What we can learn from diseasters

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What we can learn from diseasters

Jerzy Pamin e-mail: JPamin@L5.pk.edu.pl

With thanks to:

LS-DYNA http://www.lstc.com

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Lecture scope

Some construction diseasters

Modelling World Trade Center diseaster

References

[1] Z.P. Bazant, Y. Zhou. Why Did the World Trade Center Collapse? - Simple Analysis. ASCE J. Eng. Mech., 128, 2-6, 2002.

[2] Y. Omika, E. Fukuzawa, N. Koshika, H. Morikawa, R. Fukuda.

Structural Responses of World Trade Center Collapse under Aircraft Attacks.

ASCE J. Eng. Mech., 131, 6-15, 2005.

[3] Z.P. Bazant, M. Verdure. Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions. ASCE J. Eng. Mech., 133, 308-319, 2007.

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Collapse of Sleipner A platform, Norway 1991

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RC off-shore platform, founded 82 m below sea level, composed of 24 cells with 12 m diameter (4 support deck)

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Cause of sinking: cracking and leakage of concrete base during

construction due to error in desing related to FEM computations of tricell - element connecting cells (shear force underestimated by o 47%) and insufficient anchoring of reinforcement in critical zone

Pictures from www.ima.umn.edu/∼arnold/disasters/sleipner.html

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Collapse of Terminal 2E of Paris Airport, 2004

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Terminal 2E of Paris Charles de Gaulle Airport is a composite tube-like shell structure, large span freely supported vaulted roof is weakened by many openings

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Designed by architect Paul Andreu (who also designed Terminal 3 at Dubai International Airport, which collapsed during construction), admitted to service in 2003

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Combination of causes: too small safety margin in design, probably also mistakes during construction and/or insufficiently good concrete

Drawings cited from www.equipement.gouv.fr

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World Trade Center diseaster

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Collapse of World Trade Center

Built in 1966-77, 110 storeys 3.7m height each, steel frame structure based on „tube in tubeśtructural concept, 26.5×41.8m core (47 columns connected by short beams, carried 60% of self weight), outre frame (240 box columns 356x356 every 1m along perimeter, carried 40% of self weight), composite floors supported on truss girders connected by hinges with the core and outer frame, hat trusses at levels 107-110 to connect perimeter and core columns. Building weight above ground 3630MN, self weight 2890MN, service load 740MN.

Escape time for WTC1 and WTC2 was 100 and 60 min., resp.

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Simplified mechanism of WTC collapse [1,3]

Dynamic effect of high temperature which lowered steel yield strength and caused column buckling under creep con- ditions

1. Structure is weakened at impacted face, fuel fire causes temperature increase to about 600C 2. Stress redistribution takes place, viscoplastic

buckling of columns occurs at critical level 3. Floor trusses sag, buckling of columns grows,

frame joints are destroyed, about half of the columns cease to carry the weight of the storeys above

4. The upper part of the building falls to the floor below with growing kinetic energy, the impact is a dynamic load which cannot be carried by the structure below and progressive collapse begins 5. The upper part falls, its mass and energy grow

gradually

Energetic estimation of over-load coeffi- cient:

P

_dyn

/mg = 30 − 60.

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Response of WTC towers to abnormal load [2]

Simplified dynamic model (110 beam elements) with lumped masses (flood weight 33 MN), bending and shear stiffness determined from the actual space frame model, 3% Rayleigh damping assumed.

What we can learn from diseasters