‘Closure of M2 is essential’

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Johannesburg - Mayor Herman Mashaba has unequivocally defended the closing of sections of the busy M2 motorway, saying the decision had to be made to protect the lives of residents. Mashaba was speaking during his State of the City Address last Tuesday. Experts said the bridges built in the 1970s are old and were not designed to service the city's current population. “Our bridge repair work has taken centre stage of late. With over 900 bridges and only 6% of them in good condition, it is no wonder that they are crumbling to the point of requiring emergency repairs. “Our work on the M2 is the clearest example of this. Causing major inconvenience to businesses and residents alike, we had to take the decision to shut down the M2 in order to protect the lives of our residents,” Mashaba said.

Mashaba announced the closure of sections of the highway, saying some of the bridges were simply too dangerous.

“I stood on that bridge, I felt the vibrations, and I saw first-hand the cracks in the supporting structures. There is no doubt that this was a life-saving and very necessary decision. The emergency repairs on this bridge are set to be finished by October this year,” he said.

The closures are causing traffic congestion which has forced motorists to use alternative routes, resulting in longer travel times.

Chris Campbell, chief executive of Consulting Engineers South Africa, said it was important to bear in mind that when the bridges were first designed, the country did not have the technologically advanced tools and technology to do modelling and simulation of the behaviour of the structure over time under varying load conditions.

“Even if one did, the output remains only as good as the input. Back then calculations for design were based on, at best, the most rudimentary computer systems coupled with manual calculations by specialist bridge engineers.

“In addition, we have to bear in mind that these bridges were designed at a time when South Africa was still steeped in an era where, for example, vehicle ownership and hence usage would have been limited to a sector of the population and projections on increased vehicle ownership and usage coupled with population growth and increased urbanisation probably did not and could not have factored in the exponential growth in vehicle ownership that would have and has taken place under a new government post-1994,” Campbell said.

Professor Yunus Ballim of the Construction Materials School of Civil and Environmental Engineering at Wits University said: “Our older structures were not planned for the rapid urbanisation that a city like Johannesburg has seen since the late 1980s. However, the current and future planning of the city should account for this through growth of infrastructure and the necessary road and bridge systems.”

Both Campbell and Ballim have emphasised the importance of maintenance.

“Bridge collapse of the deck and other supporting components could be the consequence of a complete failure to maintain such structures.

“With growing usage driven by population growth and increasing urbanisation, maintenance of such crucial infrastructure needs to be intensified to prevent such catastrophic failure which would lead to loss of life and injury, damage to property and huge costs which could have been better utilised for equally urgent service provisioning,” Campbell said.

The bridge in Kliptown Soweto is submerged under water more than 1 meter high. This being the worst flood in 15 years. Picture: Timothy Bernard

Campell said activities or acts such as vandalism that could compromise the integrity of bridges should not be tolerated.

“Furthermore damage to bridges caused by vandalism and fires under bridges, which can cause the relaxation of the steel reinforcing embedded in the concrete, should simply not be tolerated as both can cause weakening of the bridge structure and lead to fatal outcomes in the event of an untimely collapse of the bridge deck.”

The state of bridges within the City has been largely blamed on lack of maintenance by the previous ANC administration.

Ballim said: “While our national roads and bridges are generally in very good condition, there is serious deterioration of our road and bridge infrastructure at the local and provincial levels. This seems to be mainly due to lack of inspection, reporting and maintenance, largely due to a lack of capacity to undertake these tasks and then to effect the necessary repairs.”

Campbell agreed with Ballim on whether South Africa was doing a good job in terms of maintenance of roads and bridge systems in the country, saying it depended on who owns the road or a bridge.

“This answer will vary depending on the owner of that road or bridge. Generally, Sanral (SA National Roads Agency Ltd), which has jurisdiction over national roads and bridges on these national roads is doing a good job and has been doing so for some time. At local government level, this is less so for various reasons,” he said.

Campbell concurred, adding: “If one does not act timeously enough through maintenance interventions, the structural integrity of the bridge would become compromised. Maintenance is often a factor of construction quality, age, rate of wear, changes in the immediate environment that impact on the structure and usage.”