Flexural Behavior of Ferrocement Cold-Formed Hollow Steel Composite Beams

Abstract

Experimental and numerical studies are carried out to investigate the flexural behavior of precast lightweight composite beams. This composite beam is comprised of a slender cold-formed hollow section of dimension (140x180 mm) with different thicknesses surrounded by a ferrocement layer. This composite beam is called a precast ferrocement cold-formed hollow section (FCH). The main problem in this study is the local buckling of cold-formed hollow sections before reaching yield. The objective of these studies is to examine the flexural behavior of precast ferrocement cold-formed composite beams with and without shear connectors. Nine beams with a span of 1500 mm were tested under a four-point bending system to evaluate their flexural strength. Four different parameters have been examined, which are the spacing of shear connectors, ferrocement thickness, and hollow steel section thickness. The test results showed that the presence of a 30 mm ferrocement layer increased the capacity by 18% when compared with the control specimen. The presence of shear connectors increases the capacity by 30%. Increasing the steel cross-section thickness leads to an increase in the capacity by 16-33% and finally, increasing the surface friction has a very small effect on the section capacity, which can be neglected. The finite element models were developed and validated by the test results. The results show a close agreement between the experimental and finite element results. Extensive parameters were investigated, which were mortar compressive strength (f' c ) and the position of shear connectors. The results indicated that increasing mortar strength leads to an increase in section capacity ranging between 11% and 18%. The presence of a shear connector in the web and the lower flange of the hollow section have a very small effect.