Concept on positioning of Columns

1a. Aim : To identify the symmetry of the lay out,redundancy and given and bi-directional stiffness, ductility of the gien building structural lay out.

• Symmetry:

For the given lay out if plot or cut the lay out in the centre of the building along the x-axis then the lay out is dived in to equal halfs, that means one side of the building is just like the mirror image of the other side of the building that resembles that the building symmetrical along the X-axis.

For the given lay out if plot or cut the lay out in the centre of the building along the Y-axis then the lay out is dived in to equal halfs, that means one side of the building is just like the mirror image of the other side of the building that resembles that the building symmetrical along the Y-axis.

• Redundancy:

Redundancy is nothing but the arrangement of the structural units of the building with equal space and size for the load distribution in an equal manner.

For the given building the columns in the X axis are more in number and they are arranged with an equal space between them and the space between the columns in the top and bottom slightly more but connected with beams and every column is connected with an beam and with an equal space between them.So the building is more redundant in the x-direction.

For the given building the columns in the y axis are less in number when compared to the columns in the X-axis but the spacing between the columns is equal and some of the columns are free from the connection with the beams, so te building lay out is less redundant in the y-direction when compared with the X-direction.

• Bi-directional stiffness:

The columns in the x-direction is more in number and equally spaced and the lateral force or any other load which is applied to the building from the left will transferred in a straight line with out any divergence of the force.So the building is more stiffness in the X-direction.

The columns in the y-direction are less in number and they are equally spaced with more space compared to the Xdirection, the columns are also not connected with the beams and the lateral force or any other load which is applied to the building from the one direction in the y-axis will not be transferred in a straight line ad they are diverted to X-axis and there will be the divergence of the force.So the building is less stiffness in the Y-direction when compared to the X-direction.

• Ductility:

Generally the ductility is inversely proportional to the stiffness, for the building with the more stiffness the building is prevented from the ductility.For the given building the columns in the X-axis are closely spaced and they obtain more stiffness, so the building possess low ductility in the X-axis direction.

In the given building lay out the columns in the Y-axis are less in number and the spacing is more and some of the columns are free from the connection with the beams so the stiffness is low and so the ductility nature of the building is more Y-axis. For the given building the ductility nature is more in Y-axis when compared to the X-axis.

2a. There are many irregularities based on the building and the site condition.

• Vertical irregularity:For a building if there is a change in the area between the floors then it is subjected to the vertical irregularity.In the given building the floor area of the top floors is less when compared to the bottom area then the bilding is subjected to the vertical irregularity.In the vertical irregularity there is subsequent change in the floor areas with increase in height of the building.The building offsets has to be crosschecked with reference to IS -1893-2016 table-6.
• Soft storey:For a building if there is any uncovered opening space then it falls under the irregularity soft storey and in the given building the sixth floor is uncovered with any partiotion walls and it leads to the formation of the plastic hinge at the columns. So to avoid the formation of the plastic hinge formation the building is to be designed with reference to the IS -1893-2016 figure 4A.
• Slopy base:The building constructed in an uneven ground then it falls under the slopy base irregularity.In general the ground is not uniform in the mountain areas, In such areas the building is constructed in the slopy base with various levels of the footings. For that buildings the stiffness is different for the columns and the columns are designed with the reference of IS-1893-2016 Fig 5E.

3a. In the above a four storey building is subjected to earth quake force and now the structural features of the building are studied for the seismic response of the building.The building is structural failure.

• Open ground floor:For the given building it is said that the ground floor is opened for the restaurent with out any in fill walls. so it leads to the formation of the plastic hinge and falls under the soft storey irregularity.
• Rooms along 2 bays separated by an corridor:The bays filled with the rooms will have higher mass than the corridor in the middle in between the rooms.This induces the mass irregularity along the height uniformly.
• Too short sides covered with infill walls:The short sides of the building on the two sides is covered with infilled except the corridor opening so the building is more stiff in that direction.
• Stair case portion at left top corner:Generally the stair case and the lift case are made with the strong concrete elements so they are more stiff than the other parts of the building and they will not collapse on the action of seismic force.
• No framing connection along Y axes:The beams are provided only in the x direction, there is no connection of the columns in the y direction this makes the buildng more vulnerable due to the seismic forces.
• Beams connected along column minor axes:The dimensions of the column cross section is different and the larger dimension is in the direction of the y axis that means the columns are more stiffer in the Y axes direction but the beams are connected in the direction of x axes which would attract or transfer the less lateral force or seismic force applied on the building in the X direction.
• Variation in column sizes:In the given building the sizes of the columns are different the internal column is of more size than the external column due to the demand of the high loading. But this will lead to the lateral drift of the column and the concrete floor or wall might suffered with out of plane shear which would lead to collapse of the building.