Conceptual design of a building with columns and shear walls

1) Aim:

• To investigate the suitably of given plan with respect to seismic behavior
• To schematically draw a seismic viable structural plan

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 restraints 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	Comparitively lower lateral stiffness in both X and Y	Uniform and comparatively higher lateral stiffnes 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 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 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	Un- Symmetric
	Conclusion	Only Option(c) will have static eccentrictity 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 loads supports in both axes
	Conclusion	Only option(a) and (b) are more reduntant 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 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 footings/ strip footings. Option(a) is recommended to have peripheral box foundation
Architectural constraints	Observation	Walls obstruct only corners	Walls obstruct the faces of building	Vertical walls 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:

a) Indirect lateral load transfer in X and Y directions- The beams are connecting to another beams which is ineffectively during lateral load transfer. In such consitions, the primary beam is prone to shear failure.

Incomplete Lateral load transfer in X- direction

Improper Lateral Load Transfer in Y- Direction

b) Eccentricity- The longer the distance between 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.

c) Strong beam weak column possibility:

The size of columns majorly mentioned as 25cmx25cm. 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 doubtful. It is recommended to have slight bigger sizes for column.

Alternate Scheme:

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3) a) 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 load resisting system for these torsional moments should be accomodated

b) 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.

c) 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 transfer from floor to beam. All these elements are not in order. So heavy distortion and distribution of lateral loads 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 quadrilateral). 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:

Super Structure

Sub-Structure