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.

ANSWER:

1. In the above layout of structural column there is uniformly distribution of column is showed.
2. Hence it alows short and direct transmission of inertia forces produced in the distributed mass of building.
3. There is symmetrical alignment of column is shown hencethere is uniformity in buiding.
4. Symmetrical alignment of column also increase the stiffness and strength of structure.
5. The above layout is redundant structure that is the structure becomes more reliable to resist eartquake effects by accommodating the loss of some structural element before becomining unstable.
6. The above orientation bi-directional resistance as the structural element is arranged in an in-plane orthogonal structural patern therefore the building is able to resist the seismic action in any direction.

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:

In the above building there as some irregularities like:

1. There is a discontinous columns in the ground floor and upper floor in view of obtaining an architecturally more ground floor.
2. Upper floor is much stiffer and stronger than lower floor as upper floor consists of masonary infills and shear wall.
3. Thus the lateral stiffness of the ground storey is much smaller than that of above storey.
4. This latyout can cause concentration of horizontal displacement in the ground storey as a result upper storey will likely to fall.
5. The cause of failure is soft storey is possible.
6. There is also possibility of extremely flexible structure in trosion.

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:

1. In the above structural building the column orientation is in symmetry and hence it acheive uniformity.
2. There is a discontineous columns of ground floors and upper floors in view of obtaining an architecturally more ground floor as hotel building has an open ground floor for the restuarant.
3. The building has less lateral stiffness since the left side is comparatively stiffer than right side of the building as there is closely placed column for staircase and lift.
4. The cause of failure is soft storey is possible.
5. There is also possibility of extremely flexible structure in torsion.
6. This layout can cause concentration of horizontal displacement in the ground storey as a result upper storey will likely to fall.