In the literature piece SA926, I see limiting height tables for unlined shafts, as well as regular shafts. What is the difference?
The difference is in one case the load is considered intermittent, or the load is only applied as the elevator moves by. In the other case the load is sustained or constant. This would be the case for air handling systems. The sustained load is far more severe. The codes allow us to increase the allowable stress by 1/3 if the load is considered intermittent.