show the maximum principal stresses of both slabs with joint
gaps under positive and negative temperature gradients, respectively.
The positive temperature gradient makes the slabs curl down and
the negative one makes the slabs curl up. Once there is a joint
gap, the maximum tensile stress increases slightly, but the sizes
of the joint gap do not affect the maximum stresses for both the
dowel and key joint slabs. The maximum stresses are almost the
same for both the dowel and key joint slabs.