Concept on positioning of Columns

Aim

Understanding the concept of placement of the structural members as per the seismic design criteria by aspects of symmetry, redundancy and bi-directional stiffness and ductility.

Ans 1

Symmetry

By observing the layout of the given attachment it's showing that it has good Stiffness and mass distribution because the columns and beams are placed symmetrically in both the X and Y direction.

The mass is distributed in all the way to parts of the building so the it sufficient to resist the horizontal forces of earthquake.

Redundancy

As its seem from the layout that the placement of the structural members are at the equal distance in the specific directions so it helps the structural members to resist the sufficient seismic forces. Such redadancy in the structure seems to be good to resist the seismic forces.

Bi-directional stiffness

The placement of the structural members are to in the right angle or perpendicular to the grid direction so it resist the seismic forces in the more better way in this plan it in the orthogonal direction to each other.

Ductility

This can be checked by the material used and the placement of the structural members this is simply implies to the chain theory. If the ductility is good the structure resist the imposed loading conditions very sufficient but with ductility the stiffness should also be sustained.

Ans 2

By seeing this image it's seems that it has the irregularitie of the mass, flooting column and the failure from soft storey.

Soft storey

Buildings having a soft story if that level is less than 70% as stiff as the floor immediately above it, or less than 80% as stiff as the average stiffness of the three floors above it.

Buckling of the columns occur because of the increase in the mass of the floor.

Floating column

Floating column is a type of column which is is constructed over beams or slabs of any intermediate floors of a structure. These columns are not attached to any footings or pedestal.

Mass irregularity

Mass irregularity is considered to exist where the seismic weight of any storey is more than 200 percent of that of its adjacent storey. One regular building with uniform mass is studied with 4 irregular buildings with varying masses for Base shear, Mode shapes, storey drift, story shear, Torsion moment.

Remedies that can be taken for this;

A soft story retrofit involves strengthening and stiffening the first story, might involve the addition of steel moment frames, shear walls, diagonal bracing, or fusing systems.

Additional column are to be placed for safer structure and the flooting column effect.

Ans 3

Reasons for the collapse

• The structural is some what of symmetry but stairs is in the left side which makes the structure more stiffen at that side.
• The placement of the structural column are not in proper orientation with each other.
• As the columns larger face should be faces to the longer span direction whichis not shown here.
• The size of the columns which are placed in the periphery of the layout is of smaller than that of inside.
• The infill walls are not properly palced in some of the places and some are missing.
• The redadancy of the structural members in not properly.

Result

In this we have seem some of the basis rules that should be followed during designing the building layout or placement of the structural members.

And important factors that should be considered while taking further steps for seismic design.