Concept on positioning of Columns

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.

A.) - If we split the plan vertically half, it will look mirrorred. So it would concludes that the given plan is symmetric in x direction.

- If we split the plan horizontally half, it will look mirrorred. So it concludes that the given plan is symmetric in y direction.

- Symmetry:

It is regarded as one of the positive symmetrical features. As a result, both of the two horizontal displacements in each of the two orthogonal horizontal directions tend to be reduced.

- Redundancy:

Because there is relatively low energy dissipation throughout the structure, it is an unreliable construction.

- Ductility:

Inelastic Response may occur from the building's inability to withstand the elastic earthquake forces in shorter directions. Ductility is supposed to make up for the decreased Design force in the shorter direction.

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.

A.) Vertical irregularity:

The building plan area is large in bottom stories. So the foor plan area are getting reduced with the increase in height. Referenced to IS-1893-2016 Table 6 serial number (iii).

Soft storey:

The sixth level of the building features an uncovered opening. As there is no partition wall, it would lead to plastic hinge formation at the columns. With reference to IS-1893-2016 figure 4A.

Slopy base:

The building is constructed on a sloping ground at one side. This will lead to variations in stiffness. Reference to IS-1893-2016 Figure 5E.

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).

A.) The various responsible factors are:

- Open ground floor.

- Two short sides coverd with infill walls.

- Rooms along 2 bays seperated by an open corridor.

- Extreme left hand bay Staircase filled with the concrete.

- Staircase portion at the left top corner.

- No framing connection along Y direction.

- Columns not in the same line.

- Beams connected along column minor axis.