Title: Measured and Predicted Axial Shortening in Tall Buildings: Recent Research Findings

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Publication: CIA

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Date: 2/14/2011

Abstract:
Shortening predictions of core and column elements in tall buildings is an area that is often discussed on new projects and also in research circles. In the last decade the authors have been specifically involved in research projects related to shortening. Significantly as part of this work, two tall reinforced concrete buildings were recently instrumented during construction to observe time dependent axial shortening behaviour on selected columns and core walls at various levels where access to critical areas was available for extended periods. The measurements were taken over periods of up to three years from the initial construction period to the completion of the structure. In addition, material properties of the site delivered concrete were also measured with time. In this paper, a well accepted axial shortening estimation method is utilised and analysed. The method estimates shortening based on currently used prediction equations for creep, shrinkage and elastic modulus. The typical prediction equations used in Australia are described. Actual shortening measurements made on selected column elements in the two buildings are also described. Comparisons of measured and predicted axial shortening are made.