Question

A 1200 mm deep by 750 mm wide post-tensioned simply supported beam is shown below. The beam spans 12.0 m and is subject to a superimposed dead load of 50 kN/m and a live load of 35 kN/m. Both the superimposed dead load and live load are applied after transfer (after stressing has taken place). The tendon is located at the mid-height of the beam at each end, and its centreline sits 50 mm from the base at midspan. The concrete strength at transfer is 22 MPa, and at maturity is 40 MPa. Assume E_c = 32800 MPa, γ_c = 24 kN/m³ and ignore any prestress losses.

c)            Estimate the approximate total short-term and long-term deflection under the load combination G + 0.7Q. Assume P_i = 1750 kN and Ф_cc = 2.8.

Answer 1