Behaviour and design of tubular structural members under concentrated bearing loads

Abstract

Tubular steel sections have been widely used in a variety of structural applications such as buildings, bridges, roof systems, offshore platforms and other applications. Vibrant research in the development of structural design guidance has been conducted for tubular sections such as members subjected to axial load, bending and combined axial load and bending. The investigations on tubular structural members under concentrated bearing loads are rather limited. The present study is focused on the development of design guidance for tubular structural members under concentrated bearing loads underpinned by experimental and numerical investigations.

The behaviour of hollow and concrete-filled steel tubular structural members under concentrated bearing loads was studied. Comprehensive experimental programs were firstly carried out. The investigated tubular sections comprised 12 cold-formed high strength steel sections and 9 cold-formed ferritic stainless steel sections. The experimental program for materials included 57 and 83 coupon tests at ambient and elevated temperatures, respectively. A thorough test program at member level was conducted comprised 187 web crippling tests, 5 beam tests, 28 combined bending and web crippling tests, and 59 concrete-filled tubular joint tests. The web crippling tests were conducted to study the behaviour of square and rectangular hollow sections under concentrated bearing loads. The beam tests and the combined bending and web crippling tests were performed to investigate the interaction relationship between bending moment and concentrated interior bearing load for tubular structural members. The structural response of concrete-filled tubular members under concentrated bearing loads was explored by carrying out the transverse compression-loaded concrete-filled tubular joint tests.

In conjunction with the experimental investigation, numerical modelling was also performed using the finite element analysis package ABAQUS. Finite element models were developed and validated against the experimental results. Upon validation, comprehensive parametric studies were carried out using the validated finite element models to supplement the experimental data. The parametric studies consisted of 700 web crippling specimens, 188 combined bending and web crippling specimens, and 476 concrete-filled tubular joint specimens.

The experimental and numerical data were used to evaluate the applicability of existing design provisions to the cold-formed high strength steel and cold-formed ferritic stainless steel hollow as well as concrete-filled tubular structural members under concentrated bearing loads. Improved design rules are proposed for hollow and concrete-filled steel tubular structural members under concentrated bearing loads including a newly developed Direct Strength Method for square and rectangular hollow structural members undergoing web crippling. The reliability of the existing and proposed design rules has been assessed by means of reliability analysis.