Degree Name

Doctor of Philosophy


School of Civil, Mining and Environmental Engineering


Fibre-reinforced polymer (FRP)-concrete-steel hybrid multitube concrete columns (MTCCs) are a new form of hybrid columns recently developed at the University of Wollongong. An MTCC consists of an external FRP confining tube, a number of internal steel tubes, with the space inside all the tubes filled with concrete. The external FRP tube can be square, circular, or in any other shape, while the internal steel tubes are preferably circular to maximise the confinement effectiveness. The new column form offers a range of advantages over the existing column forms, including its ample ductility, excellent durability and cost-effectiveness.

This thesis presents a comprehensive study involving both experimental and theoretical work aimed at developing an in-depth understanding of, and reliable theoretical and design models for, the compressive behaviour of MTCCs. The experimental part of the study involved extensive laboratory tests on MTCC specimens covering a wide range of variables, including the shape and scale of specimens, the volume ratio and configuration of steel tubes, and the confinement stiffness ratio of FRP tube. Notably, a number of large-scale specimens with the outer diameter/side width being 500 mm were tested to investigate the potential size effect. The test results evidently show that the concrete in MTCCs is very well confined by both the FRP tube and steel inner tubes, and the buckling of the steel tubes is effectively constrained, leading to very ductile response of the columns. Importantly, the ultimate axial strain of MTCCs is considerably larger than the corresponding concrete-filled FRP tubes (CFFTs) with the same FRP tube. Furthermore, the test results clarify the effects of various parameters on the overall compressive behaviour of MTCCs and demonstrate that the size effect is marginal for the new columns...

This thesis is unavailable until Friday, November 04, 2022



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.