Concept on positioning of Columns

Answer 1)

Symmetry:- i) X-direction - Since, the given diagram is symmetry about X- axis b'coz if it is vertically half in x-direction then it's showing mirriored image.

ii) Y-direction - The given diagram is also symmetry about Y - axis.

Redundancy:- i) X-direction - The columns in x-direction are comparatively more & evenly spaced, so the structure is more redundant in x-direction except the top & bottom column rows are having quite longer span.

ii) Y-direction - The columns in Y-direction are comparatively less but evenly spaced, so the structure is redundant but less than that of X- axis.

Bi-directional Stiffness:- i) X-direction - In x-axis the columns are connected with straight to straight beams that means any lateral load(Seismic force in x-direction) passing from left end of thr building will have its path straight till it reaches right end of the building.

So, there is less possibilities for force diversion in x-axis.

ii) Y-direction - The columns are not connected with straight to straight beams, so a lateral load passing from south side of the building will get diverted to east & west direction to reach its next bay, hence there will be major force diversion take place with seismic force in y-direction.

Therefore, bi-directional stiffness in y-direction is weak.

Ductility:- As per given diagram the columns in x-direction is more as compare to y-direction so it will result in higher stiffness of the building in x-direction which would reduce the ductility in x-axis. The force will easily pass from one bay to its next due to beam alignment.

Therefore, the given framing plan is more ductile in y-direction that that of in x-direction.

Answer 2)

Vertical Irregularity:- The building plan area is large in bottom storey, the floor plan areas are getting reduced with increase in height.

Soft Storey:- Since, there is no any partition wall at 6th floor of the building which lead to Plastic Hinge formation at the columns.

Slopy Embankment:- The building is constructed on a sloping ground at one side these lead to significiant variation in stiffness.

Refer IS code:- 1893:2016

i) Table 6 for vertical irregularities

ii) Figure 4A for soft storey

iii) Figure 5E for slopy base

Answer 3)

i) Open Storey:- The ground floor is open which lead to soft storey mechanism acting in the building.

ii) The rooms along 2bays separated by an open corridor:- The bays filled with rooms will have higher mass compared to middle bay left open for corridor which induces mass irregularities along height uniformly.

iii) Staircase portion at left top corner:- Usually Staircase & lift portions are stiffer than other parts b'coz at concentrated concrete elements,

therefore the staircase portion contains more stiffness in provided building plan

iv) Beam Alignment:- By seeing in Structural plan we can easily conclude that the beams along Y-direction is not connected with the columns which induces Seismic force in South & North direction.

v) Variation in Columns Sizes:- The internal columns are having higher sizes compared to exterrior columns which lead to significiant difference in lateral drift of columns, so the concrete floor might have suffered heavy out of plane shear which would lead to collapse.