Conceptual design of a building with columns and shear walls

Question 1:
The building shown, 20 × 35 m in plan, has columns on a 5 × 5 m grid and shear walls (with dimensions shown in m, 250 mm in thickness) in three alternative arrangements, (a), (b), (c), all with the same total cross-sectional area of the shear walls. 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.

1ans):

The structure is more restrained it will be more shrinking, expanding and cracking.

There will be more floor shrinkage and expanding in structure in A whereas there will be minimum cracks in structure B and C.

The shear walls in the structure also decide whether the floor vibration is more or less in the structure a it will be better placing a column at the corners. So that it will reduce the cracks instead of having a shear walls at the corner in the structure

The torsion in the structure C is more compared o structure A and B because in the structure C there will be an eccentricity

The redundancy in the structure A and B is more when compared to the structure C because there will be an eccentricity in the structure C in the left side where the length of the wall 10 meters which cannot carry load equally in either direction.

For the lateral stiffness structure C is more laterally stiff when compared to the structure A and structure B because there will be an eccentricity In the structure C in the left side where the length of the wall 10 meters which cannot carry load equally in either direction.

Question 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.

2) Ans: In this picture we can know that eccentricity in X direction larger when compared to Y direction that is this structure is asymmetric with unequal columns .Due to to which we can know that this structure can undergo deformation more if it is facing earthquake. It can also face torsional moments that means there is presence of torsional flexibility taking place in the structure .We can observe here are two continuous frames that are B1 and B2 in X direction whereas in the direction of Y direction there are B7,B9,B10,B11 & B 12 as well. So to prevent torsional movements we have to provide shear walls in appropriate positions so that it can help in prevent deformations. Yes, so the two fundamentals translational modes of vibration larger than the fundamental torsional mode of vibration.

Question 3:

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.

3) Ans: The structure in the figure is asymmetric which means it is placed irregularly in non uniform pattern which is not a correct choice for construction in specially earthquake prone area. As it can experience a lot of deformation when goes through it. The columns has to placed accordingly to prevent and deformation due to irregular shape and most probably flat slab is more suitable for this type and structures .Shear walls if required must be provided. Ductilty among the structure within elastic would prevent early deformation. It should have greater strength and stability to face earthquake and should make foundation should be strong enough to bear a minimum to maximum amount of movements but to earthquake. Placing of columns and beams must be done accordingly.