Engineering properties of Hınıs ignimbrites and their usability as a building stone (Erzurum, Turkey)

The survival of several ancient monuments made of ignimbrites in Hınıs town (Erzurum-Anatolia), which has suffered from intense annual temperature fluctuations and strong seismic activity, can mainly be attributed to use of suitable building stones. This paper examines the usability as building stones of Middle Miocene Hınıs ignimbrites that widely outcrop in and around Hınıs town. The petrographical, geochemical, mechanical, and physical properties determined lead to categorization of the ignimbrites as four different types. The Hınıs ignimbrites contain dasite–trachy–andesite and rhyolite. Rhyolite is the strongest material whereas the other types, being more porous, are weaker, lighter, and have good heat-insulation properties. Being light (easily transportable, machinable, and workable), good heat insulators, environmentally friendly (because of natural ventilation), sufficiently elastic to sustain seismic loading in the area under study, and more cost-effective than artificial stones, Hınıs ignimbrites are certainly a preferable option for use as light building stone. These ignimbrites are not suitable for use as floor covering, however, (because of rapid abrasion) or for building structural columns (because of low strength).     

Variation of the elastic constants of tourmaline with chemical composition

Elastic wave velocities and lattice parameters of five tourmaline specimens with different chemical compositions have been measured. The piezoelectric effects on the elastic constants have been found to be small and can be neglected. Variations of the elastic wave velocities and elastic constants of the different tourmaline specimens indicate that: (i) partial substitution of Al by Fe in the structure decreases the shear wave velocities, (ii) replacement of Na by Ca increases the resistance of the structure against shear deformation involving C ₆₆, (iii) replacement of Al by Mg seems to decrease the resistance of the structure against longitudinal deformation involving C ₃₃. Elastic constants C ₁₁, C ₃₃, C ₄₄ and C ₆₆ of the different tourmaline specimens used in this study differ individually by 1.7 percent to 6.7 percent, indicating that the large differences (up to 21%) between the values reported by previous authors cannot be explained in terms of the chemical composition alone.     

Author index 1984 (volumes 67–71)

Magnetic properties of samples from Bell Island sedimentary rocks have been studied. X-ray analysis indicates that the main magnetic mineral is hematite in all samples. The other iron-bearing minerals identified are siderite and chamosite. Microscope observations of thin sections suggest that the rocks consist of oolitic hematite in a matrix of siderite or calcite. The intensity of natural remanent magnetization (NRM) varies in the range of (0.03–0.4 A m^?1), depending on the percentage of hematite. The thermal demagnetization curves of NRM show in some cases a sharp increase in magnetization at temperatures in the range 500–600°C. The peaks that occur in these demagnetization curves are due to a chemical change of siderite during repeated laboratory heating. X-ray analysis confirmed that the newly formed material is magnetite. Since the original NRM has been masked by the new intergrown material, this would result in a serious error in the determination of paleomagnetic pole positions. The samples showing this behaviour were not considered for paleomagnetic study. The samples containing oolitic hematite in a calcite matrix exhibit very high stability of NRM, including directional stability until almost 670°C. For these samples, a virtual pole position based on N = 6 samples (32 specimens) demagnetized to 665°C is 34°N, 114°E, not far from published Ordovician poles for the North American craton.     

Chloride and Organic Chlorine in Soil

Chloride is ubiquitous in soil, but the past years of research have revealed that organic matter also contains chlorine, in amounts similar to that of phosphorus. Hence, one of the major constituents of soil organic matter has previously been overlooked, and still very little is known about the turnover of organic chlorine in soil. In spite of the obvious connection between chloride and organic chlorine, organic chlorine rarely is considered when the biogeochemical cycling of chloride is in focus, and chloride rarely is taken into account when the occurrence and formation of natural organic chlorine compounds are in focus. The aim of the paper is to review ten years of research concerning the biogeochemical cycling of organic chlorine in soil, and to tie the biogeochemical cycling of organic chlorine to that of chloride.     

Retrofit of non-seismically designed beam-column joints by post-tensioned superelastic shape memory alloy bars

A series of tests on three full-scale substandard exterior beam-column joints were performed to investigate the efficiency of the proposed retrofit configuration, which is the use of externally applied post-tensioned shape memory alloy (SMA) bars. A major group of structural deficiencies resulting from lack of shear reinforcement in the joint, use of low strength concrete and plain round bars were taken into account in the construction of test specimens. While the reference specimen represents the as-built subassembly, the other two were retrofitted by the post-tensioned SMA and steel bars to compare the contribution of superelastic and conventional material on the response. The specimens were exposed to quasi-static cyclic loading up to 8% drift ratio to simulate an intensive level of seismic hazard. The reference specimen underwent a brittle shear failure as excessive cracks mostly concentrated in the joint panel while there was almost no damage in the rest of the RC components. A joint failure with enhanced response quantities was observed in the specimen retrofitted by post-tensioned steel bars. The specimen incorporating the retrofit solution via post-tensioned SMA bars was capable of performing an adequate performance and promoting minimization of the damage in the joint panel, which results in more ductile behavior. The hysteretic response of the SMA retrofitted specimen was validated with a refined numerical model in ATENA Science software. Experimentally observed response was also verified by an analytical model based on fracture mechanics considering the nonlinear behavior of plain concrete under tension. Due to inherent uncertainties in material constitutive laws, the analytical model was evolved to a stochastic level to propose a more advanced model for estimating the capacity of the reference and retrofitted joint. It is found that the experimental results were within the prominent range of Probability Density Functions (i.e. mean ± 1 SD) of the estimated joint tensile stress especially for the shear damaged specimens.     

Daily pan evaporation modelling using multi‐layer perceptrons and radial basis neural networks

This paper reports on investigations of the abilities of three different artificial neural network (ANN) techniques, multi‐layer perceptrons (MLP), radial basis neural networks (RBNN) and generalized regression neural networks (GRNN) to estimate daily pan evaporation. Different MLP models comprising various combinations of daily climatic variables, that is, air temperature, solar radiation, wind speed, pressure and humidity were developed to evaluate the effect of each of these variables on pan evaporation. The MLP estimates are compared with those of the RBNN and GRNN techniques. The Stephens‐Stewart (SS) method is also considered for the comparison. The performances of the models are evaluated using root mean square errors (RMSE), mean absolute error (MAE) and determination coefficient (R²) statistics. Based on the comparisons, it was found that the MLP and RBNN computing techniques could be employed successfully to model the evaporation process using the available climatic data. The GRNN was found to perform better than the SS method. Copyright © 2008 John Wiley & Sons, Ltd.     

Studies on the effect of burden width on blast-induced vibration in open-pit mines

This study concerns the correlation between burden and blast-induced vibrations in open-pit mines. For this purpose, two different mines were studied. In these mines, the vibrations caused by explosions at burdens having widths ranging from 3 to 14 m were measured from various distances. From the results, it was found for these cases that burden width has a significant impact on vibrations. Consequently, it was proven that vibrations decrease as burden increases.     

Remark on rotational motions in flares and prominences

From material secured with the McMath Solar Telescope of the Kitt Peak National Observatory rotational (orbital) motion has been found in a prominence ejected from a rotating flare. A period of rotation of 32 min has been derived from the study of a periodic asymmetry of the AL i 3961 absorption line.Presented at the Physics of Prominences-colloquium at Anacapri, September 29, 1971.