Read the following statements relating to flexure of reinforced concrete beams :
I. In over-reinforced sections, the failure strain in concrete reaches earlier than the yield strain in steel.
II. In under-reinforced sections, steel reaches yielding at a load lower than the load at which the concrete reaches failure strata.
III. Over-reinforced beams are recommended in practice as compared to the under-reinforced beams.
IV. In balanced sections, the concrete reaches failure strain earlier than the yield strain in tensile steel.
Each of the above statements is either True or False.
Which one of the following combinations is correct?
A post-tensioned concrete member of span 15 m and cross-section of 450 mm $$\times$$ 450 mm is prestressed with three steel tendons, each of cross-sectional area 200 mm2. The tendons are tensioned one after another to a stress of 1500 MPa. All the tendons are straight and located at 125 mm from the bottom of the member. Assume the prestress to be the same in all tendons and the modular ratio to be 6. The average loss of prestress due to elastic deformation of concrete, considering all three tendons is
Consider two linearly elastic rods HI and IJ. Each of length b, as shown in the figure. The rods are co-linear, and confined between two fixed supports at if and J. Both the rods are initially stress free. The coefficient of linear thermal expansion is a for both the rods. The temperature of the rod IJ is raised by $$\Delta$$T whereas the temperature of rod HI remains unchanged. An external horizontal force P is now applied at node I. It is given that a = 10$$-$$6 $$^\circ$$C$$-$$1, $$\Delta$$T = 50$$^\circ$$C, b = 2m, AE = 106N. The axial rigidities of the rods HI and U are 2 AE and AE, respectively.
To make the axial force in rod HI equal to zero, the value of the external force P (in N) is _________. (rounded off to the nearest integer).
Stresses acting on an infinitesimal soil element are shown in the figure (with $$\sigma$$z > $$\sigma$$x). The major and minor principal stresses are $$\sigma$$1 and $$\sigma$$3, respectively. Considering the compressive stresses as positive, which one of the following expressions correctly represents the angle between the major principal stress plane and the horizontal plane?
