Study of bond stress–slip relationship and radial dilation in prestressed concrete

This paper presents two test procedures for evaluating the bond stress–slip and the slip–radial dilation relationships when the prestressing force is transmitted by releasing the steel (wire or strand) in precast prestressed elements. The bond stress–slip relationship is obtained with short length specimens, to guarantee uniform bond stress, for three depths of the wire indentation (shallow, medium and deep). An analytical model for bond stress–slip relationship is proposed and compared with the experimental results. The model is also compared with the experimental results of other researchers. Since numerical models for studying bond‐splitting problems in prestressed concrete require experimental data about dilatancy angle (radial dilation), a test procedure is proposed to evaluate these parameters. The obtained values of the radial dilation are compared with the prior estimated by numerical modelling and good agreement is reached. Copyright © 2012 John Wiley & Sons, Ltd.     

Mangrove ecology,aquatic primary productivity,and fish community dynamics in the Teacapán-Agua Brava Lagoon-Estuarine system (Mexican Pacific)

Aquatic primary productivity, mangrove ecology, and fish community dynamics were investigated in the Teacapán-Agua Brava lagoon-estuarine system, the most extensive mangrove ecosystem on the Pacific coast of Mexico with three species of mangroves distributed heterogeneously (Laguncularia racemosa, Rhizophora mangle, andAvicennia germinans). Tree density was 3,203 trees ha^?1 and basal area was 14.0 m² ha^?1. Litterfall was 1,417 g m^?2 yr^?1, characteristic of a productive riverine forest. The degradation constant forLaguncularia racemosa leaves varied from 1.71 to 4.7 yr^?1 and mean annual net aquatic productivity was 0.41 g C m^?3 d^?1. There were high concentrations of humic substances (up to 150 mg l^?1) early in the wet season. Seasonal variations of the above parameters seemed closely related to the ecology of fish populations. There were 75 fish species distributed in two principal assemblages associated with wet and dry seasons. Diversity and biomass analysis indicated 18 dominant species. Total biomass of the community in this coastal system was estimated at 10 g wet wt m^?2. The highest biomass occurred in the wet season. The most common fish species wereMugil curema, Achirus mazatlanus, Galeichthys caerulescens, Arius liropus, Diapterus peruvianus, Lile stolifera, Centropomus robalito, andEucinostomus sp., all of which have fishery importance. Primary productivity and fish community ecology are controlled by habitat characteristics, river discharge, and climatic seasonality.     

An anthropo-ecological approach to landscape use optimization

A method of landscape evaluation based on the anthropo-ecological approach is worked out. The procedure consists of three stages, viz., general, special and optimization. Within the general stage, the structural arrangement of the landscape is evaluated by means of the concept of geo-ecological sites (GES), which are distributed into four zones (A, B, C, D) according to the degrees of their anthropic disturbance. The zoning performed makes it possible to select those geo-ecological sites where eco-critical relationships can be expected to appear; in order to eliminate such situations, transition zones are calculated for the geo-ecological sites concerned. The outcome of this approach is a proposal of a new structural arrangement of the geo-ecological sites, solving eco-critical situations and serving as a basis for the special and optimization stages of the anthropo-ecological method.     

The magnetic structure of the langbeinite K2Mn2 (SO4)3

K₂Mn₂(SO₄)₃ orders magnetically at T_N= 1.75 K. One of the orthorhombic cell edges of the low temperature Langbeinite structure becomes doubled in the magnetically ordered state. The antiferromagnetic spin structure found is characterized by weak or vanishing molecular fields due to nearest neighbours. There are no indications of magnetic order down to 1.45 K in the isomorphic compound K₂Co₂ (SO₄)₃.     

Clinopyroxene zoning patterns in the young alkali basalts of Hungary and their petrogenetic significance

In the Upper Pliocene, during the final phase of igneous activity within the Pannonian Basin, alkali basalts were erupted. Their occurrences are restricted to two main regions in Hungary: 1) Transdanubia; 2) Nógrád County. The clinopyroxene phenocrysts of these rocks are zoned titanaugites which often have distinctive colourless or green cores. Two kinds of green cores can be distinguished: 1. olive-green cores (fassaitic augite and fassaite), and 2. grassgreen cores (salite and ferrosalite). Both types of green cores are comparatively iron-rich and they occur only in the basalts of Nógrád County. The olive-green fassaites probably precipitated from relatively evolved melts which have been mixed into their present host magmas, whereas the grassgreen salites and ferrosalites are xenocrysts derived probably from upper mantle rocks. The clinopyroxene zoning patterns suggest, that after being generated by small-degree partial melting in the mantle the Transdanubian basalts ascended to the surface with little or no modification en route, whereas those of Nógrád County had a more complex evolution, in which fractionation at depth and magma mixing played an important role.     

Estimation of seismic hazard parameters in TERESA test areas

A general overview of some of the problems involved in earthquake catalogue handling is given as part of the works carried out into the ESC/SC8-TERESA project related with the seismic hazard assessment in two selected test areas: Sannio-Matese in Italy and the northern Rhine region (BGN). Furthermore, the necessary input data to be used in the calculation of seismic hazard has been obtained, including earthquake source zones and their seismic hazard parameters.The importance is pointed out of detailed analysis of seismic catalogues, mainly in relation to the use of aftershock information, the historical records of the region, and the possible temporal and spatial variation of seismicity, which could have an important influence on short-term hazard assessment.     

Assessment of seismic hazard for the Sannio-Matese area of Southern Italy — A summary

The working group on Test Regions for Evaluation of Methods for Seismic Hazard Assessment in Europe (TERESA), consisted of 15 members from 10 different European countries. Methods and experience gathered in these countries have been compared and discussed for two test areas in Europe: the Sannio-Matese region, Southern Italy, with high seismic activity, and the border region between Belgium, The Netherlands, and Federal Republic of Germany, with low activity.This paper summarizes the results for one of the test areas, Sannio-Matese. Most of the participants used statistical procedures to assess earthquake hazard, receiving results in terms of probability of occurrence for intensity as the ground-motion parameter. It was found that careful preparation of input data and parameters is the major influencing factor, therefore most of the efforts of the working group was devoted to this task.The scatter of the obtained results of the group is considerable, mainly because of the uncertainties in the data and the subjectiveness involved in the procedures. For better control of both factors, more objective methods have to be developed.     

Seismic hazard computations for regions with low earthquake activity — A case study for the Belgium,The Netherlands and NW Germany area

The algorithms to evaluate seismic hazard, used and/or developed by five teams participating in the TERESA project, applied to the low seismicity area Belgium, The Netherlands and NW Germany are compared. The main differences in the results can be explained by the majority criterion of Egozcue et al. (1989), the differences in the upper bound and zonification and, in some cases, by a higher attenuation.     

On the relation between solar motion and the long term variability of solar activity

Summary The Sun's motion round the barycentre of the solar system was found to consist of two basic alternately repeating elements of the noose and of the arc. The mean time for solar motion around each of these elements was found to be 9.93 yr. The relation between solar motion and solar variability was determined as follows: Approximately coincident periodicities ranging from 60 to 2200 yr were traced in both phenomena and a coincidence of all prolonged minima in solar activity with the epochs of the highest deviations from the Jupiter—Saturn order was found over a time interval of 3100 yr.

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