Comparing progressive collapse due
to fire in differing structural systems.
Mark Dobossy
Graduate Student
Dept. of Civil and Environmental Engineering
Princeton University
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?
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.
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 Embassy’s and some Government
Buildings are the only U.S. structures to have strict
progressive collapse and blast provisions.
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.
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
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
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
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.
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.
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.
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.
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.
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.
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.
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.
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?
Research Summary
• Redesign the structure
using three different
structural systems.
– Moment frame.
– Moment frame with
braced core.
– Simple frame with
braced core.
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.
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.
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.
Research Summary
• Different codes are also being tested for
each structural system.
Wind Code
MF
X
NYC Code
X
Calif. Code
X
MF-BC
X
X
SF-BC
X
X
Program Overview: Input
• Step 1: Requests and receives data on
structural geometry.
• Step 2: Randomized explosion generated
and applied to structure.
Program: Randomized Explosion
X2
X3
X1
Explosion generation.
• Randomized explosion
is generated using
three random
variables.
• Resulting fires and
heat field are then
imposed on the
structure.
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.
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.
Results Obtained
• Simple Frame fails long before others (~60 min)
• MF-BC fails next (~160 min)
• Moment Frame survives longest (~200 min)
Simple Frame - Braced Core
Moment Frame
Moment Frame - Braced Core
12
12
10
10
8
8
14
12
6
Frequency
Frequency
Frequency
10
6
4
4
2
2
8
6
4
2
0
0
40
50
60
70
Bin
80
More
130
140
150
160
Bin
170
180
0
180
190
200
210
Bin
220
230
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.
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.