Public‐Safety Issues in Collapse of L'Ambiance Plaza

Abstract

Investigations of the collapse of the partially completed L'Ambiance Plaza, a 16‐story residential project under construction in Bridgeport, Connecticut, revealed four major structural deficiencies that may have triggered the collapse, along with at least five other design or construction conditions that negatively impacted structural reliability. The major deficiencies were: improper drape of posttensioning tendons adjacent to elevator openings, overstressed concrete slab sections adjacent to two temporary floor slots for cast‐in‐place shear walls, overstressed and excessively flexible steel lifting angles during slab lifting, and unreliable and inadequate temporary slab‐column connections to assure frame stability. The existence of so many deficiencies in one project raises fresh concern whether public safety is being adequately protected in the U.S. system for design and construction of major buildings. This project used a design concept that transferred major design responsibilities to the contractor via performance specifications, permitted construction procedures that were not backed up by proof of adequacy for temporary conditions, and provided quality‐assurance measures that did not include adequate review by the engineer of record. These system deficiencies led to the collapse. Recommendations for improving U.S. regulatory and structural design practice to help avoid future disasters like L'Ambiance Plaza are given.