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Short-DurationDynamics

EXPLOSIONEXPLOSION DAMAGE ASSESSMENT DAMAGE ASSESSMENT

PROF. TED KRAUTHAMMERThe Pennsylvania State University

First Structural Forensic Engineering Seminar onSTRUCTURAL FAILURE INVESTIGATIONS

University of Toronto11-12 January 1999

PennState

OUTLINE

• PROBLEM DEFINITION

• BACKGROUND

• DAMAGE ASSESSMENT TECHNIQUES

• COMPUTATIONAL SUPPORT

• EXAMPLES

• SUMMARY AND CONCLUSIONS

PROBLEM DEFINITION

HOW TO USE EXISTING KNOWLEDGE IN SUPPORTOF:

– EFFECTIVE EXPLOSION DAMAGE ASSESSMENTS.

– CORRELATING DAMAGE WITH POSSIBLE CAUSES.

– ASSESSING THE REMAINING STRUCTURAL CAPACITY.

PROBLEM (Cont.)

TERRORISM

ACCIDENTS

MODERN EXPLOSION DAMAGEASSESSMENT - HALIFAX 1917

6 DEC. 1917: SHIP COLLISION WITHA FRENCH MUNITIONS CARRIER INHALIFAX HARBOUR.

2766 T OF VARIOUS EXPLOSIVES.

OVER 2.5 KM_ OF HALIFAX'SINDUSTRIAL N END WAS TOTALLYLEVELLED. THE BLAST SHATTEREDWINDOWS 100 KM AWAY, AND WASHEARD IN PRINCE EDWARD ISLAND.

1600+ PEOPLE DIED, 9000 INJURED,200 BLINDED BY FLYING GLASS.1600 BUILDINGS DESTROYED,12,000 DAMAGED. TOTAL DAMAGEUS$35 M.

PROBLEM (Cont.)

BUREAU OF ALCOHOL TOBACCO AND FIREARMSU.S.A. CRIMINAL INCIDENTS DATA

1989 - 1993 1991 - 1995

BOMBING INCIDENTS 7,716 8,506

(ATTEMPTED) (1,705) (2,078)

INCENDIARY BOMBING 2,242 2,468

(ATTEMPTED) (557) (782)

DAMAGE (M US$) 641.3 1,257.3

BACKGROUND

• BLACK POWDER HAS BEEN USED FORSEVERAL HUNDRED YEARS.

• HIGH EXPLOSIVES HAVE BEEN USED FORABOUT ONE HUNDRED AND FIFTY YEARS.

• NITROGLYCERINE (1862) - IMMANUEL NOBEL.

• DYNAMITE (1875) - ALFRED NOBEL.

• NUCLEAR EXPLOSIVES (1945).

BACKGROUND (Cont.)

EXPERIENCE: ACCIDENTS, MILITARY

CONFLICTS AND TERRORISM.

CIVIL WAR, 1861 - 1865 RUSSIA - JAPAN, 1905

WWI, 1914 - 1918 WWII, 1939 - 1945

KOREA, 1950 - 1953 VIETNAM, 1964 - 1975

MIDDLE EAST, 1947 - INT. TERRORISM, 1960s -

CONVENTIONAL NUCLEAR

CHEMICALS AND FUELS. NUCLEAR ACCIDENTS.

VAPORS. NUCLEAR WEAPONS.

COMBUSTIBLE DUSTS.

PRESSURE VESSELS.

EXPLOSIVES.

HIGH EXPLOSIVES.

EXPLOSIVE LOAD SOURCES(MILITARY AND CIVILIAN)

EXPLOSIVE LOAD SOURCES (Cont.)

NUCLEAR DEVICESS

• YIELDS: KILOTONS (TACTICAL), OR MEGATONS(STRATEGIC) OF TNT EQUIVALENT.

• RELEASE LARGE AMOUNTS OF ENERGY(RADIATION, THERMAL, BLAST, EMP, ETC.) IN~1µsec, AFFECTING VAST AREAS.

CONVENTIONAL EXPLOSIVE DEVICES

• YIELDS: ~<1 KG TO ~>15 TONS OF TNT QUIVALENT.

• RELEASE SMALLER AMOUNTS OF ENERGY(BLAST, FRAGMENTS, ETC.) IN ~ 2µsec AFFECTINGSMALLER AREAS.

EXPLOSIVE LOADS (Cont.)

EXPLOSIVE LOADS (Cont.)

EXPLOSIVE LOADS (Cont.)

EXPLOSIVE LOADS (Cont.)

EXPLOSIVE LOADS (Cont.)

EXPLOSIVE LOADS (Cont.)

EXPLOSIVE LOADS (Cont.)

