As shown in the Figure below, a square block damper was placed above the building structure as a counterweight during seismic events. The building structure has a square floor area of 400 m2. On the other hand, a damper weighed 10,340 kgs and was placed on the concrete roof deck slab.

Situation 1:

The concrete slab had a coefficient of static friction of 0.95 when no seismic force hit the building structure.

Situation 2:

When the latter event happened, the static seismic force hit the building structure at a uniformly increasing load of 20 kN/m from ground floor to roof deck level (west to east direction).

Determine the following:

a.       Force P (kN) applied at the neural axis without considering seismic force, only consider damper block at concrete roof deck slab surface as referred to Situation 1. 15 points

b.       Force P (kN) applied at the neural axis considering summing up at the critical shear point as referred to Situation 2 (neglect effect of forces at concrete roof deck slab surface). 15 points

c.        Base share at ground floor (kN) considering the ground coefficient of static friction of 0.85, also referred to as Situation 2. 20 points

Note: The neural axis from the base of block damper before and during seismic event is 2 m and the height per floor is 3m. Consider only base share as the horizontal force acting at the ground surface of the entire building structure and neglect its weight for situation 1 and situation 2, respectively. Also, neglect other internal or external forces below earth.