Design of Collapse-resistant Structures

8/12/2019 Design of Collapse-resistant Structures

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Uwe Starossek, Maren Wolff:Design of collapse-resistant structures

Hamburg University of Technology

Design of

Collapse-Resistant

Structures


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Uwe Starossek, Maren Wolff:Design of collapse-resistant structures 2/19


robustness

progressive collapse

structural integrity

alternate load paths

continuity

redundancy

Keywords

isolation

compartmentalization

specific local resistance


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progressive collapse

disproportion between local failure and resulting collapse

Some definitions

robustnessinsensitivity to local failure

collapse resistance

insensitivity to accidental circumstances


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measurements and observations

admissible probability of failure

probability density functions(actions, resistances)

reliability theory

societal consensus

design values(actions, resistances)

Inadequacy of current design methods


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structural resistance considered on local level only

(and not on system level)

accidental circumstances are neglected

(low probability events and unforeseeable incidents)

admissible failure probability cannot be specified

(risk of the type low probability / high consequence)


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dont rely on reliability theory

use deterministic methods for design purposes

Conclusion


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Design criteria


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depend on significance as to consequences of collapse

(immediate losses, impairment of infrastructure, civil defense, national defense)

depend on exposure to accidental circumstances

(hazards of war, malicious action, natural disasters)

high for public buildings, major bridges, lifeline structures

Requirements (necessity of collapse resistance)


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assumable extent of accidental circumstances

assumable extent of initial local failure

acceptable extent of collapse progression

acceptable extent of damage to remaining structure

applicable load combinations and safety factors

Design objectives


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prevent local failure (high safety against local failure)

specific local resistance of key elements

non-structural protective measures

presume local failure (design for load case local failure) alternate load paths

isolation by compartmentalization

prescriptive design rules

Design strategies


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Design strategies Examples

key element

modification of structural system strengthening of transfer girder

design for load case local failure

provide alternate load paths (= redundancy)


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Confederation Bridge, Canada

alternate load paths cannot be provided



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43421


insertion

of hinges


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insertion of

hinges

compartment borders must be able to sustain either largeforces or large displacements

reduction of continuity can lead to increase of robustness


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More examples


Pentagon Building Paris Airport Terminal

weak strong weak weak


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Murrah Federal Building Structural system

More examples


collapse stopped at rebar discontinuityin transfer girder


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A comparison

either less continuity or

more strength

more continuity,

more strength

properties of design

measures

large initial failuressmall initial failurespreferable for

noyessensitive toinitial failure size

at discrete locationsdistributed

over system

location of design

measures

alternate load paths compartmentalization


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collapse-resistant design should be based on

deterministic methods

specific local resistance, alternate load paths, and isola-

tion by compartmentalization are all viable design options

continuity redundancy robustness collapse resistance

Some conclusions

a complete set of corresponding design criteria should

be developed and implemented in the codes


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Thank you!

Design of Collapse-resistant Structures

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