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:

a) Symmetry: In the plane we can say that mass is distributed uniformly to the columns due to the symmetry of the plan.

b)Redundancy: In the above structure the columns are placed closer to each other. It helps resisting the structure as it transfer the stresses accross columns.

c)Bi-directional Stiffness: As stiffness of structure is symmetric ,so the loads acts on structure equally.

d)Ductility: It is measured by determining the percentage of elongation during earthquake. For good structure elongation must be less.

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:

Types of irregularities

a)Weight irregularity: As we can see weight across the structure is non-uniformly distributed due to that structure will collapse.

b)Plane Discontinuity: Reduction in lateral stiffness of an element in the storey below.

c)Vertical stiffness of storey is less.

d)Discontinuity in capacity i.e storey shear strenght less than above storey.

e)Torrsional senstivity is less for that reinforcement is required for structure otherwise structure will collapse when earthquake occur.

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.

Answer:

Loads are distributed unevenly due to unsymmetric of structure.

Columns and beams are not placed properly.

More strength is provided so that ductility is low

Width of columns and beams must be same otherwise distribution of load will be eccentric.