Keynotes

Assessment of damage of post-tensioned bridges in Norway

Due to its local topography, Norway is a country with a high percentage of bridges compared to the total road length. The necessity to guarantee a functional public transport infrastructure has led to the construction of many bridges, several of which are exposed to extreme weather conditions. There are currently around 19,500 bridges and ferry quays in the national and county road network, of which over 2,000 bridges are built with prestressed concrete, both post- and pretensioned.

Post-tensioning concrete has historically been considered as a reliable and efficient construction method, demanding little maintenance in comparison to traditionally reinforced concrete. The constructions method has changed over the years with considerably more focus on execution and durability since the years between 1982 - 1986. The first post-tensioned bridges in Norway were built during the period 1958 -1960, using prestressing bars. Later in the 1960s and 1970s, post-tensioning systems with wires were commonly used (widespread use of BBRV). During the 1970’s post-tensioned bridges with high utilization of materials were executed. Prestressing strands gradually took over from wires in the early 80s.

The construction methods have changed over the years with considerably more focus on execution and durability since the years between 1982 – 1986. During these years the first regulation on grouting and properties of grout was introduced. During the years since, the practice has developed, and both the quality of the grout and the grouting has improved significantly since the early 1980s.

In Norway we expect no damages due to corrosion on strands if requirements regulated by today’s standards and regulations are followed. However, damages on post-tensioned bridges, especially those build prior to the revision of construction practice and standards, have been reported world-wide. In Norway damages are found occasionally as well, mainly coincidental during maintenance work. Norway has a considerable number of bridges built in the period of 1970 – 1990, and among these, several bonded post-tensioned, which potentially had issues during execution. Norway had no explicit requirements for the inspection of post-tensioned concrete bridges until 2021.

The awareness of the possibilities of severe damages on post-tensioned bridges build before sufficient regulations were in place, has increases considerably during the last years. The lack of systematic inspection routines was realized, and the Norwegian public roads administrations therefore initialed an activity on assessment and inspection of post-tensioned bridges during the R&D-project Better Bridge maintenance (2017-2022) which was later followed up by the R&D-project VESPA (2021-2024). The main goals for these projects have been to establish routines for systematical and periodical inspections of post-tensioned bridges. In addition, the projects aim on establishing routines for prioritizing order of inspections by a risk-rating tool adjusted to Norwegian conditions and traditions in building-technics. Also, the potential of repairs and strengthening are investigated. The methods developed within the projects are and will be implemented in the Norwegian Public Roads Administration through regulations and guidelines, courses, and by practical training. Through these activities we are aiming on getting a better overview of the condition of post-tensioned bridges in the road network and contribute to a forward-looking strategy for safe management of existing bridges.

The keynote lecture will give an overview of the historical development of construction methods for post-tensioned bridges in Norway and the potential risk of damage that may have resulted from them. The lecture will future present the results from the R&D projects and todays approach for assessing and inspection post-tensioned bridges in Norway.

Sustainability and digitalisation in bridge management: How far we are ?

Sustainability and digitalisation are two main topics in many research programs in Europe and worldwide. It seems that bridge managers can largely benefit from the current digital transformation where processes using digital technologies are able to create new or to enhance existing bridge management systems (BMS). Being the budgets for bridge maintenance also scarce, sustainability is a must to be implemented in all areas of activity for a proper use of limited resources. For this reason, sustainability and digitalisation in relation to management of the existing bridge stocks are top of the agenda for Copenhagen IABMAS 2024.

Apart from being both of paramount importance nowadays and in the next future, the concepts of sustainability and digitalisation are very different in essence and, therefore, the tools needed for their fully adoption in the bridge management environment have to be also different in their basis and formulation. For an optimal adoption and development of both topics, also the actual trends in the bridge management policies, as performance-based decision making and adaptive BMS, able to adapt to changing actions and environmental conditions, should be considered. These trends define the framework and boundary conditions where the adoption work must be developed to be succesfull.

