To improve construction efficiency in offshore engineering and extend service life of offshore platforms, a novel bamboo-raft-type floating structure (BRT-FS) assembled by FRP reinforced concrete tubes is proposed. It comprises four fundamental components: concrete tube, carbon fiber-reinforced polymer (CFRP) cable, holding beam, and bellow. This paper presents structure system and structure design of BRT-FS. Separating load-bearing and buoyant functions ensures structural safety and ease of design. It has broad application perspectives in offshore construction due to its high corrosion resistance, designability, construction efficiency, and low crack control requirement. Furthermore, to obtain the operation conditions of BRT-FS, the mechanical performance is analyzed from two levels, which are hydroelastic analysis and structural analysis. Hydroelastic analysis is conducted under different wave directions, wave periods, water depths, and structural dimensions using a new finite element-boundary element (FE-BE) method. In a specify study case, a sensitive period around 11 s for head sea, around 7 s for oblique wave, around 5 s for beam sea are noted. The hydroelastic response is not significantly affected by water depth or transverse dimension. Structural analysis indicates that the structure can work in clam harbour sea with breakwater protection. Even after concrete tubes crack in higher waves, this new structure can still float with the inside bellows in theory. These preliminary findings confirm the feasibility of this novel structure. Structural details such as tube-tube joints, tube-beam joints, CFRP cable anchorages, and other connections will be further designed and tested in the future.