral Load Path Concept - Box Building
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Lateral Load Path Concept - Box Building Basic Components Roof/Floor – Laterally supports Walls Walls – Keeps System from Racking Best to have walls on all Four Sides Walls may have Openings Basic concept of a shear wall – prevents racking by acting in shear Explain Box Bldg - use cardboard box ? With one end that you can lift out Roof laterally supports walls. If roof is burned out or removed by wind or blast, walls and other vertical load sys member loose their lateral support If wall(s) collapse roof looses vertical support, and structure may loose part of it’s lateral resistance Load Apr09

13 Lateral Load Path Concept Moment Frame
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Lateral Load Path Concept Moment Frame Basic Components Roof/Floor – Laterally supports Walls/Frames Moment Frames – Keep System from Racking Need Moment Frames in N-S & E-W directions Best to have many Load Explain - use Frame Joint of Hand - Forearm Just like a Picture Frame Joint Must be Strong and Stable Moment Frame replaces need for walls, but still need roof/floor to provide a strong/stiff horiz plane (diaph.) to complete the structure Note inset of Simpson Strong Frame. Bolted Moment Frame for house construction Apr09

14 Lateral Load Path Concept Diagonal Braced Frame
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Lateral Load Path Concept Diagonal Braced Frame Basic Components Roof/Floor – Laterally supports Walls/Frames Diag Braced Frames – Keep System from Racking Need Diag Br. Frames in N-S & E-W directions May have combo of Mo. Frames and Diag Brace Load Explain – When it starts to rack the tension diagonal would need to get longer, so tension force is generated Works in reverse in compression – Compression braces must be stout enough to resist buckling. Used in most structures (except light metal bldgs) since system is stiffer than light, tension x bracing Just like Mo. Frame, still need roof/floor diaph. To complete a stable structure Apr09

15 Redundancy Multi - Elements (at least 2 in every line of resistance)
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Redundancy Multi - Elements (at least 2 in every line of resistance) Box Buildings Diagonal Braced Frames Majority of Connections Moment Frames Dual Systems Collapse Preventers Explain – Very Important Concept 2nd way for structure to resist when primary system Yields or Fails Having secondary load path that can prevent collapse Point out Redundancy throughout remainder of presentation Apr09

16 Tension Structure Redundancy
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Tension Structure Redundancy Catenary Suspension Bridge Catenary Elegant system, but requires complete system to anchor tension forces Will see Catenary forms in collapsed structures, but what is anchoring the tension? Also in collapsed structures of this configuration, what are the concerns of cutting through the draped slab to access from the top?? Partly Collapsed Building Apr09

17 Truss Hazards – No Redundancy
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 dangerous Low volume – High surface area Gang-nail Plates & Glue Joints Very efficient structures, but often sudden collapse Efficient but often are Brittle structures, certainly not Redundant Also difficult to shore Discuss that 2x trusses have had bad performance, especially in attic fires – discussed later in section on Effects of Fire Also bar joist & lt. Steel trusses are sudden collapse problems Apr09

18 Building Characteristics Building Types - ATC-20
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Building Characteristics Building Types - ATC-20 W Dwellings & small wood buildings W2 Wood bldg over 5000sf & 3+ story S Steel moment resisting frames S Braced steel frames S Light metal buildings S Steel frames w/C I P conc walls May wish to explain that ATC is Applied Technology Council , research project coordinating body set up by STRUCT ENG ASSN of CAL This simple system is used to classify building in documents for evaluation structures. Engineers shorthand that better defines the type of building and it’s framing system Remainder of categories on next slide Apr09

19 Building types - ATC-20 C1 Concrete moment resisting frames
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Building types - ATC-20 C Concrete moment resisting frames C Concrete shear wall buildings C3/S5 Conc/steel frame w/urm infill walls TU/PC1 Tilt-up concrete wall building PC Precast concrete frame buildings RM Reinforced masonry buildings URM Unreinforced masonry building Mobile Homes & Manufactured Units Firefighters are more used to terms as defined in Building Construction for the Fire Service by Francis L Brannigan A comparison is given in the manual The next series of slides gives a quick overview of the characteristics of each bldg type. Instructor needs to cover this relatively quickly, just so all understand each type. Following this, we will look at the Collapse patterns of the various bldgs Try not to get too bogged down in detail at this point Apr09

