Seismic Behaviour of Confined Autoclaved Aerated Concrete Masonry Buildings: a Shaking Table Study

The seismic behaviour of typical residential confined masonry buildings constructed with aerated autoclaved concrete (AAC) blocks has been investigated. Two three‐ and one four‐storey models, constructed at 1 : 4 scale, have been tested by subjecting them to a simulated earthquake ground motion on a simple unidirectional seismic simulator. The floor plan of all models was the same, with symmetric distribution of walls along the shorter axis and slight asymmetry along the longer one. Lightweight prefabricated joists with AAC fillings without concrete topping represented the floor structures in the case of the three‐storey model M1, whereas reinforced concrete slabs have been cast in the case of the three‐storey model M2 and four‐story model M3. Bond beams have been provided at all floor levels and tie columns have been installed at all corners, wall intersections and along openings. The models have been instrumented with accelerometers and displacement transducers, placed in the middle and at the corners of the floor slabs at each floor level, and subjected to a series of excitations with increased intensity of motion in each successive test run. The acceleration record of the Montenegro earthquake of 1979 with peak ground acceleration of 0.43 g has been used to drive the simulator. Whereas models M2 and M3 have been tested by subjecting them to seismic motion in the direction of the long axis, model M1 has been tested orthogonal to it. In all cases, typical shear type behaviour has been observed, with diagonally oriented cracks in the walls in the first story determining the failure mechanism. All models exhibited good seismic behaviour, with resistance and energy dissipation capacity exceeding the expected values. On the basis of test results, the correlation between the damage and storey drift at characteristic limit states has been analyzed and the values of typical design parameters, such as displacement capacity and structural behaviour factor, have been evaluated. Seismisches Verhalten von Mauerwerksbauten aus eingefasstem Porenbeton: eine Rütteltisch‐Studie. Der Beitrag beschreibt die Untersuchung des seismischen Verhaltens von typischen Mauerwerksbauten des Wohnungsbaus aus eingefassten Porenbetonelementen. Zwei Drei‐ und ein Vier‐Etagen‐Modell im Maßstab 1 : 4 wurden untersucht, indem sie einer simulierten einachsigen Erdbebenbodenbeschleunigung auf einem Rütteltisch ausgesetzt wurden. Der Grundriss aller Modelle war der gleiche, mit symmetrischer Verteilung der Wände entlang den kürzeren Achsen und leicht asymmetrischer Verteilung entlang den längeren. Leichte vorgefertigte Deckenbalken mit Porenbetonelementen und ohne Aufbeton kennzeichnen das Drei‐Etagen‐Modell M1, während Stahlbetondecken aus Ortbeton im Falle des dreigeschossigen Modells M2 und des viergeschossigen Modells M3 verwendet wurden. Einfassungsbalken und ‐stützen wurden auf allen Grundrissebenen, in den Ecken, an Öffnungen und an Wandschnittpunkten vorgesehen. Die Modelle wurden mit Beschleunigungs‐ und Wegmessern überwacht. Diese wurden in jeder Etage sowohl in der Mitte als auch an den Ecken der Deckenplatte platziert und die Modelle einer Serie von Erbeben steigender Intensität unterzogen. Das aufgezeichnete Erdbeben von Montenegro 1979 mit maximaler Bodenbeschleunigung von 0,43 g wurde für die Simulation verwendet. Während die Modelle M2 und M3 entlang der langen Achse belastet wurden, ist das Model M1 orthogonal dazu getestet worden. In allen Fällen wurde für die Schubbeanspruchung typisches Verhalten festgestellt, mit diagonal orientierten Rissen in den Wänden der ersten Etage, welche den Versagensmechanismus bestimmen. Alle Modelle wiesen gute seismische Eigenschaften mit entsprechender Tragfähigkeit und Energiedissipation auf, welche die erwarteten Ergebnisse übertrafen. Auf der Basis der Testergebnisse wurden der Zusammenhang zwischen Schädigung und Verformung in den einzelnen Stockwerken für charakteristische Grenzzustände analysiert und die Werte für die typischen Bemessungsparameter wie die Duktilität und den Verhaltensfaktor ausgewiesen.     

