A portion of a building under construction at the headquarters of the Federal Government Communications Affairs Office collapsed during concrete-slab pouring.
On the afternoon of October 21,2018, in Arat Kilo the collapse affected one-third of the total 600sqm construction area of the four-basement and two-storey building. The structure is expected to be used as an auditorium and is designd to host a gym, showroom and offices in addition to a multi-purpose hall with the capacity that holds more than 340 people.
"The concrete was being poured and consolidated with a vibrator when the form-work suddenly collapsed," said Alem Amare of Yohannes Abay Consulting Architects & Engineers, the on-site consultant and designer of the project. The consultant was paid eight million Birr for the services.
After the collapse, the city's Fire & Emergency Prevention & Rescue Authority received a call at 1:10pm, and ambulances and a firetruck were sent.
Fifteen workers were rescued from the second storey where they were pouring concrete slabs. Six workers were sent to Mahatma Gandhi Memorial and Black Lion hospitals for minor injuries and released.
To carry out an investigation into the collapse of the building, a committee chaired by Construction Design and Supervision Enterprise and composed of the city's Construction Permit & Control Authority and Construction Bureau was formed. The project's owner, Government Housing Construction Project Office, the consultant and the contractor, Tekleberhan Ambaye Construction, were also made part of the committee.
The owner of the project directed Fortuneto the consultant to answer all our inquiries regarding the collapse of the building.
The consultant Alem Amare reported that the investigation focused on identifying the cause of the collapse, quantifying the damage and the ways forward. The committee concluded that the causes were a combination of unequal load distribution on the upper part of the slab and the form-work; an alignment problem with the form-work; and pressure induced by the concrete compactor.
When the consultant was asked by Fortuneon how the project consultant and contractor can be made part of the investigative body of the collapse, he responded by stating that since there was no criminal intent or corruption their participation was deemed acceptable.
The committee, which arrived at its conclusions after a week of deliberation, found no fault in the design or the construction and implementation methods of the project, according to the consultant.
The total cost of the damage was estimated to be between 150,000 Br to 200,000 Br by the consultant. This estimate is in sharp contrast to estimates reported by the contractor.
The contractor assumes responsibilities for all temporary-use constructions such as form-work, which is typically designed by the company's in-house engineers, according to the contractor's Deputy, CEO Goitom Wolde Gabriel.
"Some mistakes were made during the design phase of the form works," he said.
He relates that the company's engineers failed to account for lateral loads emerging out of the sloped nature of the building design, which rises from 3.5m to 15m in elevation. Apparently, the load that the poured concrete exerted on the form-work far exceeded its design capacity.
In addition, he reported that some pins, used to support the form-work as its height increases, were found missing from the structure.
"It will cost us around 750,000 Br," said Goitom, a much higher estimate than what was reported by the consultant.
The responsibility goes to the contractor who designed and constructed the form-work, according to Goitom.
However, the consultant too has the duty and responsibility to inspect and approve the work prior to authorizing concrete pouring.
"We have evaluated the situation internally and with the investigation committee together," he said. "And we will take it as a lesson for future construction."
The headquarters, which will cost 1.2 billion Br when completed, rests on a 14,000sqm plot and will consist of a 16-storey building with four basement floors for parking, a workshop, a generator house and a garage.
Abebe Dinku (Prof), a civil engineer and a university lecturer with over three decades of experience, stresses that the fault squarely lies on the shoulders of the consultant and the contractor.
"Negligence is the source of such problems," he related. "Form-works must be well designed for all load and stress factors before installing them."
He said that the contractor should install the form according to the specifications and drawings of the construction plans. The consultant is responsible for inspection, approval and signing off on the form-work installation prior to pouring the concrete, according to him.
Getaneh Terefe, who has more than three decades of experience in civil engineering, echoes a similar analysis.
"The contractor and the consultant should have approached the sloped nature of the auditorium because the loads distribute vertically and horizontally at the same time," he says. "This is in contrast to the flat slab which the load will only exert force vertically."
There have been 30 construction-related fatalities in the last three years, while 112 people have received minor and serious injuries.
These numbers represent only officially registered cases, while many others go unreported to the authorities, according to Negatu Mamo, public relations officer at the Fire Authority.
Currently, the form-works are being rebuilt, and debris and dried concrete from the collapsed building section are being cleaned up.