ANS:B - (C - 1)mf + eE

The combined effect of creep and shrinkage in a prestressed concrete member can be expressed as: ((C−1)mf−eE Where:

• C is the creep coefficient,
• f is the original prestress in concrete,
• m is the modular ratio,
• E is Young's modulus of steel, and
• e is the shrinkage strain.

Creep is the gradual increase in deformation over time when a material is subjected to a constant load or stress. It causes the concrete to deform further under sustained loading conditions. Shrinkage is the reduction in volume of concrete due to the loss of moisture over time. It results in tensile stresses within the concrete. In the given expression, (C−1)mf represents the contribution of creep, where (C−1) accounts for the increase in deformation over time, m is the modular ratio relating the elastic moduli of concrete and steel, and f is the original prestress in concrete. The term −eE represents the contribution of shrinkage, where −e is the shrinkage strain and E is the Young's modulus of steel. The negative sign indicates that shrinkage leads to a decrease in prestress. Therefore, the correct expression for the combined effect of creep and shrinkage is: (C−1)mf−eE