Hi
I'm trying to model a seismically strengthened building which is primarily a gravity shear wall structure, but has had some piles added to existing shear walls as part of the strengthening. I want to use compression only supports, ideally spring supports, to correctly reflect the stiffness of the shear walls.
The first issue I encountered was where a pile has only been added to one end of a shear wall (otherwise supported on spring line), when the gravity loads were applied in the model, the wall would rotate towards the unpiled end, resulting in diaphragm forces and shear in the wall (I need the gravity cases to maintain equilibrium due to the gravity shear walls so running seismic cases without gravity isn't an option). I got past this issue by staged construction - only building the piles after the main structure (incl shear walls) has been built and loaded with gravity.
There are however still issues with this - there is inconsistent 'settlement' from gravity at the spring supports resulting in demands in the structure (internal frames' moments/shears etc) in what should be a reasonably unstressed state, which leads to higher demands for seismic cases.
I think the closest approximation of the building's behavior would be for there to be zero spring support displacement in the loaded gravity condition. Can this be achieved with some type of staged construction ie build and load the structure on fixed supports and then delete the fixed supports / substitute to springs to run the seismic cases? (or any other means of achieving the same effect)
Many thanks
I'm trying to model a seismically strengthened building which is primarily a gravity shear wall structure, but has had some piles added to existing shear walls as part of the strengthening. I want to use compression only supports, ideally spring supports, to correctly reflect the stiffness of the shear walls.
The first issue I encountered was where a pile has only been added to one end of a shear wall (otherwise supported on spring line), when the gravity loads were applied in the model, the wall would rotate towards the unpiled end, resulting in diaphragm forces and shear in the wall (I need the gravity cases to maintain equilibrium due to the gravity shear walls so running seismic cases without gravity isn't an option). I got past this issue by staged construction - only building the piles after the main structure (incl shear walls) has been built and loaded with gravity.
There are however still issues with this - there is inconsistent 'settlement' from gravity at the spring supports resulting in demands in the structure (internal frames' moments/shears etc) in what should be a reasonably unstressed state, which leads to higher demands for seismic cases.
I think the closest approximation of the building's behavior would be for there to be zero spring support displacement in the loaded gravity condition. Can this be achieved with some type of staged construction ie build and load the structure on fixed supports and then delete the fixed supports / substitute to springs to run the seismic cases? (or any other means of achieving the same effect)
Many thanks
