Similitude relationship for circular concrete filled steel tube

Abstract

In high-rise building construction, concrete filled steel tubular (CFST) column has been widely used. It comprises of a hollow steel tube infilled with or without additional reinforcement or steel section. The concrete core prevents or delay the local buckling of the outer steel tube while the steel tube confining the concrete core provides enhancement in strength and ductility under high compressive load. During experimental work in studying CFST, if huge amount of sampling is required, researchers might face issue such as insufficient materials if budget is not allowed, capacity limitation of the testing machine that is readily accessible for the researchers to conduct compression test and also huge amount of waste created. The purpose of this study is to investigate the applicability of using similitude relationship to determine the axial capacity of circular concrete filled steel tube for prototype and model scaled specimen, using dimensional analysis to determine the scaling factors for each variable considered relevant to the nature of the problem. BC4: 2015 and nonlinear analysis using ANSYS software have been used to determine the axial capacity for the same prototype and model specimen to serve as reference for counter check purpose to verify if the axial capacity determined using similitude relationship is reasonable. For the nonlinear analysis using ANSYS, nonlinear material properties have been included whereby the Drucker-Prager model is used for concrete and bilinear kinematic hardening is used for steel tube. From the results obtained, it is observed that the axial capacity determined from similitude relationship shows result with maximum deviation of 0.41 % whereas ANSYS analysis results shows a percentage of maximum deviation of 2.47 % when comparing to BC4: 2015. The scaling factor of axial load capacity for model and prototype using similitude shows a percentage deviation of 0.42 % and ANSYS analysis shows a percentage deviation of 4.1 % comparing to scaling factors obtained using BC4: 2015. This shows that the current physical quantities or variables selected for dimensional analysis is reasonable where the similitude relationship developed does not distort the model by much from its prototype.