The channel shape cross-section and the rectangular cross-section shown in the Figure Q4 are made of materials with elastic-perfectly plastic behaviour. The yield stress of the material used for the channel shape cross-section is oy=402 MPa, whereas that used for the rectangular cross- section is 0.85oy. Compute the thickness of the web, t, of the channel shape section if the two cross sections have identical plastic bending moment about the z-axis. In Figure 4, h= 93 mm, b=53 mm, a=9 mm, H=93 mm, d= 53 mm Z Part a) b 0 h Figure Q4 Z d H 1. The numerical value of plastic section modulus of the solid rectangular section is mm