Experimental study for strengthening octagonal castellated steel beams using circular and octagonal ring stiffeners

Abstract

Castellated beams made by cutting web of hot rolled steel I-section in particular zigzag pattern and recollecting the two parts by welding, to form a castellated beam with hexagonal openings, or more increasing of section depth by placing expansion plates between these parts to fabricate castellated beam with octagonal openings. The main advantage of fabrication this type of beam is increasing section depth, which leads to improve its behavior compared with original beam. So as to use the castellated beams with expansion plates into its best advantages, the failure modes due to web opening need to be avoided. This paper aims to provide added strength of castellated beams with expansion plates by using two types of stiffeners (circular and octagonal ring) around octagonal web opening. This strengthening technique was suggested to reinforce web portion and avoid failure due to web-post buckling. Standard (IPE140) were chosen as a parent section for fabricating four specimens as well as original beam. The important observation through this study is that using ring stiffener leads to have significant effect on ultimate strength. In case of using circular ring stiffeners, the ultimate strength was increased up to (188%) compare with original beam. Whereas the increment in ultimate load at using octagonal ring stiffeners was reach to about (77.6%). Consequent, using circular ring stiffeners to reinforced this type of beams was more efficient than using octagonal ring stiffeners. It is worthwhile to mention that it can be used (37%) as additional steel material (Expansion plates and ring stiffeners) for increasing the load capacity of castellated beams up to (288%) relative to original beam.