20 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Problem Buildings W 1 & 2 1 to 3 story houses & 2 to 4 story Apartments (especially pre 1970) S Frames w/brittle welded conns S Frames where column capacity is less than capacity of diag braces S Light structure vulnerable to Wind C1/C3 Pre 1971 bldgs (espec pre 1941) PC2/TU Factory built precast & tilt-up wall URM to 8 story (most 3 story & less) + steel & conc frames w/URM infill Mobile Homes & Manufactured Units Others Irregular - soft story, open front Be brief – Will be discussed in detail in Collapse Patterns Section Most URM have been removed or retrofit in Cal Say a little about Irregular structures vs dynamics of Earthquake Will illustrate each ATC Type in following slides Mobile Homes & Manufactured Units have been added, since they are discussed in Quake & Wind Collapse Patterns Apr09

21 Wood Houses W1 Moment Frame
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Wood Houses W1 Some sort of roof truss is common Platform framed w/ Skin (sheathing) & Bones (2x framing) Brick chimneys are hazards Be sure to move swiftly through these Bldg Characteristics slides. You will be able to spend more time in Collapse Patterns section on the weakness of each type. If you spent time discussing collapses, you will be duplicating the Collapse Pattern Section Does everyone understand wood systems? Platform framing vs balloon framing ? Problem in EQ is Dynamic incompatibility Brick Chimney +Soft - weak crawl space Skin & Bones, Box structure Bones = Vertical Load system Skin = Lateral load system Wind effects poorly engineered / tied Note picture of Simpson Strong Wall cantilever moment frame for garage and other openings with only narrow walls Moment Frame Apr09

22 W 1 & 2 Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Aspects Many walls create redundant structures w/ significant overstrength, generally ductile failure modes, depending on sheathing type. Combinations May be built above R/C parking garage Frequently used for interior partitions in residential and commercial masonry structure Refer to Manual unless questions Apr09

23 Wood Houses Under Construction
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Wood Houses Under Construction In California In Texas Example of wood frame construction CA construction requires most wood structures to be sheathed with plywood or OSB Note picture of Simpson Metal Strong Wall – use for porch posts Moment Frame Apr09

24 Wood Houses under Construction After 50mph wind
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Wood Houses under Construction After 50mph wind In California In Texas (Lateral load Sys ?) Example of the need to install some sort of lateral bracing system, even during construction. The CA house dod well due to the ply shtg The Texas house had only a very few wall diagonals, which were not effective w/o the finish material Apr09

25 Hurricane Rita Storm Surge Damage (Grand Chenier, on Louisiana Coast
Many houses with fiberboard sheathing were swept away One house remained, Plywood Sheathing (under brick veneer)

26 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Wood Frame Apartments W-2 Those w/ wood framed, soft 1st story are most vulnerable Multi story wood have enough mass to collapse in EQ Especially if have concrete floor fill Apr09

27 3 Story Wood Apartments (also 4 story)
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Over Conc Parking 3 Story Wood Apartments (also 4 story) Over Weak st Story Parking Larger wood structures The 3 story w/weak story parking is more problematical for Quake & Wind (because of the change in strength & stuffiness at the lower story), than the 3 story over concrete slab (in the upper picture). The concrete slab and first story concrete shear walls are stiffer than the upper wood stories, which is good Apr09

28 Mobile Homes & Manufactured Units
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Mobile Homes & Manufactured Units Mobile Homes in large neighborhoods Units remain mobile w/ wheels attached Usually supported on jack stands Compact interior spaces Usually have utility connections May contain propane tanks Portable Classrooms Interconnected units, each with one open side Usually supported on temporary foundation Larger interior spaces, semi-permanent Better structure usually with moment frame supporting open side Mobile Homes and Manufactured Units are used through-out the US, and are unique, very light structures. Larger units are used for temporary classrooms and for construction offices. Their connection to their foundations (if any) are very important Apr09

29 Mobile Homes/Mfr’d Units- Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Mobile Homes/Mfr’d Units- Characteristics Structural Systems Very light, metal covered walls on steel base frame Supported on jack stands or temporary foundations Typical Occupancies Residential, classroom, office Key Performance Aspects Performance of box structure is dependent on connection to base (25ga. Straps w/ staples = poor 16ga. w/ screws = better) Base frame needs adequate connection to ground Awnings, etc are very vulnerable Combinations More than one unit may be interconnected to form larger space As noted these structures may be used many occupancy types, but their basic characteristic is that they have been made as light as possible in order to be transported efficiently Most are up to 8ft wide, due to highway limitations They may be used in pairs to form a 16ft wide space, or many may be connected together to form a larger space Apr09

30 Portable Classrooms – Seismic design
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Portable Classrooms – Seismic design Low profile, near ground w/tiedown Steel moment frame each unit at 8ft o.c. Thicker walls/roof CA Schoolhouse temp structures are designed to resist earthquakes, and are carefully reviewed by State Building Officials. These have much better connections at their bases Apr09

