The Performance of a Defective Steel Beam in a Semi-rigid Beam–Column Connection

This article aims to study the performance of the steel beam working in semi-rigid beam–column connections or joists in high-rise buildings. The major target of the paper is to establish a dimensionless equation for evaluating the performance of a defective steel beam in which the criteria for local and general instability of the structure are considered according to the specific regulation. Steel material has higher strength, stiffness, and ductility and proves to be the best choice in many various meanings; however, when studied quantitatively such material with defects in terms of slenderness (i.e., a cause for the effect of local buckling), or over exceeded vertical loadings (overall buckling, and lateral instability), the performance has been proved to be quite different. Local buckling is due to slenderness of flanges and web; this effect makes the structure deformed and lowers the frequency. This would be a base for diagnosing such a structure in high-rise buildings. By analyzing a steel beam with a specific configuration of the ratios of flanges and the webs, subjected to different cases of loadings, a dimensionless equation for evaluating the performance of the steel girder is created, then the same approach is applied to the specified beam withstanding the local buckling (due to slenderness) and overall buckling (due to Euler’s condition of the critical load). Some results about the importance of factors contributing to the performance of a steel beam, lateral displacement due to warping effect, local buckling for flanges and web, etc., are found. By recognizing the change in natural frequencies of response, together with a comparison in flexural capacity in terms of the ultimate moment, and the damage indices, a rapid decrease in the performance of a local buckling defective one is recognized.