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.

ans :

Structure (a) :

• For this structre is considered as it is assymetrical in nature.
• Here cannot be considered as a horizonatal irregularities and the shear wall shape like L.
• There is some uncertainity concerning certain features of the seismic response of non-linear rectangular walls.
• It occurs lack of tensile capacity and face configuration.
• These walls have high stiffness and strength in both direction, hence are subjected biaxial bending and bi-directional shears during earthquakes.

Structure (b) :

• For this structure frame can be considered as symmetruc in place to the shear wall.
• The shear walls are arranged in similar and symmetry, so it can be considered at every storey to fairly uniform resistant in seismic forces and deformation demands, minimizing the uncertainity about the seismic response.

Structure (c) :

• For this, structure can be considered as asymmetric in nature, because of the shear wall provided are not arranged in a two orthoganal horizontal directions.
• The center of the mass and center of gravity of such structure will not lie far away from each other, enabling transitional modes in the first two principles mode.
• The shear wall, columns and the foundation are arranged in differents, hence take up huge amount moments in case of earthquakes.
• This type of shear wall system will not carry the load equally in either directions. So this structure lack redundacy.
• On the left side , the wall provide more eccentricity, lateral stiffness is more. Therefore it occures, then the damage or the failure will be less

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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.

ans :

• In this structural frame, there is a two way eccentricity of the center of the mass in accordance with the center of stiffness, which is eccentricity of x-axis is larger than y-axis.
• Structural beams are provided at stronger column, so it is considered as weak column strong beam design in natture.
• This structure needs some shear wall to resist the column failure, when the lateral forces act about the structure
• Combination of the shear wall and column tends to prevent the failure about the structure during the seismic forces occur.
• The alignment of the beam is uniformly continuous of B1 and B2 at x-axis and B11 and B12, B9 and B10 at y-axis.
• All beams are provided at discontinuous of structural frame, s cause the difficulties in transmission pf load evenly at entire structure due to action of lateral forces.
• Beams with long spans may have their top reinforcement at the supports governed by factored gravity load, rather than by the seismic design situations.
• Therefore this structure will alternate to better portal better portal of better offset at symmetry in nature.
• The column beams connection should be in proper cross section area, then it can achieeve lateral stiffness, mass regularity, moment resisting factor.
• As we considere beam-sway mechanism in strong column weak beam design frames is better because it can achieve unform spreadings, global inelastic displacement demands at roof level, to all storeys.

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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.

ans:

• This is unsuitable for heavy seismic zone areas.
• The interior columns are in unsymmetric.
• The partition wall are provided through the base of beam, should support the lateral deformation due to the structure.
• The interiors beams will supports the slab, then the lateral load resisting the failure due to earthquakes.
• For this irregular columns in plan, there we provided the flat slabs, because its directly stay in a column centroidal axis.
• For here, the beams at different locations is irregular in plan and are continuous and is disallowed to resist the seismic load in the region.
• The flat sab is more appropriate than a regular beam column junctions, because of as its provide support to the columns without any provision of the beam, which reduces the weight of the building and also helps in the ductility of the structure by indirectly.
• For the solution of this structure, we provide the shear wall from the foundation of structure through vertical components, it should minimize the loss of sudden failure occur due to lateral force acting on structure.

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