Concept on positioning of Columns

Objective -

• To understand the impact of vertical and horizontal members in seismic behaviour of structure
• To understand different irregularities in a building

Ans 1

Symmetric

• If we split the plan vertically & Horizontally half, it will look mirrored. So we conclude the given plan is symmetric in both X & Y direction.

Redundancy

• Columns in X direction are comparatively more and evenly spread at middle except top and bottom in X direction, which conclude that redundancy of Top & bottom columns row is minimum as compared to middle portion of drawings.
• In Y direction the columns are comparatively lesser but evenly spaced, so the structure is redundant but lesser than that if in X direction.

Bi directional Stiffness

• The columns in horizontal direction are connected with straight to straight beams which results less probability of force diversion take place but same thing vertical direction the column are not connected so framing plan is weak with respect to bi directional Stiffness in Y direction

Ductility

• Ductility is inversely proportional to Stiffness
• X direction have more stiffness as compared to Y direction so the Ductility in X direction is less as compared to Y direction
• The X force will easily pass from one bay to its next due to beam alignment, where as Y force will struggle to pass through. The north- south beam are arranged in zigzag which leads to a discontinuous bracing.

Ans 2

Vertical Irregularity

The building plan area is larger in bottom Stories. The floor area are getting reduced with increase in height

Soft storey

The building has uncovered opening space in 6 th floor. As there is no occupancy or partition wall, this will lead to plastic hinge formations at the column.

Slopy Base-

The building is constructed on a slopping ground at one side. This will lead to significant varaition in the stiffness.

For reference of drawing/picture

• Vertical Irregularity - IS 1893 2016 Table-6 serial number (iii)
• Soft storey - IS 1893 2016 Fig. 4A
• Slopy bases - IS 1893 2016 Fig 5 E

Ans 3

1. Open Ground Floor - This denote soft storey mechanism acting in building
2. Rooms along 2 bays separated by an open corridor
3. Two short side covered with infill wallsstaircase portion at left top corner

The part of building retain from dismantel due to-

• There is no framing Y direction
• Beams connected along column minor axis.
• Variation in Column sizes