Analytical Modelling of LACFCST Stub Columns Subjected to Axial Compression

Yunlong Xu,Chenglu Liu,Faxing Ding,Fei Lyu,En Wang

doi:10.3390/math9090948

Abstract

This paper presents a numerical investigation of lightweight aggregate concrete-filled circular steel tubular (LACFCST) stub columns under axial compression. A finite 3D solid element model of the LACFCST stub column was established by adopting a plastic-damage constitutive model of lightweight aggregate concrete (LAC). The finite element model (FEM) analysis results revealed that the confinement effect of the steel tube on the infilled LAC was weaker than that on the infilled conventional concrete. A parametric study making use of 95 full-scale FEMs was conducted to investigate the influences of various design parameters of LACFCST stub columns on their ultimate axial bearing capacity and the composite actions. Moreover, a numerical model of the axial and transverse stress of steel tubes at the ultimate state of LACFCST columns was proposed using the regression method. Based on the equilibrium conditions and the proposed model, a practical design formula making use of an enhancement factor was derived to estimate the ultimate bearing capacity of LACFCST stub columns by using the superposition method. The validity of the proposed formula was verified against the experimental data of 49 LACFCST stub column specimens under the axial loading available in the literature. Meanwhile, the accuracy and conciseness of the proposed formula were evaluated by comparison with the formulas suggested by the existing design codes.

Highlights

In the past several decades, steel–concrete composite structures have been increasingly used in long-span bridges and super high-rise buildings around the world with the progress of social demands
Zhang et al [13] investigated the axial compressive performance of lightweight aggregate concrete-filled circular steel tubular (LACFCST) stub columns with different replacement ratios of normal gravel aggregate, and the results revealed that the ultimate bearing capacities and the corresponding displacements of the stub columns increased with an increase in the normal gravel replacement ratio
The objective of this paper is to investigate the confinement effects of LACFCST stub columns under axial loading

Summary

Introduction

In the past several decades, steel–concrete composite structures have been increasingly used in long-span bridges and super high-rise buildings around the world with the progress of social demands. Abhilash et al [9] presented an experimental investigation of CFST columns using semi-lightweight aggregate concrete as an infill, and investigated the effects of variations in the diameter, width, thickness and length-to-diameter ratio of the outer steel tube on the ultimate axial load-bearing capacity and axial shortening behaviors of both the circular and square columns. The results suggested that the load-carrying capacity of lightweight aggregate concretefilled steel tubular columns were found to be comparable to conventional concrete-filled specimens, and the circular tubes can provide substantial post-yield strength and stiffness, while the square and rectangular cross-sections cannot. The non-linear finite element (FE) analysis was carried out, and the validity of the presented numerical analysis was verified against the collected experiment results of the ultimate bearing capacity and the whole loadingshortening curves; (2) based on the validated model, a parametric study was performed, and the different composite action between the LACFCST and CFCST stub columns was discussed.

Element Type and Mesh Size

Constitutive Model Parameter Settings

Model Simplification

Findings

Conclusions