collapsed building

8/2/2019 Collapsed Building

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Building Structure

&Types of Collapse


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STRUCTURE ELEMENTS

Columns

vertical structural members ofa building

Beams horizontal structural members

of a building

Combination of columns andbeams form the frame of thebuilding


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STRUCTURE ELEMENTS

A beam is supported by oneof three methods

cantilever beam - supported

or anchored at one end only

continuous beam - supportedat both ends and at the center

simple beam - supported atboth ends


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STRUCTURE ELEMENTS (cont)

Wall (load bearing)

wide column

carry the dead

weight of building

Floor

horizontal elementsfor creatinguseable space


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STRUCTURAL BUILDING TYPES

Unframed Building Partially Framed

Fully Framed Monolithic Building


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BUILDING MATERIALS

Timber

commonly used in early 19th century

Brick

usually in columns and walls

Stone

older buildings


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BUILDING MATERIALS (cont)

Reinforced concrete

structural concrete with steel reinforcement

Structural Steel

facilitate quick erection of frame


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LOAD

Loads = forces acting upon astructure

Dead Load

weight of building itself andequipment permanently attached

eg. walls, floors, columns, girdersa. concentrated load

b. distributed load


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LOAD (cont)

Live Load any load other than dead load

buildings content

e.g. furniture, humans Axial Load

force that passes thru the center

of a structure

most efficient way by which aload can be transmitted thru a

structural support like a columnor bearing wall

can withstand greatest load


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LOAD (cont)

Eccentric Load (off-centered)

off-centre, perpendicular to planeloading

when structural elements shifted slightly

common in partial collapsed ordamaged buildings

Torsional Load (twisting) load that creates a twisting stress on a

structural members

Both can cause a collapse


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STRESS

Stress = force exerted upon astructural member that strains ordeforms its shape

Compression

a force pressing or squeezing a

structure together


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STRESS (cont)

Tension stress placed on a structural member

by a pull of forces causing extension

Steel is strong in compressive andtensile strength

Concrete is strong in compressivebut weak in tensile strength

Rope is strong in tensile strength

& has no compressive strength


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TYPES OF

COLLAPSE PATTERNS

Lean over

a wood-frame building can collapse to one side

Lean to (Supported)

support at one end of structure member gave way,and that end collapse

triangle shape void


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Cantilever Collapse (Unsupported Lean to)

unstable

support at one end of horizontal member gaveway, but that end is suspended

secondary collapse likely

TYPES OF

COLLAPSE PATTERNS (cont)


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V-shaped Collapse

integrity of horizontal member fails due toexcessive load

collapse of a floor at the center of the floor beam

void at either ends

large scale or localised

TYPES OF



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Pancake Collapse

when floor beams pull loose or collapse at both

ends

small voids created by strong supporting objectsbetween floors

extensive searching

use of natural opening e.g. stairwell provide quickaccess

TYPES OF



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EXAMPLES OF

PANCAKE COLLAPSE


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Curtain Fall Collapse

occurs when a masonry wall (stone wall) dropslike a falling curtain cut loose at the top

Chain Reaction Collapse excessive impact loading caused by collapse of

higher floors resulting in failure of lower floors

Inward/Outward Collapse

wall breaks apart horizontally

rotational collapse

TYPES OF



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90 Collapse

failure of bottom of

vertical support,causing the elementto fall straight outand the top strikingthe floor

similar to a fallingtree

TYPES OF



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EARTHQUAKE COLLAPSE

PATTERNS

This 2500-car-capacity parking structure, a 1991addition to the Cal State University - Northridge

campus, suffered partial collapse in the intense

shaking of the Northridge earthquake. A close-up of

of this entrance to the parking structure shows the

closely spaced fractures in the reinforced concrete

columns which allowed "bending" of the outer wall

6th floor of a 8-story high office

building collapsed. A high rise

building near the damaged building is

hardly affected.


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MORE PICTURES

Buckling of freeway support columns under the

Simi Valley Freeway at the north end of the San

Fernando Valley. This buckling shows thestructural failure produced by high vertical

acceleration.

Examples of ground floor collapse due to

inadequate design in vertical support


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POOR BUILDING RENOVATION

& URBAN DECAY

Gravity loading cause collapse of verticalsupport due to:

inadequate design

overloading

reduction in capacity due to age, corrosion or non-engineering alteration

May occur after a building that suffered aninitial collapse left standing


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WARNING SIGNS OF

STRUCTURAL COLLAPSE

Movement in floor or roof

Sponginess

Sagging or bulging walls

Columns and walls out of plumb

Beams twisted out of alignment

Cracks appearing

Creaking and groaning noises

Unable to close doors and windows


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VOIDS

Spaces created when building or structurecollapses

May contain trapped victims

Depend on:

type of collapse

presence of large or heavy objects


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STRUCTURAL COLLAPSE

HAZARDS

Ask these questions before proceeding withrescue:

structure?

occupancy?

HAZMAT?

storage area?

Adjacent structures affected?

Utilities affected and isolated?

5 types of structural collapse hazards


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HAZARDOUS MATERIALS

Examples:

chemicals

dust

radioactive materials

biological hazards

pressure cylinders

asbestos

Seek information


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SURFACE HAZARDS

Examples:

rough terrain

moving and falling debris

sharp objects

flooding

holes in floor

hanging objects

Personal protection

Movement with care


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BELOW DEBRIS HAZARDS

Examples:

flooded basement

oxygen deficient atmospheres

toxic environment

Clear egress

Ventilation


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DAMAGED UTILITIES

Examples:

live electrical wires

ruptured gas lines

broken water mains

broken sewer systems

Isolate as early as possible

Dont assume, always check


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STRUCTURAL STABILITY

Constantly monitored and reviewed

Shore damaged structures before enteringand commencing S&R

Eyes and ears open


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CONCLUSION

Understanding stability of collapsed/partiallycollapsed structure is an ART and SCIENCE:

intuition

logical assessments

NEVER be hasty when operating in collapsedbuildings

Make safe before proceeding


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collapsed building

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