Conceptual design of a building with columns and shear walls

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.

• With respect to the eccentricity the redundancy of the structure A and B is more than compared to the structure C as structure A and B are symmetric over the cross section on the both sides whereas the structure is symmetric over in one direction only which makes the structure weak in that particular direction of the lateral loads.

• Structure A is well designed of the torsional forces than compared to the structure B and structure C, here the l-shaped walls provide stiffness at the corners of the structure which prevents the twisting of the structure resisting the lateral forces in the both directions and in structure B and C there may be the cause of the bearing failure occurring at the corners due to the heavy lateral force acting on the structure.

• And in the structure A provision of the L-shaped walls are very ideal for the high stiffness and strength achievement and its cost of the construction will be more than compared to that of the vertical walls present in the structure B and structure C

• Architectural constraints: structure A is best as the shear walls are placed at the corners which does not interfere the openings of the structure whereas the structure B and structure C has the shear walls at the middle of the face where architectural constraints are interfered.

• It is hard to provide the effective foundation to the wall, combined footing would be more effective that that of the isolated footing.

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.

• As shown in the figure above the eccentricity of the structure along the y-direction is more compared to that of the x-direction along

• These eccentricity` can be reduced by the provision of the shear walls ideal to reduce the eccentricity of the whole structure which makes the structure torsional stiff.

• Here the beams are not continuing from span to span which is interrupting the free flow of the beam internal forces beam which not supported on the column is not providing the enough lateral stiffness to the structure.

• Beams with the long spans should be governed by the gravity loads for the top reinforcement at the supports. Rather than by the seismic design solution.

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.

• The general layout and the geometry of the induvial plane will be having the vital role in the seismic behaviour of the whole structure. So, it is important to consider the layout of the structure.

• As a structural engineer it is important govern the important geometric details of the individual plane frames. And check for the cost effectiveness of the frame.

• Provision of the waffle slabs as the slab for this place would make the structure more resistant for the lateral and the vertical loads.

• Can also consider the flat slabs

• For the foundation consider the raft foundation.

• Columns should be designed strong