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Assessment of contact laws accounting for softening in 3D rigid concrete particle models
o obtain predictions closer to concrete behaviour, it is necessary to employ a particle model(PM) that considers contact softening. A bilinear softening contact model (BL) has been adoptedin PM studies. Several limitations in PM predictions have been identified that may be due to BLassumptions. For this reason, this paper compares BL predictions with those obtained with morecomplex models to assess if PM predictions can be improved. As shown, it is possible to calibrateeach contact model to reproduce the complex behaviour observed in concrete in uniaxial and biaxialloading. The predicted responses are similar, and the known PM limitations still occur independentlyof the adopted model. Under biaxial loading, it is shown that a response closer to that observed inconcrete can be obtained (higher normal-to-stiffness ratio of
Ano: 2024
Número Páginas:
29p..
Autor(es): Azevedo, N.; Braga Farinha, M. L.; Oliveira, S.
Revista: Buildings
Editor: MDPI
Volume:
14.
Keywords: concrete fracture; contact softening laws; discrete element; particle model
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Deterioration Models and Service Life Prediction of Vertical Assets of Urban Water Systems
This study proposes a methodology for developing deterioration models and predicting the service lives of vertical assets of urban water systems (i.e., water storage tanks and pumping stations) using regression analysis. The main factors contributing to the deterioration of these assets are analyzed. Simple and multiple linear regression models of average and maximum deterioration are calculated for 22 water storage tanks and 17 wastewater pumping stations. Data on a set of four water storage tanks are used to validate the developed deterioration models. Service life prediction is carried out using the developed models and considering two maximum deterioration levels: the maximum recommended and admissible deterioration levels. Two water storage tanks are further studied to illustrate and discuss the effect of maintenance and rehabilitation interventions on asset service life by comparing the asset deterioration before and after the interventions.
Ano: 2024
Número Páginas:
19p..
Autor(es): Cabral , M.; Loureiro, D.; Amado, C; Covas, D.
Revista: Water Resources Research
Editor: AGU
Volume:
Volume 60, Issue 4.
Keywords: Urban water systems; Service life prediction; Deterioration models
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Development of a Bayesian network-based early warning system for storm-driven coastal erosion
Coastal hazards such as flooding and erosion can cause large economic and human losses. Under this threat, early warning systems can be very cost-effective solutions for disaster preparation. The goal of this study was to develop, test, and implement an operational coastal erosion early warning system supported by a particular method of machine learning. Thus, the system combines Bayesian Networks, and state-of-the-art numerical models, such as XBeach and SWAN, to predict storm erosion impacts in urbanized areas. This system was developed in two phases. In the development phase, all information required to apply the machine learning method was generated including the definition of hundreds of oceanic synthetic storms, modeling of the erosion caused by these storms, and characterization of the impact levels according to a newly defined eerosion iimpact index. This adimensional index relates the distance from the edge of the dune/beach scarp to buildings and the height of that scarp. Finally, a Bayesian Network that acted as a surrogate of the previously generated information was built. After the training of the network, the conditional probability tables were created. These tables constituted the ground knowledge to make the predictions in the second phase. This methodology was validated (1) by comparing 6-h predictions obtained with the Bayesian Network and with process-based models, the latest considered as the benchmark, and (2) by assessing the predictive skills of the Bayesian Network through the unbiased iterative k-fold cross-validation procedure. Regarding the first comparison, the analysis considered the entire duration of three large storms whose return periods were 10, 16, and 25 years, and it was observed that the Bayesian Network correctly predicted between 64% and 72% of the impacts during the course of the storms, depending on the area analyzed. Importantly, this method was also able to identify when the hazardous conditions disappeared after predicting potential consequences. Regarding the Regarding the second validation approach, second validation approach, the k-fold cross-validation procedure was applied to the peak of a set of varying storms and it demonstrated that the predictive skills were maximized (63%
Ano: 2024
Número Páginas:
1-15pp.
Autor(es): Garzon, J.L.; Ferreira, Ó.; PLOMARITIS, T.A.; Zózimo, A. C.; Fortes, C. J. E. M.; Pinheiro, L.
Revista: Coastal Engineering
Editor: Elsevier
Volume:
Vol 189 (104460).
Keywords: HIDRALERTA; Sandy beaches; Bayesian networks; Numerical modeling; Prediction system
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Dynamics of CO2, CH4, and N2O in Ria Formosa coastal lagoon (southwestern Iberia) and export to the Gulf of Cadiz
A first characterization of greenhouse gases had been carried out to study their role and impact in a productive transitional coastal system of the southern Portugal
Ano: 2024
Número Páginas:
17p..
Autor(es): Sierra, A.; Correia, C.; Ortega, T.; Forja, J.; Rodrigues, M.; Cravo, A.
