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Time to monitor bridges more closely – Dr Bakamwesiga

When Makerere University holds its next graduation ceremonies, in January 2018, HILARY BAKAMWESIGA will receive a PhD from the college of Engineering, Design, Art and Technology. He spoke to Moses Talemwa about the subject of his study.

On December 11, 2006, the bridge across the Mpologoma river in Pallisa collapsed, leaving travelers between Tirinyi and Mbale stranded.

Following the collapse, there was word that the bridge had been affected by environmental factors. Later, on May 24, 2010, the same bridge collapsed again.

This among other factors prompted Hilary Bakamwesiga to consider doing a PhD, looking at the vulnerability of bridges to environmental conditions. At the time, Bakamwesiga was teaching environmental science at Makerere.

“It was a tough decision as I would be getting out of my field to study civil engineering, among other things,” he says.

Dr Hilary Bakamwesiga

But he made up his mind and embarked on studies in 2011 with support from the Swedish International Development Agency and Lund University in Sweden.   

“I was supposed to look at how much the environment was affecting the condition of bridges … and here I was tasked to look at 22 bridges in various parts of the country.”

The bridges tested ranged from Ndaige bridge in Malaba; Katonga bridge in Mpigi; Mpanga in Fort Portal, to Kafu river bridge, as well as Kyanamira in Kabale.

During his extensive study, he was able to ascertain that Uganda’s bridges were largely well built, and there was little environmental impact to cause their collapse. However, he did discover other issues.

“I realized that there was no monitoring mechanism of the bridges in place, which is why I’m advocating for a computerized bridge management system,” he said.

“The observed flaws on highway bridges mainly constitute cracks, delamination, and spalls, abrasion and erosion of river banks, and heavy silting of river channels. These flaws become a big problem if not attended to appropriately and in time.”

In his thesis, Bakamwesiga advocates for a computerised bridge management system that would enable the Uganda National Roads Authority (Unra - which monitors bridges by informal means) to keep updated with the conditions of the bridges.

“That way they will be able to tell which bridge is in bad condition or which one to prioritize for repair or for rehabilitation or for replacement.

Bakamwesiga explains that the mechanism would work hand in hand with a conditional assessment of highways (on which the bridges are built).

“I visited 22 bridges and saw the damage types they have … some don’t have guard rails, some have cracks on top, some have their expansion joints exposed,” he explained. “I observed for example spoiling was on 9% of the bridges, overgrowth of vegetation was in 50%.”

For his work, Bakamwesiga developed a model for developing a priority index of all bridges in the country, that he hopes bodies like Unra would use to improve bridge monitoring and management.

The model, which is a series of algebraic equations, has proved effective so far.

“I fed this into the model and it was successful. Also, an engineer at Unra validated this model and his results have proven it to be just as successful, with marginal differences,” he reveals.

Asked for a comment on the innovation, Unra spokesperson Allan Ssempebwa Kyobe revealed that they welcomed Bakamwesiga’s innovation, although he admitted they had not formally been in touch with him.

“It is a very welcome innovation and it is something we are considering on the new Nile bridge, currently under construction,” he revealed. “We are calling it the structural health monitoring system, but which can be expanded to our other bridges, going forward.”

That comment is bound to put a smile on Bakamwesiga’s face, as well as the reality that he will be on the graduation list in January.


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