Civil Engineering September 2021 | Vol 29 No 8

Civil Engineering September 2021 25 I n South Africa, visual inspections for all bridge structures are required every five years. A need was identified to establish if it would be practical to utilise technologies such as drones and photogrammetry to improve inspections and to reduce the cost of inspections. Drone and photogrammetry technolo- gies are large components in the Fourth Industrial Revolution (4IR). For proof of concept, two bridges were inspected using a drone. The drone inspection data captured for the two bridges was processed and point cloud models were created. These point cloud models were then used to establish whether defects, identified on these bridges previously by way of regular TMH 19 visual assessments, could be identified from the point cloud models. The outcome of the study showed that it would be possible to use processed images from drone inspections or other image capturing methods to inspect bridges and for monitoring purposes. The use of these technologies could improve the inspection methodology, not only of individual structures, but also of a network of structures as required by road authorities. Recommendations are made for future work. Introduction Background The recommended interval for bridge and culvert inspections in South Africa is five years (COTO, 2017). However, con- ducting these visual inspections every five years is a challenging task for South Africa’s provincial and municipal road authorities. Budget and capacity constraints often lead to inspections not being done or unqualified inspectors being used, resulting in poor quality inspection data. Good quality inspection data that can be entered into a bridge management system is essential to determine maintenance budgets and sched- ules to protect the structural integrity of bridges and ensure the safety of road users. Utilising new technologies, such as drones and photogrammetry, has the potential to improve inspection method- ology, improve the quality of inspections, lead to cost and time savings, and create a safer environment for inspectors. A similar study has been conducted by the Minnesota Department of Transport together with industry stakeholders. This three-phased study investigated the use of drones for bridge inspections and focussed on rules and regulations, drone hardware and the ability of drones to collect quality inspections data. During the Minnesota study it was noted that drone technology continues to evolve substantially, making it possible to achieve what was previously considered a limitation. The ability of drone technology to conduct bridge inspections was confirmed by the Minnesota study, but the practicality to conduct network inspec- tions of thousands of structures is yet to be determined (Wells & Lovelace, 2018). The University of Sannio’s Department of Engineering has addressed some of the practical issues on the use of drones for construction inspections. It was noted that, from the top industries in the US using drones, only 9% of these industries use drones in construction (structure) applica- tions. The need to increase the use of drones in condition assessments of structures was identified (Ciampa, De Vito, & Pecce, 2019). Currently, bridges and culverts are inspected using a defects-based system as prescribed in TMH 19. During the visual inspection, defects are identified on the various structural elements and rated in terms of degree (D), extent (E) and rel- evancy (R). These DER ratings, combined with weights allocated to the different structural elements, are used to calculate a condition index for the structure. This Priority Condition Index (PCI) is then used to categorise the structure as very good, good, fair, poor, or critical (COTO, 2017). The requirements for a person to be accredited as an inspector of road structures are specified by the COTO Structures Sub-Committee and are included in TMH 19. COTO has three grades of inspectors, namely a Senior Bridge Inspector, Bridge Inspector and Culvert Inspector (COTO, 2017). The qualification and experience requirements for accreditation as a Bridge Inspector are as follows: Q Q Professional engineer with a minimum of five years bridge and culvert design experience obtained during the last 25 years; or Q Q Professional technologist with a minimum of 10 years bridge and cul- vert design experience obtained during the last 25 years. Aim and scope The aim of this study is to investigate the practicality of using drones and image processing for bridge inspections. The key considerations are: Q Q Drone regulation in South Africa Q Q Drone licencing requirements Application of drones and image processing for bridge inspections in South Africa This paper was co-awarded the SAICE Transport Engineering Division’s award for the Best Paper by a Young Professional (under 35) at the Southern African Transport Conference 2021. The co-winning paper, Modelling the impact of priority infrastructure on the performance of minibus taxi services in Southern Africa by Lourens de Beer and Christo Venter, will be published in a future issue of Civil Engineering . Michael Roux CSIR Smart Mobility Cluster mproux@csir.co.za Lana Kemp CSIR Smart Mobility Cluster lkemp@csir.co.za Mauritz Kemp CSIR Smart Mobility Cluster mkemp@csir.co.za Robin Kock Premier Mapping Africa robin@premap.co.za