Revista: Science of the Total Environment
Editor: Elsevier
Volume:
(906)167094.
Keywords: Coastal lagoon; Ria Formosa; Gas mass transport; Water - atmosphere fluxes; Greenhouse gases
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Effects of hygrothermal and natural aging on the durability of multilayer insulation systems incorporating thermal mortars with EPS and aerogel
This study evaluated the durability of three innovative multilayer insulation systems incorporating thermal mortars with EPS aggregates and silica aerogel granules after hygrothermal accelerated aging and one year of natural aging at an urban site in Portugal. The loss of performance was assessed after the accelerated aging and every three months of natural aging using non-destructive testing. Chemical-morphological analyses were alsocarried out prior to and after accelerated and natural aging. Results obtained after accelerated and natural aging were compared, thus contributing towards a deeper understanding of possible synergistic effects of several degradation agents and mechanisms on the long-term durability of multilayer insulation systems. The Coffin-Manson equation showed that the accelerated aging procedure (~13 days of heat/rain cycles and 5 days of heat/cold cycles) adopted herein corresponds to approximately 11 years of natural aging in typical urban conditions. The results show a significant increase in capillary water absorption and drying capacity after aging.Extensive surface microcracking was observed after accelerated aging and after 3 months of natural aging, especially in the systems facing North. Traces of biological growth were detected on both the artificially and naturally aged systems, whereas aesthetic alterations were more pronounced in North-oriented specimens after 3 months of exposure, with significantly lower surface gloss and a darker tone. On the other hand, color change cannot be detected in the artificially aged systems (
Ano: 2024
Número Páginas:
20p..
Autor(es): Parracha, J.; Veiga, M. R.; Lina Nunes; Flores-Colen, I.
Revista: Cement and Concrete Composites
Editor: Elsevier, Ltd.
Volume:
148 (2024) 105483.
Keywords: Aesthetic performance; Bio-susceptibility; Water resistance; Natural aging; Accelerated aging; ETICS
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Experimental study of an onshore dual chamber oscillating water column device
A wave flume is used to study a scaled model of a stepped bottom dual-chamber Oscillating Water Column (OWC) installed onshore. Compared to traditional single-chamber OWCs, the use of dual-chambers is expected to widen the range of sea states in which the OWC is more efficient, and the step, in front of the first chamber, boosts the capturing energy capacity of the device. The Power Take-Off (PTO) system is modelled as an air opening in the pneumatic chambers. Several experiments combining regular incident waves and PTO damping conditions are performed. Results of the amplitudes of the free surface elevations inside the chambers show that the device can amplify the incident wave amplitude up to 1.57 times in chamber 2. Results of the primary efficiency show that the device is highly dependent on the PTO damping characteristics and can reach around 40% for a wide range of wave periods. Results of the reflection analysis show that the reflection coefficient is also dependent on the PTO damping characteristics but remain lower than 0.6 for all the studied cases. Sloshing phenomenon (mostly in the cross-section direction) was observed for a wavelength close to the cross-section dimension, impacting negatively on the device pneumatic performance.
Ano: 2024
Número Páginas:
16p..
Autor(es): Gadelho, J.; REZANEJAD, K.; Guedes Soares, C.; Santos, J. A.; Anastas, G.; Fortes, C. J. E. M.
Revista: Ocean Engineering
Editor: Elsevier
Volume:
Volume 300 (117240).
Keywords: Reflection coefficients; Efficiency improvement; Breakwater; Experiments; Oscillating water column
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Global and local geometrical imperfections of pultruded GFRP profiles based on a modal approach
ABSTRACT - The ultimate capacity of pultruded glass fibre reinforced polymer (pGFRP) profiles depends significantly on geometrical imperfections (GIs), given their sensitivity to buckling phenomena arising from both thin walls and low elastic moduli. However, GIs are not yet comprehensively addressed in design guidance. This paper proposes a new approach to characterize the initial GIs of pGFRP profiles based on a modal approach. Given the lack of comprehensive knowledge in this area, this study presents a highly accurate and robust methodology to measure GIs and dimensional deviations (DDs) in pGFRP profiles using a 3D contact coordinate measurement machine (CMM). The modal approach encompasses the measurement of dimensional parameters and a point cloud transformation that enables the assessment of GIs associated with pure buckling modes of pGFRP profiles. This procedure allows the quantification of three types of global GIs associated to (i) minor-axis (weak axis), (ii) major-axis (strong axis) bending, and (iii) twist. Additionally, the procedure also includes the assessment of local GIs, considering the wall (plate-like) imperfections. The separation of GIs into these four types (shape and amplitude) is of major relevance as its paves the way to the development of analytical design formulas for the strength prediction of pGFRP members. The approach described in this paper also serves two important purposes: (i) the statistical analysis of DDs and GIs of pGFRP members, and (ii) the identification of distinct shapes and amplitudes of GIs that form the basis for reliable design considerations of pGFRP members.
