; fname: Footing.dat (2D)
;
;  I Have mocked up the footing example to show a similar behaviour as Nicks has shown within his figure 
;  Create an assembly and install two shallow foundations next to each other
;=========================================================================

model new
model large-strain on

;Set the domain extent and condition
model domain extent (-1,25) (-6,20)
model domain condition destroy

;generate a box and a cloud of 2000 equally sized balls
wall generate name 'box' box (0,24) (0,17) one-wall
model random 10001
ball generate box (0,24) (0,10) number 3500 radius 0.1

; Modify the default slots of the Contact Model Assignement Table
; Here we choose the linear contact model (with kn=1e6) for all contact 
; types but ball-ball contacts, to which we assign the linearpbond model.
; Note that only the linear part of the linearpbond model is activated as 
; long as the contact method bond is not called, which is done later
contact cmat default type ball-ball model linearpbond   ...
                          property fric 0.577 kn 1e8 ks 1e8       ...
                          pb_kn 1e8 pb_ks 1e8 pb_ten 1e6          ...
                          pb_coh 1e6 pb_rmul 0.8 dp_nratio 0.2

contact cmat default type ball-facet model linear       ...
                          property kn 1e8 ks 1e8 fric 0.09  ...
                          dp_nratio 0.2

;define the density of the balls and increase their radius
ball attribute density 2000 radius multiply 1.4

;define some history to plot the velocity of a ball of the assembly and 
;of the unbalanced force. Histories are stored each 5 cycles.
history interval 5
ball history velocity-y position (12,5)
model history mechanical unbalanced-maximum

; To reach a stable configuration faster, density scaling is activated.
; Gravity is introduced
model mechanical timestep scale
model gravity 0 -9.81
model cycle 1000 calm 50
model solve ratio-average 1e-5

; creation of a box-shaped foundation
; the name 'footing' is associated to the respective group of walls
wall delete range set id 3
wall generate name 'footing_left' group 'footing' box (0,5) (11,20) ;box (19,24) (11,20)
wall generate name 'footing_right' group 'footing' box (19,24) (11,20)


; parallel bonds are finally installed. LinearPBond model is active
; for ball-ball contacts. The simulation is saved at this stage
; so that further restoring is possible
contact method bond gap 0.0

model save 'Assembly'

;;; Here I have added some histories to plot the descrepancies in wall movement
;

; The foundations are supposed to settle with a constant velocity
; The contact force at the base of the foundations is stored during 
; the simulation.
wall attribute velocity-y -0.25 range group 'footing'
wall history name 'reaction force left' force-contact-y name 'footing_leftBottom'
wall history name 'reaction force right' force-contact-y name 'footing_rightBottom'

wall history name 'footing settlement base left' displacement-y name 'footing_leftBottom'
wall history name 'footing settlement base right' displacement-y name 'footing_rightBottom'

wall history name 'footing settlement sides right' displacement-y name 'footing_rightLeft'
wall history name 'footing settlement sides left' displacement-y name 'footing_leftRight'

program call 'Wall_Displacement.dat'

program call 'Bottom_Wall_Stress.dat'

; The timestep is set to its automatic value for dynamic simulations and
; an additional 5 seconds are simulated. The model is saved at the end of 
; the simulation.
model mechanical timestep auto
model solve time 7.0

; Solve to an equilibrium state again
wall attribute velocity-y 0.0
model solve ratio-average 1e-4

model save 'Footing_touch-down'

;;; So far no relative movement of each parts of the footing walls is notceable

model restore 'Footing_touch-down'


;;; From Here on I introduce the servo mechanism for the wall forces in 2 load increments

wall servo activate on gain-factor 0.6 force-y -4e6 velocity-max 0.1 range group 'footing'

model mechanical timestep auto
model solve time 10.0

wall servo activate off range group 'footing'

model save 'Footing_first-load'

model restore 'Footing_first-load'

; Solve to an equilibrium state again
wall attribute velocity-y 0.0
model solve ratio-average 1e-4


wall servo activate on gain-factor 0.6 force-y -4.5e6 velocity-max 0.1 range group 'footing'


model mechanical timestep auto
model solve time 10.0

wall servo activate off range group 'footing'

; Solve to an equilibrium state again
wall attribute velocity-y 0.0
model solve ratio-average 1e-4

model save 'Footing_final-load'

;;; Here a relative movement of the bottom wall segments as opposed to the other wall segments - see inner sides of the footings in the plots for comparison 

;=========================================================================
; eof: Footing.dat (2D)