Improving Behavior of Castellated Beam by Adding Spacer Plat and Steel Rings

Abstract

Castellated steel beams are those members which are made from hot rolled steel I-section firstly by cutting the web in zigzag pattern and rejoining the two halves by welding together to form a hexagonal castellated beam such that the depth of section will be increased. Generally, the openings made in the web are with hexagonal shape; however, octagonal shape of web openings is typically obtained by providing spacer plate which is utilized to increase the depth of beam. Nowadays, using castellated beams in building construction becomes very popular because of their useful functions such as ease of service provision, strength and low cost. This study focuses on improving the behavior of hexagonal and octagonal castellated beam with spacer plate. The ultimate strength of the original (parent) I- section beam increases due to the increasing its depth. The increment of castellated beam depth; however, leads to post buckling in its web and to many other modes of failure when these beams are subjected for loading. Hexagonal and octagonal castellated beams which are fabricated using parent I-section (IPN140) are analyzed using finite element model (FEM).The analysis results revealed that using ring stiffeners around edge of holes contributes effectively in strengthening the web. It was found that using ring steel stiffeners can reduce the stress concentration around the edge of holes and improve the behavior of these beams by increasing the ultimate strength and minimizing the deflection. From the numerical (FEM) results obtained by using ANSYS14, it is concluded that ultimate strength of castellated beam can be improved by providing spacer plate and ring stiffeners around the web hole. Also, the results showed that ultimate strength of octagonal castellated steel beam can be increased up to (53%) more than the parent beam (IPN140) with providing only (13.0%) weight of steel (spacer plate plus ring steel stiffeners).