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-

1 ) For structure (A)

• The structure is considered as asymmetric in nature.
• there is some uncertainty concerning certain features of the seismic response of non-rectangular walls.
• it occurs lack of tensile capacity and force configuration.
• These wall have high stiffness and strength in both direction , hence are subjected biaxial bending and bi directional shears during earthquakes.

2 ) For structure(B)

• The structure frame is considered as symmetric in placed the shear wall.
• The shear walla are arranged in similarity and symmetric.
• it can be considered at every storey to fairly uniform resistant in seismic forces and deformation demands, minimizing the uncertainty.

3 ) For structure(c)

• The structure is considered to bs asymmetric in nature ,because of the ahear wall are provided are not arranged in two orthogonal horizontal directons.
• The foundation shear wall and columns are arranged different arrangements,so here take up huge amount moments in case of during earthquakes.
• this structure can not be able to carry the load equally in either direction.
• in left side wall has a more eccentricity so failure will be less.

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-

• 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.

• 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 tension moment.

• Strong beam weak column possibility - The size of column majorly mentioned as 25cm x 25cm . but all the beams have much deeper section.inertia of beam is visually higher than column.

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-

• It is totally unsuitable design for heavy seismic zone areas.
• interior columns are unsymetric nature.
• the interiors beams will support the slab,then the lateral load resisting the failure due to earthquakes.
• for this type of columns we can provide flat slabs.
• in this plan the flat slab is more appropriate than regular beam because support to the columns without any provision of the beam which reduces the weight of building.