Proposal of concept for global analysis of hybrid beams – numerical investigation

: Investigation on the behaviour of hybrid beams is presented. Hybrid beam stands for an element with hybrid cross sections. This means sections that consist of steel and concrete parts, connected together with composite dowels, and both are considered for shear flow analysis. In practice, a more general solution may be used for bridges in the form of a beam in which the span sections are hybrid and the support sections are concrete. For the first time in the world, it was decided to introduce a girder in bridge construction, in which a concrete web with a thickness of only 20 cm was formed, directly connected to the steel web, so that a hybrid cross-section is created in accordance with the new European design regulations currently being developed (1994-1-102). The solution is new itself and requires also a new approach for internal forces determination. In this paper a parametric analysis of different hybrid beams with span range from 20 to 40 m and with different reinforcment ratio is performed to get knowledge on the influence of (1) concrete cracking and (2) rheology of concrete on the redistribution of internal forces. Results are analysed and conclusions are presented. As a final step, a general method for computer aided modelling of hybrid beams ( hybrid beam concept ) is proposed, which is based on the uncracked analysis. Such an analysis is designer-friendly and while appropriate benchmarked (as in this paper) can spare a lot of time needed for detailed iterative cracked analysis.