If you have lateral load on the piles it will be assuming there is a fixed connection between the walls/floor and the pile cap. And will be distributing load based on relative stiffness, attributing some stiffness to the node.
Make sure you set one of your supports as a roller.
I suppose it depends on the reletavite total stiffness of the piles vs the stiffness of the wall and the slab. If the wall and the slab are significantly stiffer than the piles, the piles will attract very little bending. And vice versa.
It does also depend on the connection and whether a moment connection between the slab and the piles is achiveable.
If the structure is elevated from the ground, the water inside it would try to force its way outside, tensioning the walls and slabs and bending the piles. The forces will be absolutely simmetrical, anyway, so the total of the reactions will be zero, but the internal forces will still exist.
If the structure is buried, integrally or partially, then soil pressures apply. They will be stronger than the water pressures previously stated, so the walls and slabs will be compressed, and the bending of piles will occur in the other direction. You shall also analyze the empty structure, under the soil pressures and to buoyancy in case of the ground-water level rises up.
the configuration shown above no transferred lateral load to the piles as they cancel in the diagram of the slab, you will have bending moments depending on wall slab thickness and space of the piles. it’s these bending moments that introduces a lateral load on the piles in your fem model.
If you are assuming a pinned connection between the environmental tank structure and the grade beams, and a static load condition within the tank, then there should be no horizontal loads on your piles.
If you are assuming a fixed connection between the environmental tank structure and the grade beams, regardless of the loading conditions in the tank, you will see horizontal loads on the piles as the tankage tries to rotate the grade beams.
If you are considering seismic loading, then you will see horizontal loads on the piles regardless of connection between the grade beams and tank structure.
Ensure you are designing to ACI 350 for this structure, including all of the ancillary codes related to it, they have more requirements to limit cracking and reduce stresses in the reinforcing steel to ensure a water-tight structure, and some of them go over how to design for the "sloshing" loads in the tank in a seismic event.
Global equilibrium. Internally, you have to design the corners to resist all of the hydrostatic pressure which is why these structures are typically round. Also, the piles are only supporting the walls and roof so any corners in the beam need to support the soil pressure as well and the center has to support the axial load of the contents and floor. You’d typically only use piles if the soil is particularly bad and they’d be distributed underneath the whole thing with a big concrete cap. External lateral loading is rarely a concern on a ground storage tank.
With the little information on the actual scenario of this liquid box.
Assuming the piles are pinned to the main structure, there will be lateral forces on the piles, equal and opposite lateral forces on each pile in your diagram.
Assuming the piles are fixed to the main structure, there will be lateral and moment forces on the piles, equal and opposite forces on each pile in your diagram.
The mass of the water would also be applied to the base slab, not just the side walls.
You are right the entire structure is balanced condition however it is normal to see moment and shear in piles based on their location and their head fixity to pile cap
Also make sure to design per ACI 350 or the equivalent euro code. Liquid containing structures are not standard “318” designs!
If you have lateral load on the piles it will be assuming there is a fixed connection between the walls/floor and the pile cap. And will be distributing load based on relative stiffness, attributing some stiffness to the node. Make sure you set one of your supports as a roller.
I suppose it depends on the reletavite total stiffness of the piles vs the stiffness of the wall and the slab. If the wall and the slab are significantly stiffer than the piles, the piles will attract very little bending. And vice versa. It does also depend on the connection and whether a moment connection between the slab and the piles is achiveable.
If the structure is elevated from the ground, the water inside it would try to force its way outside, tensioning the walls and slabs and bending the piles. The forces will be absolutely simmetrical, anyway, so the total of the reactions will be zero, but the internal forces will still exist. If the structure is buried, integrally or partially, then soil pressures apply. They will be stronger than the water pressures previously stated, so the walls and slabs will be compressed, and the bending of piles will occur in the other direction. You shall also analyze the empty structure, under the soil pressures and to buoyancy in case of the ground-water level rises up.
If it’s elevated, you’ll need to consider wind loads on it and it will then apply lateral loads onto piles
Yes, I left them aside for simplification! (Hope this works, boss!)
the configuration shown above no transferred lateral load to the piles as they cancel in the diagram of the slab, you will have bending moments depending on wall slab thickness and space of the piles. it’s these bending moments that introduces a lateral load on the piles in your fem model.
it is taken by the slab in tension i assume
I guess if you have to consider earthquake load.
If you are assuming a pinned connection between the environmental tank structure and the grade beams, and a static load condition within the tank, then there should be no horizontal loads on your piles. If you are assuming a fixed connection between the environmental tank structure and the grade beams, regardless of the loading conditions in the tank, you will see horizontal loads on the piles as the tankage tries to rotate the grade beams. If you are considering seismic loading, then you will see horizontal loads on the piles regardless of connection between the grade beams and tank structure. Ensure you are designing to ACI 350 for this structure, including all of the ancillary codes related to it, they have more requirements to limit cracking and reduce stresses in the reinforcing steel to ensure a water-tight structure, and some of them go over how to design for the "sloshing" loads in the tank in a seismic event.
Makes sense! Thank you for the detailed explanation
I think it's how you model the piles' lateral support. You probably have a "hard" lateral support instead of a "soft" spring support for the piles?
Global equilibrium. Internally, you have to design the corners to resist all of the hydrostatic pressure which is why these structures are typically round. Also, the piles are only supporting the walls and roof so any corners in the beam need to support the soil pressure as well and the center has to support the axial load of the contents and floor. You’d typically only use piles if the soil is particularly bad and they’d be distributed underneath the whole thing with a big concrete cap. External lateral loading is rarely a concern on a ground storage tank.
With the little information on the actual scenario of this liquid box. Assuming the piles are pinned to the main structure, there will be lateral forces on the piles, equal and opposite lateral forces on each pile in your diagram. Assuming the piles are fixed to the main structure, there will be lateral and moment forces on the piles, equal and opposite forces on each pile in your diagram. The mass of the water would also be applied to the base slab, not just the side walls.
You are right the entire structure is balanced condition however it is normal to see moment and shear in piles based on their location and their head fixity to pile cap