High-Resistivity Grain Boundaries in CaO-Doped MnZn Ferrites for High-Frequency Power Application

The microstructural development and magnetic properties of MnZn ferrites doped with various amounts of CaO and sintered in atmospheres containing various oxygen concentrations were investigated. The results indicate a strong link among the amount of CaO segregated in the grain boundary, the oxygen concentration during sintering, the average grain size, and the magnetic properties of the MnZn ferrites.     

Thermosolutal flow in steel ingots and the formation of mesosegregates

The influence of the thermosolutal convection of the liquid steel in the solidifying core of a 3.3-ton ingot on the formation of banded mesosegregates is investigated by a multiscale solidification model. We first show how the thermosolutal flow structure in the solidifying core depends on the relation between the interacting thermal and solutal buoyancy forces and the coupling by the phase-change kinetics. We further show that banded mesosegregates are triggered by instabilities of the solidification front, that their location is determined by flow instabilities, and that their “A” or “V” orientation depends on the global direction of the flow circulation. Moreover, the results show that local remelting is not necessary to develop a channel mesosegregate. Destabilization of the mushy zone with local variations of the solidification velocity is sufficient.     

Re-evaluation of fungicidal properties of boric acid

Minimal inhibitory fungicidal concentrations of one of the most important biocides were determined in nutrient medium and on impregnated wood specimens. The results showed, that brown rot fungi are more sensitive to boric acid than white rot ones. To inhibit growth of wood decay fungi, lower minimal effective retentions have been determined than reported in previous publications.     

Influence of dipping time on uptake of preservative solution, adsorption, penetration and fixation of copper-ethanolamine based wood preservatives

Copper-ethanolamine based wood preservatives are the most important products for protection of wood in use class III and IV applications. These preservatives can be applied using different procedures. One of them is dipping, a method which is predominantly used in less industrialised countries. The most important parameter, that influences the quality of this treatment, is dipping time. Influence of various dipping times on copper retention, adsorption, penetration, colour of the specimens and copper fixation was examined. In this paper copper-ethanolamine solutions of two different concentrations were utilised (c_Cu=0.05% or 0.25%). The results showed that longer dipping treatments resulted in higher uptakes of preservative solution, better penetrations and lower leaching of copper-ethanolamine based wood preservatives from Norway spruce wood. After one week of dipping, samples retained on average 275 kg/m³ of preservative solution, copper active ingredients penetrated on average 3 mm into the specimens, and only 2.3% of copper was emitted from wood impregnated with aqueous solution of the higher concentration, when subjected to ENV 1250 leaching procedure.     

Investigation of Macrosegregation Formation in Aluminium DC Casting for Different Alloy Systems

Direct chill (DC) casting of aluminum involves alloys employing different solute elements. In this article, a qualitative analysis and comparison of macrosegregation formation is presented for three different alloy systems: Al-Mg, Al-Zn and Al-Cu. For this purpose, a multiphase, multiscale solidification model based on a volume-averaging method accounting for shrinkage-induced flow, thermal-solutal convection and grain motion is used and applied to an industrial-scale DC-cast ingot. The primary difference between these alloys is the thermal-solutal convection with Al-Mg having a competing thermal and solutal convection, whereas the other two systems have a cooperating thermal and solutal convection. In the study, the combined effect of the macrosegregation mechanisms is analyzed for each alloy to assess the role of the alloy system on the final macrosegregation.

     

Preparation of cadmium telluride nanoparticles from aqueous solutions by sonochemical method

Cadmium telluride nanoparticles with sizes between 8 and 13 nm have been synthesized via a sonochemical route using cadmium sulfate hydrate (CdSO₄·8/3H₂O), cadmium chloride (CdCl₂) and elemental Te as precursors and aqueous solutions of NaOH and EDTA as solvents. The qualitative characterization and estimation of nanoparticle size were carried out by using X-ray powder diffraction (XRD). The morphology of nanoparticles was analyzed by transmission electron microscopy (TEM). Changes of physical and chemical properties of the prepared CdTe nanoparticles at increased temperature were studied by thermal analysis (TGA, SDTA). A probable mechanism for the sonochemical formation of CdTe is proposed.