Conceptual design of a building with columns and shear walls

Solution.1)

Aim: To compare the three alternatives, taking into 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’s redundancy, foundation systems, architectural constraints etc.

Procedure:

Restraint of Floor Shrinkage
Observation	Full Restraints at all corner	Corners are left free butt 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 effectivvely 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 bith 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	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.

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 subjectedto heavy flexural moment and twisting moment.

Conclusion

Option(c) will require higher vertical reinforcementand option(b) will require the list.

Static Eccentricity
Observation	Structural Symmetric	Structurally Symmetric	Un-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).

Foundation System
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 foundaton.	Walls are in line and concentrated. Easy to fix the geometry of foundatiion but critical in design.

Conclusion

Option(b) and Option(c) shall be incorporated with isolated footings/strip footings. Option (a) is recommended to have peripheral box foundation.

Architectural Constraints
Observation	Walls obstruct only corners	Walls obstruct faces of building	Vertical wall will not allow passage.

Conclusion

Architecturally speaking, optiion(a) is the preffered one. Option(b) is subjected to discussion.Option(c) will not be accepted both architecturally and commercially.

Result: For all the three cases,observation and comments has been done with proper justification.

Solution.2)

Aim: To discuss the suitability for earthquake resistance of the moment resisting framing plan of a three-storey building depicted here (cross-sectional dimensions in cm), the eccentricity of the centre of mass (as centroid of floor plan) to the centre of stiffness (from the moments of inertia of the columns) are shown.

Procedure:

In the given framing plane, these are the following issues:

• Indirect Lateral Load Transfer in X and Y directions: 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 the center of mass and center 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.

Red Color means Torsional Influence during X-direction excitation

Blue Colour means Torsional Influence During Y-direction excitation.

• Strong Beam Weak Column Possibility: The size of 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 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 bigger sizes for column.

Alternative Scheme:

Result: All the possible issues has been discussed and alternative scheme has been presented to overcome the existing issue.

Solution.3)

Aim: A multi-storey building with basement, with a quadrilateral (non symmetrical floor plan) plan as, has interior columns in an irregular (not in a grid) pattern in plan that serves architectural and functional considerations. Partition walls and interior beams supporting the slab have different layout in different stories. However, there is no constraint to the type, location and size of the lateral force resisting components and sub-systems on the perimeter. Proposals are to be made and justified for the choice of the lateral-load-resisting system and its foundation.

Procedure:

Observation in the given framing plan:

• Floor Plan: The floor plan of 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 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 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 key role in shear transferr from floor to beam. All these elements are not in order. So heavy distortion and distribution of lateral laods will happen.

Suggestion 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 (Irregular Quadilateral). So, corner shear walls on the left side should be heavier than the right.
• Corner Shear walls shall preferably 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:

Sub Structure

Result: Appropriate Proposal has been made for the given framing plan and suggestion on the lateral load system has been made.