Conceptual design of a building with columns and shear walls

1. Comparision of the Three Alternatives Proposed

Criteria
Restraint of Floor Shrinkage	Observation	Full Restraints at all corners	Corners are left free but restraints along the edge	Non-Uniform restraints
	Conclusion	Option (a) will have higher restraint to shrinkage, thus lead to cracks in the floor. Option (b) is average. Option (c) will not effectively restrain the shrinkage, so possibly less cracks.
The Lateral Stiffness	Observation	Comparatively Lower Lateral Stiffness in both X and Y	Uniform and comparatively higher lateral stiffness in both X and Y	Non- Uniform Lateral Stiffness in both X and Y
	Conclusion	Option (b) will provide higher lateral stiffness for a pure seismic acceleration in X and Y directions
Torsion with respect to vertical axis	Observation	Corner Walls provide more resistance to twist	Edge Walls provide good resistance to twist	Irregular wall provides very poor resistance to twist
	Conclusion	Option (a) will be 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	Wall are subjected to nominal twisting moment	Walls are subjected to heavy flexural moment and twisting moment
	Conclusion	Option (c) will require higher vertical reinforcement and Option (b) will require the least.
Static Eccentricity	Observation	Structurally symmetric	Structurally symmetric	Structurally symmetric
	Conclusion	Only Option (c) will have static eccentricity and it is significant
System’s Redundancy	Observation	Uniform placement of lateral load supports in both the axes	Uniform placement of lateral load supports in both the axes	Concentrated lateral load supports in both the axes
	Conclusion	Option (a) and (b) are more redundant than Option (c)
Foundations Systems	Observation	Due to ‘L’ shaped walls, the geometry of foundation and its design will be critical	Walls are in line. Easy to fix the geometry and design of the foundation	Walls are in line and concentrated. Easy to fix the geometry of foundation but critical in design.
	Conclusion	Option (b) and Option (c) shall be incorporated with isolated footing / strop footings. Option (a) is recommended to have peripheral box foundation.
Architectural Constraints	Observation	Walls obstruct only corners	Walls obstruct the faces of the building	Vertical Wall will not allow passage
	Conclusion	Architecturally speaking, Option (a) is the preferred one. Option (b) is subjected to discussion. Option (c) will not be accepted both architecturally and commercially

2. Issues in the given Framing Plan:

• Indirect Lateral Load Transfer in X and Y direction:
  
  • The beams are connecting to another beams which is ineffective during lateral load transfer.
  • In such conditions, the primary beam is prone to shear failure.

• Incomplete Lateral Load Transfer in X - Direction

• Improper Lateral Load Transfer in Y - Direction

• Eccentricity:
  • The longer the distance between centre of mass and centre of Stiffness (Ck), the higher torsional moment of the building.
  • As per the Given Plan eccentricity, the building is subjected to higher torsional moment i.e., more Torsional Flexibility in both X and Y direction.

• Strong Beam and Weak Column Possibility:
  • The size of columns majorly are mentioned as 25cm x 25cm.
  • But all the beams have much deeper sections i.e., 25cm x 50cm.
  • Inertia of Beam is visually higher than 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 slight begger sizes for column.

The Alternate Scheme is given as below:

3. Observations in the Given Framing Plan:

• Floor Plan:
  • The Floor Plan of the building is not either uniform or symmetric.
  • So naturally any lateral load induced in the floor will not have 100% influence in same direction.
  • Definitely a Special lateral load resisting system for these torsional moments should be accomodated.

• Random Internal Columns:
  • Since the Internal columns are random, they are unable to transfer lateral loads efficiently and can not achieve desirable building response.
  • 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 ina building and beams play 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.

Suggesion on the Lateral Load System and Its Foundation:

• Heavy Torsional forces should be controlled by respective lateral load system.
• So "Corner Shear Walls" are suggested.
• The Proportion of floor area is greater on the left side than the right side i.e., Irregular Quadrilateral.
• So corner shear walls on the left side should be heavier than the right.
• Corner shear walls shall prefarably be supported over a box foundation.
• Shear walls should be connected by Link Beams to transfer shear from one to the other.
• The internal columns shall be supported by isolated footings.
• Those isolated footings can be connected with Shear Walls through Tie beams.

Proposed Schematic Plan of Lateral Load System:

• Super Structure

• Sub Structure