Compressive resistance of hot-rolled elliptical hollow sections

Abstract

In recent years, hot-rolled elliptical hollow sections have attracted significant attention from engineers and architects owing to their complementary qualities of aesthetic appearance and structural efficiency. However, there is currently a lack of design guidance for elliptical hollow sections inhibiting more widespread use in construction. The present paper addresses this shortcoming for the fundamental loading condition of axial compression. Laboratory testing, numerical modelling and the development of design rules are described herein. The experimental programme comprised 25 tensile coupon tests and 25 stub column tests. All tested elliptical hollow sections had an aspect ratio of 2 and section sizes ranged from 150×75 up to 500×250 mm. Results, including geometric imperfection measurements and full load–end shortening curves have been presented. Non-linear finite element models were developed and validated against the generated test data. The validated numerical models were employed to perform parametric studies in order to investigate elliptical hollow sections of varying slenderness and varying aspect ratios. The resulting structural performance data have been used to establish a relationship between cross-section slenderness and cross-section compressive resistance, which demonstrates that the Class 3 slenderness limit of 90 from Eurocode 3 for circular hollow sections can be safely adopted for elliptical hollow sections based upon the proposed cross-section slenderness parameter. The equivalent semi-compact slenderness limit given in BS 5950-1, non-compact limiting slenderness in AISC 360-05 and yield slenderness limit given in AS 4100 are also valid. A modified effective area formula from BS 5950-1 can also be safely adopted. Further investigation into effective area formulations for slender (Class 4) elliptical hollow sections is currently under way.