ABSTRACT
Since 2013 the World Bank undertook emergency operations to address some urgent needs in Madagascar and the Malagasy Government identified the maintenance and improvement of the road infrastructure among the main priorities of the country. In this process, SPEA company of Autostrade Group, the main Italian transportation agency, has developed the project of the structural rehabilitation of the Kamoro bridge, a suspension bridge located along the National Road connecting the capital city Antananarivo to Mahajanga on the North-West coast. The Kamoro bridge represents a national historic landmark. It has a main span of 206 m. The deck is about 4 m wide and it is sustained by cables anchored to two towers 23 m high. Built 85 years ago, the steel structure is actually suffering from deterioration due to corrosion phenomena and fatigue effects.
After detailed inspections and health monitoring aimed at identifying structural defects and deficiencies, two different proposals have been developed to upgrade the structural safety of the bridge and improve the road infrastructure capacity.
The first solution is aimed to extend the bridge service life further 50 years, to improve both structural safety and performance, and to remove actual traffic weight restrictions. It consists of a significant repairing and strengthening interventions of the existing bridge, and includes the following operations: replacement of the whole suspension system; replacement of the Arnodin prefabricated elements; cleaning and protective coating of all the steel elements; and finally providing scouring protection for bent foundations.
The second solution is aimed at greatly improving the traffic capacity as well as the users’ safety and comfort. This proposal consists of repairing the existing construction and upgrading the traffic capacity by building a new bridge in addition to the existing one. This configuration allows to commit the existing construction to pedestrians and local light traffic, such as animal-drawn carriages and hand-carts, and the new bridge to heavy traffic. View of the Kamoro suspension bridge. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig358_1.jpg"/>
After the description of both the above mentioned proposals, the paper compares the two alternatives in terms of technical and economic feasibility, and explains the reasons why the Client has chosen the second solution.