31 Temporary Office – for 30 years?
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Temporary Office – for 30 years? 8ft wide units make 16ft x 40 ft space Jack stands may eventually rust-out Example of how poorly connected modular units may become almost permanent structures . Apr09

32 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Steel Moment Frame S1 Most common floor: Conc fill on metal deck System requires no walls - just infill Floors usually conc fill over metal deck Exterior walls may be falling hazards, Glass, masonry veneer and PC conc panels Exterior walls systems: Precast Concrete or GFRC Masonry Infill or over metal studs Window-wall Systems Apr09

33 S1 Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes S1 Type Characteristics Frame System Heavy Structural Steel (hot rolled sections) Typical Occupancies Office & Commercial, Industrial, Highway bridges 2 to 100 stories Key Performance Aspects Normally 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 Poor performance of heavy ext walls Apr09

34 Moment Frame Under Construction
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Moment Frame Under Construction New, Improved Joints Completed building in back with PC panels Frame in front Typical of past Northridge Quake , reinforced joints Apr09

35 Being repaired following Loma Prieta EQ
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Steel Frame w/URM Many of this type in SF and other older sections of cities Falling hazards, difficult to recognize, sometimes Being repaired following Loma Prieta EQ Apr09

36 Steel Diag. Braced Frame S2
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Steel Diag. Braced Frame S2 Same Floor and Exterior Wall Systems as S1 Bldgs Explain system Any ? Apr09

37 S2 Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes S2 Type Characteristics Frame System Heavy Structural Steel (hot rolled sections) Typical Occupancies Office & Commercial, Industrial, 2 to 30 stories Key Performance Aspects Normally well-engineered; Members very ductile. Overall performance dependent upon connections and proper proportioning of column strength Combinations Precast or CIP concrete floors w/ or w/o metal deck Masonry, precast or metal curtain walls Exterior precast walls may perform badly Performance depends on having strong enough columns to resist all forces that diagonals can deliver Apr09

38 Steel Diag. Braced Frame S-2
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Steel Diag. Braced Frame S-2 2 Story Retail Over Conc Parking Typical examples The diagonals shown on the outside of the wall for the 5-story are actually hidden below the finish. They are shown here to illustrate this type of system 5 Story Office Bldg Apr09

39 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Light Metal Building S3 Roof Systems: Metal deck on steel purlins with Steel Trusses or Frames Wall Systems: Metal sheathing on steel framing or Masonry Infill or on metal studs Describe system - any? Not much problem in EQ - can get some local buckling at connections of X rods Often damaged by Wind - Later Weakest link behavior As simple as no rubber grommets on screws that attach metal panels Missile penetration also problem Apr09

40 S3 Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Aspects Highly engineered Little redundancy or overstrength; very flexible Combinations May have wood or light gage metal interior partitions and mezzanine Masonry, precast, tilt-up or metal int./ext. walls Lightly engineered, Light Buildings Apr09

41 Typical 1-story S3 building
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Typical 1-story S3 building Typical Connections Hurricane Iniki Typical building and connections Apr09

42 Concrete Moment Frames C1
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Concrete Moment Frames C1 Concrete floor systems URM Infill PC Walls Explain system - no walls required Need lots of rebar ties & hoops to keep concrete around longitudinal bars to allow ductile behavior. Not until 1970s Explain Tension followed by Compression causing explosive failure of poorly confined moment resistant joint URM infill can cause unplanned stiffness that leads to failure Apr09

43 C1 Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes C1 Type Characteristics Frame System Heavy Floor Structure - CIP Non-ductile Reinf Conc CIP Ductile Reinf. Conc., CA & WA post 1980 Typical Occupancies Office & Commercial, Highway bridges 2 to 30 stories Key Performance Aspects Non-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 Combinations Various types of infill & partitions = C3 Type Don’t read the slide, Students have it in their manuals Just highline the Key Performance Aspects Apr09

44 C1 w/ Brick Infill Mexico City
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes C1 w/ Brick Infill Mexico City C1 w/ Clay Tile Infill = C Santa Monica Sea Castle Top Typical Mexico City waffle slab/Concrete column frame with infill at property lines Emphasize that this is INFILLED frame. Infill is needed for fire separation but not usually helpful to performance during Quake, Wind and Blast. This structure actually had a significant collapse at it’s interior stair & elevator Bottom CA version of masonry infill frame. Hollow clay tile. This bldg has been torn down. Others like it have had clay tile replaced by metal studs & plaster Apr09

45 Concrete Shearwall Bldgs C2
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Concrete Shearwall Bldgs C2 Wood or concrete roof systems Concrete floor sys CIP concrete walls C.I.P walls & floors - up to 13 stories or so Best performance in EQ and WIND than most other structures. (including Wood and Steel) Any ? About system ? Apr09

