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Cláudia Ferreira
CERIS, Instituto Superior Técnico, Universidade de Lisboa, Avenue Rovisco Pais, 1049-001 Lisbon, Portugal

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Journal article
Published: 11 June 2021 in Sustainability
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The increase of awareness with sustainability and the desire of reducing the energy consumption in the construction sector haved increased the application of External Thermal Insulation Composite Systems (ETICS) across Europe in the last decades. Nevertheless, the implementation of appropriate maintenance strategies is still neglected. The aim of this study is to analyse the impact of different maintenance strategies. For that purpose, a condition-based maintenance model, based on Petri nets, is used to evaluate three maintenance strategies: MS1—total replacement only; MS2—combination of minor intervention and total replacement; and MS3—combination of cleaning operations, minor intervention, and total replacement. In the end, a multi-criteria analysis is used to discuss the impact of the three maintenance strategies proposed, evaluating the remaining service life, the global costs over time, the ETICS’ degradation condition, and the number of replacements (end of service life) over the time horizon. For this purpose, a sample of 378 ETICS was analysed, based on in situ visual inspections, carried out in Portugal. The results from this study reveal that maintenance plays an important role to increase the durability of ETICS, and therefore their sustainability. Regular maintenance can promote the extension of the ETICS’s service life between 88% and 159% (between 15 to 27 years), improve the global degradation condition of the ETICS, and reduce the impact on users by reducing the number of deeper interventions. Further research is essential to optimise the maintenance strategies (time interval between inspections, stakeholders’ performance criteria, and environmental exposure).

ACS Style

Cláudia Ferreira; Ana Silva; Jorge de Brito; Ilídio Dias; Inês Flores-Colen. Condition-Based Maintenance Strategies to Enhance the Durability of ETICS. Sustainability 2021, 13, 6677 .

AMA Style

Cláudia Ferreira, Ana Silva, Jorge de Brito, Ilídio Dias, Inês Flores-Colen. Condition-Based Maintenance Strategies to Enhance the Durability of ETICS. Sustainability. 2021; 13 (12):6677.

Chicago/Turabian Style

Cláudia Ferreira; Ana Silva; Jorge de Brito; Ilídio Dias; Inês Flores-Colen. 2021. "Condition-Based Maintenance Strategies to Enhance the Durability of ETICS." Sustainability 13, no. 12: 6677.

Research article
Published: 13 May 2021 in Transportation Planning and Technology
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In this paper, continuous timed Petri nets (CTPN) are used to develop a hybrid traffic model, where the network is modelled as a macroscopic model and calibrated by microscopic models. The concept of CTPN is used to build a modular model, where first the highway traffic system is decomposed into several systems, based on structural entities (highway segment, on- and off-ramp links), which are coalesced into a complete model. The result is a light, versatile and easily scalable stochastic model for traffic flow. The calibration and validation of the traffic model is performed through the comparison of basic traffic parameters (flow rate, density, and mean speed) obtained through the traffic model implemented and the commercial micro-modelling software, Aimsun, for part of Portugal’s highway network. The results show that the proposed methodology results in a good trade-off between accuracy, simplicity, and computational cost.

ACS Style

Cláudia Ferreira; Luís Canhoto Neves. Macro modelling of traffic flow using continuous timed Petri nets. Transportation Planning and Technology 2021, 44, 503 -523.

AMA Style

Cláudia Ferreira, Luís Canhoto Neves. Macro modelling of traffic flow using continuous timed Petri nets. Transportation Planning and Technology. 2021; 44 (5):503-523.

Chicago/Turabian Style

Cláudia Ferreira; Luís Canhoto Neves. 2021. "Macro modelling of traffic flow using continuous timed Petri nets." Transportation Planning and Technology 44, no. 5: 503-523.