Ano: 2024
Número Páginas:
18p..
Autor(es): Silvestre, N.; Correia, J.; Pinheiro, A.; Ribeiro, A.; Lages Martins, L.; Lazzari, J.
Revista: Construction and Building Materials
Editor: ELSEVIER
Volume:
412 (2024) 134813.
Keywords: Modal decomposition; Geometrical imperfections; Dimensional deviation; 3D contact measurements; Pultruded profiles; Glass fibre reinforced polymer (GFRP)
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Hygroscopicity and Morphology of Bio-Based Boards
The internal structures and the hygroscopicity of bio-based boards consisting of giantreed (Arundo donax L.) and hazelnut shells as bio-aggregates, and a sodium silicate solution asthe adhesive, were investigated. The aim was to evaluate the influence of each material (the bio-aggregates and adhesive) and their distributions in the boards on the final performance. By carrying out X-ray computed tomography, the internal structures and the porosities of the boards were determined, allowing important considerations of their hygroscopicity. The voids
Ano: 2024
Número Páginas:
22p..
Autor(es): Cintura, E.; Lina Nunes; Molari, L.; Bettuzzi, M.; Morigi, M.; Brancaccio, R.; Faria, P.
Revista: Applied Sciences
Editor: MDPI
Volume:
14, 873.
Keywords: Tomography; Sodium silicate; Moisture buffering; Hygroscopicity; Hazelnut shel; Giant reed; Bio-resource; Bio-aggregate; Arundo donax; Agro-industrial waste
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Hygrothermal behaviour of external thermal insulation composite systems (ETICS) to withstand biological colonisation
ETICS are multilayer building solutions applied to the building external walls to provide animproved thermal performance to the building envelope. However, several questions have beenraised concerning the durability of ETICS, namely related to biological colonisation phenomena.Considering the high susceptibility of ETICS to bio-colonisation, the following research questions arise: (i) what is the impact of surface temperature (ST) and surface relative humidity (SRH)fuctuation on mould growth in ETICS facades? (ii) is it possible to predict mould growth onETICS under fuctuating conditions considering favourable and unfavourable growth conditions?This study aims to investigate the infuence of the hygrothermal behaviour of five different ETICS(with thermal mortars and insulation boards) on mould growth. ETICS were exposed for one yearat an urban site in Lisbon, Portugal, facing North, during which the ST and the SRH weremonitored. Concurrently, numerical simulations were performed to evaluate the hygrothermalbehaviour of the ETICS. Three theoretical indices were applied, using numerically and experimmentally obtained values of ST and SRH as input to provide an indication of the risk of mould growth. The results were complemented and validated by assessing the bio-colonisation, water performance and aesthetic properties of the ETICS. Index 1 (percentage of time with SRH
Ano: 2024
Número Páginas:
25.
Autor(es): Parracha, J.; Veiga, M. R.; Flores-Colen, I.; Lina Nunes
Revista: Journal of Building Engineering
Editor: Elsevier Ltd.
Volume:
86 e 108932.
Keywords: Numerical simulation; Onsite monitoring; Mould growth; Moisture; Temperature; Thermal insulation materials
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Integrating Uncertainty in Performance Assessment of Water Distribution Networks by Scenario Building
This paper presents and demonstrates a novel scenario-building methodology that integrates contextual and future time uncertainty into the performance assessment of water distribution networks (WDNs). A three-step approach is proposed: (i) System context analysis, identifying the main key factors that impact the WDN performance; (ii) Scenario definition, identifying the implicated WDN variables, describing its possible evolution, and conjugating them to further establish the reference scenario and the two most relevant and opposite ones; and (iii) Scenario modelling, simulating the WDN behaviour for those scenarios. The obtained spatial and temporal hydraulic results are further used to calculate performance metrics. The methodology is applied to a real WDN to assess resilience performance considering infrastructure asset robustness (real water loss performance indicator), service reliability (minimum pressure index), and service flexibility (network resilience index). A new formulation to assess the metric evolution over time is proposed, deducting the further-away performance results by using an uncertainty weight. The results demonstrate that the increase in metric amplitude for the opposite scenarios over time highlights future uncertainty, reflecting context uncertainty, and the comparison of metric spatial distribution (i.e., at the pipe/node levels) highlights critical areas with higher associated uncertainty.
Ano: 2024
Número Páginas:
18p..
Autor(es): Carneiro, J.; Loureiro, D.; Cabral , M.; Covas, D.
Revista: Water
Editor: MDPI
Volume:
Volume 16, Issue 7.
Keywords: Resilience metrics; Scenario modelling; Scenario planning; Aleatory uncertainty; Drinking water networks
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