46 C2 Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Aspects Excellent quake, windstorm, blast & fire resistance Special 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 Don’t read the slide, Students have it in their manuals Just highline the Key Performance Aspects Apr09

47 Concrete Shearwall Bldgs C2
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Concrete Shearwall Bldgs C2 12-story, Alaska EQ NASA Ames Alaska bldg = very badly damaged wall piers, but did not collapse 2 of these 12 story buildings were damaged in 1964, and are still in service today EQ was originally rated as M8.4, but has been upgraded to 9.0 since it was actually a series of 3 large quakes. The NASA Ames building is typical of many government bldgs. It has resistance to most extreme forces Apr09

48 Precast Concrete Bldgs PC2
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Precast Concrete Bldgs PC2 PC roof, floor, & walls May have concrete topping on floor May have concrete walls Discuss Frame type systems & Box type systems Very strong parts, but must be connected well to survive EQ Frame type is usually not redundant Box systems have performed much better, since they have so much redundancy Apr09

49 PC2 Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes PC2 Type Characteristics Frame System – (Residential Bearing Wall Sys) Precast Concrete columns, beams & slabs May have CIP floor fill in CA & WA Residential usually have PC bearing walls Typical Occupancies ( 1 to 12 stories) Parking Garages, Office, Residential, & Commercial Key Performance Aspects May have highly engineered prestressed systems – especially Parking Garages. Brittle connections with little reserve strength Bearing 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. Don’t read the slide, Students have it in their manuals Just highline the Key Performance Aspects Apr09

50 PC-2 Armenia Apartments
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes PC-2 Armenia Apartments Parking Garages (Common in U.S.) Top Poor example from Armenia – Infill walls – PC Frame – very poorly tied together Bottom PC Parking Garages have performed poorly, and some have collapsed during construction. In CA most have CIP conc topping to tie floors together (some have failed due to being too thin to hold rebar). In east no topping is used, and structures have performed badly Apr09

51 Post Tensioned Lift Slab Bldg (see Manual for comment)
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Post Tensioned Lift Slab Bldg (see Manual for comment) Special type of structure with many potential problems Potential punching shear problem if any joint rotation PT slabs with no beams No need to discuss in most classes This type of construction is no longer built in the US, but one collapsed in Bridgeport, CT during construction in 1988 and one in Anchorage in 1964 Quake Apr09

52 Tilt-Up Wall Buildings TU
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Tilt-Up Wall Buildings TU May have metal deck roof on steel joist in some areas Trusses on older buildings Glulam Beams since 1960 Plywood roof sheathing on 4x purlins or 2x joist Explain system & basic Wall to Roof connection problem Walls are usually plenty strong Move to following slides Concrete walls are usually cast on site: mostly 6” thick Apr09

53 TU Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Aspects Robust wall panels dependent upon diaphragms for out-of-plane support. Wall/diaphragm connection vulnerable – Retrofit in CA Combinations Light frame or steel joist diaphragms Lt wt. concrete floor fill in multi story buildings Don’t read the slide, Students have it in their manuals Just highline the Key Performance Aspects Apr09

54 Tilt Up 1 Story Lt. Industrial Most Common Light Roof 24’x60’ Bays
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Tilt Up 1 Story Lt. Industrial Most Common Sample of 1960s TU 1 story – Office/Sales room in front and warehouse in rear Light, long-span roof framing Performance will depend on Wall-Roof connection Discussed in detail under Collapse Patterns Light Roof 24’x60’ Bays Heavy Walls Apr09

55 TU 2 Story Office Large TU – Home Supply Stores
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes TU Story Office Large TU – Home Supply Stores Framed Steel Roof & Lots of Storage Racks Sample of 2 story office type – harder to recognize Many large retail stores are TU Apr09

56 Types of URM Buildings Brick bearing wall buildings -
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 & roof Tie Beam/Tie Col is currently used in Florida May also have vertical bars at edges of openings Explain each type – Brief Note CMU Tie beam, Tie Column currently being built in FL, and we will be reviewing a hurricane collapse of one during the Collapse Pattern Part Apr09

57 Types of URM Buildings UR or Under-reinforced Brick cavity walls.
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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. Be brief, and ask for questions Apr09

58 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes URM Bearing Wall Bldg Straight or diag.1x roof sheathing Wood roof trusses Heavy timber floor systems in older buildings Very common type URM walls wood floors Any questions There will be much discussion later regarding collapse patterns Note that most URM building in CA have been retrofit to provide survivability, but there may be thousands of this type in the Central US Earthquake Region Apr09

59 URM Type Characteristics
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Aspects Brittle with little capacity to resist unanticipated loads. Numerous interior walls may prevent floor collapse Combinations Heavy timber, light frame or steel joist diaphragms, with concrete floor fill in multi story buildings. Don’t read the slide, Students have it in their manuals Just highline the Key Performance Aspects Apr09