Journal article
Published: 26 March 2021 in Buildings
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Façades, as the most external building envelope component, are subject to different ex-ternal environmental loads, such as: Temperature, precipitation, damp, and wind. Therefore, the contribution of environmental actions to the occurrence of defects in façades claddings is an important subject of study since these actions strongly affect the degradation process and natural ageing of these components during their service life. In this study, a methodology to support decision-makers in the process of selecting a façade cladding system and the maintenance strategy to implement is presented and discussed. This methodology covers the performance of four façade claddings (ceramic tiling systems (CTS), natural stone claddings (NSC), external thermal insulation composite systems (ETICS), and architectural concrete façades (ACF)) over time, according to three environmental exposure variables (exposure to damp, distance from the sea, and orientation). The databases were established based on the diagnosis of the degradation condition of these claddings in-service conditions, in Portugal. The results reveal that the environmental exposure variables have a significant impact on maintenance requirements and costs. For all the categories of the environmental exposure condition variables, under all scenarios, ETICS is the least favorable constructive solution while CTS is the most advantageous solution. Furthermore, the results show that properly implemented maintenance activities enhance the performance level of building components, which positively affects their degradation behavior over time.

ACS Style

Cláudia Ferreira; Joana Barrelas; Ana Silva; Jorge de Brito; Ilídio Dias; Inês Flores-Colen. Impact of Environmental Exposure Conditions on the Maintenance of Facades’ Claddings. Buildings 2021, 11, 138 .

AMA Style

Cláudia Ferreira, Joana Barrelas, Ana Silva, Jorge de Brito, Ilídio Dias, Inês Flores-Colen. Impact of Environmental Exposure Conditions on the Maintenance of Facades’ Claddings. Buildings. 2021; 11 (4):138.

Chicago/Turabian Style

Cláudia Ferreira; Joana Barrelas; Ana Silva; Jorge de Brito; Ilídio Dias; Inês Flores-Colen. 2021. "Impact of Environmental Exposure Conditions on the Maintenance of Facades’ Claddings." Buildings 11, no. 4: 138.

Journal article
Published: 10 February 2021 in Journal of Building Engineering
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In façades design, the selection of constructive solutions plays an important role. The materials used should withstand the expected degradation agents and mechanisms. However, this choice is still based on intuitive criteria. To support decision-makers in the cladding system selection process, this study considers the behaviour of the constructive solutions over time, their maintenance needs, and costs on a multi-criteria analysis methodology. For that purpose, six façade claddings are evaluated: ceramic tiling systems; natural stone claddings; rendered façades; painted surfaces; ETICS; and architectural concrete façades. The databases were established based on the diagnosis of the degradation of these claddings in real in-service conditions, in Portugal. The findings of this study provide an objective framework for selecting façades claddings’ solutions. The results reveal that, according to the different criteria and preferences of the owners/managers of the buildings, different solutions can be achieved, allowing selecting more suitable and economical materials and maintenance strategies. By comparing to the most usually selected conditions of constructive solutions (initial costs and no preventive maintenance), the maintenance strategy can be changed if the weight of the durability and performance criteria is, at least, 1%, and the constructive solution can be changed if the weight is, at least, 17%.

ACS Style

Cláudia Ferreira; Ilídio S. Dias; Ana Silva; Jorge de Brito; Inês Flores-Colen. Criteria for selection of cladding systems based on their maintainability. Journal of Building Engineering 2021, 39, 102260 .

AMA Style

Cláudia Ferreira, Ilídio S. Dias, Ana Silva, Jorge de Brito, Inês Flores-Colen. Criteria for selection of cladding systems based on their maintainability. Journal of Building Engineering. 2021; 39 ():102260.

Chicago/Turabian Style

Cláudia Ferreira; Ilídio S. Dias; Ana Silva; Jorge de Brito; Inês Flores-Colen. 2021. "Criteria for selection of cladding systems based on their maintainability." Journal of Building Engineering 39, no. : 102260.

