Project 1_Comparative study of different storey buildings for Seismic forces

Comparative study of different storey buildings for Seismic forces:

Factors Influencing the Dynamic Characteristics of a Building:

1. Mass Distribution – Heavier buildings generally have longer natural periods.
2. Stiffness Distribution – Stiffer buildings have shorter natural periods and higher frequencies.
3. Building Height & Geometry – Taller buildings tend to have lower frequencies and longer natural periods.
4. Foundation Conditions – Softer soil increases flexibility and lengthens the natural period.
5. Structural System & Materials – RCC and steel structures exhibit different dynamic responses.
6. Damping Characteristics – Higher damping reduces response amplitudes but does not significantly alter natural frequencies.
7. Irregularities (Plan & Vertical) – Irregularities cause complex mode shapes and may introduce torsional effects.

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Factors Influencing the Natural Period of a Building:

1. Height of the Building – T∝HT \propto HT∝H; taller buildings have longer periods.
2. Mass Distribution – Higher mass results in a longer period.
3. Stiffness of Structural Elements – Greater stiffness shortens the period.
4. Foundation Flexibility – Softer foundations increase the natural period.
5. Structural System – Shear wall, moment-resisting frame, or braced frame systems affect stiffness and period.

Empirical formulas from IS 1893 (Part 1):

• Moment Resisting Frame: T=0.075H0.75T (for RC buildings)
• Shear Wall System: T=0.09H/d

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Factors Influencing the Mode Shape of Oscillations:

1. Building Configuration – Regular buildings have predictable mode shapes, while irregularities cause complex behavior.
2. Stiffness and Mass Distribution – Uniform stiffness leads to symmetric mode shapes; non-uniform stiffness results in localized effects.
3. Torsional Irregularity – Buildings with asymmetric mass or stiffness experience coupled torsional modes.
4. Boundary Conditions – Fixed or flexible base conditions affect the mode shapes.
5. Soil-Structure Interaction – Soft soil can modify mode shapes by introducing additional flexibility.
6. Damping and Energy Dissipation Devices – These alter the amplitude but do not significantly affect mode shapes.

ETABS MODEL AND AANALYSIS REPORT :

MODEL-A

MODEL-B

MODEL-C

MODEL -D

MODEL-E

MODEL-F

MODEL-G

MODEL-H