Concept on positioning of Columns

Q.1)

Answer -

1) Symmetry -

• The layout is symmetric.
• The load distributed in this symmetrical structure is distributed evenly throughout the structure.
• It has very good uniformity.
• The structure is symmetric then redundancy is increased and more reliable in the areas where there is more earthquake and also if the structure is symmetric the uniformity of structure is also increased.

2) Redundancy -

• In this plan,there are missing structural element.
• This causes uneven distribution of earthquake action effects in non linear range across the plan.
• And the energy dissipation across the structure is very low because of unreliable.

3) Bi - Directional stiffness -

• Horizontal seismic motion by nature a bi-directional phenomenon and thus the building structure must be able to resist horizontal actions in any directional.
• Hence,the structural element should be arranged in plan orthogonal pattern,so that the building structure is able to direct the seismic action in any direction.
• The structure may not be able to resist the horizontal seismic actions in the shorter direction.

4) Ductility -

• Ductility plays a very important role in structure where strenght is high,and the area is low probability prone earthquake.
• 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 lateral stiffness so no damage for the building.

Q.2)

Answer -

1) Stiffness Irregularity -

• It is observed that the open storey causes reduction in stiffness in the building and attracts lateral seismic excitation more in that floor which causes severe damage to upper floor of building.
• The lateral stiffness at mid height which is open and it is discontinued.
• The irregularity can be solved by providing shear wall to this floor.

2) Mass Irregularity -

• In this building,open story causes mass irregularity because of high mass concentration is present above the open floor.

3) Floating column -

• The column is a vertical member of structure that resists lateral forces.
• Horizontal forces acts on the structure and they transfer through the vertical member and to the base shear foundation.
• The column is discontinuous in structure and it is unable to withstand the lateral forces acting on building during earthquake because the load cannot transfer to the bottom of foundation.

4) Failure of soft story -

• Ground floor is considered as soft story because it has short column and no shear wall.
• The structure may damage due to buckling of column and collapse.

Q.3)

Answer -

• The structure is not symmetrical.
• Redundancy in the vertical direction is inadequate.
• There is no proper masonary infill wall placement.
• The ground floor of the building is open,which is soft story and due to this the ground floor excitation the column unable to resist the earthquake and get collapse.and this is avoided by providing strong column weak beam mechanism.
• The mass has been undisturbed in all the sides of the building in all storey because it is given that the two sides of the perimeter of the building is in filled which causes irregular distribution of mass.and it is avoided by providing shear walls in two sides which resist the lateral loads.
• The extreme left hand bay has staircase and due to this the mass get concentrated in that area due to which torsional effects are formed.and this type of failure is avoided to kept the staircase in middle portion of structure.
• The size of column and beam is improper. and The width of column and width of beam need to be same otherwise the load distribution is eccentric.