Cinitha.A
Scientist, Structural Engineering Research Centre, Chennai - 600 113, INDIA
Rama Raju. K
Senior Assistant Director ,Structural Engineering Research Centre,Chennai-600 113
Nagesh.R. Iyer
Director Grade Scientist , Structural Engineering research centre, Chennai 600 113
Keywords: Small-scale model, Dynamic Characteristics, Normalized stiffness, Fundamental Frequency.
ABSTRACT:
The design of structures subjected to natural hazards such as earthquakes and typhoons demands
safety of structures which is governed by the natural frequencies and the amount of damping in each mode of
vibration. Fundamental frequency of a building and its damping have a remarkable effect on the magnitude of its response. The ability to predict these characteristics at the design stage would enable to design safe
structures.This paper presents the numerical and experimental dynamic characteristics of steel moment resisting space frames. An experimental investigation was carried out on a small-scale (1:15) 3-storey moment resisting steel frame and its fundamental frequencies are obtained. A numerical simulation of the model was performed using the finite element analysis.The numerical results of the model are compared with the experimental results. Numerical studies are extended to find the influence of the plan and bay dimensions, normalized stiffness and height of storeys of multi bay multi storey frames on the fundamental frequency of the moment resisting frames. Based on the experimental and the numerical investigations, the free vibration characteristics of moment resisting steel space frame are established.
1. Introduction
The design of structures subjected to natural hazards such as earthquakes and typhoons demands safety of
structures which is governed by the natural frequencies and the amount of damping in each mode of vibration. It is evident that structures designed for static loads need not be safe under dynamic loads. Fundamental frequency of a building and its damping have a remarkable effect on the magnitude of its response. The ability to predict these characteristics, at the design stage, would enable to design safe structures. Small-scale model testing is a viable option to predict the dynamic characteristics. Mills (1979), Krawinkler and Wallace (1985) and Kim (2003) have carried out extensive experimental studies for finding the dynamic characteristics such as natural frequencies and modal damping of the small scale models. Lagomarsino (1993), Tamura (1996), Goel (1997) and Tremblay (2005) have conducted several field studies on the dynamic characteristics of moment resisting frames.However, not much published work is reported on the free vibration characteristics of 3D frames. An experimental investigation was carried out on a small- scale (1:15) 3-storey moment resisting steel space frame and its fundamental frequency is found. A numerical simulation of the model was performed using finite element analysis. The numerical results of the model are compared with the experimental results. Numerical studies are extended to find the influence of the plan and bay dimensions, normalized stiffness and height of storeys of the multi bay multi storey frames on the fundamental frequency of the moment resisting frames.
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