José C. Matos

MOEA/PC: Multiobjective Evolutionary Algorithm Based on Polar Coordinates

The need to perform the search in the objective space constitutes one of the fundamental differences between multiobjective and single-objective optimization. The performance of any multiobjective evolutionary algorithm (MOEA) is strongly related to the efficacy of its selection mechanism. The population convergence and diversity are two different but equally important goals that must be ensured by the selection mechanism. Despite the equal importance of the two goals, the convergence is often used as the first sorting criterion, whereas the diversity is considered as the second one. In some cases, this can lead to a poor performance, as a severe loss of diversity occurs.

Visual inspection and bridge management

Abstract This paper estimates visual inspection quantitatively prior to its implementation in a Bridge Management System using a Value of Information (VoI) approach employing a Bayesian pre-posterior analysis. Information from a significant number of real bridges from Ireland and Portugal are considered in this regard following existing commercial practices. The variation of different parameters on the estimated VoI is investigated including the assumed probabilistic models of the prior bridge state, the likelihood of inspector assigned condition ratings and the economic setting surrounding the cost matrix for maintenance decision alternatives. The values of no information, perfect information and imperfect information are presented and the change in the optimal strategy based on such information is assessed. The effect of human imperfections in assessment and difference in condition rating scale are also estimated. The studies and findings of this paper are expected to allow a better insight for practising engineers and researchers working in bridge management.

Integrating multivariate techniques in bridge management systems

The use of bridge management systems (BMS) by infrastructure stakeholders has led to the collection and retention of large quantities of data concerning the condition states of bridges throughout national and regional networks. The database for the BMS is often populated by the results of routine visual inspections, based on a prescribed scale for defining the condition state of the bridge’s individual elements, and of the bridge structure as a whole. The populating of the database also leads to the storage of large quantities of so-called metadata; which can describe the physical parameters of the bridge. The availability of this data allows the assessment of the BMS using multivariate techniques to enhance the life-cycle assessment of bridge networks, through advanced descriptive and predictive techniques applied to deteriorating network assets. Multivariate techniques such as principal component analysis have been demonstrated by the authors to be effectively applied as a descriptive tool to an existing BMS, and the results of a case study of a large dataset of bridges indicate its viability to be integrated into data-based approaches to infrastructural asset management.

Two-Stage Multiobjective Optimization of Maintenance Scheduling for Pavements

The authors wish to thank ANI (“Agencia Nacional de Inovacao”) for the financial support given to the RD and FCT (“Fundacao para a Ciencia e a Tecnologia”) for the Ph.D. scholarship (reference to SFRH/BD/85984/2012).

A Computational Framework for Infrastructure Asset Maintenance Scheduling

Abstract This paper presents a computational framework for the optimization of maintenance activities for infrastructure assets, with particular emphasis being placed on road network assets. This framework incorporates degradation and maintenance models for infrastructure assets along with multi-objective optimization for searching optimal maintenance schedules. Given a schedule of maintenance actions, the future performance is estimated by means of a Monte Carlo simulation that enables to account for inherent uncertainties. The design variables of optimization are the types of maintenance actions and their timing over the planning horizon. The objectives are to minimize both the asset degradation and maintenance cost. This includes satisfaction of constraints representing performance demands. The proposed framework is general and can be applied to different types of infrastructure assets. The numerical results, obtained for a road bridge managed by a highway operating agency, demonstrate the validity and usefulness of the proposed framework.

Introduction: The Value of Health Monitoring in Structural Performance Assessment

Structural health monitoring (SHM) has evolved over decades of continuous progress in measuring, processing, collecting and storing massive amounts of data that can provide valuable information for owners and managers in order to control and manage the integrity of their structures. The data sets acquired from SHM systems are undoubtedly of the “big data” type due to their sheer volume, complexity and diversity, and conducting relevant analyses of their content can help to identify damage or failure during operation through the relationships between the measurements taken by multiple sensors. A great deal can be learned from these large pools of data, resulting in significant advances in efficient integrity control. From banking to retail, many sectors have already embraced big data, which is often synonymous with “big expectations”; in the present case, it offers opportunities to apply dataprocessing research to the development of more efficient SHM systems with real-time capabilities. By presenting various examples of bridge monitoring systems, this paper contributes to the ongoing cross-disciplinary efforts in data science for the utilization and advancement of SHM.