60 Brick Bearing Wall Bldg
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Brick Bearing Wall Bldg URM Should be Retrofit if in CA CMU-Tie Beam/Tie Col Top Common type URM red-brick walls w/ wood floors This one has been retrofit w/wall anchors and interior shear walls Bottom (make sure all understand what CMU means) Modern CMU – Tie Beam/Tie Column bldg in FL w/wood roof. Following Hurricane Charley – not all survived like this one. Collapsed version later in Collapse Patterns CMU Currently Built in FL Apr09

61 Review Key Learning Points
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Review Key Learning Points The Student should be familiar with the following Basic Engineering Concepts Brittle vs. Ductile Materials Vertical & Lateral Loading Systems Framed and Un-Framed Structures Redundancy Building Characteristics Review these important concepts Brittle vs Ductile Framed vs Unframed Redundancy All should understand what is ment by each of the building types Apr09

62 Structural Collapse Technician Training
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Structural Collapse Technician Training Module : 1c Structural Engineering Systems Part 2- Causes of Collapse Changes to 2007 SCT01c Now there are now 5 Parts. The number of slides has been reduced from abt 500 to 300 Part 1 Basic Struct Sys & Bldg Characteristics Part 2 Causes of Collapse Part 3 Collapse Patterns Part 4 Hazard Assessment w/ optional Case Study Part 5 US&R Strategy & Size-up The new sequence is intended to save time and reduce some of the duplicate discussion of Collapse Patterns during the description of Bldgs and the Collapse Pattern Section. Hopefully, you will like this improvement Many slides have been combined and some have been added or changed for more contemporary incidents Feb08 Apr09

63 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 structure Wind Blast Fire Need to understand how Quake Aftershocks will effect US&R Operations – Need to Plan for them Apr09

64 Earthquake Basics Extent of damage is determined by
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 disaster Just keeps on giving May want to explain Harmonic response now or - little later – using the vibrating balls on different length piano wires is usually remembered Don’t get hung up on how Magnitude is defined - Energy release is approx. 30x greater for each whole number increase in Magnitude. What it means to US&R is that size of Incident is related to Mag. Nice to know, but it already happened by time US&R gets there Aftershock is much more important - defined later Apr09

65 Aftershocks Smaller quakes that occur on same fault as original quake.
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 original Some 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. Aftershocks may Collapse structures & will effect US&R We MUST plan for them Apr09

66 How Many Aftershocks ? USGS - Rule of Thumb If original quake is M 7
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes How Many Aftershocks ? USGS - Rule of Thumb For every single decrease in magnitude, get 10 fold increase in number If original quake is M 7 1 or so aftershock in range of M 6 “ “ “ “ 5 “ “ “ “ 4 “ “ “ “ 3 Have fewer as time passes Day 2 = 1/2 as many as day 1 Day 3 = 1/3 as many as day 1 Day 4 = 1/4 as many as day 1, etc Very approximate 1 or so could mean 5 10 or so could mean 50 Fewer w/ time, but no guarantee that a big one will not occur the day after a previous big one Nice to know this, but US&R must plan for a big one Apr09

67 1989 Loma Prieta Aftershocks
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 1989 Loma Prieta Aftershocks Magnitude There were no large aftershocks,M 6 or so Just lucky This gives good graphical picture of concept Days after original shock Apr09

68 San Andreas Fault Trace Fault is 5 + km deep
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes World Map of E.Q Faults Keep it short Circum Pacific Belt caused by rotating Plate EQ also occur elsewhere Inset shows Fault Trace, easy to see from the air for San Andreas, but many faults are very difficult to see Northridge Fault was not even known to exist San Andreas Fault Trace Fault is 5 + km deep . Apr09

69 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Large Offset shown in Creek Bed This is due to creep over centuries, not one quake Fault Trace Point out bend in Creek caused by fault movement over centuries This is not an offset from just one earthquake, but the total movement over centuries. In New Zealand, part of the South Island has moved up to the North Island over many centuries Creek Bed Offset Apr09

70 Earthquake Loading Quake Motion Produces Forces in Buildings
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Earthquake Loading Quake Motion Produces Forces in Buildings Force = Mass x acceleration Explain Harmonic response -use balls if not done previously Earthquakes produce Motions – Response in structure & ground beneath produces Forces Explain Load Distribution - higher parts of building move further, therefore generate more force More the more weight, the more Force Generated Acceleration of the bldg causes Lateral Force Example of Accel Effects = sit in Car, push on Gas, your head snaps back due to accel. Then quickly put on breaks, your head snaps forward, due to deceleration. You have created the effects of E.Q motion Apr09

