Full Height Rectangular Opening Castellated Steel Beam Partially Encased in Reinforced Mortar

This paper discusses analysis and test results of full height rectangular opening castellated steel beams without encasing and with partially encasing using reinforced mortar. Each contains two types of beam span namely short span beams to study the shear failure mechanism and long span beams to study the flexural failure mechanism. Test results show that the beams without encasing have lower load capacity than the original section due to Vierendeel truss mechanism. On the other hand the application of partially reinforced mortar encasing in the long span beam can avoid the Vierendeel truss mechanism and increases the yield moment capacity around 3.5 times of original steel section yield moment. However the short span one failed in brittle shear mechanism due to diagonal crushing in the mortar and then followed by Vierendeel truss mechanism so that the flexural strength could not be achieved. Shear strength of the full height rectangular opening castellated steel beam partially encased in reinforced mortar is larger than the calculated conventional reinforced concrete shear capacity but is less than the steel web shear capacity. It is recommended that the shear strength is calculated using diagonal strut mechanism of the mortar to give more appropriate shear strength prediction.