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:

• In this, the layout of the framing plan is Symmetric.
• A symmetrical well-distributed plan layout of structural elements is appropriate to achieve uniformity.
• The use of many, evenly distributed structural elements increases the redundancy of the structure, that is the structure becomes more reliable to resist the earthquake effects.
• In this plan, there might be a chance of arising plastic hinges.

To calculate the limit load for finding the plastic hinge.

Limit load = 4MP/L

Where,

MP - Plastic moment

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:

• A building 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.
• In such a case the building configuration must be revised.
• Out of the many possible irregularities in building structures, the final structural design should, in absolute terms, avoid the two most dangerous irregular situations

1) Soft storeys

2) Extremely flexible Structure in torsion

• Both cases correspond to extremely irregular stiffness distributions: the former regarding the distribution in height/elevation with a very weak story and the latter regarding the distribution in plan, with the concentration of the stiffness at the center or at a corner.

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:

• Looking toward the plain we see that it consist of one way slabs , beam and columns in the structural plan.
• The reinforced concrete beam is provided in x direction .
• No beams are provided in y direction thats way structure is failure .
• We see at bottom floor looking open at may lead soft story failure mechanism acting in the building .
• As per the given instructions, the middle portion is the corridor which means that portion has no mass as compaired to other sides having room and which results in greter mass , due to this irregularity building may collapse.