EUROCODE 8 DESIGN RESPONSE SPECTRA EVALUATION USING THE K-NET JAPANESE DATABASE

The Eurocode 8 (EC8) currently proposes two standard shapes for the design response spectra. Type 1 spectra are enriched in long period and are suggested for high seismicity regions. Conversely, Type 2 spectra are proposed for low to moderate seismicity areas (like France), and exhibit both a larger amplification at short period, and a much smaller long period contents, with respect to Type 1 spectra. These propositions, however, were constrained using few events mostly recorded on analogical instruments. In the present study, we use the Japanese high quality digital K-net array in order to evaluate the proposed ECS response spectra. Furthermore, all K-net stations have geotechnical characterisation. We first constructed a database of shallow events, depth less than 25 km, to avoid subduction related records. The database spans six years of seismicity from 1996 until 2003. Thus, 591 events were selected with moment magnitude between 4 and 7.3, recorded at 691 stations, giving a total of 6812 two horizontal components accelerograms. Using these records, we computed spectral ground-motion prediction equations and we used them to review the shape of the proposed EC8 spectra. In particular, we studied the plateau-PGA ratio level, the period interval where this plateau is constant, and site amplification effects. The results show surprisingly that the Type 2 rock better envelope the Japanese data. Another interesting observation is that the K-net data corresponding to all soil classes are rich in short periods around 0.1 s. This characteristic has not been observed in other worldwide databases. Normalised empirical predictions show a widening of the plateau as the soil conditions degrade. This suggests that the Type 2 EC8 spectra do not cover enough the long periods for EC3-soil classes C, D and E. Finally, the computed ground-motion prediction equations show that the peak ground acceleration (PGA) is nearly invariant to the soil conditions. Soil effects are mainly seen in the shape and plateau level.     

Europe,the rise of Asia and the future of the transatlantic relationship

This article examines how, in a global strategic context presided by the rise of Asia and the US rebalance towards that region, Europeans are contributing to transatlantic burden‐sharing—whether individually or through the EU/NATO. As Asian powers reach westward and the US shifts its strategic priorities eastward, classical geostrategic delimitations become gradually tenuous. Particularly important are the ‘middle spaces’ of the Indian Ocean, central Asia and the Arctic, in that they constitute the main avenues of communication between the Asia–Pacific and the European neighbourhood. The article seeks to understand how evolving geostrategic dynamics in Europe, the ‘middle spaces’ and the Asia–Pacific relate to each other, and how they might impinge on discussions on transatlantic burden‐sharing. It is argued that the ability of Europeans to contribute to a more equitable transatlantic burden‐sharing revolves around two main tenets. First, by engaging in the ‘middle spaces’, Europe's key powers and institutions are helping to underpin a balance of power in these regions. Second, by stepping up their diplomatic and economic role in the Asia–Pacific, strengthening their security ties to (US) regional allies and maintaining an EU‐wide arms embargo on China, Europeans are broadly complementing US efforts in that key region. There are a number of factors that stand in the way of a meaningful European engagement in the ‘middle spaces’ and the Asia–Pacific, including divergent security priorities among Europeans, the impact of budgetary austerity on European defence capabilities and a tendency to confine foreign policy to the immediate neighbourhood. The article discusses the implications of those obstacles and outlines some ways in which they might be overcome.     

DUCTILITY AND LOAD CARRYING CAPACITY PREDICTION OF STEEL BEAM-TO-COLUMN CONNECTIONS UNDER CYCLIC REVERSAL LOADING

Abstract

The economy and reliability of steel-framed buildings in seismic areas depend basically on the hysteretic behaviour of its individual components, such as members and joints. With reference to the latter, despite the recent semi-continuous frame approach (which appears generally very convenient for the design of low- and medium-rise steel buildings), the present state of knowledge does not allow for a complete understanding of the behaviour and the low-cycle fatigue life of beam-to-column connections under dynamic loads.

This paper presents a criterion for the definition of the low-cycle fatigue strength of steel connections, and proposes two approaches for the design of steel frames in seismic zones via the assessment of the fatigue damage, which is evaluated alternatively on the basis of either the ductility or of the load carrying capacity.     

Development of a Methodology for the Assessment of Vulnerability Related to Wildland Fires Using a Multi‐Criteria Evaluation

In the geography of risk, vulnerability may be defined as a physical characteristic that describes the tendency of a territory to suffer damage as a result of the occurrence of certain phenomena. According to this synthetic definition, there are two main components of vulnerability in the context of wildland fires. The first is internal, and is related to the effects of fires on the value of the affected assets affected and their capacity for recovery. The second is external, and is related to the characteristics of fires and the ability of society to deal with the hazards of wildland fires. The aim of the present study is to develop an assessment of spatial vulnerability in the context of wildland fires, at a scale appropriate for planning (1/25 000), in a mountainous region of the Spanish Mediterranean coast (Sierra Calderona). The proposed methodology entailed the definition of a synthetic index associated with the management of the risk of wildland fires, which was made up of significant factors such as the difficulty of extinction, the need for forest defence, the need for civil protection, and territorial value. To define and calculate the factors, variables and indicators that reflected aspects of the components of vulnerability (such as exposure, sensitivity, and the capacity to fight fires) were used. These were combined in a hierarchical structure, each having its own cartographical representation. Geographical information systems and multi‐criteria evaluation were then used to provide a successful framework for the analysis of vulnerability in relation to wildland fires. The cartographical outputs of the various components of the index are of particular interest to the planning of certain activities (e.g. forest, wildland fire, and civil protection), all of which are directly involved in the management of risk. In turn, the final synthetic index provides comprehensive spatial information that is useful for spatial planning and also enables the assessment of potential future land use in view of its usefulness in simulations.