Journal article
Published: 20 November 2020 in Applied Sciences
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In condition-based maintenance plans, the schedule of inspections is an important step. Condition-based actions are performed according to prescribed condition criteria (i.e., condition, cost, availability, among other factors), and the main purpose of inspections is to evaluate the façade’s condition and plan its correction in order to reduce the risk of failure of the cladding. Therefore, the main goal of this study is to implement multi-objective optimization to understand whether there is an optimal time interval for performing the inspections. For that purpose, a Petri-net condition maintenance model is used to assess the influence of different maintenance plans on the overall degradation of natural stone claddings. In this model, the maintenance activities can only be performed after an inspection has been carried out. The definition of the best maintenance policy results in a conflict of objectives. Owners/managers seek to achieve a maintenance strategy that minimizes service life costs and maintain the cladding in a safe and minimal degradation condition. Multi-objective optimization procedures are capable of considering several conflicting objectives. In this paper, the objective functions considered are minimization of the service life costs, maximization of the efficiency index, maximization of the service life, and minimization of the total number of replacements over the time horizon.

ACS Style

Cláudia Ferreira; Ana Silva; Jorge De Brito; Ilídio S. Dias; Inês Flores-Colen. Optimization of Inspection Period in Natural Stone Claddings. Applied Sciences 2020, 10, 8236 .

AMA Style

Cláudia Ferreira, Ana Silva, Jorge De Brito, Ilídio S. Dias, Inês Flores-Colen. Optimization of Inspection Period in Natural Stone Claddings. Applied Sciences. 2020; 10 (22):8236.

Chicago/Turabian Style

Cláudia Ferreira; Ana Silva; Jorge De Brito; Ilídio S. Dias; Inês Flores-Colen. 2020. "Optimization of Inspection Period in Natural Stone Claddings." Applied Sciences 10, no. 22: 8236.

Journal article
Published: 22 September 2020 in Infrastructures
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Existing maintenance policies have several limitations, mainly due to the lack of knowledge regarding the durability and performance of buildings. Usually, the maintenance policies are insufficiently accurate, neglecting the risk of failure over time and the global costs associated with repairs. In this study, a condition-based maintenance model, based on Petri nets, is proposed to evaluate the impact of three maintenance strategies of ceramic claddings in pitched roofs (CCPR): MS1—only total replacement; MS2—composed of total replacement and minor intervention and MS3—composed of total replacement, minor intervention and cleaning operations. In this study, 146 CCPR were inspected in situ, with a total area of 43,991.6 m2. The remaining service life of the CCPR; the global costs over the claddings’ lifetime (considering inspection, maintenance, replacement and disposal costs); the claddings’ degradation condition and the number of replacements during the time horizon are used to evaluate the performance of the different maintenance strategies through a simplified multi-criteria analysis. The results show that the gains in performance, in terms of expected service life and durability, of the consideration of preventive maintenance actions (minor interventions or cleaning operations) outweigh the increase of the operation costs.

ACS Style

Cláudia Ferreira; Ana Silva; Jorge De Brito; Ilídio S. Dias; Inês Flores-Colen. Maintenance Modelling of Ceramic Claddings in Pitched Roofs Based on the Evaluation of Their In Situ Degradation Condition. Infrastructures 2020, 5, 77 .

AMA Style

Cláudia Ferreira, Ana Silva, Jorge De Brito, Ilídio S. Dias, Inês Flores-Colen. Maintenance Modelling of Ceramic Claddings in Pitched Roofs Based on the Evaluation of Their In Situ Degradation Condition. Infrastructures. 2020; 5 (9):77.

Chicago/Turabian Style

Cláudia Ferreira; Ana Silva; Jorge De Brito; Ilídio S. Dias; Inês Flores-Colen. 2020. "Maintenance Modelling of Ceramic Claddings in Pitched Roofs Based on the Evaluation of Their In Situ Degradation Condition." Infrastructures 5, no. 9: 77.