200 300 400 500 600 700 800 900 1000 1100 1200

TIME (ms)

0

500

1000

1500

2000

2500

3000

PR

ES

SU

RE

(kP

a)

LOAD COMPARISONS FOR TYPICAL WEAPONS

Mk 84 100m - INCIDENTMk 84 100m - REFLECTED15 KT - INCIDENT15 KT - REFLECTED1 MT - INCIDENT1 MT - REFLECTED

EXPLOSIVE LOADS (Cont.)

200 220 240 260 280 300 320 340 360 380 400

TIME (ms)

0

10

20

30

PR

ES

SU

RE

(kP

a)

LOAD COMPARISONS FOR TYPICAL WEAPONS

Mk 84 100m - INCIDENTMk 84 100m - REFLECTED

TECHNICAL RESOURCES

CONVENTIONAL AND NUCLEAR WEAPONSEFFECTS ARE WELL DOCUMENTED.

NUCLEAR CONVENTIONAL

EARLY: DOD, 1957 NDRC, 1946

RECENT: ASCE, 1985 TM 5-855-1, 1986

Schuster et al., 1987 ESL-TR-87-57, 1989

TM 5-1300, 1990

CONWEP, 1992

TECHNICAL DIFFICULTIES

• LOAD DEFINITION: P(x,y,z,t) .

• MEDIUM - STRUCTURE INTERACTION.

• NONLINEAR DYNAMIC STRUCTURAL BEHAVIOR:

– GEOMETRIC.

– MATERIAL.

• STRUCTURE - CONTENTS INTERACTIONS.

• CONTENTS’ SURVIVABILITY (OR FRAGILITY).

• DAMAGE DEFINITIONS.

MANY OF THESE ISSUES ARE NOT WELL DEFINED !

COMPUTATIONAL SUPPORT FORDESIGN AND ASSESSMENT

• WEAPON EFFECTS CALCULATIONS.

• CLOSED-FORM SOLUTIONS.

• SDOF, MDOF (SIMPLE AND ADVANCED).

• STRUCTURAL MODELS (BEAM, PLATE, ETC.).

• ADVANCED TOOLS (FE, FD, HYBRID, ETC.).

• SYMBOLIC AND SYMBOLIC-NUMERIC TOOLS.

SDOF RESPONSE CALCULATIONS

F(t)

M

K or R(x)C

SDOF RESPONSE CALCULATIONS

T / Tn

Xm /

XeFigure 3-54. Maximum deflection of elasto-plastic,one-degree-of-freedom system for triangular load

0.1 1.0 10 1000.1

1.0

10

100 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

0.9

1.0

1.2

1.5

2.0

Numbers next to curves are Ru/P

PRESSURE - IMPULSE DIAGRAM

• STRUCTURAL RESPONSE DEPENDS ON td/T

td = DURATION OF THE APPLIED LOAD

T = NATURAL PERIOD OF THE ELEMENT:

T = 2PI/OMEGA, OMEGA = (K/M)0.5

• THREE BEHAVIORAL DOMAINS:

td >> T td << T td ~ T

PRESSURE - IMPULSE DIAGRAM

1/[XMAX (KM)0.5]

2F /

(KX

MA

X)

DAMAGE ASSESSMENT ANDSCALED RANGE

DIFFERENT EXPLOSIVE EVENTS CAN BE COMPARED WHENUSING THE CONCEPT OF SCALED RANGE:

λ = RW1 3/

8 = SCALED RANGE.

R = DISTANCE IN FEET OR METERS.

W = EQUIVALENT TNT EXPLOSIVE WEIGHT, IN POUNDSOR KG.

DAMAGE CAN BE RELATED TO SCALED RANGE.

DAMAGE ASSESSMENT FOR FRAMES

DAMAGE ASSESSMENT FOR SLABS

DAMAGE CRITERIA

ELEMENTTYPE

MATERIALTYPE

TYPE OFFAILURE

CRITERIALIGHT

DAMAGE

MODERATEDAMAGE

SEVEREDAMAGE

Beams ReinforcedConcrete(ρ>1/2%/face)

GlobalBending/MembraneResponse

Ratios ofCenterlineDeflection toSpan, ∆/L

4% 8% 15%

Shear Average ShearStrain acrossSection, γv

1% 2% 3%

Steel Bending/Membrane

∆/L 5% 12% 25%

Shear ∆/L 2% 4% 8%

Slabs ReinforcedConcrete(ρ>1/2%/face)

Bending/Membrane

∆/L 4% 8% 15%

Shear γv 1% 2% 3%

Columns ReinforcedConcrete(ρ>1/2%/face)

Compression Shortening/Height

1% 2% 4%

Steel Compression Shortening/Height

2% 4% 8%

oad BearingWalls

ReinforcedConcrete(ρ>1/2%/face)

Compression Shortening/Height

1% 2% 4%

Shear Walls ReinforcedConcrete(ρ>1/2%/face)

