Die Stabilisierung biegedrillknickgefährdeter Träger durch Sandwichelemente und Trapezbleche

Adjacent members like trapezoidal sheeting or sandwich panels can reduce the problem of lateral torsional buckling of beams by providing stabilization either by shear stiffness or by torsional restraint. Both types are investigated in this thesis by tests and numerical calculations with finite elements. This concerns the shear stiffness of steel sheeting diaphragms with only two edges fastened against lateral displacements of the compression chord of the beam and the torsional restraint of the rotation of the beam by sandwich panels. The statistical evaluation of experimental investigations and parametric analyses by means of a verified finite element model show that the torsional restraint of sandwich panels with polyurethane or mineral wool core material can be expressed by a trilinear moment-rotation relationship. Formulae are given for different profile types combined with sandwich panels for all common constructions and fields of application to calculate the parameters of this relationship. The rotational stiffness of the connection which governs the torsional restraint behaviour can be taken from this relationship as secant stiffness depending on the lateral load of the beam. The basis for the investigation of profiled steel sheeting diaphragms with fastening along two edges are numerical calculations with a finite element model which was verified by comparison with analytical calculations as well as with full-scale diaphragm tests. The flexibility of the fasteners which connect the sheeting to the supporting structure as well as the number and type of the seam fasteners are included in the numerical calculations. The result of the investigation are knock-down-factors which allow to calculate the shear stiffness of diaphragms fastened only along two edges from that of diaphragms fastened along all four edges.