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.
ans:
A)we can see symmetry structure and columns and beams are evenly distribute the load in layout and the distribution of mass, stiffness is across the plan has good symmetrical.
B) When the loads are uniformly distributed a structure can withstand the semsimc loads.
C)Redundancy can cause structural elements in the Periphery of the plan leads to the uneven distribution of earthquake
D)Bi-directional Stifness may not be able to resist the horizontal seismic actions in the shorter direction Y-axis and also the resistance and stiffness shorter direction (Y-axis) is less when compared to longer direction X-axiS. stiffness of the strucutre is symmetry so mass act on buliding also be safe.
E)the smaller the strength the larger ductility is required as more forces is reduced more ductility is required so if the area is less earthquake prone then the structure is ductile and also the structure is symmetric it has a lateralstiffness so no damage for the building.
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.
ans:
Ans:
The possible type of irregularities for the given structure are:
1)Soft storey
A. The structure contains irregularites in the column placing.
B.The structure is torsionally irregular.So the structure framing must be changed. is said to be torsionaly irregular when the maximum horizontal displacements of any floor in the direction of the lateral force at one end of the floor is more than 1.5 times its minimum horizontal displacement at the far end of the same floor in that direction.
C.the irregularities in building structures,it should avoid Extremely flexible Structure in torsion
D.In this structure twisting the total build and torsion mode is heavy we need to provide additional reinforcment to arrest the torsion in this building otherwise the structure can be collapse easily
E. The stiffness is concentrated in the centre or cornor of the building, the very critical structure load distributin are very less and weak structure.
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).
ans:
1. We can see the structure is not symmetric and Larger strength is provided hence low ductility.
2.In this given structure, Redundancy in the vertical direction is not provided properly.
3.Then the load are not distribute evenly its unsymmerty structure.
4.Bi directional stiffness and ductility: seismic forces are bi directional in nature, which can dominate the structure from any horizontal direction.right of left. in order to sustain these forces, structural elements should be arranged orthogonally. the column are orthogonal to each other, therefore we can say that they have good resistance to seismic forces.
5.the increased strength and stiffness of a structure in the stairway region will influence the seismic torsional distress of the structure and may lead to shear failure of the staircase itself or of other elements of the structure.