Conceptual design of a building with columns and shear walls

Q.1)

Properties	Case a	Case b	Case c
Restraint of floor shrinkage	L - type shear walls are positioned at corners. It offers strong resistance to floor shrinkage. The floor will be tightly held in place by these shear walls at the corners, and shrinkage will be controlled	Shear walls are positioned along the sidewalls. So better stability to floors near the walls. Shrinkage can occur at corners due to absence of shear walls	Shear walls are placed in an order less manner and are incomplete, so high chances to shrinkage exposure .The Floor Diaphragms are stressed heavily in Y direction due to the Irregularity in the placement of shear walls,also other factors may come in to consideration
Lateral Stiffness	The Lateral stiffness is very high because the shear walls are arranged in an IN-PLANE orthogonal sttructural Pattern combining with the columns	The Lateral stiffness of the plan is better but may be less when comapred to TYPE 1 structure of arrangement	The Building plan Lateral stiffness is very less when compared to the other Cases but it is better than the Building without Shear walls
Torsional stiffness with respect to Vertical axis	There is no eccentricity between the centre of mass and the centre of stiffness; they both coincide, making the model less prone to torsion and allowing it to be classified as torsional stiffened model.	There is no eccentricity between the centre of mass and the centre of stiffness as the shear walls are positioned symmetrically and As a result, this configuration is less vulnerable to torsion.	The shear wall is placed asymmetrical in the y direction, so as a result, the centre of stiffness shifts to the left edge, resulting in an eccentricity between the centre of mass and the centre of stiffness, causing torsional instability in this configuration
Vertical Reinforcement at base	Since the shear reinforcements are positioned at the corners, they play a little role in the lateral force resistance to the remainder of the wall As a result, less reinforcement will be required for these walls.	Here the shear walls are arranged along the main directions, they absorb a substantial amount of lateral forces. As a result, considerably more reinforcing should be added to these walls in order to withstand these forces	The shear walls are asymmetrically arranged here, the shear walls will take up a significant amount of lateral forces. Especially the wall on the left side of the room. As a result, these walls must be heavily reinforced.
Static Eccentricity	There is no eccentricity because the shear walls they are symmetrically located at the corners, the centre of mass and stiffness coincides in this layout	There is no eccentricity because the shear walls are symmetrically arranged around the edges, the centre of mass and stiffness coincide in this arrangement	There will be eccentricity in the arrangement because there is only one shear wall along the left edge with a larger mass than the other two shear walls in the y direction. As a result, the centre of stiffness shifts to the left, resulting
System's Redundancy	The system has Moderate Redundancy	The system has Very high Redundancy	The system has Very less Redundancy
Foundation Systems	As the shear walls are at the structure's corners, an isolated footing with a tie beam can be used as a foundation.	A raft foundation or a box foundation can be used.	A combined footing can be provided along the y direction and isolated footing in X direction
Architectural Constraints	From an architectural standpoint, this shear wall configuration is pleasing. since it does not interfere with other elements such as doors, windows, and so on	While this design is stable, there is a potential that these shear walls will interfere with the wall openings, which is not ideal	In this configuration, the two walls on the right side along the X direction are architecturally sound, but the shear wall on the left edge along the y direction takes up over half of the wall, obstructing open spaces.

Q.2)

i) This structural frame has a two-way eccentricity , the centre of mass in relation to the centre of stiffness,

with the eccentricity of the x-direction being greater than the eccentricity of the y-direction.

ii) As a results there is a chances of Torsional flexibility .

ii) As the beams in this building are stronger than the columns, it can be considered a weak column strong beam design in nature.

iii) So therefore , when lateral forces acts around the structure, a shear wall is required to prevent column failure.

iv) The combination of a shear wall and a column tends to keep the structure from collapsing when seismic forces strike.

v) The beam alignment is uniformly continuous of B1 and B2 in the X-direction, and Bll & B12, B9 & B10 in the

Y-direction, as shown in the frame plan.

vi) However, because all beams are provided at a discontinuous in the structural frame, the transfer of load equally

throughout the structure is difficult due to the action of lateral forces.

vii) Top reinforcement at the supports of long-span beams may be determined by calculated gravity load rather than seismic

design circumstances.

viii) As a result, this structure will alternate to a better portal with a better offset in nature.

ix) The connections between the column beams should have a proper cross section area so that lateral stiffness, mass regularity,

and moment resisting factor may be achieved.

x) We believe that the beam-sway mechanism in strong column/weak beam design frames is superior because

it achieves a consistently distributed global inelastic displacement requirement across all storeys at the roof level.

xi) As we could see that there is vertical irrregularity in structure .

The Alternatives to be considered for this Building are -

1) Repositioning of columns in the same line by cuuting down the offsets.

2) Ensuring the eccentricity of the Centre of mass and the Centre of stiffness to coincide.

3) To design for shear walls without creating more restrictions for architectural constraints

Q.3)

The following given considerations are need to be followed for the Design of appropriate Lateral load system

1) A quadrilateral (non symmetrical floor plan) plan -

i) For this type of system it is observed that there is no symmetry; therefore it has Symmetrical Irregularity.

ii) It has interior columns in an irregular (not in a grid) pattern in plan to serve architectural and functional considerations:

iii) This creates disturbances in the Symmetry as well as it creates Translational and Torsional effects in the Building.

iv) When lateral load acts on the structure there is an disturbance in transfering the load to the foundation .

2) Partition walls and interior beams supporting the slab have different layout in different stories -

i) This causes huge eccentricity for each storey which means the centre of mass and centre of stiffness are not near to each other.

ii) In order to neutralize all the above considerations and given that

iii) The slab will be supported by the internal beams, with the lateral load resisting failure due to earthquakes

3) There is no constraint to the type, location and size of the lateral force resisting components and

sub-systems on the perimeter -

i) The Best lateral loading system applicable is the WALL SYSTEM or DUCTILE WALL SYSTEM.

ii) The wall system acts as a Vertical cantilever,not prone to Soft storey mechanism and overshadows all the constraints in the proposal.

iii) The partition wall is given through the base of the beam and should support the structure's lateral displacement.

4) Random internal columns

i) Since the internal clumns are random , they are unable to trasnsfer lateral load efficiently and can not achieve desirable

building response .

ii) So we have to design those columns for only gravity loads .

Suggestions on the lateral load system -

i) Heavy torsional forces should be controlled by respective lateral load system . So Corner Shear wall are suggested

ii) The proportion of floor area is greater on the left side than the right side . So corner shear wall should be heavier than right side

iii) Corner Shear wall preferably be supported over a box foundation.

iv) Shear wall should be supported by link beams to transfer the shear from one to another .

Foundation for multi-storey building -

i) Box founation is suitable under Corner shear wall

ii) And for Individual columns , Isolated footings are suggested by connecting with each other by Tie beams