Cristóbal Ramos-Salgado1, Jesús Muñuzuri1, Pablo Aparicio-Ruiz1 and María-Luisa Muñoz-Díaz1
1 Organization Engineering Group, School of Engineering, University of Seville, Camino de los Descubrimientos s/n, 41092, Seville, Spain.
Abstract. Maintenance strategies have been long developed for individual pipes. However, when performing interventions, the street’s topography is usually considered by water companies. In this work, we use street sections between intersections as the smallest replacement unit on which to base maintenance strategies. Also, an original method to rank every section for replacement is proposed.
Keywords: water and sewer networks, maintenance planning, risk management.
1. Introduction
A successful maintenance strategy consists in correctly planning the maintenance activities on the infrastructure assets. This task has long addressed for individual pipes. However, since pipelines might not be in consonance with the street’s layout, this hydraulic element constitutes a theoretical concept, rather than practical and functional.
Instead, the consideration of geographical and urban criteria to design work programs not only minimizes the impact on pedestrians or the traffic flow, but boosts the possible coordination of the hydraulic network intervention with other infrastructures maintenance projects. This can help avoid unnecessary or duplicated streets interruptions, which might undermine the image of the company or municipality.
2. Literature review
Even though the definition of a practical infrastructure ‘unit’ is key to establish suitable maintenance strategies [1], works targeting this issue are scarce in the literature.
For instance, Elsawah et al. [2] define the potential replacement units as the set of supply and sewerage network sections, as well as pavement, comprised between the two nearest intersections, while Tscheikner-Gratl et al. [3] refers to entire street sections among valves or manholes. Another example is proposed by Kielhauser et al. [4], that assign every network asset to a predefined square grid cell.
In this work, we propose complete streets and street sections as the smallest replacement unit and streets and pipes are linked by geometric superposition.
3. Street sections: definition and intervention priority
Should a certain operational unit, i.e., street section, be intervened, then all the infrastructure elements within that section, i.e., geographically coincident, will be affected.
To determine the intervention needs for a given street section, the weighted sum model developed by Muñuzuri et al. [5], that calculates a risk index (RI) for every section, was utilized. It has to be noted that street sections are mere geographic objects and a procedure to incorporate the information from their underlying pipes is needed.
4. Case study
This procedure has been applied to the city center of Seville (Spain), whose network comprises of a total length of 107 km and 1,902 street sections, that are assigned a RI.
On the account that that the water company wishes to replace the 5% of most urgent street sections in a 5-year time horizon, a total length of 5.36 km should be intervened. The sections to be replaced are selected one at a time, starting with the most urgent one, until the target replacement length is achieved. Thus, a RI threshold can be defined as the RI of the least urgent section to be intervened within the 5-year planning. This value is set to. Out of the 1,902 street sections from the historic center, 93 of them have a RI higher than 4,57 and should be targeted. The required investment is 5.43 M€.
5. Conclusions
The utilization of street sections as operational units may be advantageous for it minimizes the impact on pedestrians or the traffic flow and allows the possible coordination of various coincident infrastructures projects.
Also, an original method to calculate the replacement needs of every section is used. It has shown to be useful to identify the sections that most urgently need to be replaced.
Finally, since geographic and contiguity data for each section are perfectly known, the development of grouping methodologies to aggregate several street sections into more complex work programs seems to be a promising direction for future research.
References
- Shahata, K., Zayed, T.: Integrated risk-assessment framework for municipal infrastructure. J. Constr. Eng. Manag. 142, (2016).
- Elsawah, H., Bakry, I., Moselhi, O.: Decision support model for integrated risk assessment and prioritization of intervention plans of municipal infrastructure. J. Pipeline Syst. Eng. Pract. 7, (2016).
- Tscheikner-Gratl, F., Sitzenfrei, R., Rauch, W., Kleidorfer, M.: Integrated rehabilitation planning of urban infrastructure systems using a street section priority model. Urban Water J. 13, 28–40 (2016).
- Kielhauser, C., Adey, B.T., Lethanh, N.: Investigation of a static and a dynamic neighbourhood methodology to develop work programs for multiple close municipal infrastructure networks. Struct. Infrastruct. Eng. 13, 361–389 (2016).
- Muñuzuri, J., Ramos, C., Vázquez, A., Onieva, L.: Use of discrete choice to calibrate a combined distribution and sewer pipe replacement model. Urban Water J. 17, 100–108 (2020).