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.
Procedure : In the above given plan
2. If we split the plan X direction in half then we will find that the plan is symmetry
3. It will look mirrored
4. And hence the plan in X direction is Symmetry
5. If we split the plan Y direction in half then we will find that the plan is symmetry
6. It will look mirrored
7 And hence the plan in Y direction is Symmetry
8. There are more columns in X direction and the spacing given between this columns is equal
9. In the X direction at the Top and bottom there are less columns as compared in between.
10. Structure in Y direction is redundant but it is less redundant than the X direction
11. Distribution of mass in X direction is good
12. Columns in X direction are connected with staright beams that is if there is if there is any sesmic force on right end then it will have its path through beams till it reaches left end.
13. Columns in Y direction are not continuously connected so the load will be diverted.
14. The stiffness in the X direction is more as compared to the Y direction because of more columns
15. Y direction will face more problem for passing the force than the X direction.
16. Plan is more ductile 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.
Procedure : 1. Plan area is more at the bottom as compared to the Top flor areas
2. On the sixth floor there is no partition wall this will lead to plastic hinge at the column
3. Building is contructed to sloping ground on one side so this will lead to significant vaiations is stiffness
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).
Procedure :
1. There is a open ground floor which indicates there is a soft storey mechanism acting on building
2. There is a mass irregularity
3. Two short sides covered with infill walls that means building left and right side is more stiffer for the sesmic force
4. Staircase portion is more stiffer as it contains concentrated concrete elements
5. In vertical direction there are no beams in between as compared to horizontal so there is no load transfer in between as compared to horizontal Direction.
6. In internal column has high dimension than compared to external column. This will lead to significant difference in lateral drift of columns