Stability of a six storey steel frame structure

Abstract

The world nowadays requires more tall buildings to overcome limited land space and creating high esthetic value. However, these high rise buildings require high frame structure stability for safety and design purposes. This research focused on non linear geometric analysis to be compared to previous studies on linear analysis. The linear analysis did not consider deformed configuration which can be considered as least accurate. On top of this, several designers did not incorporate the wind load which could lead to sway effect to tall buildings. In this study, a six storey 2-D steel frame structure with twenty four meter height has been selected to be idealized as tall building model. The model was analyzed by using SAP2000 structural analysis software with the consideration of geometric non linear effect. At the same time, several factors including the use of bracing, varying distributed loads on beam’s element and an increased in column size at bottom part of the building were also applied to study the sway and stability of the building. In addition, several cases including placing a fully bracing, bracing at half height of the building and alternate bracing were also studied. This study showed that a steel frame with the consideration of wind load produce greater sway value as compared to the steel frame without wind load. The sway prediction by using linear analysis was found to be less than 4% compared to the sway prediction from non linear analysis. This indicates that the non linear analysis is vital and significant element to be adopted for the analysis of tall building. The study also found that the use of bracing system results in small sway values compared to the frame without bracing system. As for consideration to costing aspect, the use of alternate bracing provide better option compared to half bracing in terms of stability of the building. The analysis results also showed that the adjustment of distributed load at upper part of steel frame structure able to provide different sway values, creating higher stiffness at lower part of the building which reduces the sway values and increases the stability of the building. SAP2000 software is found as reliable tool in evaluating structural analysis especially when involving non linear analysis