1-31. The column is subjected to an axial force of 8 kN, which is applied through the centroid of the cross-sectional area. Determine the average normal stress acting at section a-a. Show this distribution of stress acting over the area's cross section. 8 kN 75 mm -75 mm 10 mm 10 mm 10 mm 70 mm 70 mm Prob. 1-31