Capacity of limestone Stair Threads
Capacity of limestone Stair Threads
(OP)
Does anyone have references for calculator the capacity of limestone steps? I'm looking at a project where the client wants 7"x10" limestone pads to form the steps which will span roughly 5 ft. I know it would depend on the quality of the rock itself.
Thanks
Thanks






RE: Capacity of limestone Stair Threads
RE: Capacity of limestone Stair Threads
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Capacity of limestone Stair Threads
Limestone is a natural material and has inherent imperfections that are sometimes not apparent, particularly in bulk sections
Even though Indiana limestone is much more consistent than limestone in the lower US, it remains a sedimentary material that is relatively soft...not yet morphed to marble
When you analyze the section, don't forget the concentrated load check as well, keeping in mind that a flexural failure will be brittle, not ductile
Steps are often on a critical life safety path...consider this
Think about bonding a 1/4" thick aluminum plate to the tension side of the section to add ductility to any failure that might occur. It can be completely hidden so that it doesn't detract from the appearance
RE: Capacity of limestone Stair Threads
Sika Carbodur strips is a product that I have had success using.
On stairs, impact must be considered as someone might run up or down the stairs hence the need for tensile strength on the bottom side of the treads since brittle materials don't always perform well for impact. That is one reason why I discourage architects from using glass hand rails on balconies and stairs.
I saw one shattered once one someone fell against the railing.
RE: Capacity of limestone Stair Threads
RE: Capacity of limestone Stair Threads
Considering the application is a residential house, and the small span, I'm tempted to not reinforce the bottom. Still considering it though.
I think I'll keep the reinforcement option in my back pocket, and aim to get mechanical properties data from the quarry they are sourcing the limestone from. I've also requested a visual inspection of each slab prior to placement.
I know I can't hang my hat on this, but this project is in "Limestone City" (Kingston Ontario) where many many buildings are built out if this limestone which is considered to be of high quality.
RE: Capacity of limestone Stair Threads
RE: Capacity of limestone Stair Threads
We may opt to backfill the underside of the stairs to provide continuous bearing for the stone slabs.
RE: Capacity of limestone Stair Threads
I have another book "Stone Cladding Engineering" by Rui de Sousa Camposinhos that has a modern approach in line with Eurocode.
Try running FEA on the panels and check the stress concentration. You should get stone specifications from the supplier. They meet ASTM standards. Stone is not man-made or highly tested and graded, it's like the wild west. You get a few properties and soldier on.
If you're limited to 1 1/4" thick I would say you are going to have to add a stainless angle support. 25 PSF was the practical limit for wind loads +/- at about that span. Its cheap insurance.
RE: Capacity of limestone Stair Threads