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The intense traffic on existing pavements not only induces increased deterioration but also decreases vailability of pavements for monitoring and maintenance interventions. In Europe, in general, the existing pavement network requires maintenance in order to comply with traffic requirements. In an economic scenario of financial requirements, it is crucial to plan and justify maintenance measures needed for an efficient management. This paper presents future trends in pavement engineering focu...
O LNEC encontra-se a prestar assessoria ao Ministério da Defesa Nacional (MDN) num conjunto de questões técnico-ambientais suscitadas pela presença, nos últimos 60 anos, do contingente da Força Aérea Americana (USAFE) na Base das Lajes, nos Açores, relacionadas essencialmente com a contaminação de solos e de águas subterrâneas decorrentes do armazenamento e manuseamento de reservas de combustíveis e de outras substâncias, tendo em atenção as práticas adotadas no passado. No âmbito desta asses...
The final technical report of the project “UBEST – Understanding the biogeochemical buffering capacity of estuaries relative to climate change and anthropogenic inputs” (ref. PTDC/AAGMAA/ 6899/2014), funded by the Portuguese Foundation for Science and Technology (FCT), is presented. The project contributed to improve the knowledge on the biogeochemical dynamics in estuaries and coastal lagoons, in particular the Tagus estuary and the Ria Formosa. A detailed characterization of the current wat...
In this study, a novel computational modeling strategy is proposed to estimate the lateral load capacity and behavior of unreinforced masonry (URM) structures. All commonly noted failure mechanisms are captured via the proposed modeling strategy using the discrete element method (DEM) in three-dimensions (3D). Masonry walls are represented as a system of elastic discrete blocks, where the nodal velocities are evaluated by integrating the equations of motion using the central difference method...
This study presents a numerical investigation on the fracture mechanism of tension stiffening phenomenon in reinforced concrete members. A novel approach using the discrete element method (DEM) is proposed, where three-dimensional randomly generated distinct polyhedral blocks are used, representing concrete and one-dimensional truss elements are utilized, representing steel reinforcements. Thus, an explicit representation of reinforced concrete members is achieved, and the mechanical behavior...
This study proposes an alternative approach to modeling the failure mechanisms of brickwork assemblages under combined shear–compression, shear–tension (parallel to bed joints), and compression–flexural loadings using the discrete element method (DEM). In this context, recently developed elastic-softening contact constitutive laws considering the mode-I and mode-II fracture energies are implemented into the dynamic solution scheme of the DEM to simulate the mechanical interaction between mort...
The paper investigates the effectiveness of two-dimensional Discrete Element Method as a tool for structural analysis of arches provided with buttresses and backfill and strengthened with externally bonded reinforcement. Masonry vault and buttresses are modelled as an assembly of 2D rigid blocks interacting through non-linear contact joints, the backfill is discretized into deformable elastic-plastic triangular elements, while the reinforcement is modelled by means of truss elements bonded to...
Today, there are several computational models to predict the mechanical behaviour of masonry structures subjected to external loading. Such models require the input of material parameters to describe the mechanical behaviour and strength of masonry constructions. Although such masonry material parameters are characterised by stochastic‐probabilistic nature, engineers are assigning the same material properties throughout the structure to be analysed. The aim of this paper is to propose a metho...
During the last decade, many vibration-based structural health monitoring systems have been successfully implemented in different structures such as bridges, towers, stadia and wind turbines, with the aim of studying the structure dynamics and its evolution over time, eventually detecting the occurrence of novel structural behaviour that may indicate the presence of damage. Such vibration-based monitoring systems generally rely on the identification of modal properties, which are then used as...
In this paper three historical masonry minarets in Istanbul, Turkey, are assessed for the dependency between the input harmonic motion and structural response parameters. Their heights are 40, 73 and 74 m, while the slenderness is 12, 6 and 12, respectively. The discrete element method is used in dynamic nonlinear analyses. Models were calibrated with measured natural frequencies. A series of sine-wave excitations is created for different frequency- amplitude pairs varying between 0.4 and 10 ...
