Presentation1.ppt
L’Ambiance Collapse
Group 15
David Lawlor
Emma Quinn
Daniel O’Sullivan
Cian O’Sullivan
Introduction
Bridgeport, Connecticut
April 23, 1987
Sixteen-story building, Thirteen apartment levels, topping three parking levels
Consisted of two offset rectangular towers
Elevator
Design
Seven inch thick posttensioned, concrete slabs
Steel columns comprised its Structural Frame
Lift-Slab method of construction
Hydraulic lifting apparatus used to put slabs into position
Two shear walls in each tower – Lateral
Resistance (except top two floors)
Collapse
Building little more than halfway completed
First the West Tower, then the East
Took five seconds for entire building to collapse
28 construction workers died in collapse
Unusually prompt legal settlement ended all investigations
Consequently – the exact cause of the collapse has never been established
Number of deficiencies – which was the trigger?
Theory 1
National Bureau of Standards (NBS)
“An overloaded steel angle welded to a shearhead arm channel deformed, causing the jack rod and lifting nut to slip out and the collapse to begin”
Theory 2
Thornton-Tomasetti Engineers
“The instability of the wedges holding the twelfth floor and roof package caused the collapse”
Theory 3
Schupack Suarez Engineers Inc
“The improper design of the posttensioning tendons caused the collapse”
General Layout of Posttensioning
Theory 4
Occupational Safety and Health
Administration (OSHA)
“Questionable weld details and substandard welds could have caused the collapse”
Theory 5
Failure Analysis Associates (FaAA)
“The sensitivity of L’ambiance Plaza to lateral displacement caused its collapse”
Wedged Slab-to-Column Connection
Other factors contributing to disaster
Gross negligence on part on management
Variations in control of lifting operations
Cutting corners to save money (use of broken rock fill under certain footinginstead of direct bearing on rock)
Building regulations not adhered to for innovative “lift-slab” method
Conclusions
Insure lateral stability and safety during construction when using lift-slab method
Responsibility for each aspect of design should be clearly allocated
Ensure a high standard of structural safety during construction by constant monitoring by engineer
Independent Engineers from building authorities to check progress
