Concept on positioning of Columns

AIM -

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.

ANS - 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 vertically half it will look mirrored.

so we conclude the given plan is symmetric in -Y Direction.

Investigation of the framing Plan With Respect To Redundancy In x -Direction -

The column Are in X-Direction Camparitively more and evenly Spaced. So The Structure is More Redundant in X-Direction

EXCEPT The Top and bottom column rows are having quite longer span.

Investigation of the framing Plan With Respect To Redundancy In y-Direction -

The column Are in X-Direction Camparitively lessere but evenly spaced. so the structure is redundant but lesser than that of in x-direction.

Investigation with Respect to Bi-directional Stiffness -

. The column in horizontal direction is connected with straight to straight beams. this means any lateral load (seismic force in any x-direction ) passing from left end of the building will have its path straight till it reaches right end of the building. so no or less possibility of force diversion take place.

. the column in vertical direction are not connected straight to straight beams. so a lateral load passing from south side of building will get diverted to east and west direction to reach next bay. there will be major force diversion take place with seismic force in y-direction. the framing plan is weak with respect to bi-directional stiffness in y-direction.

Investing The Framing Plan With Respect To Ductility -

. prima facia, the aspect ratio of the plan clearly 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 easilly pass from one bay to its next due to beam alignment. whereas the y-force will strugle to pass through the north south beams are arrange in zig- zag which leads to a discontinuous bracing.

. we can concloud that the given framing plan is more ductile in y-direction than that of in x-direction.

AIM -

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.

ANS- THE FOllowing Irregularity Building Has.

1. Vertical Irregularity -

the building plan area is large in bottom stories. the floor plan area getting reduce with increase in height. these building offset has to be crosschecked with reffrence to 1893-2016 table (6) serial no. (3)

2. Soft Story -

the building has un-covered opening space in 6th floor as there is no occupancy or partition wall, this will lead to plastic hinge formation at the columns( with reffrence to 1893-2016 figure 4A)this has to checked and sufficiently designed.

3. Slopy Base -

the building is constructed on a slopy ground in one side. this will lead to significant variations in the stiffness.( with reffrence to 1893-2016 figure 5E) FEW LEVEL IS SUBJECTED TO SOFT STOREY Mechanism.

AIM -

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).

ANS -

1. Open Ground Floor -

this denotes soft storey mechanism acting in the building.

2. Rooms Along Two Bays Seperated by an open corridor -

the bays filled with rooms will have higher mass compared to the middle bay left open for corridor. this induce mass iregularities along height uniformely.

3.TWO Side Cover With Infilled Walls -

this means the building's lefts and right sides periphery is more stiffer during seismic forces (especially along north south )

4. Staircase portion at left top corner -

usually staircase and lift portions are stiffer than other parts because of concentrated concrete elements. so the staircase portion contains more stiffnes in the provided building plan.

5. No Framing Connection Along Y - Direction -

we could see no structural beam provided along the vertiocal direction between columns. this makes the building more vulnerable during the north south seismic force.

6. Beam Connected Along column Minor Axes -

the column are having longer dimension in y-direction. this means they are more stiffer along y-direction.but the beams are running only along x-direction which would attrack much lesser latteral forces and hardly transfers it.

7. Variation In Column Sizes -

the internal column having higher size compared to exterior column. but this will lead to significant diffrence in latteral drift of columns. so the concrete floor might have sufferewd heavy out of plane shear which would lead to collapse.