Collapse of 2000 Commonwealth Avenue: Punching Shear Case Study

On January 25, 1971, two thirds of a 16-story apartment building collapsed while under construction at 2000 Commonwealth Avenue, Boston, Massachusetts. Four workers died after a failure on the roof instigated a progressive collapse all the way to the basement, where the men were found. Fortunately, the collapse occurred slowly enough for most of the other workers to run to safety. An investigation, conducted by a commission assembled by the Mayor of Boston, painted a picture of a troubled project, with considerable confusion about responsibility for structural safety. The surviving workers’ descriptions of the failure provide a textbook definition of punching shear. Low concrete strength due to inadequate protection against cold weather contributed to low punching shear strength of the flat slab. Inspection, quality control, planning, and supervision were for all practical purposes absent from the project. This paper investigates the numerous causes and lessons learned of this structural failure. Two similar cases are also reviewed.