Table 7: The effect of a hollow ration on the strength of double skin concrete-filled uPVC tube specimens.

Internal Tube Ext. Tube
Label t1 D1 d t D h h/D D/h (D-d)/D Strength (MPa)
C3P3H1 0 0 0 3 110 220 2 0 1 26.99
C3P4H1 0 0 0 3 140 280 2 0 1 24.57
C3P3H2 0 0 0 3 110 440 4 0 1 24.59
C3P3H3 0 0 0 3 110 660 6 0 1 23.15
C3P3H4 0 0 0 3 110 880 8 0 1 20.98
C3D1H1 3 63 57 3 110 220 2 0.52 0.48 22.27
C3D2H1 3 75 69 3 140 280 2 0.49 0.51 22.29
C3D3H1 3 63 57 3 140 280 2 0.41 0.59 23.49
C3D1H2 3 63 57 3 110 440 4 0.52 0.48 20.14
C3D1H3 3 63 57 3 110 660 6 0.52 0.48 18.37
C3D3H2 3 63 57 3 140 560 4 0.41 0.59 20.71
C3D3H3 3 63 57 3 140 840 6 0.41 0.59 18.43