Charalampos P Andriotis

Delft University of Technology | TU · Faculty of Architecture & the Built Environment

Scheduling of inspection and maintenance policies during the life-cycle of operating infrastructure necessitates optimization of long-term objectives in stochastic environments. Modern answers to the problem should focus on quantitative decision-making techniques, taking advantage of informative but uncertain data that become available in time. As...

Fragility functions indicate the probability of a system exceeding certain damage states given some appropriate measures that characterize recorded or simulated data series. Presented in two main parts, this paper develops fragility functions in their utmost generality, accounting for both (1) multivariate intensity measures with multiple damage st...

Decision-making for engineering systems can be efficiently formulated as a Markov Decision Process (MDP) or a Partially Observable MDP (POMDP). Typical MDP and POMDP solution procedures utilize offline knowledge about the environment and provide detailed policies for relatively small systems with tractable state and action spaces. However, in large...

Efficient integration of uncertain observations with decision-making optimization is key for prescribing informed intervention actions, able to preserve structural safety of deteriorating engineering systems. To this end, it is necessary that scheduling of inspection and monitoring strategies be objectively performed on the basis of their expected...

Determination of inspection and maintenance policies for minimizing long-term risks and costs in deteriorating engineering environments constitutes a complex optimization problem. Major computational challenges include the (i) curse of dimensionality, due to exponential scaling of state/action set cardinalities with the number of components; (ii) c...

The application of Deep Reinforcement Learning (DRL) for the management of engineering systems has shown very promising results in terms of optimality and scalability. The interpretability of these policies by decision-makers who are so far mostly familiar with traditional approaches is also needed for implementation. In this work, we address this...

To preserve structural safety of deteriorating engineering systems through optimal maintenance, it is imperative to efficiently integrate structural health information with decision-making optimization frameworks. Although there may be abundance of available data, these are often uncertain and incomplete. In addition, joint inspection and maintenan...

A key computational challenge in maintenance planning for deteriorating structures is to concurrently secure (i) optimality of decisions over long planning horizons, and (ii) accuracy of real-time parameter updates in high-dimensional stochastic spaces. Both are often encumbered by the presence of discretized continuous-state models that describe t...

Maintenance planning of engineering systems is often posed as a stochastic optimal control problem, aimed at determining a series of discrete interventions that upkeep structural integrity. Advanced algorithmic schemes within the joint framework of Partially Observable Markov Decision Processes (POMDPs) and multi-agent Deep Reinforcement Learning (...

To preserve structural safety of deteriorating engineering systems through optimal maintenance, it is imperative to efficiently integrate structural health information with decision-making optimization frameworks. Although there may be abundance of available data, these are often uncertain and incomplete. In addition, joint inspection and maintenan...

The application of Deep Reinforcement Learning (DRL) for the management of engineering systems has shown very promising results in terms of optimality and scalability. The interpretability of these policies by decision-makers who are so far mostly familiar with traditional approaches is also needed for implementation. In this work, we address thi...

This work develops a computational method that produces algorithmically generated design forms, able to overcome inherent challenges related to the use of cast glass for the creation of monolithic structural components with light permeability. Structural Topology Optimization (TO) has a novel applicability potential, as decreased mass is associated...

Bridge structures are exposed to several chronic and abrupt stressors, among which the combined effects of corrosion and earthquakes pose a major threat to their long-term safety. Probabilistic risk assessment frameworks that quantify and propagate uncertainties inherent to these phenomena are necessary to mitigate this threat. This paper proposes...

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...

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...

Inspection and maintenance (I&M) optimization entails many sources of computational complexity, among others, due to high-dimensional decision and state variables in multi-component systems, long planning horizons, stochasticity of objectives and constraints, and inherent uncertainties in measurements and models. This paper studies how the above ca...

Fragility analysis aims to compute the probabilities of a system exceeding certain damage conditions given different levels of hazard intensity. Fragility analysis is therefore a key process of performance-based earthquake engineering, with a number of approaches developed and widely recognized, including Incremental Dynamic Analysis (IDA), Multipl...

In the context of modern environmental and societal concerns, there is an increasing demand for methods able to identify 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 compone...

Forest management can be seen as a sequential decision-making problem to determine an optimal scheduling policy, e.g., harvest, thinning, or do-nothing, that can mitigate the risks of wildfire. Markov Decision Processes (MDPs) offer an efficient mathematical framework for optimizing forest management policies. However, computing optimal MDP solutio...

Civil and maritime engineering systems, among others, from bridges to offshore platforms and wind turbines, must be efficiently managed, as they are exposed to deterioration mechanisms throughout their operational life, such as fatigue and/or corrosion. Identifying optimal inspection and maintenance policies demands the solution of a complex sequen...

