Material supplier Formscaff allegedly failed to provide adequate proprietary information about some of the elements of the temporary structure that collapsed onto the busy M1 freeway in October last year.
Two people were killed and several injured in the incident that took place around 15:25 on October 14 2015.
Without this information from Formscaff, the designer of the temporary structure could not have been able to meaningfully undertake a rigorous analysis of it to ensure the stability of the structure, civil engineer Richard Beneke told an enquiry into the event on Monday. Beneke has 40 years of experience in designing temporary works.
The Department of Labour is conducting the enquiry into the cause of the collapse, which will see testimony by among others contractor Murray & Roberts, Formscaff and the Johannesburg Development Agency that commissioned the construction of the bridge.
Beneke was appointed by contractor Murray & Roberts (M&R) to check the design after the event, an exercise usually carried out before construction, he said. He studied Formscaff’s drawings for this purpose and did not assess the actual way it was constructed.
Formscaff is expected to present testimony later this week about the status and purpose of the drawings.
Beneke said he detected nine instances of minor concern, 29 of inadequate information and 61 involving an element of structural risk on the drawings. He said the 61 instances of structural risk would result in a high risk of the structure collapsing due to wind forces, if constructed according to the drawings.
He said the connections between some of the major components were not sufficiently considered. The connections are important with regard to the transfer of loads from one component to another, he said. This alleged oversight could see the structure becoming unstable and collapsing, he said.
He said an experienced person with the necessary knowledge and skill, could have redesigned the structure to ensure its ability to carry the necessary loads.
He said with regard to industry practice, it was likely that a construction contractor would use the drawings for construction, as some contractors consider this normal practice. Formscaff however failed to add a clear and unambiguous warning on the drawings, stating that they should not be used for construction purposes, Beneke said.
In the light of industry practice there was a bigger responsibility on Formscaff to give clear and unambiguous instructions and clearly state the status of the drawings, Beneke said.
He said the person designing temporary works does not necessarily have to be an engineer, depending on the complexity of the structure. Different persons or teams of persons could do different aspects of the design, but it is important for each to supply the necessary information to the subsequent designer.
He said Formscaff did the design of several key components. Its designs and drawings however featured a large number of “unsatisfactory” aspects and it failed to provide the necessary information regarding its proprietary components.
He further pointed to an alleged design flaw in Formscaff’s ski-bracket, which he said a temporary works designer would not have been able to foresee.
He supported previous testimony disputing the findings by Australian engineer Amog, experts in collapse analysis, which investigated the matter on behalf of the scaffolding supplier Formscaff. Amog found bad workmanship by M&R resulted in under-tightening of swivel clamps. Beneke said it is normal practice in South Africa to tighten such clamps by hand with a normal spanner, without undue force and without using a torque wrench.
Amog did not take local conditions and practices in consideration in its report, he said.
Beneke described the language used in the Amog report as “emotive and disparaging” and said he was misquoted in the report in an apparent effort to distort the intention of his statements.
Beneke will be cross-examined on Tuesday.