Explanation: The characteristics of under-reinforced section and over a reinforced section when compared with balanced section are given below in the tabulated form. Under – reinforced section when compared with Balance section Over – reinforced section when compared with Balance section Steel yield first then concrete Concrete will reach to maximum stress first Reinforcement is less than a balanced section Reinforcement is more than a balanced section Primarily tension failure Primarily Compression failure Ductile failure Sudden or brittle failure Depth of Neutral axis shifts upward i.e. it is less than that of balanced section (Xu u,lim) Depth of Neutral axis shifts downward i.e. it is more than that of balanced section (Xu > Xu,lim) Strain in steel is greater than that of in balanced section. Strain in steel is less than that of in balanced section. Larger section is required because it has less steel Smaller section is required because it has more steel. More deflection because it has less steel Less deflection because it has more steel. Moment of Resistance is less than that of Balanced section Moment of Resistance is more than that of Balanced section [ alt="F3 N.M Madhu 23.03.20 D6" src="//storage.googleapis.com/tb-img/production/20/03/F3_N.M_Madhu_23.03.20_D6.png" style="width: 595px; height: 348px;"> So, For an under-reinforced beam, steel yield prior to concrete failure. Stresses in steel reach permissible value whereas stress in concrete has not reached up to its permissible value. σs = fy and σc c