Concept on positioning of Columns

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.

SYMMENTRY:

It is observed that the distribution of mass, stiffness is across the plan has good symmetrical aspects

This tends to reduce the horizontal displacements inn both of the two horizontal displacements in both of the two orthogonal horizontal directions.

It also has very good uniformity also.

REDUNDANCY:

There are missing structural elements in the periphery of the plan. This causes the uneven distribution of earthquake action effects in non linear range across the plan.

The energy dissipation across the structure is very low which results in non reliable structure.

DUCTILITY:

The building may not be able to resist the elastic earthquake forces in shorter direction (y axis). So it mat result inelastic response.

The reduction may not in design force in the shorter direction y axis is to be compensated bh ductility.

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.

QUESTION 2:

The possible type of irregularities for the given structure are:

Soft storey irregularity:

1. Stiff and strong upper floor due to masonary fill
2. The column in one storey is longer than the above.

Some provisions to avoid the irregularities:

The building is torsionally irregular. So the building framing must be revised.

The mass irregularity is avoided by providing light weight concrete/ low weight masonary or by providing structure with more wood materials.

Thee structure should be built in a well symmetric manner.

The columns which are provided on the structure should be of same size and height through out the building.

The weight of the building from ground floor should decrease towards top.

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).

QUESTION 3:

1. Structure is not symmetric.
2. Larger strength is provided hence low ductility.
3. In this building, there is no proper placement of masonary infill walls
4. In this building, redundancy in the vertical direction is not provided properly.