Shear Average ShearStrain AcrossSection

1% 2% 3%

ADDITIONAL DAMAGE CRITERIA

DAMAGE VS. SUPPORT ROTATIONS

FOR BEAMS AND SLABS

SUPPORT ROTATION DAMAGE

(DEGREES)

< 2 LIGHT

2 TO 5 MODERATE

5 TO 12 SEVERE

OBSERVED STRUCTURAL DAMAGE

DAMAGE ASSESSMENT

SITECONDITIONS

BACKRAOUNDDATA

EXPERTASSESSMENT

MEASUREMENTSNUMERICALANALYSIS

POSSIBLECAUSE

POSSIBLECAUSE

POSSIBLECAUSE

DETERMINECAUSE

POSSIBLEEFFECTS

POSSIBLEEFFECTS

POSSIBLEEFFECTS

DETERMINEEFFECT

ADVANCED DAMAGE ASSESSMENT

INVESTIGATOR

INTELLIGENT INTERFACE

EXPERT SYSTEM

DESIGNMANUALS

ANDSUPPORT TOOLS

NUMERIC FACILITIESAND

COMPUTER CODES

TEST ANDOPERATIONSDATA BASE

SIGNAL ANALYSIS

SENSORDATA

TOA

A

THE OKLAHOMA CITY BOMBING

19 APRIL 1995

THE EXPLOSIVE CHARGEWAS ESTIMATED BASED ONCRATER DIMENSIONS.

~4000 lbs. TNT EQUIVALENTPLACED ~14 ft. FROM THEBUILDING, 4.5 ft. ABOVEAN 18-in.-THICK PAVEMENT.

EXTENSIVE DAMAGE, FAREXCEEDING WHAT WASSHOWN IN TYPICAL NEWSREPORTS.

THE OKLAHOMA CITY BOMBING

5 6 7 8 9 10

TIME (MS)

0

200

400

600

800

1000

1200

1400

PR

ES

SU

RE

(P

SI)

BLAST LOADING ON COLUMN G24

FRONT

REAR

3 4 5 6 7 8 9 10

TIME (MS)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

LA

TE

RA

L D

EF

LE

CT

ION

(I

N.)

DYNAMIC RESPONSE OF COLUMN G24 AT MIDHEIGHT

FAILURE

DIFFERENTIAL PRESSURE BETWEEN THE FRON AND REAR OFCOLUMN G24 CAUSED ITS FAILURE 3.75 MILLISECONDS

AFTER THE BLAST ARRIVAL.

THE OKLAHOMA CITY BOMBING

DIFFERETIAL UPWARD PRESSURE ON 5TH FLOOR SLAB CAUSEDITS FAILURE LONG AFTER THE BLAST LOADS DIMINISHED.

7 8 9 10 11 12 13 14 15 16 17 18 19 20

TIME (MS)

0

20

40

60

80

100

120

140

160

PR

ES

SU

RE

(P

SI)

BOTTOM

TOP

BLAST LOADING ON 5TH FLOOR SLAB BETWEEN COLUMNS 20 AND 22

0 100 200 300

TIME (MS)

0

2

4

6

8

10

12

DE

FL

EC

TIO

N

(IN

.)

SLAB FAILURE AT 183 MS (8.4 IN.)

PEAK DEFLECTION AT 284 MS (9.3 IN.)

5TH FLOOR SLAB RESPONSEBETWEEN COLUMNS 20 AND 22

THE OKLAHOMA CITY BOMBING

NUMERICALLY SIMULATED EFFECT OF RAPID COLUMN REMOVALON BUILDING BEHAVIOR (Crawford, 1996)

KHOBAR TOWERS - SAUDI ARABIA

EXTENSIVE DAMAGE TOPRECAST APARTMENTBUILDING.

EXPLOSIVE CHARGE WASESTIMATED BASED ONCRATER DIMENSIONS,GLASS BREAKAGE, ANDADVANCED SIMULATIONS.

KHOBAR TOWERS - SAUDI ARABIA

KENYA AND TANZANIA, 1998

PETROCHEMICAL EXPLOSIONS

SUMMARY AND CONCLUSIONS

EXPLOSIVE DAMAGE ASSESSMENT IS DIFFICULT.

EXPERIENCE: EXPLOSION MECHANICS AND EFFECTS

STRUCTURAL MECHANICS AND DYNAMICS

COMPUTATIONAL MECHANICS.

USE DATA TO DERIVE POSSIBLE CAUSE-AND-EFFECTRELATIONSHIPS, AND VALIDATE WITH NUMERICALSIMULATIONS.

ACTIVITIES COULD BE VERY TIME CONSUMING.

URGENT NEED TO DEVELOP INTELLIGENT EXPLOSIONDAMAGE ASSESSMENT TOOLS.