Boris Androić

Reliability of short seismic links in shear

This paper presents the results of research in reliability of short seismic links in shear based on tests. Four types of short links were analysed, each having the same cross section and the same length, but with different number of web stiffeners. The main purpose of the stiffeners is to preserve buckling of the seismic link web, i.e. to achieve plastification of the cross section by shear. The design model of shear resistance according to Eurocode 8 is applicable only to short links without web stiffeners. By adding the web stiffeners nonlinear inelastic behaviour of short seismic links differs depending on the number of stiffeners, so that the calculation model of shear resistance according to Eurocode 8 for short seismic link with stiffeners should be improved. This fact is considered by introducing the improve factors that were determined from the laboratory tests conducted on 16 specimens. On the base of tests in the second part of this paper the reliability of short seismic link is performed by forming limit state equations. These equations are formed by using the stochastic model, i.e. by describing the statistical nature of basic variables calculating the reliability index as an operational value of failure probability. The reliability level was determined by using the probabilistic analysis based on the first order reliability method which resulted with the conclusion that the short seismic links with two and three couples of web stiffeners designed according to requirements of Eurocode 8 have enough reliability for the reliability class RC2 and the mean recurrence interval of 50xa0years.

Composite columns made of concrete-filled hollow steel sections with embedded steel cores

A review of current surveys related to composite columns made of concrete filled tubes with embedded steel cores, known as Geilinger columns, is presented in the paper. Advantages and scope of application of this innovative composite column type are presented. Calculation of such columns according to the general method given in EN 1994-1-1, which is applied with known geometrical and structural imperfections, is explained. The simplified calculation method suitable for engineering practice is also considered. The aspects of fire resistance design are discussed. The load introduction into composite columns is also presented as well as some shearhead connection details to provide shear and moment transfer between reinforced concrete flat slabs and composite columns.

Primjena hladno oblikovanih šupljih čeličnih profila

Prema EN 1993-1-1 primjena supljih profila dopustena je u izradi celicnih konstrukcija neovisno o tome jesu li profili toplo dogotovljeni prema EN 10210 ili hladno oblikovani prema EN 10219. Kod projektanata cesto postoji dvojba u vezi s primjenom hladno oblikovanih profila uslijed negativnog utjecaja hladnog oblikovanja na njihovo ponasanje. Nedoumicu može izazivati i nedorecenost u normi EN 1993-1-8 koja se odnosi na mogucnost zavarivanja u hladno oblikovanim zonama. Osnovna svrha rada je prikazati smjernice za odabir pravokutnih supljih profila kod projektiranja celicnih konstrukcija, a posebno se obrazlaže opravdanost primjene hladno oblikovanih profila.

Safety indices obtained by calibration of existing steel structures in Croatia

Taken from the Journal of Constructional Steel Research, 1998, 46:1-3, Paper No. 088. -------------------------------- The selection of target safety indices for particular classes of structures should be made on the national level of every country. It is necessary that such a selection is made because of different technical achievements and economic potentials. Before decisions on adoption of target values have been made, safety levels of the existing structures should be determined. Such a procedure is called calibration. The selection of safety level poses a serious problem. Any requirement that is too high can cause economic or social problems. The Ministry of Science and Technology of the Republic of Croatia has funded a project titled � Safety degree harmonization of steel structures in Croatia.� Some results that were obtained during the probabilistic calibration in Croatia are in the following field: fatigue of railway steel bridges, composite structures, thin-walled structures and sandwich element. The results obtained can serve for harmonizing safety levels of particular classes of structures. Besides, the results can be used for preparing National Application Document (NAD) in applying Eurocode to the national standard.