SAISC feature times
By Amanuel Gebremeskel , Technical Director SAISC
We are lucky in South Africa that we have few natural hazards of such magnitude and frequency . However South African seismologists have identified two types of earthquakes that are likely primarily in the Western Cape and Gauteng areas .
Scientists have warned that central Italy faces a serious risk of suffering further devastating earthquakes soon . On August 24th there was a 6.2-magnitude earthquake near Amatrice that killed more than 250 people . This was followed by a 6.1 earthquake which struck Visso on 26 October . The latest series of quakes have forced over ten thousand people to seek refuge in hotels and shelters , with many more sleeping in tents , cars or campers .
We are lucky in South Africa that we have few natural hazards of such magnitude and frequency . However South African seismologists have identified two types of earthquakes that are likely , primarily in the Western Cape and Gauteng areas . While Cape Town sits on crust that is vulnerable to natural earthquakes of the Italian variety , the area around Johannesburg is vulnerable to earthquakes caused by mining activities .
Cities and other large settlements are most at risk to earthquake damage because of large populations and buildings . The likelihood of death , injury and economic loss is much higher in built-up areas also because of fire risks from damage to electrical and gas lines . For these reasons , the Steel Institute has taken a leadership role in pushing for standards that aim to reduce seismic risks to South Africans .
Basic provisions for the design of buildings and other structures to withstand earthquake loads have been available in the SANS codes since 1989 . However , compliance with the requirements has not been vigorously enforced by the authorities and owners over the past two decades . This is largely due to lack of awareness by design engineers and academics . In some cases , it has also been caused by scepticism about the level of seismic risk that exists in South Africa .
A forthcoming revision of SANS 10160-4 – Seismic actions and general requirements for buildings – addresses the omission of structural steel design provisions from the standard , as well as contradictions between SANS 10160 and SANS 10162 , the steel design standard . The proposed revision is based on the American Society of Civil Engineers standard . Relevant parts of ASCE 7 have been adapted for the new SANS standard .
A paper that is authored by Amanuel Gebremeskel of the Steel Institute – chair of the South African Bureau of Standards seismic committee – and Chris Roth of the University of Pretoria , who chairs the overall loading code committee , discusses the background to the proposed provisions . The paper has now been refereed and accepted by the SAICE journal for publication .
We urge our readers to get a hold of it and familiarize themselves with the new standard . It should help to manage risks in these seismic times .
Photo courtesy en . wikipedia . org
RIGHT : On August 24th there was a 6.2-magnitude earthquake near Amatrice , Italy , that killed more than 250 people .
6 Steel Construction Vol . 40 No . 6 2016