Many text book literature on braced excavation mention the necessity to consider additional load due to temperature effect on struts. But nothing is mentioned about waling. Why is this so? Wouldn't axial load in waling be significant for waling with large cross sections? Is the consideration any different from struts? How would such effect be considered for waling, if temperature is a necessary consideration?
I think the important difference to consider in a typical excavation is that:
A strut will span the whole excavation and only be supported at the ends.
For a typical waling it will potentially span the whole excavation but it would typically be rigidly connected frequently to the excavation walls.
By rigidly connecting the waling to the wall it would behave in a composite manner with the wall. Any development of axial strain the waling would be counteracted by restraining actions such as the restraint of the wall itself and friction in the surrounding ground.
This doesn't however mean that you do not need to do a check on the waler for high temperature conditions. If the strut heats up and additional forces are introduced due to the temperature rise then these additional forces would probably end up in the walers potentially introducing additional bending into the waler which would need to be checked.