A pre-tensioned rectangular concrete beam $$150$$ $$mm$$ wide and $$300$$ $$mm$$ depth is prestressed with three straight tendones, each having a cross-sectional area of $$50$$ $$m{m^2},$$ to an initial stress of $$1200$$ $$N/m{m^2}.$$ The tendons are located at $$100$$ $$mm$$ from the soffit of the beam. If the modular ratio is $$6,$$ the loss of prestressing force (in $$kN,$$ up to one decimal place) due to the elastic deformation of concrete only is ________

In a pre-stressed concrete beam section shown in the figure, the net loss is $$10\% $$ and the final prestressing force applied at $$X$$ is $$750$$ $$kN.$$ The initial fiber stresses (in $$N/m{m^2}$$ ) at the top and bottom of the beam were:

A rectangular concrete beam $$250$$ $$mm$$ wide and $$600$$ $$mm$$ deep is pre-stressed by means of $$16$$ high tensile wires, each of $$7$$ $$mm$$ diameter, located at $$200$$ $$mm$$ from the bottom face of the beam at a given section. If the effective pre-stress in the wires is $$700$$ $$MPa,$$ what is the maximum sagging bending moment (in $$kN$$-$$m$$) (correct to $$1$$-decimal place) due to live load that this section of the beam can with stand without causing tensile stress at the bottom face of the beam? Neglect the effect of dead load of beam.

A concrete beam prestressed with a parabolic tendon is shown in the sketch. The eccentricity of the tendon is measured from the centroid of the cross-section. The applied prestressing force at service is $$1620$$ $$kN.$$ The uniformly distributed load of $$45$$ $$kN/m$$ includes the self-weight. The stress (in $$N/m{m^2}$$) in the bottom fibre at mid-span is