As I know, it is common to use a rigid body model for equivalent static analysis in masonry arch structure. So, all masses in the structure receive the same lateral acceleration.(According to this assumption, we can use the tilting ground model)

However, if the model acts as a deformable body, this assumption is not correct, e.g. in the first mode of oscillation of a masonry wall we can use triangular distribution of seismic load.

-How much is the rigid body model accurate and reliable?

-If we use a rigid body model we can claim that the filling above the arch can improve the arch-buttress structural stability against lateral acceleration (by keeping thrust line in the structure section) . However, if we use the deformable body model, we can claim that increasing the weight in the top of the structure affects the equivalent static distribution of force in a negative way. So, it must be avoided.

-which of these claim is reliable?

For example in my country Iran it is usual the lightening of the roof of arch structures, by removing some of the filling, to stabilize structure against earthquake, stressing on second claim. According to above claims is this method correct or not?

Best Regards,

Farzin Izadpanah