Expert weighs in on integrity of buildings near Joburg explosion

Buildings near Lilian Ngoyi (formerly Bree) Street in the Johannesburg CBD are likely to have been affected by the explosion on Wednesday afternoon but the buildings' structural integrity depended on the foundations used.

This is the view of Prof Felix Okonta, head of geotechnical and pavement engineering research at the University of Johannesburg.

Speaking on Thursday, he said the explosion happened close to buildings  and "we can assume those vibrations affected them".

Okonta said the question was whether the buildings had the ability to absorb vibrations without suffering any form of structural damage.

Okonta said the buildings in the area were old and their ability to withstand vibrations depended on the foundations used during their construction.

He said there was a possibility some of the buildings had the simple shallow part foundations, while others had more robust basement foundations as used in shopping malls, moving to the more expensive raft foundations while others had pile foundations used in the construction of tall buildings such as Carlton Centre.

"These are not new buildings and are built on old specs. The brick and mortar system used may not be very modern."

Okonta said it would be good for a structural site investigation to be carried out to determine the ability of the buildings to manage vibrations.

"This should be done by investigators who are able to run tests. Such tests should include instrumentation to determine the ability of buildings to manage vibrations.

"They will run structural integity tests for vibration, for the ability of the structure to manage vibration and advise on ways to retrofit the buildings to ensure they remain stable," Okonta said.

Meanwhile, Gauteng premier Panyaza Lesufi announced the evacuation of several buildings close to the explosion site. 

He said the area had been deemed unsafe and that barbed wire would be unrolled to prevent access to the area. 

Lesufi said alternative housing had been provided for all those affected. 

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