Foot bridges have existed for years particularly in Kenya’s urban setting.
Nevertheless, the majority of the city residents had been numb to the crosses as jaywalking remained the order of the day causing harm to both pedestrians and motorists on Kenyan highways.
A re-modelling of the structures has however sparked life into the seemingly obsolete facilities.
In the next few weeks, both motorists and pedestrians at the Garden City Mall are set for great relief as works on a modern footbridge by the Kenya National Highways Authority (KeNHA) winds down.
With 75 per cent of the project done at present, motorists on the Thika Super Highway can look forward to days of smoother traffic flow at the crossing while pedestrians will be less jittery of making the trip across the highway.
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The highways agency is meanwhile assured of the maximum deployment of the bridge by pedestrians having integrated consumer needs into its design.
“The biggest bridges in the past were not user friendly. The facilities were usually poorly lit, rigid to users with physical disabilities and damp after rainfall,” said Anthony Macharia, an architect attached to KeNHA.
After the consideration of the needs of Kenyans, modern foot-bridges have a greater design incorporating a ramp, a greater width to accommodate handcarts and supportive infrastructure such as shops and washrooms.
“We have had to conduct case studies before breaking ground. This has been informative in terms of understanding the size of human traffic,” added Mr. Macharia.
“The question has been on how to make the facilities more practicable for Kenyans. People want to use things that look nice. We wanted to put up something people can associate with. For instance, one could find a mama mboga at work at the end of the bridge. We have had to think of how to accommodate everyone.”
The transformation has seen projects infuse both the expertise of not only engineers but also architects.
The construction of the modern footbridges is however not a walk in the park as many would assume.
Tony has worked on seven such bridges, there are about a total of 13 bridges planned to cross the 42 kilometre modern highway.
Case studies into such projects are usually followed by a long and winding procurement process with parts being sourced from as far as China.
The contractor in any one project then has to assemble a dry run testing the bridge for functionality.
What follows next is the audacious task of piecing together the jig saw with parts which weigh in the range of 100 tons being chopped up to ease transportation.
From the 100 tons of steel, the contractor has to come up with six portable pieces each averaging 20 metres in length.
Thereafter, the project kicks into high gear as works begin to weld pieces into place and the fastening of bolts.
For instance, the fastening of bolts on a single section of the bridge takes upwards of two and a half hours.
A single bridge would require a total of 1764 bolts which are first bolted in testing and then unbolted for transportation and bolted again for a final hoisting into the bridge’s ‘final resting place’.
It takes about 2 mins to fix a single bolt into place, multiply this by the number of bolts in place and it would take roughly 59 hours or an equivalent two and a half days to put all bolts on a single bridge into place.
To raise the stakes in amounts of time involved, only 4 people can undertake this exercise at a time.
Some procedures meanwhile fall outside the scope of the contractor leading to the extended extension of projects as seen in the construction of the footbridge at the Garden City Mall.
For instance the setup of the bridges’ columns may encounter services such as water pipes, fibre cables and drainages forcing new works by the services’ respective agencies.
Danger is never far but an integral part of the exercise.
For instance, engineers are usually suspended up to 12 metres in the air, which is an equivalent of being at the apex of four storey buildings.
Works also occur as live traffic flows beneath the bridge making it a high stakes exercise with lives typically on the line.
In total, the construction of a single bridge requires an average of 18 months with the later six being to run maintenance services.