Hh Bert Snijder

Bending-shear interaction of steel I-shaped cross-sections : statistical evaluation

Clause 6.2 of EN 1993-1-1 covers the cross-sectional resistance of steel sections. The bending-shear interaction design rules for I-shaped cross-sections make use of a reduced yield stress for the web area. On this basis, a reduced design plastic resistance moment allowing for the shear force is presented. The effect of shear on the bending resistance may be neglected if the shear force is less than half of the plastic shear resistance of the cross-section. Plasticity in the Eurocode is described by the well-known Von-Mises yield criterion, however, the formula used for the reduced yield stress deviates from this criterion, resulting in sometimes greater and sometimes smaller values. The background of the Eurocode formula for reduced yield stress can be found in a publication by Drucker. The purpose of the present research is to investigate the influence of shear on the bending resistance of I-shaped steel cross-sections with as result a possible reconsideration of the Eurocode design rules. At Eindhoven University of Technology an experimental investigation on bending-shear interaction in rolled steel I-shaped sections was performed. A numerical model was developed in Abaqus Finite Element software to simulate the experiments. With the validated numerical model a larger database of numerical ‘test’ results was generated, which was subsequently used in a statistical analysis following Annex D of EN 1990 as further developed in the RFCS project Safebrictile. The statistical distributions of the steel properties recommended by Safebrictile were adopted. This paper presents the results of the statistical analysis and safety assessment of the strong axis bending-shear interaction design rule currently present in Eurocode 3. The parametric test group consists of HEA, HEM and IPE sections in the steel grades S235, S355 and S460: in total 180 numerical simulations with increasing amount of shear. A stress-strain model including strain hardening was used in the numerical simulations, since the influence of strain hardening is also largely present in the experimental test program. Based on strain hardening material behavior it is show in this paper that the current partial factor is un-conservative for shear dominated beams and should be increased. Alternatively, the design rule should be modified.

Composite action of steel frames and precast concrete infill panels with corner connections – Part 2 : finite element analysis

When precast concrete infill panels are connected to steel frames at discrete locations, interaction at the structural interface is neither complete nor absent. The contribution of precast concrete infill panels to the lateral stiffness and strength of steel frames can be significant depending on the quality, quantity and location of the discrete interface connections. This paper presents preliminary finite element results of an investigation into the composite behaviour of a square steel frame with a precast concrete infill panel subject to lateral loading. Earlier, a full scale experiment was performed on a one-storey one-bay 3 by 3 m infilled frame structure which was horizontally loaded at the top and yielded a load displacement curve. The infill panel was connected at the corners to the ends of the top and bottom beams. This way the connection acts either in tension or compression. Experimental pullout tests on individual Frame-to-Panel-Connections, FPC4, allowed the load deflection characteristics to be established. This made it possible to model the experimental non-linear behaviour of the connection by multi-linear tensile and compression springs in the finite element model. The results from the finite element model of the infilled frame structure with FPC4 connections compares well with the experimentally obtained values for initial lateral stiffness, yielding level and ultimate strength. The proposed finite element model of the structure can be used for further parameter studies.