The aim of this presentation is to analyze the actual bridge management policies, trying to evaluate their actual level of sustainability and digitalization and seeking to their level of accomplishment in relation to an optimal implementation (where to go and how far we are?), analyzing possible causes of the actual distance from that optimum and proposing possible actions to decrease it.

Bridge Management – Past, Present, Future

The history of bridge engineering is a story of human innovation. As long as humans have existed there has been a need to bridge gaps such as streams, gullies, canyons etc. The moment the first bridge was created from a tree or a stone slab was most likely the moment bridge engineering first began and knowledge about durability and maintenance thus followed, whether it was understood or not at the time. The history of bridge management is also a story of innovation as bridge owners eventually began to be responsible for many structures, constructed using various materials, in different exposures carrying different loadings. Indeed, bridge management is sometimes defined as the process of combining management, condition assessment, engineering, and economic information in order to determine the best actions to take on bridges in a network over a specific time and these activities have become more and more sophisticated over time.

In response to this we have seen the development of bridge management systems or BMS - computer solutions to aid in the management of transportation structures. Today these powerful systems are linked to other advanced tools and systems that help bridge owners responsibly manage these important assets. In addition to traditionally managing lifecycle costs, risk, and determining optimized priority programs, modern BMS report current and forecasted condition and other performance measures and help sustainably maintain the inventory while considering a variety of socio-economic factors. Today BMS are instrumental in helping owners manage the effects of climate change and extreme weather. The integration with advanced condition assessment tools, bridge health monitoring systems, and other new technologies offer tantalizing possibilities for future bridge managers.

In this lecture, we will take a high level review of bridge management practices in the past, present, and postulate where bridge management is heading in the future.

Bridge engineering - Proving the sustainability case for refurbishment v replacement

The demands on our existing transportation infrastructure are growing as our cities increase in size. We are constantly faced with the need of increasing the capacity of our existing networks. So do we rebuild or refurbish? We live in a world of finite resource and the idea of simply knocking something down and rebuilding it afresh is counter-intuitive to a society that seeks sustainable solutions.

So how do we assess the sustainable benefit of refurbishing an existing structure? There are also attendance risks associated with the age and capacity of existing structures that will impact the case for refurbishment.

There are several tools recently developed to measure the extent of embedded carbon in new projects that help us compare the sustainability of new construction and determine the most effective scheme. However, the same tools cannot be used to assess the relative sustainability of refurbishment versus replacement and yet decisions on this critical point are having to be met by bridge owners worldwide. In the author's country, all infrastructure projects need to assessed to demonstrate how they can be built minimising embedded carbon so we need good tools and data to assist us in providing a justifiable means for decision making.

There are many decisions to be made in any carbon assessment around traffic flow changes and duration, durability of existing assets, access for inspection and, critically, loss of embedded carbon in the existing structure that might be replaced. The paper will describe the challenges that exist in determining the comparative sustainability of new versus rebuild and extend. It will set down the sets of choices that need to be made and the extent of the influences that affect the sustainability demand.

Thermo-Mechanistic Approach for Evaluating Service Life of Bridges and Structural Concrete

To ensure the preventive maintenance of bridges, it is essential to assess both their current safety status and their remaining service life. To address this engineering challenge, a comprehensive approach that combines expertise in structural mechanics and thermodynamic materials science is proposed. This approach has been verified and validated across various scenarios as: (1) RC bridge decks under the high cycle traffic, (2) Long-term cracking and deflection in PC viaducts and pre-tensioned girders, (3) Remaining capacity of beams damaged by fire, (4) Cathodic protection measures, and (5) Remaining capacity of rehabilitated bridges affected by significant earthquakes.

From empirical and subjective O&M to statistical and objective asset management

This lecture will focus on the Danish Road Directorate’s (DRD) ambition for future asset management across all of DRD’s asset classes and describe the specific opportunities and challenges this entails for the future asset management of DRD’s structures.

