HiAs i understand, in every cut-cover project piles are built as a primary strucure and its capacity after construction of final lining (final structure) is ignored.
does any one has any experience to account for long-term capacity of piles for contribution in long-term load carrying capacity of final structure?
Hi Ahmad, my experiences are that piles provide long term load capacity, but perhaps you're referring to piles that are used in tension to resist uplift of the cut and cover project before the final structure is constructed and the uplift resistance is no longer required (because of the weight of the structure). If the piles were designed as purely tension piles then they might not have the structural capacity to resist compressive loads and hence are ignored in the load carrying capacity of the final structure.
Martin
No,common practice in my country (Iran) and as far as i know in Us and Canada is that we have a primary structure ( pile and strut for example in cut and cover).
so we design primary structure and after that for designing final structure( for example concrete underground box) we don't count on that primary structure load carrying capacity. this could be true for simple and relatively weak primary structure like shotcrete and is true because in years (100 years as a common practice) it will be degraded and will loose load carrying capacity. But for strong systems like piles, that's definitely not trueyou have any idea or experience accounting that load carrying capacity?
Oh I see 'primary' as in a temporary structure where the piles are for excavation support and not part of the final design. I have experience using secant piles and concrete diaphragm walls for temporary and permanent construction, but not steel H piles. This is probably because like you say the steel would be likely to corrode a lot in the exposed below grade conditions and loose structural capacity after a 100 years. Although you could account for the loss of capacity and add extra thickness of steel into the design.
I meant temporary structure indeed.we built concrete piles for temporary structure and we don't count on their long-term load capacity. when we want to design final structure, we ignore that piles while they're there for sure.
Hello Ahmad,
One comment I have about a common misunderstanding is about changing the stiffness while no other change is applied on the model. Please check the following article and take it into consideration: https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/45962/reduction-of-stiffness-does-not-lead-to-a-change-in-displacements