Comparing progressive collapse due to fire in differing

Presentation Outline • Progressive Collapse and Homeland Security. • Case Study: The Bankers Trust

What is Progressive Collapse? • Progressive collapse occurs when a key member, or members

H. S. and Progressive Collapse • In many situations, an attack on a structure

Bankers Trust: Specs • Location: 130 Liberty St. • Owned by Deutsche Bank. •

Bankers Trust: September 11 th • Bankers Trust was in debris field of collapsing

Bankers Trust • The survival of the Bankers Trust building left several questions: –

Research Summary • Redesign the structure using three different structural systems. – Moment frame

Research Summary • Different codes are also being tested for each structural system. Wind

Program Overview: Input • Step 1: Requests and receives data on structural geometry. •

Program: Randomized Explosion X 2 X 3 X 1 Explosion generation. • Randomized explosion

Program Overview: Fire Model • Step 3: Sends signal to fire progression module to

Program Overview: Structure • Step 5: Checks members for failure. If a member has

Results Obtained • Simple Frame fails long before others (~60 min) • MF-BC fails

Impact of Results • This research will aid in the development of easy to

Conclusions • The prevention or delay of progressive collapse in large buildings is an

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

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 with braced core. – Simple frame with braced core.

Research Summary • Redesign the structure using three different structural systems. – 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 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 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 MF-BC SF-BC NYC Code X X Calif. Code 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 X 2 X 3 X 1 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)

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.