Isolated Rectangular Footings under Biaxial Bending: A Critical Appraisal and Simplified Analysis Methodology

Abstract

The case of isolated rectangular footings being subjected to eccentric loads along both directions is very conventional as columns are ordinarily subjected to horizontal loads, vertical loads, and moments simultaneously. Also, its design has not been of much concern for engineers due to the availability of simple mathematical equations for the case when the eccentricity lies within the kern. However, the eccentricity in the case of footings subjected to high biaxial moments normally lies outside the kern area and conventional analysis becomes invalid in those scenarios. Various approximate graphical or analytical methods are available for the analysis in this case. It has been observed that most of these developed models for the biaxial bending scenario are based on the same postulation, and thus it commonly leads to confusion among designers about the most effective and straightforward method to follow during design. Therefore, to avoid the possibility of related confusion and to provide more clarification regarding the existing methods, all the available solutions for the design of the biaxially eccentric condition are critically reviewed in the present study. Moreover, recommendations are proposed for the use of a simple method based on a justifiable comparison highlighting the shortcomings in the applications of other available solutions. Additionally, to enhance the computational efficiency of computer-aided studies and manual assessments, a simplified approach to automate the recommended procedure for the design of rectangular footings is also developed, and correspondingly a pseudoalgorithm is proposed for its easy implementation.