DRD is responsible for over 3800km of national road, which consists of a multitude of different assets such as roads, bridges, tunnels, drainage, noise barriers, utilities, signals, bus shelters and much more. These assets have until now been managed under different assumptions and in separate processes and IT-solutions, obfuscating the overview across assets and limiting the opportunities to optimise operation and management (O&M) budgets. DRD’s needs for O&M funding are reported yearly to the government and are then part of the coming finance act (finance bill) debated and approved by the Danish Parliament. Depending on the state of the country and current affairs, the budgets coined out to DRD’s O&M may vary from the re-ported needs. DRD’s responsibility is therefore to ensure that decision makers are informed about the loss incurred by not meeting the reported needs and ultimately to ensure that the provided budget is leveraged to provide the most beneficial effect in the entire road network, i.e. best value for money given all known conditions.

As assets have different performance requirements and degradation curves, the cross-asset optimisation has until now in parts been handheld and based on subjective evaluation. The development of data compu-tation has however opened for a possible major improvement of this approach, so that more automated, data-driven and objective reasoning can lead to improved maintenance strategies across the different asset classes. In order to do this, DRD is setting out and firming up guidelines to ensure that assets are treated under same constraints and to ensure that needs from different assets can be compared and aggregated to provide an optimum cross-asset strategy.

When available budgets differ from the needs, the future asset management system shall revert the analysis of needs and identify the preferred sub-optimal solution that ensures minimum monetary loss. The loss is calculated as the loss from maintenance not being performed at the right time leading to increased mainte-nance costs later; or the loss because maintenance is carried out too early resulting in the loss of the remaining lifespan of an asset.

In addition to the above, the development of data collection (e.g. drones, photogrammetry, damage detec-tion, structural health monitoring, etc…), data capacity and machine learning, have opened up for new op-portunities to analyse the remaining lifespan of assets and improve our understanding of optimum mainte-nance strategy, especially for structures. DRD’s current practice for assessing the condition of structures is an empirical model that has been well tested over the last 40 years and is grounded in qualified but subjec-tive engineering assessments. The focus going forward is to establish objective and statistical forecast to get better precision. This in turn, however, will require stricter measures on data quality, determining data that has statistical significance, and thereby defining the type of data collection DRD should carry out in the future.

The lecture will delve into further details on the above-mentioned considerations and provide examples on how DRD’s asset management of structures is set to change.

Innovations in building and bridge engineering associated with Circular Economy – CE with focus on recovery from secondary sources (todays waste)

The overconsumption of the earth’s resources causes increasing concern worldwide, and in Europe, a strategy for circular economy has been developed to combat the overconsumption of resources. In “A new circular Economy Action Plan - For a cleaner and more competitive Europe, 2020” by the European Commission, the building and construction sector was pointed out as a key sector in the transformation from a linear to a circular material use because this sector requires vast amounts of resources - it accounts for about 50% of all extracted materials. At the same time, the sector is responsible for over 35% of the EU’s total waste generation. Greenhouse gas emissions from material extraction, manufacturing of construction products, construction, and renovation of buildings are estimated at 11% of total national GHG emissions.

These are strong incitements for transforming the sector towards CE value chains as greater material efficiency could save about 80% of those emissions. The transition to CE can be achieved through an agenda based on three strategies a) using fewer materials e.g. simultaneously optimizing the raw material input, material properties, and environmental burden b) lengthening the use phase, and c) closing loops through recycling of materials at end of life. In a circular economy, the recycling options are prioritized based on the environmental benefits and reuse rates higher than recovery.

The building sector is paying increased attention to circular strategies, but new buildings or renovation projects based on circular principles are still a niche and are generally in the stage of unique demonstration buildings.

In the bridge construction sector optimization of design with focus a) using fewer materials, b) increasing the service life and c) recycling of materials and elements at end of life is in focus using new standards and best practice.

To speed up the transition to a circular economy, there is a strong need to bridge the gap from niche to “new normal”. A key challenge in choosing to reuse components today is the barrier constituted by the lack of standards, certification, and documentation systems for these materials. Such lack entails a significant documentation burden and economic risk for the building and bridge owner when e.g. choosing to reuse components from another building and bridge. This barrier must be overcome by the development of systems and methods that ensure equality in the choice between reused and new components.

