Concept on positioning of Columns
Ans.1.
Looking from the aspect of symmetry of framing plan in x direction :-
As we can clearly see that the plan has been mirrored if we split it in the half in vertical direction, so the given plan is symmetric in X direction.
Looking from the aspect of symmetry of framing plan in Y direction :-
If the plan is split horizontally into half then it will look like mirrored and hence the plan is symmetric in Y direction also
Looking from the aspect of redundancy of framing plan in X direction
From the figure we can clearly see that the number of columns in the X direction are comparatively more and evenly spaced then in the Y direction. So the structure is more redundant in X direction.Here excepting the top and bottom column rows which are having longer spans.
Looking from the aspect of redundancy of framing plan in Y direction :-
We can see that the columns in direction Y are lesser than the columns in X direction but they are evenly spaced so here the structure is redundant but it is lesser than the X direction.
Looking from the aspect of Bi-directional stiffness :-
From the figure the columns are seen to be in a horizontal direction and also connected with straight to straight beams. So any seismic force or any lateral load passing from one end to the other end of the building will be in a straight path until it reaches the other end so therefore there will be no or less possibility of force diversions.
For the columns in vertical direction we can see that they are not connected with straight to straight beams that if the load passing from one side to other side of the building is getting diverted until it reach next Bay. Due to the section there will be a major force diversion with force in Y direction and also the framing plan is weak with respect to bi directional stiffness in Y direction.
Looking from the aspect of ductility :-
Due to the presence of more columns in X direction compared to Y direction it will result in higher stiffness of the building in X direction therefore due to high stiffness the ductility will be reduced in X direction.
Also the forces in X direction will reach out to the next Bay more easily than compared to the Y direction force because of the beam alignment
Hence we can say in conclusion that the framing plan will be more ductile in Y direction as compared to the X direction.
Ans.2.
Possible sources of irregularity for the given building are as follows :-
1. Vertical irregularity
From the given figure it is clearly shown that the building plan area is large in bottom stories. And also the floor plan areas are getting reduced with the increasing height. It must be cross checked with the reference to IS CODE 1893-2016 Table 6 serial 3
2. Soft storey complication
In the 6th floor of the building we can clearly see that there is an uncovered opening space and that will lead to the soft storey complications. As there are no Occupancy or a partition wall, there will be the formation of plastic Hinge at the columns of the building. To check the efficiently designed building we have to take the reference of IS 1893 2016 figure 4A
3.Base angle is more slopy
The building is constructed on a sloping ground at one side and due to this the variations in stiffness will occur and it can be cross checked with the reference to is 1893 2016 figure 5E
Ans.3.
Comments on Features of structual design and layout of infills are as follows :-
1.Open groud floor :-
As the figure clearly says that it has an open ground floor so due to that soft storey mechanism will be there in the building due to the open ground floor.
2. Separation of rooms along twobays by an open corridor :-
As given in the figure that the bays are filled with rooms in the left and right but the middle Bay will left open for corridor. And hence in the bays filled with rooms will be having a higher mass compared to the open corridor Bay. So there will be mass irregularity along height uniformly.
3. Staircase at left top corner :-
As we have studied that the staircase and lift portions are more steffer then the other parts because of the concrete elements are placed in concentrated manner their and hence the staircase portion will be more stiff during the earthquake or seismic force
4. Two short sides are covered with infill walls :-
As given, from the figure , that the left and right sides of the building Periphery will be more stiffer during the seismic forces.
5. Different size of columns :-
There is a difference in the sizes of columns as compared to the internal and external columns of the building. This is a very common process but it can also laided to significant difference in lateral load bearing capacity of columns due to which the concrete floor might have suffered heavy shear force which led to collapse.
6. No framing connection along Y direction
As it is clearly visible in the structural diagram that there are no structural beam setter provided in the vertical direction between the columns to make the column and beam connection stable and hence this will be making the building more reactive during the north south seismic forces.
7.Beams are connected along column's minor axes :-
We can see that the columns are having longer dimensions in Y direction from the figure that means columns would be more stiffer along Y direction when any seismic load occurs and they also bear much lateral load but the beams are running only along X direction which would attract less lateral force and there is no or less chance of transferring them to the columns.