71 Damage to Heavy, Weak URM
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Damage to Heavy, Weak Buildings Damage to Heavy, Weak URM Emphasize that Earthquakes produce motions, (Accelerations) not direct forces. The forces that are generated in buildings depend on its weight and response to the motion. The heavier the bldg the more force is generated by the Acceleration Heavy & Weak is very bad Common damage to URM Heavy, Weak = much collapse Also shows damage to heavy, brittle concrete bldg Apr09

72 Damaged to Under-Engineered Wood
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Damaged to Under-Engineered Wood Stucco w/o Good Sheathing Top Un-engineered wood No plywood or Diag Shtg However did not collapse – redundant and light Bottom Quake effects heavy, brittle veneer on flexible wood bldg - incompatibility Brick Veneer on old Wood Sheathing Apr09

73 KOBE Severe Damage due to Near Fault Effects
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes KOBE Severe Damage due to Near Fault Effects Top Near Fault effects Large Pulses as initial rupture passes Bottom Far field effects, usually tall bldgs on soft soils MEXICO CITY Harmonic, Far Field Effects Apr09

74 Quake Effects Bldg & Contents
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Quake Effects Bldg & Contents EQ shakes everything within buildings as well Storage racks are especially vulnerable. If they are bolted down, they may not turn over, but if contents are not restrained, they will fall Apr09

75 Wind Loading Force is proportional To speed squared
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Wind Loading Force is proportional To speed squared Force from 100mph = 4 times from 50mph Similar to EQ for tall bldgs Uplift pressures are different than EQ Here heavy structure is helpful, but brittle is still bad Basis of design is Elastic Most important for wind to be prevented from entering structure envelope Apr09

76 Hurricanes Winds 75 to 175mph + Missiles
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Hurricanes Winds 75 to 175mph + Missiles Discuss how to wind pressure increases proportional to the Square of the Speed Best example is with the 2x speed = 4x force. Increase from 100mph to 125mph = 60% inc in Force A 150mph wind produces 4 times the force of a 75mph wind Significant damage starts to occur around 125mph Missiles + Storm surge can be significant problems However, Usually have warning Almost opposite from quakes – here lighter bldgs do poorly and heavier ones do better. Much Damage to Light Structures Apr09

77 Hurricane Storm Surge Force of Moving Water
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Hurricane Storm Surge Force of Moving Water Example of significant damage to even concrete structured due to Tidal Surge Apr09

78 Tornado - winds to 250mph little warning
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Tornado - winds to 250mph little warning Can have very high winds and little warning for a specific area Hardened building shelters are the best defense Again a 250pmph wind produces 4 times the force of a 125mph wind Apr09

79 Mile Wide Path OKC-1999 44 Dead 795 Injured 3140 Destroyed Bldg
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes OKC Dead 795 Injured 3140 Destroyed Bldg Mile Wide Path This very destructive Tornado produced extensive damage to a fairly broad area. Apr09

80 2001 Kansas Tornado Path of Destruction
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 2001 Kansas Tornado Path of Destruction Unbroken Window In Tornados, most of the houses in Path are destroyed and many trees are uprooted or shredded One will often see some houses that are just at the edge of the Tornado's path. The roofing and top of chimney are gone, but the main structure remains Apr09

81 Explosion Basics Explosion is chemical reaction involving:
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Explosion Basics Explosion is chemical reaction involving: Rapid expansion of Gas Liberation of Heat Explosion 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) See Encyclopedia for more information This and next 2 slides give “Nice to Know” info. May wish to refer students to Manual and move quickly Apr09

82 Explosion Basics Low Explosive (or Propellants)
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Explosion Basics Low Explosive (or Propellants) Deflagration (rapid burning) results when a combustion zone proceeds from the ignition point at less than speed of sound Black Powder, Rocket Fuel, Flammable Gas, Dust If Low Explosives are confined they can Detonate Detonations vs Deflagrations Detonation pressures usually much higher Deflagration duration is normally longer If collapse is not initiated, effects of Detonation can be more localized Explain High Order vs & Low Order Explosive, speed of shock wave, detonation vs deflagration (study encyclopedia prior to class) May want to refer to Manual Apr09

83 Explosion Effects Rapid release of Energy Shockwaves (Pressure Wave)
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Structures Diffracts, creates both amplifications & reductions Short 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 Rapid conversion of energy to heat, light (fireball) + shock wave Shock wave causes most damage to structures Interior explosion damages structure as shock wave builds up and eventually escapes/dissipates Small gas caused explosion may fail only one column, but lead to progressive collapse Apr09

