Concept on positioning of Columns

Q1)

Investigation of the framing plan with respect to symmetry in X-direction:

if we split the plan vertically in half, it will look mirrored. So we conclude the given plan is symmetric in the X-direction.

Investigation of the framing plan with respect to symmetry in Y-direction:

if we split the plan horizontally in half, it will look mirrored. So we conclude the given plan is symmetric in Y-direction.

Investigation of the framing plan with respect to redundancy in X-direction:

The columns in the X-direction are comparatively more and evenly spaced. So the structure is more redundant in X-direction. Except the top and bottom column rows have quite longer spans.

Investigation of the framing plan with respect to redundancy in Y-direction:

The columns in the Y-direction are comparatively lesser but evenly spaced. So the structure is redundant but lesser than that of in X-direction.

Investigation of the framing plan with respect to Bi-directional stifness:

• The columns in horizontal direction are connected with straight beams. This means, that any lateral load (Sismec force in X-direction) passing from the left end of the building will have its path straight till it reaches the right end of the building. So no or less possibility of force diversion takes palce.
• The columns in the vertical direction are not connected with straight-to-straight beams. So a lateral load passing from the south side of the building will get diverted to east & west direction to reach the next bay. The framing plan is weak with respect to bi-directional stiffness in the Y-direction.

Investigation of the framing plan with respect to Ductility:

· Prima facia, the aspect ratio of the plan clearly hints at more columns in the X-direction compared to the Y-direction. It will result in higher stiffness of the building in the X-direction, which would reduce ductility in the X-axis.

· Moreover, the X-force will easily pass from one pay to its next due to beam alignment. Whereas, the Y-force will struggle to pass through. The north-south beams are arranged in a zig-zag which leads to a discontinuous bracing.

· We can conclude that the given framing plan is more ductile in the Y-direction than that in X-direction

Q2)

• Vertical irregularity - The building plan area is large in the bottom stories. The floor plan areas are getting reduced with an increase in height. these building offsets have to be crosschecked with reference to IS-1893-2016 Table-6 serial number(iii)
• Soft storey - The building has over curved opening space in the 6th floor. As there is no occupancy or partition wall, this will lead to plastic hinge formation at the column (with reference to IS-1893-2016 Figure 4A). This has to be checked and sufficiently designed.
• Slopy base - The building is constructed on a sloping ground at one side. This will lead to significant variation in the stiffness (with reference to IS-1893-2016 Figure 5E). Few levels may be subjected to a soft storey mechanism.

Q3)

• Open ground floor - This denotes soft storey mechanism acting in the building
• Rooms along 2 bays separated by an open corridor - The bays filled with rooms will have higher mass compared to the middle bay left open for corridor. This induces mass irregularity along height uniformly.
• Two short sides covered with infill walls - This means the building's left and right sides periphery is more stiffer during seismic forces (especially along North-south)

• Staircase portion at Left top corner - Usually staircase and lift portions are stiffer than other parts because of concentrated concrete elements. So the staircase portion contains more stiffness in the provided building plan.
• No framing connection along the Y-direction - We could see no structural beams provided along the vertical direction between columns. This makes the building more vulnerable during the North South seismic force.

• Beams connected along column minor axes - The columns are having longer dimension in Y-direction. This means they are more stiffer along y-direction. But the beams are running only along x-direction which would attract much lesser lateral forces and hardly transfers it.

• Variation in column sizes - The internal columns are having higher sizes compared to exterior columns (This is common because of higher load demands). But this will lead to significant difference in lateral drift of columns. So the concrete floor might have suffered heavy out-of-plane shear which would led to collapse.