Efficient integration of uncertain observations with decision-making optimization is key for prescribing informed intervention actions, able to preserve structural safety of deteriorating engineering systems. To this end, it is necessary that scheduling of inspection and monitoring strategies be objectively performed on the basis of their expected...

This work presents a hybrid shear‐flexible beam‐element, capable of capturing arbitrarily large inelastic displacements and rotations of planar frame structures with just one element per member. Following Reissner’s geometrically‐exact theory, the finite element problem is herein formulated within nonlinear programming principles, where the total p...

Determination of inspection and maintenance policies for minimizing long-term risks and costs in deteriorating engineering environments constitutes a complex optimization problem. Major computational challenges include the (i) curse of dimensionality, due to exponential scaling of state/action set cardinalities with the number of components; (ii) c...

Civil and maritime engineering systems, among others, from bridges to offshore platforms and wind turbines, must be efficiently managed as they are exposed to deterioration mechanisms throughout their operational life, such as fatigue or corrosion. Identifying optimal inspection and maintenance policies demands the solution of a complex sequential...

Civil and maritime engineering systems, among others, from bridges to offshore platforms and wind turbines, must be efficiently managed as they are exposed to deterioration mechanisms throughout their operational life, such as fatigue or corrosion. Identifying optimal inspection and maintenance policies demands the solution of a complex sequential...

In the present work, a hybrid beam element based on exact kinematics is developed, accounting for arbitrarily large displacements and rotations, as well as shear deformable cross sections. At selected quadrature points, fiber discretization of the cross sections facilitates efficient computation of the stress resultants for any uniaxial material la...

Decision-making for engineering systems management can be efficiently formulated using Markov Decision Processes (MDPs) or Partially Observable MDPs (POMDPs). Typical MDP/POMDP solution procedures utilize offline knowledge about the environment and provide detailed policies for relatively small systems with tractable state and action spaces. Howeve...

Management of structures and infrastructure systems has gained significant attention in the pursuit of optimal inspection and maintenance life-cycle policies that are able to handle diverse deteriorating effects of stochastic nature and satisfy long-term objectives. Such sequential decision problems can be efficiently formulated along the premises...

A life-cycle approach to infrastructure design and management involves decisions pertaining to operation, maintenance, intervention, and rapid response measures. Such an approach may only be conceived when formulated on the basis of observations during the life-cycle of these systems. Structural Health Monitoring (SHM) offers a tool to such an end,...

Modern structural analysis necessitates numerical formulations with advanced nonlinear attributes. To that end, numerous finite elements have been proposed, spanning from classical to hybrid standpoints. In addition to their individual features, all formulations originally stem from an underlying variational principle, which can be deemed as a unif...

Extended and generalized fragility functions support estimation of multiple damage state probabilities, based on intensity measure spaces of arbitrary dimensions and longitudinal state dependencies in time. The softmax function provides a consistent mathematical formulation for fragility analysis, thus, fragility functions are herein developed alon...

Performance-based engineering and risk assessment of structures entail fragility analysis as a process that connects seismic intensity measures to damage state exceedance probabilities, in order to eventually evaluate different mean annual frequency metrics. In the simplest case, fragility functions describe binary damage states, e.g. collapse frag...

Risk assessment in earthquake engineering necessitates effective predictive models for structural damage evolution, compatible with current decision support frameworks. Such models should be able to handle stochastic seismic excitations and structural responses, probabilistically associating characteristic earthquake features of reduced dimensions...

Fragility functions are widely used in performance-based analysis and risk assessment of structures, readily addressing the earthquake and structural engineering needs for uncertainty quantification. Fragility functions indicate the probability of a system exceeding certain damage states given some appropriate intensity measures characterizing reco...

Optimized maintenance of operating aging infrastructures is of paramount importance to ensure safe and cost effective operation during their original design lifetime and even beyond that. Modern answers to the problem should focus on automated planning and decision making techniques taking advantage of informative but uncertain data that become ava...

Optimized maintenance of operating aging infrastructures is of paramount importance to ensure safe and cost effective operation during their original design lifetime and even beyond that. Modern answers to the problem should focus on automated planning and decision making techniques taking advantage of informative but uncertain data that become ava...

Inspection and maintenance of aging structures are key components for a safe and secure performance of infrastructure systems. To ensure optimum allocation of resources along the structural life-cycle, this scheduling problem can be formed in an optimization framework that can specify the inspection and maintenance types and time instances. Unfortu...

In this work, a new smooth model for uniaxial concrete behavior that combines plasticity and damage considerations, together with unsymmetrical hysteresis for tension compression and nonlinear unloading, is presented. Softening and stiffness degradation phenomena are handled through a scalar damage-driving variable, which is a function of total str...