84 Interior Explosion Loading
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Interior Explosion Loading Devastating effect on structures may be mostly caused by Uplift Pressures (anti-gravity) especially to gravity designed, concrete bldgs Prestressed concrete may be the worst Blast effect surfaces of structures, especially undersides of gravity designed conc slabs. Steel beams & columns may survive Apr09

85 Interior Explosion Light Frame
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Interior Explosion Light Frame Interior Explosion Concrete Frame Quickly cover these effects now Will discuss in detail in Collapse Patterns Apr09

86 Interior Explosion - WTC, Flat Slabs
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Interior Explosion - WTC, Flat Slabs Lift pressure of shock wave very bad for concrete slabs Move on Apr09

87 Exterior Explosion Loading
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Exterior Explosion Loading over pressure over pressure spherical shock wave Explain: Spherical shock wave Initial reflected pressure Over pressure Drag forces reflected pressure drag over pressure stand-off Apr09

88 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes The video file needs to be in same directory as PPT This video shows the formation of a shock wave from explosion at rocket fuel plant next to Marshmallow Factory. Look closely during the Slow-motion clip (following original) You can see the roof of the Marshmallow Plant at the left of main explosion ripple as the Shock Wave Passes Apr09

89 Exterior Explosion Loading
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Exterior Explosion Loading A Exterior walls, columns & windows Roof & Floor slabs B Successive Loading of structure - in milliseconds Also mild EQ Frame C Ground shock Apr09

90 Exterior Explosion Murrah Bldg
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Exterior Explosion Murrah Bldg Horrific example, discussed later Crater & E Q Apr09

91 Fire Effects on Steel Structures
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 reduced Deflected 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% These are the effects of fire on steel structures. They all have caused failures The next slide will expand on this It is suggested that the instructor reads Building Const for the Fire Service, Brannigan, Ch 7. There is also some info in the AISC Steel Manual At 10000F, both Yield Point and E are reduced 50% All should order the FEMA sponsored Report 403, WTC Building Performance Study Apr09

92 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Effects of Fire – Expansion (10 “ in 100 ft) Can cause restrained connections to fail Can destabilize columns Expansion is especially a problem in structures where restraint is provided by in plane, shear walls or very rigid columns. Connections may be broken or anchor bolts may be pulled out of concrete or sheared off Expansion can also push out perpendicular walls Note that concrete also expands at similar rate, but is a greater heat sink Apr09

93 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Effects of Fire – Loss of Rigidity Catenary forces can cause connections to fail and can destabilize columns Deflected floor can warn of collapse These tension forces can fail connections or if the connections are strong enough, the columns can receive destabilizing horizontal forces Expansion can occur first, pushing the structure out, and then above 8000 F or so when the catenary is formed the forces may be reversed The good news is that the deflected floor will serve as a warning of potential collapse Apr09

94 Heat Effects on Steel Strength
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Heat Effects on Steel Strength You may need to explain the table in detail Comment on how the strength raises initially, but then drops rapidly Apr09

95 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Effects of Fire – Strength Loss Can lead to floor collapse and eventually collapse columns Floor members and connections fail much more often than columns, see next slide Apr09

96 Effects of Fire – Strength Loss
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Effects of Fire – Strength Loss Worst effects on Joist, Beams, & Girders Heat Concentrates and is Trapped on Horizontal Surface Less effect on Columns Usually have some Protective Covering Columns are thicker members Heat dissipates into Continuous Column Sections in Floors, Above & Below Members with small cross-section and large surface (like members in trusses and bar joist) heat-up the fastest, and are most likely to suddenly collapse The good thing about continuous columns is that they will conduct heat away from the fire area. (this may also be a bad thing and cause fire spread) Apr09

97 Building Code Fire Resistive I.D.
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Building Code Fire Resistive I.D. Type 1 - Non-combustible Construction 4-hour Exterior Walls Structure 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 May 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 This slide is presented in order to make sure that all are familiar with the Building Code ratings for varies types of construction, since they ate referred to in the following slides Apr09

98 Fire Effects on Steel Structures
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 hours One Meridian Plaza, Philadelphia, 1991, 19 hours (11 hours uncontrolled) Interstate Bank, L.A., 1988, 4 ½ hrs MGM Grand Las Vegas, 1981, 11 hrs Multi-Helicopter Rescue from Roof Changed Fire Protection Requirement See manual for discussion regarding past experience with Type 1 buildings and unprotected buildings The first 2 buildings mentioned are discussed in Report 403 Apr09

99 Fire Effects on Steel Structures
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Fire Effects on Steel Structures Unprotected Steel Building problems Long span, low rise truss and bar joist structures had spectacular collapses McCormick 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 & Arenas High School to Professional The McCormick Pl is discussed in Brannigan, Ch 7 (previously mentioned) Apr09