This presentation will focus on the ongoing standardization of circular economy in the building and bridge construction sectors and, research and innovation need towards mainstream implementation in the sectors. There will be a specific focus on reuse of structural elements and materials.

AI support for bridge SHM and life cycle assessment

This paper focuses on opportunities that AI models bring to the monitoring and life cycle assessment of bridge structures. The paper examines different phases of data collection and generation and presents a holistic approach to curation of data. The paper then discusses various analytics that could be used to translate data to information that is useful in learning the fundamental characteristics of the structures and producing diagnostic measures for assessing the state of the structures. New classes of neural networks are developed to perform these analytical tasks accurately and in a scalable platform. These methods allow large volumes of data from various sources, including data from mobile sensors, to be utilized for assessment of critical structural systems.

Different sources of data are used for this research. This includes conventional wired sensors, wireless sensors that are less expensive and more convenient to implement for short to medium term deployments, as well as mobile sensors that use data generated by phones inside cars that travel over bridges. Using mobile sensors is presenting the opportunity for a paradigm shift in scaling analysis of bridge structures to include all or a large part of the bridge assets across the nation. In addition to physical sensors, virtual sensors relying on mathematical processing to generate the desired data are developed to circumvent the need for expensive and labor-intensive direct measurements. A comprehensive strategy, based on sophisticated cloud-based storage solutions, is proposed to efficiently manage the large volumes of data collected or generated for the subsequent processing operations aim at extracting damage-sensitive features, detecting and localizing damage, quantifying its extent, and providing a prognosis about the structural remaining useful life.

This research introduces novel approaches to transform data into information that is useful for structural condition assessment, advancing dynamic identification, damage diagnostics, and fatigue life estimation. It provides methodologies for scalable infrastructure monitoring via mobile sensing in the civil engineering field, incorporating the interaction of vehicle suspension effects and vibrations caused by road roughness, enabling dynamic response extraction from vehicle data. Additionally, it presents techniques for bridge modal identification using asynchronous mobile data, a crucial step in integrating mobile sensing into system identification. In parallel, advanced deep learning architectures have been designed to efficiently detect and localize damage, such as cracks, utilizing long-term data availability. They excel in identifying abstract features and complex classifier boundaries for damage diagnosis, offering high accuracy and computational efficiency. Furthermore, cutting-edge AI algorithms, including Transformers, Convolutional Neural Networks, and Graph Neural Networks, are exploited to improve traditional bridge fatigue assessment. Deep neural network architectures are designed for indirectly sensing strain response from bridge acceleration data, overcoming equipment cost and accessibility limitations associated with critical structural areas. The outcomes demonstrate the feasibility and significant progress over existing methods.

Innovations in bridge management in Australia to rise to the challenges of today and the future

Australia has a relatively small and dispersed population across a significantly large continent. Its economy is heavily based on the movement of freight which is primarily done on its road network due to capacity and access limitations on other alternatives such as rail, air, and water. The freight task is growing rapidly due to unprecedented population growth, coupled with increased demand from trading partners in Asia and rapid changes in technology, e-commerce, and consumer behavior. To remain competitive in a global market, the movement of freight must be fast, efficient, and effective. This is a significant challenge with an ageing road bridge network designed and built to outdated standards, loads increasing in frequency and mass and more frequent extreme climatic events like floods and bushfires.

Australia’s road infrastructure managers are investing in research to seek innovations and practical and im-plementable improvements. Partnerships between researchers and infrastructure managers are critical to en-sure innovations are identified, best practice is furthered, and the ever-increasing risk is appropriately man-aged. To achieve this and rise to the challenges faced research programs have covered many areas including the refinement of structural assessments, assessing structural risk, identifying innovative materials and main-tenance, rehabilitation and strengthening techniques, improved monitoring practices and enhanced testing and analysis. The outcomes of this research will be shared along with recommendations for future investment and research.