Conceptual design of a building with columns and shear walls
1. A
| Criteria | A | B | ||
|---|---|---|---|---|
| Restraint of Floor shrinkage | Observation | Corners are left free but restrains along the egd | Non-unifrom restrains | |
| CONCLUSION: a) Will have higher restrain to shrinkage, thus lead to cracks in the floor. b)is average. c) Will not effefctively restra | ||||
| The Lateral Stiffness | Observation | Comparatively Lower Lateral Stiffness in | Unifrom and comparatively higher lateral stiffness in both Xandd Y | Non uniform Lateral stiffness in both X and Y |
| CONCLUSION | b) will provide higher lateral stiffness accleration in X and Y | |||
| Torison with respect to vertical axis | Observation | Corner walls provide more resistance to twist | Edge Walls provide good reistnace to twist | Irregular Walls provide very poor resistance to twist |
| CONCLUSION | a) Will be best option with repect to Torisional resistance whreas . c) is the worst one. | |||
| Vertical reinforcement for similar base capctiy | Observation | Walls are subjected to no,inal flexural moment and hevy twisting moment | walls aree subjected to nominal twisting moment | walls are subjectes to heavy flexural moment and twisting moment |
| CONCLUSION | c) will require higher vertical reinforcement and (b) will required the least. | |||
| Static eccentricity | Observation | Structural symmetric | Structural symmetric | UN-symmetric |
| Conclusion | Only Option c) Will have static eccentricity and it is significant | |||
| System's redundancy | Observation | Uniform placement of lateral loads supports in both the axes | Uniform placements of lateral load supports in both axes | Concentrated lateral load supports in both the axes |
| Conclusion | Option a) and b) are more redundant than option (c) | |||
| Foundations 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 foundation | walls are in line & concentrated.Easy to fix the geometry of foundation but critical in design. |
| Conclusion | Option b) and Oprtion (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 | Wall obstruct the faces of building | Vertical wall will not allow passage |
| Conclusion | Architecturally speaking, Option (a) is the preffered one. Option (b) is subjected to discussion. Option (c) will not be acceptance both architecturally and commercially | |||
2.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. Suggest an alternative. Also, is there torsional flexibility? Are the two fundamental translational modes of vibration larger than the fundamental torsional mode of vibration. Discuss qualitatively.
A) Indirect lateral Load Transfer in X and Y directions - The beams are connecting to another beam which is ineffective during lateral load transfer. In such conditions, the primary beam is prone to shear failure.
ISSUES In the given Framing Plan :
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. (Trosional fexibilty ) in both X and Y
Strong beam weak column possibility
-The size of column majority mentioned as 25 cm x 25cm. But all the beams have much deeper section. Inertia of beam is visually higher than column. If the column reinforcement is adequately greater than that of beams, we are okya and since we do not have the reinforcement details, this is doubtful. It is recommended to have slight bigger sizes for column.
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.
A)
Observations in the given framing plan:
Floor Plan:-The floor of building is not either uniform or symmertical. So naturally any lateral load included in the floor will have 100% influence in same direction. Definitely a special lateral load resisting system for these torsional moments should accommodated.
Random Internal Columns:- Since the internal columns are random, they are unable to transfer lateral loads effeciently 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:- Patrition walls provide an important maas control in a building and beams play key role in transfer from floor to bem. All these elements are not in order. So heavy ditortion and distribution and distrbution 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 . so corner shear walls on the left side should be heavier than the right.