An Analysis of the Structural Behaviour of Irregular Structures in Response to Earthquake Monitoring

Abstract

Since the existence of lace in horizontal space has encouraged people to soar higher, there has been a consistent trend towards the creation of taller structures. However, pushing the vertical limit further increases the hazard factor. We must assess the building for a range of loads to ensure safety. An examination of a building is required to ascertain its seismic resistance because the behavior of a structure is critical during an earthquake. An earthquake may bring a high-rise structure to the ground, a risk that is difficult to predict. Therefore, it is necessary to do a seismic force assessment on different types of buildings. The seismic officious can use the seismic coefficient technique to analyses small and medium-sized buildings up to a height of forty meters. d of analysis that requires less manual computation. The overall shape, size, and geometry of a structure all have a significant role in defining its behavior. since asymmetry is because asymmetrical structures are more likely to exhibit critical behavior during an earthquake than symmetrical ones. of the characteristics of symmetrical, L-shaped, and T-shaped and build RC structures during earthquakes to better understand the variations in seismic loading and behavior that may arise due to form variances. The seismic ETABS software aids in the seismic coefficient study of a ten-story building with three-meter-tall levels and a varied plan shape, including symmetrical, L-shaped, and T-shaped configurations. al inspection of a ten-story structure takes a long time and increases the chance of errors. ETABS can simplify, improve efficiency, and increase the accuracy of a structure\'s analysis. The analysis is conducting the analysis by adhering to IS 1893:2002 (Part 1). shaped RC structures have their own response, which includes, among other things, lateral pressures, base shear, storey drift, and storey shear. We use the reaction of the variously shaped buildings to compare the findings.

Introduction

• An earthquake is a tremor caused by a sudden release of energy in the Earth's crust.

• Can vary in intensity — from barely noticeable to extremely destructive.

• Main cause: rupture of geological faults.

• Other causes: volcanic activity, landslides, nuclear tests, and mining explosions.

2. Impact on Buildings:

• Seismic waves cause the foundation to move, while the top of the building initially resists due to inertia (Newton's First Law).

• This differential movement creates internal forces, stressing the walls and columns.

• Similar to a person losing balance in a suddenly moving bus — the base moves, but the upper body resists.

3. Research Objectives:

1. Study movement of high-rise reinforced concrete buildings during earthquakes.

2. Analyze design flaws contributing to poor seismic response.

3. Use formulas to compute lateral seismic forces at each level.

4. Determine the maximum structural response.

5. Compare behavior of different building shapes (Rectangular, L-shaped, T-shaped).

6. Analyze torsional movement from unequal mass/stiffness distribution.

7. Use ETABS software for accurate simulation and results.

4. Methodology:

• Used Seismic Coefficient Method (simple and suitable for buildings up to 40m tall).

• Steps:

  • Calculate design base shear.

  • Distribute it across all floors.

  • Model three building shapes in ETABS: Rectangular, L-shaped, and T-shaped.

Input Materials:

• Concrete: M25

• Steel: Fe415

Building Shapes Modeled:

• Rectangular

• L-shaped

• T-shaped

5. Results & Evaluation:

A. Center of Mass & Rigidity:

• Varies slightly by shape, leading to torsional effects during seismic events.

B. Seismic Weight:

• Heaviest: Rectangular (118,022.96 kN)

• Lightest: T-shape (75,078.63 kN)

C. Story Shear:

• Shear forces increase with building height.

• Rectangular building has highest story shear values due to higher mass.

D. Story Drift (Lateral Movement per Floor):

• Maximum story drift observed: ~32 mm

• As per Indian Standards (IS Code):

  • Allowable drift = 0.004 × height = 0.004 × 30 m = 120 mm

  • ? All values are within safe limits

Conclusion

1) The underlying mass of the structure is necessary for base shear to occur in a building. Base shear is performed by the building\'s foundation. 2) In the event that the suggested construction has an irregularity, the centre of mass and the centre of stiffness will take on an eccentricity as a consequence. Given the irregularity, this eccentricity will be the result of the irregularity. 3) There is a difference in the behaviour of all three-shaped buildings in both directions due to the fact that the size of the building changes in both directions. The reason for this is because the dimensions of the structure change in a different way in each direction. 4) When compared to the patterns of the rectangular and L-shaped constructions, the T- shaped construction has a greater degree of irregularity in its arrangement. This is because the T-shaped construction is divided into three sections. 5) It has been shown via thorough observation that the three levels of all three-shaped buildings exhibit a larger drift value than any other level. This is true regardless of the direction in which the three-shaped constructions stand. It does not matter which way you go; this is always the case. 6) The displacement of the building is found to be greater when the direction of the earthquake is perpendicular to the longer face of the structure. This is something that has been discovered. The reason for this is that the earthquake is having an effect on the longer face of the construction of the building. Within the context of this particular circumstance, there is a considerable amount of displacement originating from the x- direction. 7) The torque movement that is created as a result of eccentricity is proven to have a direct link with mass, as evidenced by the observations that have been made. An increase in the torsional movement of a structure occurs in a manner that is directly proportional to the mass of the building. 8) There is a substantial amount of base shear that takes place in buildings that have a rectangular shape. Rectangular structures are capable of suffering large torsional movements since they are exposed to a huge amount of base shear. This is because they are rectangular in shape. 9) When an earthquake strikes in a direction that is perpendicular to the shorter face of a structure, the rotational movement of the building is relatively bigger than when the earthquake strikes in a vertical direction. This is because the shorter face of the structure is facing the direction of the earthquake. In this particular instance, the direction that displays the largest degree of torsional movement is the Y-direction. 10) In addition, we are able to establish a direct relationship between eccentricity and shape, in addition to the connection that exists between mass and torsion inside anything.

References

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Copyright

Copyright © 2025 Chengala Krishnaveni , Dr. Aruna Prasur. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.