One of the many challenges in infrastructure management liesin managing built assets. Managing means repairing, rehabilitating and replacing assets to ensure they are able to safely fulfill their functions. To manage infrastructure assets, detailed information about the condition of all components of the asset is required to make substantiated decisions. Assets are composed of several elements and components. Individual component condition reports represent the condition found during visual inspection.

The challenge for infrastructure asset managers is how to convert data about component inspections into useful information which are

aggregated to make sounds decisions on the maintenance of assets in systems. Useful data that provides information about the condition of assets in systems, which are used to support budget allocation and to prioritize maintenance, is scarce. Information may be lacking, may be incomplete, may be unorganized or may need to be deciphered before it becomes useful in decision making. Furthermore,this data would be unhelpful statistics if one does not know how to apply this information to identify problems and create solutions.

At a systemlevel, infrastructure managers need to prioritize maintenance and allocate scarce resources.

Author: Ahmet Yazan MSc. 


1. Creating useful data

The problem of creating useful data out of large volumes of component condition inspections and reports causes decision making to be more difficult for asset owners and managers and this influences the performance of assets . Condition inspection is an activity which generates data regarding the state of an object or system. Condition inspections are based on visual inspections of assets. The inspections attempt to ascertain the presence of defects. The condition of the asset is affected by various properties of the defect. The properties are quantified along different dimensions: how serious is the defect, how extensive is the defect and what is the size of the defect?

Asset owners and managers face difficulties in converting condition inspection data into useful data that enables them to compare the condition of assets or systems. An asset manager oversees many infrastructure objects. This can range from a couple of hundred to potentially thousands of objects. The aggregation of condition scores may help, but a potential problem arises when there is an abundance of condition scores. This research aims to develop a method to aggregate the component condition scores of assets to the system level. To achieve this, uniformity and objectivity need to be captured in the condition inspections and transferred to the condition aggregation phase to provide reproducible and avoid incorrect communication.

Research question:

How can we improve the current aggregation method, for aggregating component condition scores to object and system level, making it more uniform, objective and reproducible in its application?

To answer the research question this thesis has developed the OCA method, which stands for Objective Condition Aggregation.

2. Steps to take.

A first step in the development of the OCA method is the identification of the problems encountered in the current NEN aggregation method. A literature review and a small but in depth case study are performed to determine current shortcomings and to identify the requirements for the OCA method. The first part of this step identifies which aggregation criteria could impact condition aggregation and the second part includes a selection process to select appropriate aggregation criteria. As a second step in the development of the OCA method, options are identified which are able to translate criteria into numerical values. The numerical values help determine the importance of components and eventually the aggregated condition scores. As a third step the OCA method is applied to a set of 31 assets. The engineering firm Sweco provided non-aggregated condition scores for these 31 assets


3. Insights.

The differences in the OCA and current NEN aggregationmethod have been considered. The aggregation of 31 bridges is split in three groups to compare results of aggregated condition measurements. The NEN-aggregation provides condition score results (score of 2 = good), which qualifies the asset as being in ‘good’ condition. The OCA is more critical and provides lower scores (score of 3 = reasonable and score of 4 = moderate), which would classify the asset condition as reasonable or moderate. As a final step, the OCA method is validated. The validity is performed by reasoning with arguments and allegations from multiple experts gathered from interviews.

The information includes disadvantages of the NEN-aggregation and possible ideas to overcome them in a new developed method. It can be concluded that the current aggregation method can be improved by using condition measurements in combination with a uniform table. The OCA method shows its value by providing a step by step approach to aggregate components condition scores to system level. This approach embeds uniformity, objectivity and reproducible. Therefore, the OCA is a better substantiated approach than the NEN-aggregation


4. Recommendations.

Finally, recommendations are given about the use of OCA. Although current inspection forms providing component condition are quite impressive, they fail to collect a crucial piece of information about the condition of the asset.

Practical recommendations are:

  • Determine affected surface of components;
  • Add a new heading to the inspection form called affected surface;
  • Coach inspectors in how to determine the affected surface in a uniform way.

Asset Management Systems: See The Line of Sight-Deepening the subject


Scientific recommendations are:

  • Test the design of the OCA for different assets;
  • Design new uniform tables for different assets;
  • Cost estimations do influence the aggregation. A different view on cost estimations will give insight in cost and aggregation accuracy;
  • Design a procedure for decision making/maintenance policy with aggregated OCA condition data;
  • Design a risk assessment for aggregated OCA condition data.

By doing so, an important step can be set towards standardization.


5. Give your opinion 


Bron: TUDelft: Asset Aggregation

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