Axial behavior of seawater sea-sand coral concrete-filled basalt fiber-reinforced polymer tubular columns containing pre-bonded basalt fiber-reinforced polymer bars

The seawater sea-sand coral aggregate concrete (SWCC) is believed to have a wide application prospect in the field of ocean engineering, even if research problems are still open. In this paper, the axial performance of SWCC-filled basalt fiber-reinforced polymer (BFRP) tubular columns were experimentally tested and theoretically calculated. Considering that the BFRP tubes manufactured by spiral winding impregnated basalt fiber sheets can normally only provide strength in hoop direction, a new type of integrated prefabricated BFRP tube with longitudinal BFRP bars pre-bonded on the inner wall was manufactured. Ten SWCC columns were built, instrumented, tested, and analyzed. First, the influences of the wall thickness of the BFRP tubes (i.e., 2 mm and 4 mm) and the containing of pre-bonded BFRP bars or not were compared. Then, based on the modification of existing models, a calculation model applicable to the peak bearing capacity of the new integrated BFRP tube confined SWCC was preliminarily proposed. The results showed that the integrated BFRP tube designed in this paper has good application prospects in the marine environment and the proposed equation can be used to predict the ultimate strength of this new BFRP tube confined SWCC. The established numerical model had good accuracy in predicting the stress-strain relationship and the failure modes of the proposed SWCC-filled BFRP tubular columns under axial compression.