Ultimate strength capacity of composite self-compacting castellated steel beams

Abstract

Castellated steel profile sections can be used in order to increase the flexure strength of composite concrete-steel beams for building large spans. Castellated beams are fabricated by cutting I-section steel girders in a special manner before welding to produce an opening throughout the web. The depth of the new section is enhanced by a specific percentage, which increases the performance of the beam against bending. Castellated beams can be used compositely in long span floors where floor beam heights are kept to a minimum by passing services through the web-openings. This paper will focus on the composite behaviour of specimens in two types of concrete with different strengths. The ultimate strength for these types of structures with different degrees of castellation will be considered. The study consisted of two parts: the first part tested six specimens using push out test specimens to understand the real behaviour of their shear connectors. The second part tested eight specimens under a third point static load. Three of the push out test specimens were of normal concrete, and the others were self-compacting concrete.Four of the composite beam specimens were normal concrete slabs, while the other four specimens were made from self-compacting concrete. The experimental programme also included fabrication of I-section steel beams with different castellation degrees of 0%, 25%, 33.8%, and 50%. The effects of concrete type and degree of were thus studied. It was found that the maximum load capacity was significantly affected by these parameters such that it was increased with both the increase of compressive strength of the concrete and the degree of castellation. The push out test showed that the slip behaviour was linear below 70 to 80% of the ultimate load capacity. At this linear stage, the amount of slip is very low and rarely exceeds 0.5 mm.