The effect of creep on modular ratio is

Answer: Option B

The modular ratio is defined as: m = Es / Ec Where: Es = Modulus of elasticity of steel (approximately constant) Ec = Modulus of elasticity of concrete

What is Creep? Creep is the long-term deformation of concrete under a sustained load. Over time, concrete subjected to constant stress will slowly deform. This is a time-dependent increase in strain, even when the stress remains constant.

How Creep Affects Modulus of Elasticity: Due to creep, the concrete shows more strain for the same level of stress. This means its effective modulus of elasticity reduces over time. In other words, Ec becomes smaller than its short-term value.

Impact on Modular Ratio: Since modular ratio = Es / Ec, and Es remains constant, a reduction in Ec (due to creep) results in an increase in the modular ratio.

Why Some Get Confused: In some design approaches (e.g. working stress method), to indirectly account for creep and long-term deflection, a lower modular ratio is used empirically. This is a correction based on behavior, not a direct mathematical consequence of the creep effect on elasticity.

But theoretically and fundamentally, the effect of creep is to increase the modular ratio.

Therefore, the correct answer is: Option B — To increase it.