Conceptual design of a building with columns and shear walls

AIM -

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 -

(A) (B) (C)

1. STATIC ECENTRICITY -

OBSERVATION -

. Structurraly symmetric . Structurraly symmetric . un -symmetric

CONCLISION -

ONLY OPTION (C) will have static eccentricity and it is significant.

2. SYESTEM REDUNDANCY -

OBSERVATION -

. Uniform placement of latteral . uniform placement of latteral . concentrated latteral load supports

loads support in both the axes load supports in both the axes. in both the axes.

CONCLUSION -

OPTION (A) AND (B) ARE MORE REDUNDANT THAN OPTION (C).

2. SYESTEM REDUNDANCY -

OBSERVATION -

. Uniform placement of latteral . uniform placement of latteral . concentrated latteral load supports

loads support in both the axes load supports in both the axes. in both the axes.

CONCLUSION -

OPTION (A) AND (B) ARE MORE REDUNDANT THAN OPTION (C).

3. FOUNDATION SYESTEM -

OBSERVATION -

. Due to (L) Shaped walls the . walls are in line easy to . walls are in line and concentrated. easy to

goemetry foundation and fix the geometry and design fix geometry of foundation but critical in design.

its design will be critical. of foundation.

CONCLUSION -

Option (B) and Option (C) shall be incorporated with isolated footing/ strip footings option a is reccomondade to have

peripheral box foundation.

4. ARCHITECTURAL CONSTRAINTS -

OBSERVATION

. WALL Obstruct Only Coorners. . walls obstruct the face of building. . vertical wall will not allow passage.

CONCLUSION -

Architecturally speaking option (A) is the preffered one. option (B) is subject to discussion. option (C) will not be accepted for both architecturally and commercially.

AIM -

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 - The FOllowing issue has given in the framing plan.

1. Indirect Latteral Load transfer in X and y Directions -

the beam are connecting to another beams which is ineffective during latteral load transfer. in such condition the primery beam is prone to shear faillure.

incopmplete latteral load transfer in x - direction. which is marked in red circle.

improper lateral load transfer in y - direction. which is shown in blue circle in the above given sketch.

2. ECCENTRICITY -

the longer the distance between center of mass and center of stiffnes 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.

a blue mark is shown torsional influence during x direction excitation.

and a red mark is shown torsional influence during y- direction excitation.

3. STRONG BEAM WEAK COLUMN POSSIBILITY -

The size of column majorly mention as 25x25 cm but all the beams have much deeper section (50cm). inertia of beam visually higher then column. if the column reinforcement is adequetly greater then that of beam we are okey and since we do not have the reinforcement detail this is doughtful. it is recommendet to have slight bigger size of column.

in above given sketch red circle is shown the column size which is (25x25) cm. and blue circle showing the beam size which is (25x50)cm. which is larger then the column. so it is shown the STRONG BEAM WEAK COLUMN POSSIBILITY.

ALTERNATE SCHEME -

UN SEMMETRY POSITION OF THE COLUMN.

SYEMMETRY POSITION OF THE COLUMN. AND BEAM

Following Thing which i have adjust to create inlinged column.

1. center column was not in line so i inlinged the column in center position.

2. shifting the right side column to make it inlinged column. and cantiliver length has reduce and its become (0.7)

3. in bottom side center column has extended size. so i reduce the extended size and make it horizontal inlinged column.

AIM -

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 - THE FOLLOWING OBSERVATION OF GIVEN FRAMING PLAN.

1. FLOOR PLAN -

The floor Plan of building is not either uniform or symmetric. so naturally any load induce in the floor will not have 100% influence in same direction. definetly a special lateral load resisting syestem for these torsional moment should be accommodated.

2. RANDOM INTERNAL COLUMN -

Since The Internal columns are Random, they are unable to transfer lateral load and can not achive desirable building response. so we have to assume and design those columns for only gravity loads.

3. FLOOR TO FLOOR VARIATIONS IN PARTITION WALLS AND BEAM -

Partition walls provide an important mass controle in building and beam play key role in shear tansfer from floor to beam. all these elements are not in order. so heavy distorsion and distribution of lateral loads will happen.

SUGGETION ON THE LATERAL LOAD SYESTEM AND ITS FOUNDATION -

1. Heavy torsional forces should br controlled by respective load syestem. so " corner shear wall suggested "

2. The proportion of floor area is greater on the left side or then the right side (irreegular quadrilateral). so corner shear wall on the left side should br heaviour then the right.

3. corner shear wall shall preferably be supported over a box foundation. shear wall should b connect by link beams to transfer shear from one to other.

4. the internal column shall be supported by isolated footings. those isolated footings can be connected eith shear walls to tie beams.

PROPOSED SCHEMETIC PLAN OF LATERAL LOAD SYESTEM -

All Corner shear wall will be supported by a box foundation. they will provide stiffer supported syestem shear wall which are subjected to torsion.

for sub structure

internal columns are supported to isolated footings and to avoid to floor damage column are not design for gravity.

to avoid those kind of effects we are connecting the isolated footing foundation with tie beam.