Conceptual design of a building with columns and shear walls

1) Aim & Introduction : 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.

Procedure :

1)For Condition Restraint of floor Shrinkage

a) Observation :Full Restraints are observed at all Corners

Result : a will Have Higher restraint to Shrinkage thus leads to Crack in Floor.

b) Observartion : Corneres are Left free But The Restraints along the edges

Result : b has Average restraint to Shrinkage

c) Observation : Non - Uniform Restraints developed as seen

Result : c will not effectively Restrain the Shrinkage as possiblity of less cracks occurs.

2) For Condition for Lateral stiffness

a) Observation : lower Lateral stiffness in both x and Y axis

b) Observation : Uniform and Comaparatively higher lateral stiffness in both X and y

c) Observation : Non Uniform lateral Stiffness in both X and y

Result : Option b will Provide Higher lateral Stiffness for a pure Seismic Acceleration in X and y Directions

3)For Condition Torsion with Respect to Vertical Axis

a) Observation : Corner Wall provides more resistance to twist

b)Observation : Edge walls provide good resistance to twist

c) Observation : irregular Wall Provides Very Poor Resistance to twist

Result : Option a will be the Best option with respect to Torsional Resistance whereas Option c is Worst at Scenario.

4)For Condition Certical Reinforcement for Similar base Capacity

a) Observation : Walls are Subjected to nominal Flexural moment and heavy twisting Moment

b) Observation : Walls are Subjected to Nominal twisting moment

c) Observation : Walls Are Subjected to Heavy Flexural moment and twisting Moment.

Result : Option c will require higher vertical reinforcement and option b will require the least.

For Condition Static eccentricity

a) Observation : It is Structurally Symmetric

b) Observation : It is Structurally Symmetric

c) Observation : It is Un-Symmetric

Result : Only Option c will have static eccentricity and it is significant.

For Condition System redundancy

a) Observation : Uniform placement of lateral load supports in both the axes

b) Observation : Uniform placement of lateral load supports in both the axes

c) Observation :Concentrated lateral load supports in the both the axes

Result : Option a and b are More redundnat that OPtion c

For Condition Foundation System

a) Observation : Due to L shaped walls the geometry of the foundation and its design will be critical

b) Observation : Walls are in line.easy to fix the geometry and design of foundation

c) Observation : wall are in lines and Concentrated.easy to fix the geometry of foundation but critical in design

result : Option a and c shall be incorporated with isolated footing option b is reccommended to have periphreal box founfaation

Condition for architectural Constraints

a) Observation :walls obstruct only Corners

b) Observation : walls Obstruct the Faces of Buildinh

c) Observation : vertical wall will not allow passage

Reult :Option a is preffered one.OPtion b Subjected to Discusion and option c it cant be preffered.

2) Aim & Introduction :

To 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.

Procedure :

Issues in the Given framing Plan

• the Issue Occurs at C5 to C8 path
• also occurs at dislocation of C6

Indirect Lateral Load transfer in X and Y Directions - The beams Connecting to the 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 centre of mass and centr eof stiffness the higher the torsional moment of the building.As per the given plan eccentricity the building is subjected to higher torsional Moment in both x and y directions.

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 the column.If the column reinforcement is adequately greater than that of beams,we are okay and since we do not have reinforcement detail it is doubtful.It is recommended to have slight bigger size columns.

Result :

The alternate scheme can be represented by having the beams and columns at straight line so that it can withstand the load and distribute the load as per the reactions takes place.

3) Aim & Introduction : To know 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.

Procedure :

Observation in the frame plan

• Floor Plan - the floor Plan of the building is not either unifor nor symmetric.So naturally lateral load induced in the floor will not have 100% influence in same direction.Definitely a Special lateral load resisting system for these torsional moments should be accomdated
• Random internal Columns - Since the Internal Column are random,they are unable to transfer lateral load efficiently and can not achieve desirable building response.so we have to assume and design those columns for only gravity load.
• Floor to floor variation in partition walls and Beams - partition walls provide an important mass control in a Building and beams play key role in shear transfer from floor to beam. All these elements are not in order.So heavy Distortion and Distribution of lateral load will happen.

Result:

Suggestion in lateral Laod and Foundation design :

• 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. so Corner shear walls on the left side should be heavier than the right side.
• Corner Shear walls shall preferably be supported over a box foundation.shear walls should be connected by link beams to transfer shear from one to the other.
• the internal columns shall be supported by isolated footings.those isolalted footings can be connected with shear walls through the beams.