Experimental Study and Fragility Analysis of Effective-Length Factors in Column Buckling

Abstract

The design of columns relies heavily on the basis of Leonhard Euler's Theory of Elastic Buckling. However, to increase the accuracy in determining the maximum critical load a column can withstand before buckling, a constant was introduced. This dimensionless coefficient is K, also known as the effective-length factor. This constant is often found in building design codes and varies in value depending on the type of column support that is applied. This paper presents experimental and analytical studies on the determination of the effective-length factor in the buckling stability of columns with partially-fixed support conditions. To this end, the accurate K value of the columns tested by the Instron Testing Machine (ITM) at California State University, Northridge's (CSUN's) Mechanics Laboratory is determined. The ITM is used in studying the buckling of columns where the supports are neither pinned nor fixed, and the material cross-section rather rests upon the machine while loading is applied axially. Several column specimens were tested and the experimental data were analyzed in order to estimate the accurate effective-length factor. The calculations from the tested results as well as the conducted probabilistic analysis shed light on how a fragility curve may aid in predicting the effective-length value of future tests.