3D models of infrastructure will soon be a prerequisite for maintenance work

23.10.2019 / Poul Linneberg

The traditional asset management system based on specifications, drawings and other documents is expected to die out. This will result in an increasing demand for 3D models of existing large infrastructure components. The potential advantages in terms of speeding up and optimising maintenance work are obvious, but how do we move ’old-school’ systems into the new digital age?

In recent years the concept and use of Building Information Modelling (BIM) has attracted increasing attention and they are now widely used during construction. The core of BIM is a 3D model of the assets under consideration. For new structures, this is not a problem as they will usually be designed by using 3D models.

For existing structures on the other hand, this poses a challenge, as 3D models of the structures will usually not exist.

Together with some of our major clients we are currently working to create the basis for applying the principles of BIM to existing infrastructure facilities as part of an asset management system (AMS).

The aim is to explore and take advantage of BIM to optimise and improve efficiency in maintenance work. Also, as Asset Management systems based on an alphanumeric object identification system are expected to die out and be replaced by systems based on BIM, the industry needs to have an alternative in place for existing structures too.

Detailed digital images reveal condition of infrastructure

One of the projects where we have introduced new technology and concepts to gain further knowledge and move the maintenance of existing infrastructure into the digital age, is a project concerning the inspection and rehabilitation planning of the 106 tunnels on the Vrbnica – Bar railway line in Montenegro. This is the main railway line through Montenegro from the Adriatic Sea in the south to the border with Serbia in the north.

The first step in creating a BIM at the operational stage was to establish a 3D model of all the 106 tunnels. This was achieved with a combination of laser scanning and video imagery sampled by a 360° camera, called COWI Panoramic View (CPV).

All observations revealing the condition of the infrastructure were then recorded in a structured manner in an inspection database. From the database it is possible to export data in formats that can be fed into a BIM based asset management system.

Many advantages over a paper-based system

As a versatile means of handling and presenting the georeferenced data obtained from CPV and laser scanning we used a special tool called COWI MultiViewer.

This tool, developed by COWI, is fully web-based and can be used to store and present georeferenced data in a number of different formats.

A special application of the COWI MultiViewer – known as COWI Virtual Inspection Tool (CVI) – can be used to carry out desk inspections of structures based on digital images fed into the viewer.

Effective handling of data from the detailed inspection, by means of a purpose built inspection database, made it possible to develop individual rehabilitation plans for all the 106 tunnels on the main railway through Montenegro.

The use of databases has a number of advantages over a paper-based system:

Predefined defects.
A core component of the databases is a hierarchy of predefined defects. The predefined defects will usually cover more than 95% of the observations. The use of predefined defects assure a uniform registration of defects even when 5 or more inspectors are involved in an inspection.
Easy registration in the field.
The database is installed on a tablet PC so data can be entered directly into the database while carrying out an inspection.
Optimum data handling.
As 95% (or more) of the defects are described by a rather quite small number of predefined defects it is easy to process the data and create reports directly from the database.
Easy exchange of data between systems.
Data from the inspection databases may be easily interchanged with higher level Asset Management Systems or BIMS by means of standardized data formats such as Excel, csv-format, txt-format or similar.
Intuitive link to data
Further, in BIMS a direct link can be established between a main structural component and the inspection database containing inspection data. Currently COWI is involved in the development of tools that may combine data in such inspection databases with the COWI Virtual Inspection Tool in COWI MultiViewer.

The CPV recording device was installed on top of a car that was placed on a flatbed wagon driven through all the tunnels and galleries by a draisine. The point clouds produced are so detailed that they almost resemble a black and white 3D image of the tunnels (see top image).

An effective screening tool – but should not stand alone

The project in Montenegro confirmed that video recordings and high resolution digital images are effective screening tools to optimise the planning of detailed inspections. They should not stand alone, however, as some defects cannot be effectively observed without being close to the structure, but digital images can be used in the office to prepare and plan detailed inspections, support structural assessment and provide input to reporting.

Repeating a full video inspection at regular intervals is also an effective way to monitor changes in the condition of infrastructure that are often large in size and a challenge to access in details.

Also, it will soon be possible to detect some defects by means of automated image processing. This may include:

development and changes in crack patterns,
concrete spalling,
ingress of water in concrete structures,
corrosion on steel surfaces,
degradation of surface treatment on steel structures,
settlements,
changes in scour protection.

In the future, all of the above information will most likely be handled, documented and communicated by means of BIM.

Be prepared for the future

The main advantage of implementing an asset management system incorporating the special features of BIM on existing infrastructure components, compared to a traditional AMS, is the fact that a direct and intuitive link between the components and the related information can be obtained by means of a 3D model.

The project in Montenegro was an example of a rational way to establish a functional 3D-model for existing assets.

Moreover, as mentioned earlier, systems that are based on an alphanumeric object identification system are expected to die out. We - and our clients - need to be prepared for this.

The future will reveal more about how AMS and BIM can co-exist and be combined to provide a more effective and rational way to handle the huge amounts of information related to infrastructure components from the first conceptual studies through commissioning and operation to final decommissioning.

One thing is certain; establishing 3D models is essential if we are to be prepared, reap the benefits and move existing infrastructure into the new digital age.

FACTS

The National Building Information Model Standard Project Committee defines BIM as:
Building Information Modeling (BIM) is a digital representation of physical and functional characteristics of a facility. A BIM is a shared knowledge resource for information about a facility forming a reliable basis for decisions during its lifecycle; defined as existing from earliest conception to demolition. (NBIMS-US 2017)

BIM is currently used mainly on new construction projects as part of Computer Aided Engineering (CAE). In a BIM system each object is assigned a unique code describing its type and location. The type code will also show the hierarchal position of the object within the structure, the object assemblage.
A number of attributes containing information about the object are then assigned to all the objects.
Attributes traditionally concerns material properties, supplier information, date of purchase/delivery, specification of spare parts, etc.
In the future it is expected that attributes related to operation and maintenance (O&M) will be added also. This could include O&M specs, drawing references, inspection data, condition assessment data, etc.

MEET THE EXPERT

I am a civil engineer specialising in maintenance of bridges. I have worked in this area for more than 20 years on a number of major projects in Denmark and abroad.

Operation and maintenance is a challenging field of work as it integrates knowledge of structures with an understanding of materials as well as deterioration mechanisms.

From my work on large infrastructure projects, I am very interested in the development of tools for quick and effective collection and handling large quantities of data from inspections.