Conceptual design of a building with columns and shear walls

Answer to Q.No:1:

Although the given set of shear wall arrangements are of equal length, area, and stiffness, due to their position their application or performance can vary based on various other factors that are listed as follows.

Given Data :Area=20x35m. The total length of shear walls is 5x5=25m. The thickness of the wall= 250mm

		For option A (From the left)	For Option B	For Option C
Restraint of Floor shrinkage	Observation	At corners, higher displacements demand full restraints. Floors are similar to simply supported slabs near the corners.	The walls shall have intermediate shrinkage to (a) and (b). Slabs are free near corners but restrained near edges.	The non-uniform restraint of the slabs will cause minor cracks in the structure.
	Conclusion	Option(a): This will show the highest restraint to the shrinkage due to the presence of walls at the corners of the building. Cracks at the corners are more fatal than those forming on the edges because the former provides freedom for the crack to proceed in two orthogonal directions as the former spreads the crack in one direction.	Option(b): This option provides a single-direction restraint to the wall, along the edges.	Option(c): This option does not completely provide restraint along the edge nor along the corners so shall not restrain the shrinkage in any direction.
The Lateral Stiffness	Observation	Comparatively, Lower stiffness in both directions, because the continuity of the wall matters along with its length in one particular direction to resist the flexure.	The best location to place a shear wall is along the edge of the plan. So that there is a continuous wall whose's full depth is utilized in the lateral load resistance.	The stiffness distribution i.e, the distribution of the column wall depths along each direction should be such that it has a plan symmetry, otherwise, it can produce unwanted torsion in the building.
	Conclusion	Option(b) will provide higher lateral stiffness for a pure seismic acceleration in X and Y directions
Torsion with respect to the vertical axis.	Observation	Corner walls provide more resistance to twist	The edge wall's resistance to twist could be nearly about that of walls near the corner due to the same wall area.	Irregular wall placement will provide very poor resistance to all.
	Conclusion	Option(a) will be the best option with respect to Torsional resistance whereas option(c) is the worst one.
Vertical reinforcement for similar base capacity	Observation	Walls are subjected to nominal flexural moment and heavy twisting moment	Walls are subjected to nominal twisting moment	Walls are subjected to heavy flexural moment and twisting moment
	Conclusion	Options(c)will require higher vertical reinforcement and option(b) will require the least.
Vertical reinforcement for similar base capacity	Observation	Walls are subjected to nominal flexural moment and heavy twisting moment	Walls are subjected to nominal twisting moment	Walls are subjected to heavy flexural moments and twisting moments.
	Conclusion	Option(c) will require higher vertical reinforcement and option(b) will require the least.
Static eccentricity	Observation	Structurally Symmetric in plan	Structurally symmetric in plan	Un-symmetrical in the plan view.
System's redundancy	Observation	Uniform placement of lateral loads supports along both axes. The placement of structural elements is done uniformly i.e., the structural walls. In both the plan directions.	Uniform placement of lateral load supports in both the plan directions.	Concentrated lateral load supports along both axes.
Foundation Systems	Observation	Due to L-shaped walls, the geometry of the foundation and its design will be not easy to consult and construct.	Walls are in line, therefore, easy to fix the geometry and design the foundation.	The walls are in line and concentrated. Easy to fix the geometry of the foundation but critical in design.
	Conclusion	Option (b) and option(c) shall be incorporated with isolated footings/strip footings. Option(a) is recommended to have a peripheral box foundation
Architectural constraints	Observation	Walls obstruct only the faces of the building	The vertical wall will not allow passage.
	Conclusion	Architecturally speaking. Option(a) is the preferred one. Option(b) is not recommended architecturally because the walls could obstruct the balconies present along the edges of the building. Option(c) will not be accepted both architecturally and commercially.

Answer to Q.No:2:

Indirect Lateral Load Transfer in X and Y directions- The beams are connecting to another beam which is ineffective during the lateral load transfer. In such conditions, the primary beam is prone to shear failure. The transfer of the axial force from the beams from the B7 and B3 due to the story lateral loads will cause the minor axis moment in the beam to which it is transferring. Usually, we design the beams to resist the major loads along the major axes. Hence, it is not favorable for a good structural design.

Issues in the given Framing plan:

Eccentricity- The longer the distance between the center of mass and the center of stiffness of a story, the greater the torsional moment caused in that particular story. As per the given plan eccentricity, the building is subjected to higher torsional moment(Torsional flexibility) in both X and Y directions. The resultant eccentricity shall be the square root of the sum of the squares of the eccentricities in the X and Y directions.

Strong Beam- Weak Column Possibility: The beam sizes should not be more than the column sizes because there shall be shear force balance and moreover, the beams are expected to fail former to the columns to avoid the progressive collapse of the building. The size of columns is majorly mentioned as 25cmx25cm. But all the beams have a much deeper section.

The inertia of the beam is visually higher than the column. If the column reinforcement is adequately greater than that of beams, we are okay, and since we do not have the reinforcement detail, this is doubtful. It is recommended to have slightly bigger sizes for columns.

Answer to Q.NO:3:

Floor plan- The Floor plan of the building is not either uniform or symmetric along any assumed X and Y axes. So, naturally, any lateral load induced in the floor shall definitely influence the same direction, in the form of a torsional moment. Nonetheless, a spectral lateral load resisting system for these torsional moments should be accommodated. The twisting systems could to outrigger, shear-wall, or any suitable for the scenario.

Random Internal columns- Since the internal columns are random, they are unable to transfer lateral loads efficiently and cannot achieve desirable building responses. So, we have to assume and design those columns for only gravity loads.

Floor-to-floor variations in partition walls and beams- Partition walls provide an important mass control in a building and beams play a key role in shear transfer from floor to beam. All these elements are not in order. So, heavy distortion and distribution of lateral loads will happen. Heavy torsional forces should be controlled by respective lateral load systems. So "Corner Shear walls" are suggested.

The Proportion of floor area is greater on the left side than on the right side(Irregular quadrilateral). So, the Corner shear walls on the left side should be heavier than on the right.

The internal columns shall be supported by isolated footings. Those isolated footings can be connected with shear walls through the tie beams.

Proposed Schematic plan of Lateral load system:

Also in the case when the forces along the tie beams are to be distributed orthogonally to the shear walls.