Assessing the Life Cycle of Existing Maritime Structures – Application to a Harbour Bridge in Porto Port

Since the construction industry is the one that bears most expenses, both in financial and environmental terms, it is of the upmost importance that these expenses originate a product with a long term exploitation, so as to mitigate them. Having this problem in consideration, in this paper the bridge located in the north of Portugal, near Porto, in the oil tanker terminal at the Leixoes port was studied. This structure is located in one of the most aggressive environments for concrete structures, a maritime zone. The most accepted durability models in the country, related to deterioration induced by sea chlorides penetration, were then implemented. Thereby, it was possible to identify which model better reflects reality, since the structure in analysis is now at the end of its lifetime, after 50 years of service and shows advanced degradation due to chloride attack.

Life Cycle Cost, As a Tool for Decision Making on Concrete Infrastructures

The use of Life Cycle Cost (LCC) tools in civil engineering is increasing, due to the need of infrastructure owners and operators to guarantee their assets maximum performance with an optimized budget. By considering these tools it will be possible to manage assets along their lifetime in a more sustainable and efficient way. Due to this reason, it was recently constituted a Task Group on fib to deal with existing LCC tools for concrete infrastructures. This paper gives an introduction to these tools, with a special emphasis to the added-value of LCC, and to the main contents of the fib TG 8.4 state-of-art technical report. This covers a description of existing LCC standards and guidelines, their applicability, the definition of different cost elements, the incorporation of risk in the analysis, etc.

Robustness assessment—A new perspective to achieve a performance indicator

Robustness has been recognized as interesting research topic due to several collapses that have been occurring over last years. Indeed, this subject is related with global failure or collapse. However, its definition is not consensual since several definitions have been proposed in the literature. This short-paper aims to present a framework for assessing bridge’s robustness as a probabilistic performance indicator. In this study, a non-linear model of a clamped beam with two point loads using DIANA software was developed to validate the framework presented. By means of a probabilistic approach, the load carrying capacity and structural safety were evaluated. In this regard, special focus is placed on an adaptive Monte Carlo simulation procedure to achieve a proper meta-model.

COST Action TU1406: eBook of the 1st Workshop Meeting

Bridges, being complex and large infrastructure projects, can suffer from meager levels of performance and lukewarm users’ satisfaction. In order to avoid such undesirable results, it is essential not only to undertake a rigid feasibility study and establish an efficient contractual strategy, but also to optimize the relevant performance indicators (be it technical, sustainable or managerial) through the concepts of constructability and sustainability. Constructability, being a holistic lifecycle project edifice, relies heavily on the assessment and improvement of performance indicators (be it technical, sustainable or managerial), towards design and construction integration, close stakeholders’ cooperation and, ultimately, the attainment of the best possible overall project performance. Its interconnection with sustainability is close, since the latter is one of the most important dimensions of quality – one of the key project performance objectives – and extrapolates towards the rest, which are cost (of integration), time (of completion) and client satisfaction. Risk analysis, being used extensively in project management but not as of yet integrated deeply in the unified themes of constructability and sustainability, can provide the cognitive and mathematical basis for the establishment of a new methodology of assessing the performance indicators, thus helping in their improvement for the existing and ongoing projects and their documentation into lessons-learned databases for future projects. In this early work, a coarse conceptual framework for the integration of risk analysis in the combined notions of constructability and sustainability in order to assess performance indicators for bridges is defined, being an early step in an ongoing research effort towards the establishment of a holistic methodology.