Conceptual design of a building with columns and shear walls

* Objective of this challenge is to understand the concept of lateral stiffness, torsional resistant, flexural capacity. Also understand the concept of symmetric vs non symmetric floor plan. Understand the concept of framing structures in seismic force and investigate the suitability of the given plan with respect to seismic behaviour.

1)

Criteria	First Figure (Observation)	Second Figure (Observation)	Third Figure (Observation)	Conclusion
Floor Shrinkage	Full restraints at all corners.	Corners are left free but restraints along the edge.	Non-uniform restraints.	Option (a) will create higher restraints than the other.
Lateral Stiffness	Lower lateral stiffness in both X & Y	Uniform and higher lateral stiffness in both X & Y	Non uniform lateral stiffness in both X & Y	Option (b) will provide higher lateral stiffness.
Torsion with respect to vertical axis	Corner walls will provide more resistant to twistion/torsion force.	Edge walls will provide more resistant to twist.	Irregular walls provide very less resistant to twist.	Option (a) is best option to go for design to resist the torsion force.
Vertical reinforcement with similar base capacity	Walls are subjected to nominal flexural moment and heavy twisting moment	Walls are subjected to nominal twisting moment	Walls are subjected heavy flexural moment and twisting moment.	Option (a) will be the best option.
Static eccentricity	Structurally Symmetric	Structurally Symmetric	Structurally unsymmetric.	Only option (c) will have the static eccentricity.
System Redundancy	Uniform placement of lateral load supports on both axis.	Uniform placement of lateral load supports on both axis.	Concentrated loads on both axis.	Option (a) & (b) are more redundant than option (c)
Foundation System	Due to L Shaped walls the geometry for designing the foundation will be difficult.	Walls are in line easy to design the foundation and load distribution at base will be equivalent.	Walls are in and concentrated easy to fix the geometry of the foundation but critical to design.	Option (b) & (c) can go for the isolated footing design & option (a) have to go for peripheral box foundation
Architectural Constraints	Walls are obstructed only at the corners	Walls are obstructed at the faces of the building	Vertical Wall will not allow for passage or placing of windows will be difficult.	Here option (a) is preferrable in architectural point of view.

2) Issues in the framing plan:

a) Indirect Lateral Load transfer in both X & Y direction: The beams are connected to another beam which is in effective during lateral load transfer. In such conditions beam is prone to shear failure.

b) Eccentricity: The longer the distance between the center of mass and center of stiffness, the higher is the torsional moment of the building. As per the given plan of the building it is subjected to the higher torsional moment in both X & Y direction.

c) Strong beam weak column: The size of the column is 25cm x 25cm. But the beams are much deeper in section i.e 50cm. Thus the inertia of beam is higher. If the column reinforcement is higher than beam than it is ok but the details of reinforcement is not given. Thus bigger sizes of column will be better.

3) Floor Plan: The floor plan of the building is not uniform or symemetric so any lateral force acting in the floor will not have 100% influence in the same direction.

Random Columns: The internal columns are placed randomly thus they are unable to transfer lateral loads efficiently and can not achieve desirable building response. These columns are designed only for gravity loads.

Floor to Floor variation in partition walls & beams: Partition wall and beams are not in order. So mass distribution is not even, heavy distortion and distribution lateral loads will happen.

Suggestion on lateral load system:

Heavy torsional forces should be controlled by lateral load systems i.e corner shear walls are to be provided.

The portion of the floor is greater on the left side as compared to the right side. So corner shear walls should be greater in width than the left side.

Shear walls to be connected by link beams to transfer shear from one to the other.

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