Journal article
Published: 29 July 2020 in Journal of Building Engineering
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Nowadays, the degradation of the built environment is becoming a serious economic, cultural and environmental problem in several developed countries, after several decades of adopting an attitude of “built and let decay”. The lack of maintenance policies led to additional costs and risks for owners and increased the aesthetic degradation of our cities. In this study, a condition-based maintenance model, based on Petri nets, is used to analyse the influence of alternative maintenance strategies on the overall degradation of natural stone claddings. For this purpose, three maintenance strategies are considered: i) total replacement; ii) combination of minor intervention and total replacement; and iii) combination of cleaning operations, minor intervention and total replacement. The impact of the alternative maintenance strategies on the future performance and remaining service life of natural stone claddings is discussed. In this study, a sample of 203 natural stone claddings, located in Portugal, is analysed and the degradation of these claddings in-service condition is evaluated through in-situ inspections. Furthermore, a simplified multi-criteria analysis is carried out to evaluate the economic impact of each maintenance strategy in comparison with the increased durability achieved through its adoption. The results reveal that the adoption of other maintenance activities (minor interventions or cleaning operations) increases the operational costs, as expected, but promotes the durability of the claddings. The adoption of maintenance actions allows increasing the predicted service life of NSC (148 years for MS2 and 177 years for MS3), when compared with NSC that are not subjected to any kind of preventive maintenance (70 years).

ACS Style

C. Ferreira; A. Silva; J. de Brito; I.S. Dias; I. Flores-Colen. Definition of a condition-based model for natural stone claddings. Journal of Building Engineering 2020, 33, 101643 .

AMA Style

C. Ferreira, A. Silva, J. de Brito, I.S. Dias, I. Flores-Colen. Definition of a condition-based model for natural stone claddings. Journal of Building Engineering. 2020; 33 ():101643.

Chicago/Turabian Style

C. Ferreira; A. Silva; J. de Brito; I.S. Dias; I. Flores-Colen. 2020. "Definition of a condition-based model for natural stone claddings." Journal of Building Engineering 33, no. : 101643.

Journal article
Published: 25 June 2020 in Journal of Building Engineering
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Usually, maintenance models consider maintenance actions as perfect, i.e. these interventions can restore the components to the “as good as new” state. However, in many situations, this assumption is too simplistic, and moreover it is not true. In this study, imperfect maintenance actions are considered. For that purpose, a new methodology is developed to quantify the impact of maintenance actions on buildings' envelope components. This methodology is based on a probabilistic approach, implemented through a stochastic maintenance model based on Petri Nets (PN). The quantification of the impact of maintenance actions on building components is estimated by assessing the impact of these actions on the overall degradation condition of the component, which is expressed by a numerical index called severity of degradation index, Sw. This is a conceptual study, in which the maintenance plans are composed of condition-based maintenance actions, and the schedule of the actions is carried out based on the condition of the components. In the definition of the maintenance plans, four levels of interventions were considered: inspections; cleaning operations; minor interventions; and total replacement. The results reveal that the adoption of minor interventions or cleaning operations increases the operational costs but, when performed with an adequate periodicity, allows maintaining the components’ performance at high standards for most of their service life, thus promoting their durability.

ACS Style

C. Ferreira; A. Silva; J. de Brito; I.S. Dias; I. Flores-Colen. The impact of imperfect maintenance actions on the degradation of buildings’ envelope components. Journal of Building Engineering 2020, 33, 101571 .

AMA Style

C. Ferreira, A. Silva, J. de Brito, I.S. Dias, I. Flores-Colen. The impact of imperfect maintenance actions on the degradation of buildings’ envelope components. Journal of Building Engineering. 2020; 33 ():101571.

Chicago/Turabian Style

C. Ferreira; A. Silva; J. de Brito; I.S. Dias; I. Flores-Colen. 2020. "The impact of imperfect maintenance actions on the degradation of buildings’ envelope components." Journal of Building Engineering 33, no. : 101571.

Journal article
Published: 16 August 2019 in Structure and Infrastructure Engineering
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ACS Style

Cláudia Ferreira; Luís Canhoto Neves; Ana Silva; Jorge De Brito. Stochastic maintenance models for ceramic claddings. Structure and Infrastructure Engineering 2019, 16, 247 -265.

AMA Style

Cláudia Ferreira, Luís Canhoto Neves, Ana Silva, Jorge De Brito. Stochastic maintenance models for ceramic claddings. Structure and Infrastructure Engineering. 2019; 16 (2):247-265.

