Artigos de Revista

Timber-concrete composite structures are often used as upgrade solutions for existent timber floors. The timber cross section is maintained and a concrete layer is poured over the floorboard surface. Floorboards help with loading distribution on the beams. The study presented is based on laboratory tests that used specimens made with a lightweight aggregate concrete (LWAC). The use of this type of concrete, compared with normal weight concrete (NWC), has the advantage of lower dead weights, and might be very important in many cases, namely, when the supporting structure has limited strength. Many design works of timber-concrete composite connections do not take into account the timber interlayer, which is known to reduce the load-carrying capacity and the stiffness of the connection. Previous investigations of NWC found that the inclusion of the interlayer leads to average reductions of 30% and 50% for the load capacity and slip modulus, respectively. The current investigation with LWAC found that such reductions are up to 10 and 30%, respectively. DOI: 10.1061/(ASCE)ST.1943-541X.0000299. © 2011 American Society of Civil Engineers.

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This research provides an overview of the large-scale physical model experiments conducted at the Canal d’Investigaciò i Esperimentaciò Marìtima, Laboratori d’Enginyeria Marìtima, Universitat Politècnica de Catalunya, Barcelona, within the EU-Hydralab III Integrated Infrastructure Initiative. The model tests have been carried out in a flume with a sandy dune exposed to a combination of water levels and wave conditions. Different regimes of wave attacks on the sandy beach/dune system were investigated. In particular, the study provides a unique set of large-scale physical data concerning the wave-induced dune overwash. Measurements of velocities, sediment concentrations and beach–dune profile evolutions were considered. The profile measurements have been used to calibrate and validate a numerical model predicting the beach–dune profile modifications over the near-shore region. The numerical model compares well with the experimental data.

Sea level change is an important consequence of climate change due to its impact on society and ecosystems. Analyses of tide-gauge data have indicated that the global sea level has risen during the 20th century and several studies predict that the mean sea level will continue to rise during the 21st century, intensifying coastal hazards worldwide. In Portugal, the Ria de Aveiro is expected to be one of the regions most affected by sea level change. The main aim of this study is to evaluate the potential impacts of the mean sea level change on the hydrodynamics and morphodynamics of the Ria de Aveiro. With this purpose, local mean sea level change was projected for the period 2091–2100 relative to 1980–1999, for different Special Report on Emission Scenarios (SRES) scenarios developed by the Intergovernmental Panel on Climate Change (IPCC). These projections revealed an increase in the mean sea level between 0.28 m under scenario B1 and 0.42 m under scenario A2. The results obtained for sea level rise scenario A2 projection were used to force the morphodynamic model MORSYS2D, previously implemented for the Ria de Aveiro. The modelling results were compared with model forecasts for the present sea level. The residual sediment transport and its balance at the lagoon inlet were computed and analysed for both situations. While the residual sediment transport is generally seaward, sediments tend to deposit inside the inlet due to the weak sediment transport at its mouth. The direction of the residual flux will not change with the sea level rise, but sediment fluxes will intensify, and accretion inside the inlet will increase. The rise in mean sea level will also affect the lagoon hydrodynamics. The tidal prism at the lagoon mouth will increase by about 28% in spring tide. In the lower lagoon only a slight increase of the tidal asymmetry is predicted.

ABSTRACT: Structural Health Monitoring is an emergent powerful diagnostic tool that can be used to identify and to prevent possible failures of the various components that comprise an infrastructure. In the particular case of a suspension bridge, the measurement of the vertical and transversal displacements plays an important role for its safety evaluation. Taking into account the restrictions usually found on these structures, an enhanced solution comprises a non-contact vision-based measurement system with dynamic response, accuracy and amplitude range well suited to the physical phenomenon to measure. The paper describes a methodology to perform the vision system calibration that can be carried out in-situ, while the deck is moving, requiring little effort and a minimum set of information. Specifically, only a set of active targets fixed on the deck and the knowledge about the distances between them is required. Results related to the performance evaluation, obtained by numerical simulation and by real experiments with a reduced structure model, are presented and they show that, even in an environment severely affected by disturbance noise, it is possible to measure the vertical and transversal displacements with a standard accuracy better than 10 mm.

This article presents a study on stress-laminated timber bridges. The technique is useful for the rehabilitation and construction of bridges. It consists of a series of timber planks placed side by side and compressed transversely with highstrength steel prestressing bars. A prototype of this kind of structure was built in the Department of Civil Engineering at the University of Coimbra. The prototype, a stress-laminated timber bridge deck with butt joints, was 6 m long, 2.7 m wide, and 0.20 m thick. The experimental program was developed with two main objectives: to study the evolution of the prestress value applied to the structure and to observe the bridge structural behavior under the effect of loads simulating the action of a standard vehicle. Practical difficulties and/or limitations and potentialities of the system when maritime pine is used as the timber material are also discussed. This article reports the experimental program and the results, with emphasis on the tension losses in the prestressed steel bars.

This paper presents a direct power control (DPC) for three-phase matrix converters operating as unified power flow controllers (UPFCs). Matrix converters (MCs) allow the direct ac/ac power conversion without dc energy storage links; therefore, the MC-based UPFC (MC-UPFC) has reduced volume and cost, reduced capacitor power losses, together with higher reliability. Theoretical principles of direct power control (DPC) based on sliding mode control techniques are established for an MC-UPFC dynamic model including the input filter. As a result, line active and reactive power, together with ac supply reactive power, can be directly controlled by selecting an appropriate matrix converter switching state guaranteeing good steady-state and dynamic responses. Experimental results of DPC controllers for MC-UPFC show decoupled active and reactive power control, zero steady-state tracking error, and fast response times. Compared to an MC-UPFC using active and reactive power linear controllers based on a modified Venturini high-frequency PWM modulator, the experimental results of the advanced DPC-MC guarantee faster responses without overshoot and no steady-state error, presenting no cross-coupling in dynamic and steady-state responses.

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Following an experimental campaign involving APP and SBS-modified bituminous membranes and TPO polyolefin membranes (to be used in mechanically fastened single-layer flat roof waterproofing systems), with two different joint execution procedures (welding with an open gas torch and with hot air) and varying lap joint width, subjected to standard shear and peel resistance tests, this paper presents the results of the tests on the SBS-modified bituminous membranes with the purpose of evaluating the consequences of (water and heat) weathering on their mechanical performance. This work is important because of the frequency with which waterproofing membranes exhibit problems at the mechanical attachments in lap joints and it shows how environmental agents affect their performance over time.