As we know that the design of a pavement is governed by the analysis so, this is very important to know the various combinations of stresses that will be induced in the slab. There are two kinds of loading:
- Traffic Loading
- Temperature variation.
That makes total of three kinds of stresses that will be induced in the pavement slab. Now, we have to find out the critical combination of these three.
- In Summer Season:
In the after mid-noon hours in summer season, the temperature at the top layer will be higher as compare to the bottom layer. That will make the slab to tend to warp in downward direction. Under the self weight of the slab warping will be restricted and therefore will result in the tensile stress in the bottom layer.
Downward warping results in contraction of the bottom layer which is restricted through the induction of the tensile warping stress. So, warping stress of tensile nature is induced.
Now, at the edge region the traffic load stress of tensile nature is also induced and that is where the critical load combination is formed.
Critical stress combination(At the edge) = Traffic stress + Warping stress - frictional stress.
- In Winter Season:
So, the Critical stress combination(At the edge) = Traffic stress + Warping stress + frictional stress.
At the corners the critical load combination is that of the traffic load and the warping stress at the top layer at the mid-night hours.
See, in the night the temperature at the bottom layers will be higher as compare to the temperature at the top layers so, there will be upward warping. That will induce tensile warping stress at the top layer.
So, Critical stress combination(At the corner) = Traffic stress + Warping stress
Thank you for your time!