Concept on positioning of Columns

ans. (1)

symmertry:

• it is observed that the distribution of mass, stiffness is across the plan has good symmetrical aspects.
• this tends to reduce the horizontal displacement in both of the two horizontal displacements in both of the two orthogonal horizontal directions. it also has a very good uniformity also.

Redundancy:

• There are missing structural elements in the periphery of the plan. this cuases the uneven distribution of the earthquake action effects in non linear range across the plan .
• The energy dissipation across the structure is very low which results in non reliablr structure.

Bi-directional stiffness :

• The building plan may not be able to resist the horizontal seismic action in the shorter direction (Y-axis) and also the resistance and stiffness in the shorter direction (Y-axis) is less when compared to longer direction (X-axis).

ductility:

• The building may not be able resist the elastic earthquake forces in shorter direction (y-axis) . so it may result in inelastic response.
• The reduction in design force in the shorter direction (Y-axis) is to be compensated by ductility.

ans.(2)

The possible type of irregularities for the given structure are:

Soft storey iirregularity:

1. stiff and strong upper floor due to masonary fill

2. The column in one storey is longer than the above.

Some provisions to avoid the irregularities:

• The building is torsionally irregular. so the building framing must be revised.
• the mass irregularity is avoided by providing light weight concrete / low weight masonry or by providing structure with more wood material.
• The structure should be built in a well symmetric manner.
• The columns which are provided on the structure should be of same size and height through out the building.
• The weight of the building from ground floor should decrease towards top.

ans.(3)

The building collapse occured due to the ground excitation in both orthogonal horizontal direction and also due to the torsional effects.

The following are the responsible factors:

• Structure is not symmetric .
• larger strength is provided hence low ductility.
• in this building , there is no proper placement of masonry infill walls.
• in this building, redundency in the vertical direction is not provided properly.