Conceptual design of a building with columns and shear walls

ANSWER:

. Restraint of Floor Shrinkage:

Observation: (a) Full restraints at all corners.

(b) Corners are left free but restraints along the edge.

(c) 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 effectively restrain the shrinkage, so possibly less cracks.

. The Lateral Stiffness:

Observation: (a) Comparatively lower lateral stiffness in both X and Y.

(b) Uniform and comparatively higher lateral stiffness in both X and Y.

(c) 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: (a) Corner walls provide more resistance to twist.

(b) Edge walls provide good resistance to twist.

(c) 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: (a) Walls are subjected to nominal flexural moment and heavy twisting moment.

(b) Walls are subjected to nominal twisting moment.

(c) 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:(a) Structurally symmetric.

(b) Structurally symmetric.

(c) Unsymmetric.

Conclusion: Only Option(c) will have static eccentricty and it is significant.

. System's Redundancy:

Observation:(a) Uniform placement of lateral load supports in both the axes.

(b) Uniform placment of lateral load supports in both the axes.

(c) Concentrated lateral load supports in both the axes.

Conclusion: Option(a) and (b) are more redundant than Option(c).

2) AIM: To discuss about the suitability for the earthquake resistance of the moment resisting framing plan of a three-storey building depicted in the figure. And also to discuss about the torsional flexibility, about the topic on whether the two translational modes of vibration larger than the fundamental torsional mode of vibration.

ANSWER:

a) 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.

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 25 cm x 25 cm. 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 sizess for column.

3) AIM: To make proposals and justifications for the choice of the lateral load resisting system and foundation of a multistorey building with basement with a quadrilateral plan shown in figure.

ANSWER: OBSERVATIONS 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 load resisting system for these torsional moments should be accomodated.

RANDOM INTERNAL COLUMNS- Since the internal columns are random, they are unable to transfer lateral loads efficiently and cannot 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 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 shouid 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.