Inference and dynamic decision-making for deteriorating systems with probabilistic dependencies through Bayesian networks and deep reinforcement learning

In the context of modern engineering, environmental, and societal concerns, there is an increasing demand for methods able to identify rational management strategies for civil engineering systems, minimizing structural failure risks while optimally planning inspection and maintenance (I&M) processes. Most available methods simplify the I&M decision problem to the component level, often assuming statistical, structural, or cost independence among components, due to the computational complexity associated with global optimization methodologies under joint system-level state descriptions. In this paper, we propose an efficient algorithmic framework for inference and decision-making under uncertainty for engineering systems exposed to deteriorating environments, providing optimal management strategies directly at the system level. In our approach, the decision problem is formulated as a factored partially observable Markov decision process, whose dynamics are encoded in Bayesian network conditional structures. The methodology can handle environments under equal or general, unequal deterioration correlations among components, through Gaussian hierarchical structures and dynamic Bayesian networks, decoupling the originally joint system state space to component networks conditional on shared random variables. In terms of policy optimization, we adopt a deep decentralized multi-agent actor-critic (DDMAC) reinforcement learning approach, in which the policies are approximated by actor neural networks guided by a critic network. By including deterioration dependence in the simulated environment, and by formulating the cost model at the system level, DDMAC policies intrinsically consider the underlying system-effects. This is demonstrated through numerical experiments conducted for both a 9-out-of-10 system and a steel frame under fatigue deterioration. Results demonstrate that DDMAC policies offer substantial benefits when compared to state-of-the-art heuristic approaches. The inherent consideration of system-effects by DDMAC strategies is also interpreted based on the learned policies.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Architectural Technolog

Innovative Concepts in Navigation Lock Design and Gate Contact Aspects

This paper presents the new report n°106 of PIANC InCom WG29 on Innovations in Navigation Lock Design, published by PIANC in August 2009, as well as some additional contributions on lock gates (gate contact technology). The paper highlights the main objectives and issues of his PIANC report with a specific emphasis on gates and specifically on the contact aspects. Locks are key structures for the development of the navigation in canals and in natural rivers where weirs regulate water levels to enable navigation. They may also be strategic infrastructure for port development. The core of this report has three major parts. The first part presents an exhaustive list of design goals associated with locks. This section is particularly important for decision makers who have to launch a new project. The second part reviews the design principles that must be considered by designers. This section is methodologically oriented. The third part is technically oriented. All main technical aspects (hydraulics, structures, foundations, including computational aspects, etc.) are reviewed, focussing on changes and innovations occurring since 1986. Perspectives and trends for the future are also listed. When appropriate, recommendations are listed. It is impossible to give the details of all lock innovation areas in this paper. As an example, the lock gates and, in particular, the modern views on their contact issues have been chosen. These new solutions are welcome to limit the maintenance and to extend the service life of lock gates

Managing offshore wind turbines through Markov decision processes and dynamic Bayesian networks

Efficient planning of inspection and maintenance (I&M) actions in civil and maritime environments is of paramount importance to balance management costs against failure risk caused by deteriorating mechanisms. Determining I&M policies for such cases constitutes a complex sequential decision-making optimization problem under uncertainty. Addressing this complexity, Partially Observable Markov Decision Processes (POMDPs) provide a principled mathematical methodology for stochastic optimal control, in which the optimal actions are prescribed as a function of the entire, dynamically updated, state probability distribution. As shown in this paper, by integrating Dynamic Bayesian Networks (DBNs) with POMDPs, advanced algorithmic schemes of probabilistic inference and decision optimization under uncertainty can be uniquely combined into an efficient planning platform. To demonstrate the capabilities of the proposed approach, POMDP and heuristic-based I&M policies are compared, with emphasis on an offshore wind substructure subject to fatigue deterioration. Results verify that POMDP solutions offer substantially reduced costs compared to their counterparts, even in traditional problem settings.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Design & Mechanic

Position paper: Inland waterways classification for South America: Core concepts and initial proposals

South America, as of yet, has not been able to take full advantage of its extensive system of naturally navigable waterways and in making them an integrated part of the region’s transport network to cater for the ever increasing demand for cargo and human mobility. Infrastructure limitations are one of the major obstacles for the development of inland navigation in the region and, to a certain extent, they are being addressed in most national and regional transport plans and projects. However, this effort, in most cases, remain isolated, and the potential and role of inland shipping as a “natural resource” in itself, but also for transporting the region’s natural resources is, in general, absent as an integral part of the countries transport, mobility and or logistics policies. In this sense the economic and social value of the region’s inland waterway system is still underestimated. A common classification of the inland waterways (rivers, canals and lakes), which currently does not exist in the region, could be instrumental for achieving greater, better and more sustainable use and governance of inland navigation. The experiences of other regions in the world demonstrate that inland waterway classifications, far from being public sector formality or a purely academic exercise, are an essential, powerful and dynamic tool for supporting and implementing inland waterways policies and projects inasmuch as they allow to identify the limitations and the economic potential of navigable waterways in the region and to encourage and monitor the development of their capacity for transport of goods and people. Against this backdrop and in order to encourage reflection on a potential inland waterways classification for the South American region, this document uses the example of the European system of classification to demonstrate the role of classifications in the inland navigation development. Specifically, it looks at the 1996 European Agreement on Main Inland Waterways of International Importance (AGN Agreement). Signed in 1996 and ratified by 18 European countries, the AGN Agreement continues to be one of the main instruments for inland water transport development in Europe, as demonstrated by the growing number of ratifications by the countries of the region.1 This Working Document describes the main elements of the European classification system of navigable waterways (Section I) and existing mechanisms for the monitoring and use of the established network of inland waterways (Section II) and then analyses the role of the classification in the development of inland water transport in Europe (Section III). It goes on to discuss lessons learned and presents a preliminary proposal for the establishment of a regional classification for South America (Section IV). The concluding section addresses the institutional processes and next steps needed to develop a classification of this kind. Bearing in mind that the process for the elaboration of the South American classification is still at an early stage and several open question still remain, the overall goal of the document is to highlight and illustrate relevant issues, which have to be discussed at national level and among the experts of the South American countries to identify and implement a harmonized scheme of classification on a regional basis.Rivers, Ports, Waterways and Dredging Engineerin

Resilience to flooding: Draft building code

A significant issue associated Flood Defence Systems (FDS) is the difficulty of predicting how these structures will behave when inevitably they have been loaded beyond their designed capacity by a flood. The flood can cause these structures to fail catastrophically with loss of life and substantial damage to property. For a limited incremental investment, by including resilient features shown in this document, the FDS can dramatically lessen the chances for loss of life and property damage. While not a building code, the following provides guidance on how to improve the resilience of FDS so they will not fail catastrophically when overloaded beyond their designed capacity. Of all "lessons learnt" most important is to explicitly incorporate the consequences of failure and the possibility of being wrong in one's assumptions into the design process. Building in the flood plain will always have risk; the public should not become over confident just because a FDS is place. While it is recognized that an Integrated Water Basin perspective would include retention zones, restricted developments in flood plains, land use planning, awareness raising, flood resistant construction, drainage and water storage improvement, effective evacuation planning and other measures.Hydraulic EngineeringCivil Engineering and Geoscience