Concrete Q&A: Design Loads for Concrete Pan Joists and Concrete Cover and Design Service Life
Appears on pages(s):
code, durability, crack, structure
I am working on a renovation of a building that has existing concrete pan joists. The building is from the 1930s. The concrete joists are 10-1/2 in. (267 mm) deep with a 2-1/2 in. (64 mm) slab and spaced at 25 in. (635 mm) on-center. They have one bottom bar that is continuous and another bar that is at the bottom at midspan and bent to create top bars at the supports. The joists also appear to widen in plan near the supports. I have been searching for load tables for pan joists online in vain. Does ACI have any historical publications with the design loads for concrete ribbed slabs/pan joists?
With regard to concrete cover, for example, Table 126.96.36.199.1 in ACI 318-19,1 what is the assumed or anticipated design life of the structure that these values are given for: 30, 50, or 100 years? It is important for us to understand this from a durability perspective in the event these values do not cover the required design life of the concrete members in our project design, which needs to be for 120 years.