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.

the restraint of floor shrinkage :

a) this building looks like symmetric in both directions  and the shear walls are located at all coeners with L shape.so.. which one is having higher restrain to shrinkage so it will lead to cracks on the floor.

b) this building also looks like symmetric both directions and the shear walls are located at all edges. so.. this having medium restrain to shrinkage.

c) this building is unsymmetrical in y- direction . shear walls are counstructed at edges and corners . so it will produce less restrain to shrinkage so it will lwead to less craks on the floor.

the lateral stiffness :

a) comparitively lower lateral stiffness  in both directions

b) it have uniform and higher lateral stiffness.in both directions

c) this is non uniform in both directions.

the torsional one with respect to the vertical axis :

a)corner walls are more effective resistance to twisting.

b) edge walls are good effective.

c) irregular walls are provided. this condition is worst for torsional resistance.

the vertical reinforcement required for the same total flexural capacity at the base :

a and c are subjected to fluxural moments and heavy twisting moments so those required more vertical reinforcement.

b)this walls are subjected to nominal twisting moment. so it will require less vertical reinforcement.

the static eccentricity :

a and b are symmetrical structures so they are excused and only C is unsymmetrical structure this have the static eccentricity it is worthy 

the system’s redundancy :

a and b having the lateral loads are placed uniformly in both direction. but c is have concentrated loads on both axes.so a and b are more redandant than c.

foundation systems :

a) this structure is in shape of L so it is hard to connect the geometries.so it is recommended to have the pherperal box foundation.

b and c ) those are straight line structures so it is easy to fix the geometries .it might be with the isolated / strip footings.

architectural constraints :

a) it is well suited for the architectural porpuse.

b) the structure may be discussed with the client it could be constaraint to the walls .

c) it does no t suit for the architectural and commertial purpose.

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.

Deffects in the given plan : 

Actually beams will connect to the columns ,but in this case the beams are conneting to the other beams. so.. the indirect lateral load is transferd beam to beam then the main beam might have effect 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 torsional moment (Torsional flexibility) in both X and Y directions.

Strong beam and weak column - here, columns = 25 x 25 and beams are 25 x 50 .the beam depth is greater then the column size, this will takes place of strong beam and weak column case is considered..so..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 sizes for column.

Arrangement of columns to correct way :

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.

observations in the plan :

  this plan not suited for the seismic zone areas ,why because in this plan columns does not arranged symmetriclly and uniformly ,and the interior columns are provide less even the span ration is more. those are also in irregular pattern and they are not in a stright line.defently the lateral load will distributed in random ways.so there is a lot of chances to failure.

Suggestion on the Lateral load system & Its foundation:

• suggested shear walls around the corners and provide them with box foundations.the columns should be supported by the foundation of isolated / strip.
• 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 should be heavier than the right
• Corner Shear walls shall preferably be supported over a box foundation. Shear wallsshould be connected by Link beams to transfer shear from one to the other.
• The internal columns shall be supported by isolated footings. Those isolated footingscan be connected with Shear walls through Tie beams.