Conceptual design of a building with columns and shear walls

1. Aim: To create by taking the three alternatives taking into an account the restraint of floor shrinkage, the lateral stiffness and the torsional one with respect to the vertical axis, the vertical reinforcement required for the same total flexural capacity at the base, the static eccentricity, the system redundancy, foundation systems, architectural constraints etc..,

Introduction: To create by taking the three alternatives taking into an account the restraint of floor shrinkage, the lateral stiffness and the torsional one with respect to the vertical axis, the vertical reinforcement required for the same total flexural capacity at the base, the static eccentricity, the system redundancy, foundation systems, architectural constraints etc..,

Procedure:

A. Restraint of Floor shrinkage:

Observation:

• Full restraints at all corners.
• Corners are left free but restraints along the edge.
• Non-Uniform restraints.

Conclusion: First option 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.

B. The lateral stiffness:

Observation:

• Comaparatively 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 provode higher lateral stiffness for a pure seismic accleration in X and Y directions.

C.Torsion with respect to vertical axis:

Observation:

• Corner walls provide more resistance to twist.
• Edge walls provide good resistance to twist.
• Irregular walls provide very poor resistance to twist.

Conclusion: Option A will be best option with respect to torsional resistance whereas option C is the worst one.

D.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: Option C will require higher vertical reinforcement and option B will require the least.

E. Static eccentricity:

Observation:

• Structurally symmetric.
• Structurally symmetric.
• Un-Symmetric.

Conclusion: Only option C will have static eccentricity and it is significant.

F. System's eccentricity:

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.

G. Foundation 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 foundation.
• Walls are in line & Concentrated. Easy to fix the geometry of foundatin but critical in design.

Conclusion:Option B and C shall be incorporated with isolated footings/Strip footings. Option A is recommended to have peripheral box foundation.

H. Architectural Constraints:

Observation:

• Walls obstruct only corners.
• Walls obstruct the faces of building.
• Vertical wall will not allow passage.

Conclusion:Architecturally speaking, Option A is the preferred one. Optuon B is subjected to discussion. Option C will not be accepted both architecturally and commercially.

2. Aim: To discuss about the suitability for earthquake resistance of the moment resisting framing plan of a three storey building depicted here.

Introduction: To discuss about the suitability for earthquake resistance of the moment resisting framing plan of a three storey building depicted here.

Procedure:

Issues in the given Framing plan:

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

Eccentricity: The longer the distance between the centre of mass and centre of stiffness, the higher torsional moment of the building. As per the given plan eccentricity, the building is subjected to higher torsional moment (Torsional flexibility) in both X and Y directions.

Strong beam and weak column possibility: The size of the columns majorly mentioned as 25cm x 25cm. But all the beams have much deeper section (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 doubtfull. It is recommended to have slight bigger sizes for column.

3. Aim: To create a multi storey building with basement, with a quadrilateral (non symmetrical floor plan) plan as interior columns in irregular (not a grgid) pattern in plan that serves architectural and functional considerations.

Introduction: To create a multi storey building with basement, with a quadrilateral (non symmetrical floor plan) plan as interior columns in irregular (not a grgid) pattern in plan that serves architectural and functional considerations.

Procedure:

Observations in the given framing plan:

Floor plan: The floor plan of building is not eitther uniform or symmetric. So naturally any lateral load induced in the floor will not have 100% influence in same direction. Definitely special lateral load resisting system for these torsional moments should be accommodated.

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 deisgn those columns for only gravity loads.

Floor to floor variations in Partiition walls and Beams: Partition walls provide an important mass control in a building and beams play key role in shear transfer from floor to bams. All these elements are not in order. So heavy distortion and distribution of lateral loads will happen.

Suggestion on the lateral load system & 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 (Irregular Quadrilateral). So corner shear walls on the left side should be heavier than the right.
• Corner shear walls shall preferabley 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 the Tie beams.