Structural Performance of Concrete - Filled Elliptical Hollow Section Columns Under Concentric and Eccentric Loading Conditions

Structural Performance of Concrete-Filled Elliptical Hollow Section Columns under Concentric and Eccentric Loading Conditions

CIV 1169: Final Project

Submitted by: Jiaying Fu

Student Number: 1002230659

Date: Mar 23, 2016

1.0 Introduction

Concrete-Filled Elliptical Hollow Sections (EHS) were developed as a new method of composite construction in early 2000s, and have been widely adopted during recent years. In the concrete-filled EHS structures, the combination of concrete and steel effectively utilizes the advantages of both the materials in composite construction. The outside elliptical steel tube provides strength and stiffness, while the concrete core is responsible for providing local and overall stability to the whole structure. In the modern construction industry, the circular, square, and rectangular hollow sections are the dominated tubular shape, however, elliptical tubes occurred to provide an alternative option. The special geometry of elliptical hollow sections with major and minor axes greatly improves the geometric efficiency and architectural aesthetics, and is examined to show better strength and ductility. Because of their high strength, concrete-filled hollow sections are highly recommended to be used as columns, thus, concrete-filled elliptical tubes used as columns are the main focus of this report. This report aims to provide an overview of the structural performance of concrete-filled elliptical hollow section columns under different loading cases and the comparison to circular and rectangular concrete-filled hollow sections.

2.0 Structural Behaviour under different loading cases

With high geometric efficiency, the elliptical hollow sections (EHS) became more and more popular these years. However, to generalize the use of EHS, many efforts should be given to analyze its structural behaviour under various loading cases. Three loading cases, including axial loading, compression and bending, and biaxial bending, are discussed as follows.

2.1 Performance under Concentric Axial Compressive Loading

Compared to circular and rectangular hollow sections, geometry is the main difference and benefits of elliptical hollow sections. The major and minor axes are indicated by figure 1 (2a represents the major outer diameter and 2b indicates the minor outer diameter), meanwhile, the thickness of the steel tube also influences the overall structural behaviour (Zhao & Packer, 2009). Under axial compression loading case, the sectional sizes, column lengths, slenderness ratio, and the strength