In the present work, and for the first time, totally biosourced low-density particleboards were produced using cardoon particles (a no added value by-product from the Portuguese cheese making industry), bound with a potato starch adhesive. Different starch/cardoon ratios (0.6, 0.8, 1 and 1.2) were tested and the effect of different bio-based additives (chitosan, wood fiber and glycerol) on the performance of the adhesive system was evaluated. The best result was obtained for a formulation w...
In recent years, interest has increased in new renewable energy solutions for climate change mitigation and increasing the efficiency and sustainability of water systems. Hydropower still has the biggest share due to its compatibility, reliability and flexibility. This study presents one such technology recently examined at Instituto Superior Técnico based on a transient-flow induced compressed air energy storage (TI-CAES) system, which takes advantage of a compressed air vessel (CAV). The CA...
The collapse of bridges inevitably leads to economical losses and may also be responsible for human fatalities. A bridge may fail due to several reasons, with local scouring around its foundation being the most common. Despite decades of scouring research, there are still many uncertainties affecting the design process of bridge piers. The most critical and least explored are the hydrological and hydraulic variables. The recent intensification of floods may also increase the vulnerability of ...
The vegetation capacity to protect the coasts from wave action is becoming more important and attractive due to ongoing sea level rise and increasing storminess. In addition, it is a quite environmentally friendly way. Quantifying the vegetation effect in wave propagation will be relevant for coastal management. A non-hydrostatic wave model based on the nonlinear shallow water equations, SWASH, offers opportunities to quantify the wave dissipation effect in vegetation fields. However, limited...
This paper describes a program under the responsibility of LNEC for the systematic observation and monitoring of maritime works that has successfully been applied to a number of maritime structures on the Portuguese mainland coast. The now-called OSOM+ program comprises the following four main components for each structure: i) periodic visual inspections by an experienced technician; ii) periodic aerial inspections with a UAV/ drone; iii) a ANOSOM-WEB database, to store and/or query obtained ...
De acordo com a legislação portuguesa e tendo em consideração o risco sísmico da zona de construção das barragens é obrigatório a implementação de um Sistema de Observação Sísmica (SOS), incorporando instrumentação para caracterizar a ação sísmica induzida nas obras e a respetiva resposta estrutural. Em complemento, têm sido instalados Sistema de Monitoramento Dinâmico Contínuo (SMDC). O SOS permite não apenas a caracterização da ação sísmica, mas também a sua propagação ao longo do maciço ro...
The characterization of the dynamic behavior of an arch dam, and its evolution throughout the structure's lifetime, provides important data for the safety control process. Forced vibration tests remain a reliable technique for this purpose. The Baixo Sabor dam is a 123 m high arch dam recently built in Portugal. Forced vibration tests were performed before and after the reservoir filling. Two techniques for forced vibration test are compared, discrete frequency scanning, the standard methodol...
This article presents an overview of the current European practices with regards to protecting surface water and groundwater bodies, in what concerns the application of legislation to protect water resources and to evaluate the vulnerability of water bodies to traffic related activities. This is achieved through the application of the EU Water Framework Directive and all Directives containing procedures to identify pressures affecting the state of water and environment, and the establishment ...
The effluents from agriculture practices usually contain several contaminants creating an environmental concern to downgradient water bodies. The use of SAT systems to improve the effluents water quality, during the transport of infiltrated water through the unsaturated and saturated zones, can bring a solution for water reclamation, water reuse, and overall as a water resources management tool. The research was carried out under MARSOL project were SAT experiments were executed in a physical...
Railway track designers and maintenance entities have long been pursuing for a robust and reliable method to predict the track’s long-term behaviour. The complexity of this railway system, in terms of its changing structural and material behaviour throughout its life cycle, have hindered that quest. This paper presents a novel computer implementation focused on the estimation of the ballast and sub-ballast long-term deformation that provides a realistic reproduction of the actual behaviour of...
LNEC's Scientific Repository
The LNEC Scientific Repository has the purpose of publicizing and allowing free access to the scientific production of its research community in the fields of civil engineering and related areas, promoting the sharing and visibility of scientific information and assuring the preservation of the institution's intellectual memory.
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