Concept on positioning of Columns

AIM:

• Concept on positioning of Columns.

PROCEDURES AND DETAIL:

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.

Symmetry of Structure in X axis

• structure is partialized in X direction it is found that the structure is symmetrical. Hence the structure is symmetrical about X axis.

Symmetry of Structure in Y axis

• structure is partialized in Y direction it is seen that the structure is symmetrical. Hence the structure is Symmetrical in Y axis.

Redundancy in X direction

• The columns in X direction are more when comparitively to Y direction and also the columns are placed evenly.
• structure is more Redundancy in X direction.
• Top and bottom of the columns are placed with more spacing.

Redundancy in Y direction.

• The columns in Y direction are less but splitted evenly spaced.
• The structure is redundant but lesser than X axis.

Bi-directional Stiffness of the Structure in X axis

• The columns in direction of X axis are connected with straight line to straight line beams.
• The seismic forces occur it will travel in the straight Path from one end to other.
• So no force diversion takes place in X axis.

Bi-directional Stiffness of the Structure in Y axis

• The columns in vertical direction are not connected in a straight path.
• Lateral force passing Via the one end will get diverted due to non-availability of straight line path for transfer of loads in Y direction.
• So the structure is weak with respect to Bi-directional stiffness along Y axis.

Ductility of structure in X axis

• Since there are more number of columns in the x direction. It will result in high stiffness of building in X direction. Because of that ductility in X axis is deducted.
• The force in x direction will be transferred easily due to straight beam connection.

Ductility of structure in Y axis

• The force in y axis will struggle to transfer from one end to other due to discontinuity in beam connection.
• It leads to conclude that frame is more ductile in Y axis than in X axis.

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.

Vertical irregularity

• The area of building is high but the provided floor height is less due to that this is happened. It needs to be verified with the IS 1893 2016 Table 6.

Soft Storey

• The building has uncovered space in 6^thas there is no partition walls provided it will lead to the formation of soft storey mechanism in the columns in that storey. As per IS 1893 2016 Figure 4A it has to be checked and well designed.

Slopy base

• The building is constructed on slopy ground in one side. It leads to difference in stiffness. With reference to IS 1893 2016 Fig 5E few levels may be subjected to soft storey mechanism.

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.

Open Ground floor.

• Since there is a open ground floor as mention in the question. This will lead to soft storey mechanism in the columns in Ground floor due to no shear walls in it.

Rooms are separated by a Corridor.

• The Rooms are separated by a corridor. There is higher mass at rooms when compared to middle. This include mass irregularity along the height of building.

Two short sides covered with infill walls

• This means the outer left and right side is more stiff during seismic force.

Staircase portion at left top corner

• Usually staircase and elevators are stiffer than other elements because of concentrated concrete elements.
• So the staircase portion is more stiff.

No beam connections in Y direction.

• In this beams are only connected in X direct. No beams are connected in the Y direction.
• This leads to weak connection in Y direction during earthquake.

Beams Connected along Column minor axis

• The columns are having longer dimension in Y direction. This means they are more stiff in Y direction. But beams are running only in x direction which would attract lesser lateral force and hardly transfer.

Variation in column size.

• The internal columns are having higher size when compared to exterior columns. But this will lead to significant difference in lateral drift of column.
• So the concrete floor might have suffered heavy out of plan shear which would led to collapse.

RESULT:

• Concept on positioning the column challenge is completed.