wR / 4d

wR/2d

wR/d

2wR/d

compressive everywhere

tensile everywhere

partly compressive and partly tensile

zero

(i) and (iii)

(i)and(iv)

(ii) and (iii)

(ii) and (iv)

forces of tension and compression change but lever arm remains unchanged

forces of tension and compressions remain unchanged but lever arm changes with the moment

both forces of tension and compres-sion as well as lever arm change

both forces of tension and compres-sion as well as lever arm remain unchanged

to provide adequate bond stress

to resist tensile stresses

to impart initial compressive stress in concrete

all of the above