Chicago/Turabian Style

Cláudia Ferreira; Luís Canhoto Neves; Ana Silva; Jorge De Brito. 2019. "Stochastic maintenance models for ceramic claddings." Structure and Infrastructure Engineering 16, no. 2: 247-265.

Research paper
Published: 17 August 2018 in Building Research & Information
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A stochastic Petri-net formalism is proposed to predict the degradation of ceramic claddings over time in order to understand how different environmental exposure conditions contribute to the overall degradation of these claddings. For that purpose, the degradation condition of 195 ceramic claddings located in Lisbon, Portugal, is evaluated through in situ visual inspections. In the first part of the study, a stochastic deterioration Petri-net model is proposed for the entire sample. In the second part, the original sample is divided according to the environmental exposure conditions, evaluating the influence of these conditions on the deterioration process of ceramic claddings. Four main degradation agents are analyzed: exposure to moisture; distance from the sea; orientation; and wind–rain action. The results reveal that Petri nets can accurately describe the deterioration process of ceramic claddings, providing relevant information regarding the performance of these claddings through their life cycle and according to the environmental exposure conditions to which they are subject. These results are extremely relevant for different practitioners: the approach allows the adoption of more sustainable and durable solutions at the design stage, as well as improving the durability of the ceramic claddings by performing optimized maintenance plans and strategies.

ACS Style

Cláudia Ferreira; Luis Neves; A. Silva; J. De Brito. Stochastic Petri-net models to predict the degradation of ceramic claddings. Building Research & Information 2018, 47, 697 -715.

AMA Style

Cláudia Ferreira, Luis Neves, A. Silva, J. De Brito. Stochastic Petri-net models to predict the degradation of ceramic claddings. Building Research & Information. 2018; 47 (6):697-715.

Chicago/Turabian Style

Cláudia Ferreira; Luis Neves; A. Silva; J. De Brito. 2018. "Stochastic Petri-net models to predict the degradation of ceramic claddings." Building Research & Information 47, no. 6: 697-715.

Journal article
Published: 01 March 2018 in Automation in Construction
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In this study, a methodology to model and predict the life-cycle performance of building façades based on Stochastic Petri Nets is proposed. The proposed model evaluates the performance of rendered façades over time, evaluating the uncertainty of the future performance of these coatings. The performance of rendered façades is evaluated based on a discrete qualitative scale composed of five condition levels, established according to the physical and visual degradation of these elements. In this study, the deterioration is modelled considering that the transition times between these condition states can be modelled as a random variable with different distributions. For that purpose, a Stochastic Petri Nets model is used, as a formal framework to describe this problem. The model’s validation is based on probabilistic indicators of performance, computed using Monte- Carlo simulation and the probability distribution parameters leading to better fit are defined as those maximizing the likelihood, computed using Genetic Algorithm. In this study, a sample of 99 rendered façades, located in Portugal, is analysed, and the degradation condition of each case study is evaluated through in-situ visual inspections. The model proposed allows evaluating: i) the transition rate between degradation conditions; ii) the probability of belonging to a given degradation condition over time; and iii) the mean time of permanence in each degradation condition. The use of Petri Nets shows to be more accurate than a more traditional approach based on Markov Chains, but also allows developing future research to consider different environmental conditions, maintenance actions or inspections, amongst other aspects of life-cycle analysis of existing assets

ACS Style

Cláudia Ferreira; L. Canhoto Neves; A. Silva; Jorge de Brito. Stochastic Petri net-based modelling of the durability of renderings. Automation in Construction 2018, 87, 96 -105.

AMA Style

Cláudia Ferreira, L. Canhoto Neves, A. Silva, Jorge de Brito. Stochastic Petri net-based modelling of the durability of renderings. Automation in Construction. 2018; 87 ():96-105.

Chicago/Turabian Style

Cláudia Ferreira; L. Canhoto Neves; A. Silva; Jorge de Brito. 2018. "Stochastic Petri net-based modelling of the durability of renderings." Automation in Construction 87, no. : 96-105.