i am modelling a concrete slab on a base in abaqus.now in step initial i set temperature of top and bottom layers both as zero.then in coupled temp-displacement step i chnge the temp of top and bottom layers through boundary conditions as -20 and 0 and also use gravity as load and add component 2 as -9810 in the same step?But  in the stress profile the slab should show maximum stress near the middle portion,which i not happening.Am i doing wrong anywhere?please help.