Firstly
ITS A TRISTAR!!!!!!!
consider the two things together.
aircraft at max zero fuel landing at max landing weight.
max landing - max zero fuel = fuel in wings( bending relief) the little arrows on the wing tips.
now same ac above max zero fuel at max landing weight
less fuel in wings smaller little arrows on the tips. ergo more stress on roots.
on the L1011s with 1and 3"A" tanks. if the 1 and 3 are not full the "A" tank fuel is considered zero fuel weight. The A tanks are in the belly.