=+shear (Vmax, in kN) is influenced by x15transversereinforcement yield stress (MPa) and x25concrete cylinder compressive strength (MPa).

y: 314.9 359.0 300.7 271.3 266.9 x1: 469 469 469 400 400 x2: 21.10 21.10 20.90 25.60 25.60 y: 240.2 231.3 315.8 338.1 355.9 x1: 400 400 400 400 400 x2: 33.10 33.10 25.70 27.60 27.60 y: 378.1 101.9 110.8 103.2 101.9 x1: 400 46 46 365 365 x2: 25.70 4.65 4.34 23.00 20.20 y: 120.5 111.6 219.3 213.1 x1: 365 365 392 392 x2: 23.00 20.20 30.70 30.70 Use a statistical computer package to fit

(a) a 1 b1x1 1 b2x2,

(b) a 1 b1x1 1 b2x2 1 b3x1x2, and

(c) a 1 b1x1 1 b2x2 1 b3x1x2 1 b4x1 2 1 b5x2 2