Comments on L'Ambiance Plaza Lifting Collar/Shearheads

Abstract

The writer is engaged by the Occupational Safety and Health Administration (OSHA) to study the National Bureau of Standards (NBS) report on the L'Ambiance Plaza Building collapse and develop supplemental information for its use in legal proceedings. The study includes a review of the design of the lifting collar/shearhead assemblages. The paper is a summary of that review and the, writer's interpretation of subsequent evidence. Copies of design calculations and contract drawings are studied. In the paper, the absence of consideration of the effect of the lifting conditions on stresses in the arm channels in these calculations is noted. Questionable design details for welds connecting lifting angles to arm channels and header bars to header channels are also noted. The faulty condition of some of these welds as shown by lifting collar sectioning is illustrated. Evidence presented after the negotiated settlement of November 1988 reinforces the writer's finding that any of these deficiencies, and particularly the combination of unwise welds poorly executed, could have resulted in the initiation of the collapse. Recommendations for further investigation of these deficiencies are presented.