TAILIEUCHUNG - Lifetime-Oriented Structural Design Concepts- P13

Lifetime-Oriented Structural Design Concepts- P13: At the beginning of 1996, the Cooperative Research Center SFB 398 financially supported by the German Science Foundation (DFG) was started at Ruhr-University Bochum (RUB). A scientists group representing the fields of structural engineering, structural mechanics, soil mechanics, material science, and numerical mathematics introduced a research program on “lifetimeoriented design concepts on the basis of damage and deterioration aspects”. | 318 3 Deterioration of Materials and Structures intended to use the secant modulus of elasticity. On this background the statistical analysis of 684 was repeated when specifying the national parameters of the German Annex of Eurocode 4 34 . In this analysis additionally the new results of the static tests of series S1 - S6 and the results of larger headed studs with a diameter of 25 mm 343 were considered taking into account the revised secant modulus of elasticity Ecm according to the edited version of DIN 1045 25 . In total 101 push-out tests could be included which are summarized for the different failure modes in Table Table and Table . In these tables n means the number of studs per test specimen and h d the ratio of the height of each stud after welding to its shank diameter. In 58 cases the criterion failure of the concrete and in 43 cases the criterion shear failure of the stud was relevant. Further information regarding specimen geometry and determination of the material properties are given in 345 . The result of the reanalysis according to EN 1990 16 are shown in Table and Figure . In accordance with the background report 684 the following coefficients of variation Vx were chosen. Vx 3 for the stud diameter d Vx 20 for the modulus of elasticity secant modulus Ecm Vx 15 for the cylinder compressive strength fcm Vx 5 for the tensile strength of the headed stud fu. In the case of relation of the equations of the theoretical model Pt c and Pt s to the characteristic values Xk of the cylinder compressive strength fck and the tensile strength of the headed studs fuk instead of each mean value Xm the required partial safety factors yR shown in Table can be reduced by the correction factors Akc and Aks according equation . In the case of failure of the concrete Akc lies between and for a compressive strength range 20 fck 60 N mm2 thus a value of Akc can be applied on the safe side. In the case of shear failure of

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