Concept on positioning of Columns

Challenge 4

Question 1:

• The given layout of framing plan is symmetric.
• Generally, a well distributed symmetrical plan layout of the structural elements like beams, columns is appropriate to achieve uniformity.
• The symmetric nature also makes the structure more reliable to resist the earthquake forces.
• Having same or equivalent resistance and stiffness in all direction is one among the desired features to resist the seismic effect, thus it should also be considered
• The Horizontal seismic motion is a bi-directional phenomenon and, thus the building should able to resist this horizontal actions in any direction
• The structural pattern of the building in plan should be made orthogonal to make it resistant to the seismic action in any direction.

Question 2:

• The building is said to be torsional irregular when the maximum horizontal displacement of any floor in the direction of lateral force at any floor is more than 1.5 times its minimum horizontal displacement at the far end side of the same floor in the same direction, In this case the building configuration must be revised and the seismic response of the building must be done using dynamic analysis.
• Generally, the modal response spectrum analysis is done for building with irregularities in elevation, ie; on the linear elastic response. Along with this the distribution in plan of the lateral stiffness and mass should be symmetrical with the two horizontal axis.
• The damage in the given building can be due to various reasons, and these can be due to the combined failure also some of them are include soft storey irregularity, Stiff and strong upper floor due to masonary fill, redundancy irregularity, In plane flexibility irregularity(in torsion), mass irregularity.
• The first storey must have lesser strength and stiffness compares to the other storeys which are stiffened by masonry in fill walls. Extreme deflections are the result of increased flexibility. This is called the Soft storey irregularity, which can be minimized by providing least partitions in the particular levels.
• The load carried by each levels in the horizontal element differs, as we go on with rise rise structures, in this case the lateral force will also vary for each coloumn with respect to the demanded load. This is known as the Redundancy irregularity, which can be minimised by equvalizing and maintaining the uniform distribution of load to all the load bearing element.
• When the mass of the lower floors are higher when compared to the upper floors, then an irregularity can occur. This is known as Mass irregularity, which can be minimized by adopting light weight construction material , thus making the mass almost equal.
• Thus, to avoid all these above mentioned irregularities,

1. The structure should be build in a symmetric manner
2. The building framing should be revised, if the structure is torsionally irregular.
3. Use light weight masonry, if there is mass irregularity
4. Coloumns with same size should be provided in the whole structure

Question 3:

• From the given images, we can observe that:-

1. The masonry fill provided is very high, which provide higher stiffness
2. Mass irregularity within the building which is caused as a result of the providing the top and bottom bays as full of room and the middle bay for corridor, which created internal collapse of the structure, which we can see from the third figure
3. The disscipation of the lateral force can be also observed as there is no beams provided in the plan, this can also lead to internal collapse of the structure, creating redundancy irregularity, especially during earth quakes.

• As a solution, we can list out the following:-

1. Masonry filling should be provided appropreately
2. Adopt light weight construction material in the lower floors, so thatthe mass of the floors will be equal
3. Keep the floor width as same as possible to withstand the longitudinal irregularity of the structure to any impact.
4. Provide columns and beams, to carry the load uniformly, thus reducing the redundancy irregularities.