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Progressive Collapse

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Dept. of Civil and Environmental Engineering. Princeton University. Presentation Outline ... Progressive collapse occurs when a key member, or members of a ... – PowerPoint PPT presentation

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Title: Progressive Collapse


1
Comparing progressive collapse due to fire in
differing structural systems.
Mark Dobossy Graduate Student Dept. of Civil and
Environmental Engineering Princeton University
2
Presentation Outline
  • Progressive Collapse and Homeland Security.
  • Case Study The Bankers Trust Building.
  • Overview of the research.
  • Initial Results.
  • Where do these results lead us?

3
What is Progressive Collapse?
  • Progressive collapse occurs when a key member, or
    members of a structure fail.
  • The isolated failure of this key member or
    section then initiates a sequence of events,
    causing failure of the entire structure.
  • Current U.S. building codes contain few
    provisions as to designing with progressive
    collapse in mind.

4
H.S. and Progressive Collapse
  • In many situations, an attack on a structure
    initiates catastrophic progressive collapse.
  • Both the World Trade Center, and the Murrah
    Federal Building failed in a progressive manner.
  • In the wake of the many IRA bombings in England,
    the English Building Code was changed to include
    progressive collapse provisions. (Ronan Point)
  • Currently Embassys and some Government Buildings
    are the only U.S. structures to have strict
    progressive collapse and blast provisions.

5
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

Map of Bankers Trust location.
6
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

A photo of the BT Building
7
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

A photo of the BT Building
8
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

A photo of the BT Building
9
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

Bankers Trust floor plan. Bays highlighted.
10
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

Bankers Trust floor plan. Bays highlighted.
11
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

Bankers Trust floor plan. Columns highlighted.
12
Bankers Trust Specs
  • Location 130 Liberty St.
  • Owned by Deutsche Bank.
  • Built in 1974.
  • 40 stories tall.
  • Moment frame system.
  • Each bay 26 wide.
  • 7 bays x 7 bays.
  • Central group of columns off-center.

Bankers Trust floor plan. Columns highlighted.
13
Bankers Trust September 11th
  • Bankers Trust was in debris field of collapsing
    tower 2.
  • Sustained substantial damage from falling debris.
  • Load bearing column removed from 18th down to 8th
    floor.
  • No fires, and no progressive collapse.

Aerial shot of BT, Sept 17, 2001.
14
Bankers Trust September 11th
  • Bankers Trust was in debris field of collapsing
    tower 2.
  • Sustained substantial damage from falling debris.
  • Load bearing column removed from 18th down to 8th
    floor.
  • No fires, and no progressive collapse.

Second floor lobby.
15
Bankers Trust September 11th
  • Bankers Trust was in debris field of collapsing
    tower 2.
  • Sustained substantial damage from falling debris.
  • Load bearing column removed from 18th down to 8th
    floor.
  • No fires, and no progressive collapse.

Damage to load bearing column.
16
Bankers Trust September 11th
  • Bankers Trust was in debris field of collapsing
    tower 2.
  • Sustained substantial damage from falling debris.
  • Load bearing column removed from 18th down to 8th
    floor.
  • No fires, and no progressive collapse.

Shot of surviving BT building.
17
Bankers Trust
  • The survival of the Bankers Trust building left
    several questions
  • What areas of the buildings design helped to
    prevent progressive collapse?
  • Would the structure have performed significantly
    different if it were a different structural
    system?
  • How would the building have performed if fires
    had occurred (as in WTC 7)?
  • What can we take from this design to decrease
    risk of progressive collapse in other structures?

18
Research Summary
  • Redesign the structure using three different
    structural systems.
  • Moment frame.
  • Moment frame with braced core.
  • Simple frame with braced core.

19
Research Summary
  • Redesign the structure using three different
    structural systems.
  • Moment frame.
  • Moment frame with braced core.
  • Simple frame with braced core.

Moment frame model.
20
Research Summary
  • Redesign the structure using three different
    structural systems.
  • Moment frame.
  • Moment frame with braced core.
  • Simple frame with braced core.

Moment frame w/ braced core model.
21
Research Summary
  • Redesign the structure using three different
    structural systems.
  • Moment frame.
  • Moment frame with braced core.
  • Simple frame with braced core.

Simple frame w/ braced core model.
22
Research Summary
  • Different codes are also being tested for each
    structural system.

Wind Code NYC Code Calif. Code
MF X X X
MF-BC X X
SF-BC X X
23
Program Overview Input
  • Step 1 Requests and receives data on structural
    geometry.
  • Step 2 Randomized explosion generated and
    applied to structure.

24
Program Randomized Explosion
  • Randomized explosion is generated using three
    random variables.
  • Resulting fires and heat field are then imposed
    on the structure.

X3
X2
X1
Explosion generation.
25
Program Overview Fire Model
  • Step 3 Sends signal to fire progression module
    to progress the current state of the fire.
  • Step 4 Checks time step. If not at time step
    for structural check, progresses fire again.

26
Program Overview Structure
  • Step 5 Checks members for failure. If a member
    has failed, initiate progressive collapse module.
  • Step 6 Check for structural survival. If
    structure has failed, output data. If not, check
    fire.

27
Results Obtained
  • Simple Frame fails long before others (60 min)
  • MF-BC fails next (160 min)
  • Moment Frame survives longest (200 min)

28
Impact of Results
  • This research will aid in the development of easy
    to use design provisions for progressive
    collapse.
  • It will also help to identify current structures
    at high risk, and will aid in developing
    effective retrofits.
  • Finally, it will help in the placement of sensors
    throughout a structure, by identifying key weak
    areas throughout the system.

29
Conclusions
  • The prevention or delay of progressive collapse
    in large buildings is an important area to
    strengthen in our current infrastructure.
  • Initial results indicate the need for more
    redundancy in how structures are designed.
  • There is still much to be learned from this
    research, which may change the way buildings are
    designed.
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