Conceptual design of a building with columns and shear walls
1.ANS:-
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Criteria |
Diagram-A |
Diagram-B |
Diagram-C |
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Restraint of floor shrinkage |
Observation |
Full restraints at all corners |
Corners are left free but restraints along the edge |
Non-uniform restraints |
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Conclusion |
A will have higher restraints to shrinkage, thus lead to cracks in the floor |
B is average |
C will not effectively restrain the shrinkage, so possibly less cracks |
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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 |
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Conclusion |
B will provide higher lateral stiffness for pure seismic acceleration in X and Y direction |
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Tortion with respect to vertical axis |
Observation |
Corner walls provide more resistance to twist |
Edge wall provide good resistance to twist |
Irregular walls provide very poor resistance to the twist |
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Conclusion |
A will be the best option with respect to torsional resistance |
C whereas is the worst one |
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Vertical reinforcement for similar base capacity |
Observation |
Walls are subjected to nominal flexure moment and heavy twisting moment |
Walls are subjected to nominal twisting moment |
Walls are subjected to nominal heavy flexure moment and twisting moment |
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Conclusion |
B will require the least reinforcement |
C will require high vertical reinforcement |
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Static eccentricity |
Observation |
Structurally symmetric |
Structurally symmetric |
Structurally un-symmetric |
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Conclusion |
C will have static eccentricity and it is significant |
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Systems redundancy |
Observation |
Uniform placement of lateral load support in both the axes |
Uniform placement of lateral load support in both the axes |
Concentrated lateral load supports in both the axes |
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Conclusion |
A is more redundant |
B is more redundant |
C is less redundant than A and B |
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Foundation Systems |
Observation |
Due to L shaped walls, the geometry of foundation and its design will be critical |
Walls are in line. Easy to fox the geometry and foundation |
Walls in line and concentrated. Easy to fix the geometry of foundation but critical in design |
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Conclusion |
A is recommended to have peripheral box foundation |
B shall be incorporated with isolated footing/strip footing |
C shall be incorporated with isolated footing/strip footing |
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Architectural constraints |
Observation |
Walls obstruct only corners |
Wall obstruct the face of the building |
Vertical walls will not allow passage |
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Conclusion |
A is preferred one |
B is subjected to discussion |
C will not be accepted both architecturally and commercially |
2.ANS:-
- Indiredct lateral load transfer in X and Y direction- The beams are conncecting to another beam which is ineffective during lateral load transfer. In such conditions, the primary beam is prone to shear failure.
- Eccentricity - The longer the distance beween center of mass and centre of stiffness, the higher tortional moment of the building. aaas per the given plan eccentricity, the building is subjected to hgher tortional moment ( Torsional flexibility) in both X and Y direction.
- Strong beam weak column possibility - The size of column majorly mentioned as 25cm X 25cm. But all the beams have much deaper section (50cm). Inertia of beam visually higher than column. If the column reinforcement is adequately greater than beams, we are okay and since we do not have the reinforcement detail, this is doubtful. It is recommended to have slight bigger size of column.
3.ANS:-
- Floor plan - The floor of the building is not either uniform or symmentric. so any natural load induced in floor will not have 100% influence in same direction. Definetely a special lateral load resistance system fo those torsional moment should be accomodated.
- Random lateral column - Since the inernal columns are random, they are unable to transfer lateral load efficiently and cannot achieve desirable building response. So we have to assume and design those columns for only gravity loads.
- Floor to floor variation in partition walls and beams - Partition walls provide an important mass control in building and beam plays key role in shear transfer from floor to beam. All these elements are not in order. So heavy dostortion and distribution of lateral loads will happen.
- Heavy tortional force should be controlled by respective lateral load system. So corner shear walls are suggested.
- The proportion of floor area is greater on left side than the right side ( Irregular quadrilateral). So corner shear walls on left side should be heavier than right.
- Corner shear walls shall preferably be supported over box foundation. Shear walls should be connected by link beams to transfer shear one to the other.
- The internal column shall be supported by isolated footing. Those isolated footing can be connected with shear walls through tie beams