A welding failure is the cause of the collapse of a crane in downtown Halifax during post-tropical storm Dorian, as per a new report from Nova Scotia’s Labor Department.
In its investigation, the department’s safety branch said a welded part around 6 to 9 meters above the base of the mast became separated as the crane was pummeled by wind gusts of up to 107 km/h on September 7, 2019.
The weld failure transferred “the weight supported by the mast’s four vertical posts to only three of its posts, causing the tower section to rotate and fail, which resulted in the total collapse of the crane,” according to the report.
The machinery, owned and operated by Lead Structural Formwork Ltd. of Moncton, N.B., fell onto a 13-storey building under construction on South Park Street, causing major damage to the top three levels.
A neighboring structure was additionally destroyed when the crane hit the top corner and a balcony. Counterweights from the tower crane fell to the street.
Localized state of emergency
Not a single person was injured in the incident, though the surrounding area, which is a mix of homes and businesses, had to be evacuated. Some businesses were forced to remain shut when their entrances became inaccessible, losing out on significant revenue.
The provincial government gave a localized state of emergency, saying the order was necessary to ensure the quick and safe removal of the machinery.
Nova Scotia covered the $2-million bill in an effort to get the job done as soon as possible and the area reopened to the public.
Work to safely remove the crane and debris from the struck building was completed on November 4, 2019.
Cranes meant to withstand stronger gusts
The report said the tower crane was a Manitowoc model Potain 8520Ps. Generally, cranes of this size are designed to withstand winds of 15—160 km/h. On the day of the storm, winds were recorded to be much lower with wind gusts of 97 – 107 km/h.
On June 4, 2019, Nova Scotia’s safety branch was advised by the general contractor that the turntable at the top of the tower crane had seized, preventing it from “weather vaning”, basically spinning freely in the wind when not in use.
The contractor informed N.S that the top section of the crane, consisting of the cabin, jib and turntable, would be repaired or replaced as soon as possible to deal with the inability to spin freely. The repair was made June 7, 2019.
Crane operator met requirements
The investigation determined Lead Structural Formwork met with the legislative and regulatory requirements to prevent the event from happening and no extra action would be taken with regard to the crane collapse.
Nova Scotia said recently the Department of Labour would meet with all crane owners and operators in the region, plus require that all tower crane masts be thoroughly cleaned, inspected and tested to identify any defects or potential deterioration.
Many businesses that were affected by the collapse have unveiled a proposed class-action lawsuit against WM Fares Architects Inc. and WM Fares & Associates Incorporated, the developer of the structure that was under construction when the tower crane fell, in an attempt to recover lost sales. The claim also names Lead Structural Formwork and the Manitowoc Company.