100 Collapse of WTC - 7 Fire started at about 1000hrs
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Collapse of WTC - 7 Fire started at about 1000hrs FDNY abandoned fire suppression by 1200hrs Sprinkler system ineffective due to break in water main Design 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 collapse Building imploded – stayed within its own footprint Instructor should become familiar with this collapse See FEMA Report 403 First Type I Steel Fireproofed High Rise to ever collapse due to Fire Apr09

101 Collapse of WTC - 7 Collapse Observations Potential Problems
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Collapse of WTC - 7 Collapse Observations East Penthouse disappeared first West 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 & gal fuel, “Day Tanks” - on 5th, 7th, 8th & 9th floors Some Generators & Tanks were near Trans Trusses Fuel from tanks or broken pipes MAY have contributed to the fire – DISPUTED BY RECENT REPORT The combination of 3 transfer trusses (3 main columns stopped at 8th fl) near the Day Tanks that were fed by a total of 4200 gals from below was a very bad configuration The generators would have turned on when the power was cut and even if a Day tank or supply pipe was ruptured, the oil could have continued to be pumped to the area and fed the fire Video on next slide shows the Penthouses dropping out of sight first Collapse scenarios are discussed in Report 403 There was a report released in 2008 that disputes the claim that the burning of the fuel in the oil tanks was the main reason for the collapse Apr09

102 From the Northwest East West
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes East West Collapse of WTC-7 You may need to toggle off your laptop monitor and show this only on the LCT projector. To do this hold down Fn key along with F6 , F7,or F8 depending on your laptop If your laptop has a 163meg or more video card, you may not need to toggle off the monitor Point out that the interior of the building collapses first, which supports the theory that it was started by the collapse of the transfer trusses that supported columns, just above the area were the Day Tanks were From the Northwest Apr09

103 WTC 1 & 2 Effect of Aircraft Impact
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 One can clearly see that 1/2 of the columns on this face of Tower 1 were non functional Fireproofing was spray-on type Airplane fuel was probably dissipated within the first 10 minutes, but it provided for ignition of the building’s contents Collapse of WTC 1 & 2 were slightly different, see Report 403 Apr09

104 FEMA US&R Response System Structural Collapse Technician Training
Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Collapse of WTC – 1 & 2 Redundancy permitted structure to resist initial damage Load re-distribution highly stressed many elements Reduced lateral support for other highly stressed elements Fire effects Further increase stresses due to expansion Caused failure of some connections Weakened highly stressed elements Once collapse initiated, debris weight on lower floors caused progressive collapse Information is based on report by the World Trade Center Report, sponsored by FEMA, Report 403 Tower structures were Exterior Tube/Frame w/ interior, “vertical load only” columns around the stair/elevator core Core walls were only gypsum “panel wall” Apr09

105 Fire Effects on Other Structures
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 thru 1999 Bldg’s with Lt. Steel Trusses have collapsed suddenly Furniture Warehouse in 2007 – 9 Firefighters killed Type 5 Bldgs – Wood Walls & Wood Roof Many have Attics w/Light Wood Framing (1x & 2x) Same Problem of Intense Attic Fires Usually less Collapse Issue due to many walls Still has Deadly Potential Roof framing with any type of wood trussed, especially when concealed by a ceiling, is a sudden collapse threat during a fire. This has been well documented by NFPA Roof burn-out in Heavy Wall buildings is another common occurrence. Stability of the exterior walls is a significant problem – see manual for discussion Fire can cause structural damage to concrete buildings from spalling of concrete and expansion Apr09

106 Worcester Fire Dec99 Burnout caused 6 story unbraced walls
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Worcester Fire Dec99 Burnout caused 6 story unbraced walls Very bad fire in old Cold Storage Warehouse 6 Firefighters were trapped and killed. 2 got trapped and lost and the remaining 4 were lost as the roof collapsed on the R.I.T. Walls w/o openings caused very fast burning of old wood floor, due to chimney effect MATF-1 sent Struct Spec, Riggers and Search to help Brick walls were monitored by Theodolites as Search using K9 found bodies of trapped firefighters. They also partially cut down parts of the URM walls away from the corners to reduce collapse potential Apr09

107 Refer to Manual for Following
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes Refer to Manual for Following Damage by Floods Storm Surge & Tsunami Landslide, Mudslide, Debris Avalanche Construction Bracing, Overload Vehicle Impact Loading Students need to review this on their own in order to reduce time of presentation Apr09

108 Review Key Learning Points
FEMA US&R Response System Structural Collapse Technician Training Module 1 c Structural Eng Sys Part 5- Instructors Slides + Notes 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 Review and answer any questions Apr09


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