Normativer Hintergrund für den Entwurf und die Berechnung von Krankonstruktionen

Normative background for the design of crane structures. For the design of crane structures the CEN Technical Specification CEN/TS 13001‐3‐1: 2005 has been prepared in CEN/TC 147. This Technical Specification refers to EN 1990 – Eurocode: “Basis of Structural Design” and to EN 1993‐1‐1: Eurocode 3: “Design of steel structures”, Part 1‐1: “General rules and rules for buildings”, however there are significant deviations from the Eurocode‐rules. Examples for such deviations are the rules for the choice of material to avoid brittle fracture and the detail classes for the fatigue strengths of various details. Also CEN/TC 13001‐3‐1 does not yet contain design rules for plate buckling. This contribution shows examples for such deviations which possibly are based on different approaches to the experimental background of rules. A standardized approach is given in EN 1990 that specifies how to determine characteristic values of resistances from tests and recommended values for partial factors for the Eurocodes. For plate buckling the design methods given in EN 1993‐1‐5 and the reliability background of these rules are explained.     

Are there really high-tech clusters? The geographic concentration of German manufacturing industries and its determinants

The agglomeration of industries has recently received much interest both in empirical and theoretical works time. Especially in Germany politicians became inspired by the notion of high-technology industry clusters, and regional policy has seen a wave of initiatives aiming at the formation of such clusters. This paper explores in a systematic way the geographic concentration of German manufacturing industries and relates it to industry characteristics and agglomeration forces proposed by theory. The main finding is that there is no general relationship between agglomeration and high-technology related business which suggests that hope put in the fast and effective development of “high-tech” clusters might see some disappointments in the future.

---

Isochronicity-induced bifurcations in systems of weakly dissipative coupled oscillators

We consider the dynamics of networks of oscillators that are weakly dissipative perturbations of identical Hamiltonian oscillators with weak coupling. Suppose the Hamiltonian oscillators have angular frequency y ( f ) when their energy is f . We address the problem of what happens in a neighbourhood of where d y /d f = 0; we refer to this as a point of isochronicity for the oscillators. If the coupling is much weaker than the dissipation we can use averaging to reduce the system to phase equations on a torus. We consider example applications to two and three weakly diffusively coupled oscillators with points of isochronicity and reduce to approximating flows on tori. We use this to identify bifurcation of various periodic solutions on perturbing away from a point of isochronicity.     

Spider colonization of former brown coal mining areas — time or structure dependent?

Colonization of former mining areas by a highly mobile arthropod group, spiders (Arachnida), is studied based on a comparative analysis of four mining areas of different age and habitat structure including adjacent undisturbed areas. Species number was lowest in sparsely vegetated sites, and highest in dense vegetation regardless of age. Species number may exceed that of undisturbed adjacent sites after 70 years. Similarity among the sites ranges from 26 to 75% (Sörensen index). A DCA ordination of sites revealed a grouping into three relatively distinct clusters, one including the vegetation free sites, the second the sparsely vegetated short grass sites, and the third both the plant species rich, mature, short grass sites and the tall grass stands. Environmental variables were related to the species composition by means of CCA. However, most of these relations proved to be spurious being either not significant or if so, showing a low contribution to variance explanation. The influence of scale parameters such as area size and distance (when analysing all data, data from mining areas only, or data from one mining area separately) becomes visible in all analyses. A detailed analysis including age as an independent variable shows that age has some influence on the structure of the whole data set including undisturbed sites, but not within the subset of the mining areas. Using data from one mining area only it is shown that the influence of age and spatial autocorrelation effects cannot be properly distinguished on the larger scales. A more detailed account on the known autecology of the species encountered showed that biological spectra of the communities remain similar in the course of development. Initial colonization occurs very rapidly during the first years after dumping. The most decisive aspect of population establishment is the structure of the vegetation, as expressed by height or volume amenable for colonization. Despite some developmental trends such as increase in species number clearly separated successional stages cannot be distinguished.