Stability coefficient of moment resisting frame structure for different building parameters

Abstract

High Rise Moment Resisting Frame structures are exposed to both static and dynamic loads. The process of designing high-rise buildings depends on many parameters. Stability Coefficient is one of them. It indicates whether a Moment Resisting frame Structure needs a second order analysis or not.

P-delta effect is secondary effect on a structure. It is also known as “Geometric non-linearity effect”. As number of stories increases P-delta effect becomes more important. If the change in bending moment and displacement due to lateral load is more than 10% of primary moment and displacement P-delta effect should be considered in design, that is, second order analysis is required.

There are many important factors which take part in determination of stability coefficient. Load, base shear, earthquake load characteristics, story drift etc. play vital role in this factor. This study covers stability coefficient determination of ninety (90) moment resisting frame buildings for different building parameters to determine when it is necessary to perform the second order analysis.

Moment resisting frames are considered as frames which resist 100% of seismic force and are not enclosed or adjoined by components that are more rigid and will prevent the frames from deflecting under seismic forces. In this study, three different aspect ratios of structure are compared individually in same seismic zone namely Seismic Zone II of Bangladesh. As a case study a commercial building located at Dhaka city of Bangladesh with a floor area around 1000 square meter per floor has been considered in this study. Each structure was analyzed, and designed separately for comparison. Comparisons were made for height of structure varying from two storied to thirty storied building. Comparisons were made for both symmetric and asymmetric buildings. The comparisons were made in terms of their stability coefficient obtained from Finite Element analysis. Finally, it is concluded that for up to 24 storied RCC building at Dhaka city in both the cases of symmetric and asymmetric commercial buildings considered in the case study one does not need to consider P-delta effect in the analysis.