The Namibia bridge management system: a tool for preservation of structures on the road network

Abstract

This paper describes the development and implementation of a bridge management system (BMS) for the Namibia Roads Authority (NRA). Namibia is a vast country (825 420 km2) with a very low population density and the NRA is currently responsible for the management of 6 200 km of paved roads and 35 900 km of unpaved roads, which includes 1 430 bridges and major culverts (>3m span length) and 1 290 lesser culverts (<3 m span). In 2001, the NRA embarked on a project to upgrade their existing BMS, which was essentially an inventory database, to a fully-fledged BMS, which would be capable of utilising visual assessment data to prioritise structure maintenance and rehabilitation needs. The system selected was the locally developed STRUMAN BMS, which is used by various road authorities in South Africa, Botswana, Swaziland and Taiwan and was developed by the Built Environment division of the Council for Scientific and Industrial Research (CSIR) in Pretoria. During the first phase of the project, the inventory and inspection modules were customised to meet the needs of the NRA, which included integration of the BMS database with the Road Management System (RMS). A map module front end was also customised and integrated with the other BMS modules for graphical viewing of the structure population. The second phase of the project involved the appointment of suitably experienced structural engineers to carry out the visual assessments. These consultants were required to attend a training course (including an inspector calibration exercise) on the assessment methodology, which is based on a 4-point DERU (Degree, Extent, Relevancy and Urgency) system for rating observed defects. The Relevancy rating forces the bridge inspector to evaluate the consequences of the defect in terms of the structural integrity and serviceability. Each of these parameters is combined in the condition module to determine priority rankings of all assessed structures. A remedial work sheet is used during structure inspections to summarise the items requiring repair. A visual assessment manual was utilised to improve uniformity of the inspector rating standards. The third phase of the project involved the validation of assessments and prioritisation of structures in terms of maintenance needs. The final selection of maintenance projects will also take into account planned road maintenance projects and the relative locations of structures with similar defects.