CALCULATION OF FUNDAMENTAL PERIOD OF INFILLED REINFORCED MOMENT RESISTING FRAMES

للكاتبين

G.B. SHERIF, H.E.EL KHORAIBIE, M.H. KOTB and A.A.SUMMRA

Department of Civil Engineering

Faculty of Engineering, Al-Azhar University

Abstract

Ambient vibration measurements of many buildings have been recorded across the

world in the past to determine their dynamic properties, in particular, to ascertain the

properties of the fundamental modes of vibration. It is also recognized that the

experimental data from one region may not be used in another owing to the

differences in the construction methods and materials.

During an ambient vibration survey [Arlekar and Murty, 1997][1], a total of nineteen

buildings in Kanpur (India) seismic zone III are investigated to determine the

fundamental lateral transitional natural periods and the corresponding mode shapes of

vibration, as per the current seismic code for India. The investigated buildings are

reinforced concrete moment resisting frame (RC MRF) with un-reinforced masonry

bricks (URM) as infill walls.

Some infilled frame structures are analytically modeled using the standard analysis

software, ETABS & SAP 2000 [12] where the diagonal strut model is considered.

Regression analysis of fundamental lateral natural period data from experiments is

performed and empirical expressions are obtained for fundamental lateral natural

periods of (RC MRF) buildings with brick infill walls.

The expressions in the current codes are found unsuitable for estimating the

fundamental natural period of (RC MRF) buildings with brick infill. As these

expressions grossly overestimate the natural periods, improved expressions are

proposed.

The analytical numerical technique based on diagonal strut model, using the available

analysis software is found to be inadequate for determining the fundamental natural

periods of buildings. Thus new ratios of experimental and analytical natural periods

are determined.

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