Shaking table testing for masonry infill walls: unreinforced versus reinforced solutions

Several factors influence the behaviour of infilled frames, which have been a subject of research in the past with moderate success. The new generation of European design standards imposes the need to prevent brittle collapse of the infills and makes the structural engineer accountable for this requirement, yet it fails to provide sufficient information for masonry infills design. Therefore, the present work aims at understanding the seismic behaviour of masonry infill walls within reinforced concrete frames, using both unreinforced and reinforced solutions (bed joint reinforcement and reinforced plaster). For this purpose, three reinforced concrete buildings with different infill solutions were constructed at a scale of 1:1.5, all with the same geometry, and were tested on the shaking table of the National Laboratory for Civil Engineering, Portugal. All solutions performed adequately for the design earthquake, with no visible damage. Still, the experimental tests show that the double‐leaf‐unreinforced infill walls underperformed during a large earthquake, collapsing out of plane by rotating as rigid bodies with multiple configurations. Also the reinforced concrete buildings collapsed, because of the adverse interaction with the infill walls. The infill walls with bed joint reinforcement and reinforced plaster did not collapse out of plane, because of their connection to the concrete frame, which is an essential requirement. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of seismic risk and mitigation strategies for the existing building stock: application of LNECloss to the metropolitan area of Lisbon

Decisions to mitigate seismic risk require a consistent approach to evaluate the effects of future earthquakes on population, on civil engineering structures and infra- structures. The mathematical and probabilistic methods that are the support to those approaches are generally called Risk Analysis; in the particular case of seismic events and mitigation strategies it will be named Seismic Risk and Mitigation Analysis, SRMA. The paper will address the subject of estimating the seismic risk and evaluate mitigation strategies for the existing building stock of the metropolitan area of Lisbon by describing the methods and showing preliminary results obtained with LNECloss numerical tool. Even though such a sophisticated tool needs validation on some parameters to become more reliable, it is shown that it is possible to compare results of different mitigation strategies.     

Oceanographical patterns during a summer upwelling–downwelling event in the Northern Galician Rias: Comparison with the whole Ria system (NW of Iberian Peninsula)

Summer upwelling and downwelling processes were characterized in the Northern Galician Rias during July and August 2008 by means of sampling carried out onboard R/V Mytilus (CSIC) and R/V Lura (IEO). Thermohaline variables, dissolved oxygen, nutrients, chlorophyll, phytoplankton, ciliates and zooplankton abundances were measured at sections located in the Rias of Viveiro, Barqueiro and Ortigueira and their adjacent shelves. Ekman transport was calculated from QuikSCAT satellite, upwelling intensity estimated with upwelling index from the average daily geostrophic winds, and SST maps obtained from NASA GHRSST satellite. Ekman transport and SST behaviour showed two different patterns: (i) offshore and upwelling favourable conditions on 13–22nd of July; (ii) onshore and downwelling favourable conditions from 23rd July to 19th August. During upwelling, TS diagram showed an intrusion of Eastern North Atlantic Central Water affecting the continental shelf but not the rias. Nutrient salt concentrations increased with depth, reaching their maximum values near the mouth of Ortigueira Ria. During downwelling, coastal water increased its temperature (18.5–19.8 °C) and was retained inside rias; nutrients were nearly depleted, except for the innermost ria (estuarine zone) due to fluvial nutrient inputs. In this inner area, the maximum of chlorophyll-a (Barqueiro Ria) was observed. Low phytoplankton abundances were measured in both cases, even though a short increase in the plankton biomass was observed inside rias during upwelling, while under downwelling a small red tide of Lingulodinium polyedrum was detected. During the upwelling period Northern Rias tend to be mesotrophic systems as revealed by nutrient concentrations, chlorophyll levels and plankton abundances. On the contrary, in similar situations, the Western Rias behaves as eutrophics.     

On the dissipation rates for Alfvén waves in the solar transition region

The present paper concerns Alfvén waves, in a resistive and viscous atmosphere, under a steep temperature gradient (Section 1). The dissipative Alfvén wave equation is deduced assuming uniform vertical background magnetic field, and allowing for arbitrary profiles of Alfvén speed, and viscous and resistive diffusivities as functions of altitude (Section 2). A three-parameter family of temperature profiles, allowing for independent choice of initial and asymptotic temperature, and of initial temperature gradient, is used to re-write the wave equation, with the temperature as the independent variable, instead of altitude (Section 3). It is shown that, for the conditions prevailing in the solar transition region between the chromosphere and corona, two approximations of the dissipative wave equations may be considered, the simplest leading to solution in terms of Gaussian hypergeometric functions (Section 4). The exact analytical solution allows calculation of the (i) velocity and (ii) magnetic field perturbations, (iii) kinetic, (iv) magnetic and (v) total energy density, (vi) energy flux, (vii) rate-of-strain and (viii) electric current, and (ix) viscous, (x) resistive and (xi) total rate of dissipation (Section 5). These are plotted versus temperature, across the transition region from the chromosphere to the corona, for the quiet and active Sun (Section 6). The feasibility of heating of the transition region by dissipation of Alfvén waves is discussed (Section 7), by comparing empirical heating rates, with theoretical values for a range of physical conditions, including initial velocity perturbations 5 to 15 km s ^–1, background magnetic field 12 to 120 G, wave periods 60 to 300 s, thickness of the transition region 100 to 300 km, resistive and anomalous diffusivities to 100 and viscous and turbulent diffusivities to 100 . The conclusion is that dissipation of Alfvén waves is not an effective heating mechanism for the transition region and corona, although it may be for the chromosphere (see Campos and Mendes, 1995, and references therein).     

Waveshapes of continuing currents and properties of M-components in natural positive cloud-to-ground lightning

This work analyses the waveshapes of continuing currents and parameters of M-components in positive cloud-to-ground (CG) flashes through high-speed GPS synchronized videos. The dataset is composed of only long continuing currents (with duration longer than 40 ms) and was selected from more than 800 flashes recorded in São José dos Campos (45.864°W, 23.215°S) and Uruguaiana (29.806°W, 57.005°S) in Southeast and South of Brazil, respectively, during 2003 to 2007 summers. The videos are compared with data obtained by the Brazilian Lightning Location System (BrasilDAT) in order to determine the polarity of each flash and select only positive cases. There are only two studies of waveshapes of continuing currents in the literature. One is based on direct current measurements of triggered lightning, in which four different types of waveshapes were observed; and the other is based on measurements of luminosity variations in high-speed videos of CG negative lightning, in which besides the four types above mentioned two additional types were observed. The present work is an extension of the latter, using the same method but now applied to obtain the waveshapes of positive CG lightning. As far as the authors know, this is the first report on M-components in positive continuing currents. We also have used the luminosity-versus-time graphs to observe their occurrence and measure some parameters (duration, elapsed time and time between two successive M-components), whose statistics are presented and compared in detail to the data for negative flashes. We have plotted a histogram of the M-components elapsed time over the total duration of the continuing current for positive flashes, which presented an exponential decay (correlation coefficient: 0.83), similar to what has been observed for negative flashes.