Concept on positioning of Columns

Answer to The Question No. 1

Question:1

Comment on the layout of the framing plan concerning earthquake resistance in the two horizontal directions X or Y (dots are columns, lines depict beams). Look into aspects of symmetry, redundancy and bi-directional stiffness and ductility.

Answer:

Aim: Aim to the question id to Comment on the layout of the framing plan concerning earthquake resistance in the two horizontal directions X or Y (dots are columns, lines depict beams). Look into aspects of symmetry, redundancy and bi-directional stiffness and ductility.

Objective:

• Ovjective to te question is to understand the impact of vertical & horizontal members in seismic behavious of a structure
• To understand different irregularities in a building.

Theory:

Investigation of the framing plan with respect to Symmetry in X- Direction:

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

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

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

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

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

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

• The Column in the y-direction are comparatively lesser but evenly spaced So the structure is redundant but lesser than that of in the x-direction.

Investigation with respect to bi-direction stiffness:

The column in horizontal direction are connected with straight to straight beams. This means, any lateral load (Seismic force in X-direction) passing from left end of the building will have its path straight till it reaches right and of the building. So no or less possibility of Force diversion takes place.

THe Column in vertical direction are not connected with straight to straight beams. So a lateral load passing from sought side of building will get diverted to east& west direction to rech net bay . There will be major force diversion take place with Sesmic force y-direction . The framing plan is weak with respect to bi-directional stiffness in Y-direction.

Invstigation of the framing plan with respect to ductility:

• Prima facing, the aspect ratio of the plan cleary hints more column in x-direction compared to y-direction. it will result in higher stiffness of the building in x- direction, which would reduce ductility in x- axis.
• Moreover, the x -force will easily pass from one bay one to its next due to beam alignment. whereas the y- force will strucgle to pass throght the north south beams are arranged in zigzag leads toa discontinuous bracing.
• We can conclude that the given framing plan is more ductile in y-direction than that of in x-direction.

Result:

Answer to The Question No. 2

Question:2

What are the possible sources of irregularity in the building shown here? Explain how, as an engineer, each of these irregularities should be dealt with.

Answer:

Aim: To understand the possible sources of irregularity in the building shown and to explain how, as an engineer, each of these irregularities should be dealt with.

Objective:

• This building's structure may be affected by seismic forces in the categories of soft storey, vertical geometry irregularities, floating columns, mass irregularities, and inconsistent seismic forces.

Theory:

Vertical irregularity: The building plan area is large in bottom stories. The floor plan areas are getting reduced with increases in height. These building offsets has to be crosschecked with refrences to IS- 1893-2016 table- 6 serial number(3)

Soft Storey : THe building has uncovered opening space in 6th floor. As there is no occupancy or a partition wall, tis will lead to plastic to plastic hinge foramation at the column (with reference to Is-1893-2016 figure 4A). Ths 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 variations in the stiffness (with refrence to IS- 1893-2016 figure 5e ). Few levels may be subjected to soft storey mechanism.

Answer to The Question No. 3

Question:3

A 4-storey hotel building has an open ground floor for the restaurant. Story 2 to 4 have one row of rooms along each long side in plan, separated by a corridor. The two short sides of the perimeter are fully in-filled in all storeys, except for certain openings at the ends of the corridor at storeys 2 to 4 and along the right-hand side of the ground floor. There is a staircase near the upper left-hand corner, with straight flights between landings at floor levels and in-between floors. Cross-section dimensions are written next to the member no. in meters.

Comment on the features of the structural design and of the layout of infills which are important for earthquake resistance and seismic performance. How do they relate to the almost full collapse of this building (the extreme left-hand bay with the staircase survived, as well as one long-side façade in the rear end, and the frame along the right-hand side in plan).

Answer:

Aim: To comment on the features of the structural design and of the layout of infills which are important for earthquake resistance and seismic performance. How do they relate to the almost full collapse of this building (the extreme left-hand bay with the staircase survived, as well as one long-side façade in the rear end, and the frame along the right-hand side in plan).

Theory:

Structure failure reasons for the given figure are:

• Improper arrangement and placement of structural elements
• Structure is not symmetric Which must required for standard structure
• Larger strength is provided hence low ductility.
• No proper placement of masonry infill walls.
• Redundancy in the vertical direction of this building is not provided properly.

1. Open Ground Floor:-

• The ground floor of the building is open,which may be a softstorey (having long columns) due to this the Ground floor excitation the columns could have been unable to resist the Earthquake and form collapse. This is called as soft storey mechanism.This can be avoided by having Strong column-weak beam mechanism.

2. Rooms along two bay separated by an open space:-

• The bay that are filled with the rooms will have higher mass than the middle bay whic is opened for the corridor.So this will cause mass mass irregularity along the height uniformity

• As we can see at the above image that the upper portion and the bottom portion is for the rooms and because of that rooms these portions have higher mass because of the various furniture load,live loads etc. And the middle portion they left for the corridor as we can see in the above given image.

3. Two short sides coveres with the infill walls:

• As we can see that the two shorter sides of the perimeter are not in filled in all the storeys,except for the certain openings at the ends of the corridor at the 2nd and the 4th floor and along the right-hand side of the ground floor. This means that the building at the left and the right of the given building is more stiffer during the earthquake. And they have built non structural wall.

4. Staircase portion at the left top corner:

• As we can see that the staircase and the lift portion of the building is not affected with the seismic force. These are the only elements that are not affected during the earthquake force. This is because the usually the staircase and the lift portion are more stiff than the other members of the building. It m eans it does not bend easily with the external forces and that is the reason that the staircase and the lift is intact in the polsition with much harm.

5. Columns not in the same line

• It is observed that the columns in the Extreme left hand middle line columns has the deviation in the line of the Construction at the staircase which again a reason for the Irregularity in plan having the Torsional flexibilty. To avoid this the Eccentricity should be maintained for the deviation to be with in the limits of Beam size and the Columns sizes. Also the sizes of the Beams and Columns in the Plan should be redesigned in such a way that the line of the columns doesn't deviate even in the staircase area.

6. Variation in column sizes:

• As we can see in the above given image that the sizes of the columns are different. We can say that the size of the interior column is big in size and the size of the exterior column is smaller as wecan see in the above image.And because of the difference in the size of the columns the structure collapse because it may suffered heavy out of plan shear.

7. Beams connected along column minor axis:-

• As we can see in the above image that the columns have the longer direction in the Y-direction.But there is no direct connection or frame in the Y-direction which may connects the beam in the Y-direction.There are columns that are connected in the X-direction but the large side of the column is in the Y-direction which means that they are more stiffer in that direction whic can attract more lesser lateral force and this is one of the reason for the collpase of this building.

Result: we to understood the column of column and beams.