Investigation on the Structural Behaviour of High-Rise Structures Exposed to Dynamic Loading in a Seismic Zone using Various Bracing Methods

Abstract

Bracing is a common method used by multi-story buildings to counteract the lateral stresses that are applied by the environment. In a frame construction, the use of bracing is a method that is both highly effective and cost-efficient in resisting horizontal forces. Structures that have their frames braced are meant to be more resistant to the effects of earthquakes and wind loads. Because of their exceptional rigidity, braced frames are well suited for seismic retrofitting. Steel members are almost always used in the construction of braced frames. Vertical loads are supported by the structural parts of the building, such as beams and columns, whereas lateral loads are supported by the bracing system. By using braced frames, it is possible to minimize the amount of side displacement as well as the bending moment in the columns. Steel bracing is adaptable and can be constructed to fulfill the needed strength and stiffness requirements. In addition to being cost-effective, quick to install, and taking up less space than wood bracing, steel bracing is also gentle on the environment. It makes it possible to obtain a large increase in lateral stiffness while simultaneously increasing weight just a little. This indicates that preexisting constructions that have low side stiffness may considerably benefit from incorporating it. Bracings are given in RCC constructions in order to withstand lateral stresses such as those caused by earthquakes and wind pressure. There are several different kinds of conventional bracing that may be employed. The purpose of this examination is to analyze the dynamic behavior of a multi-story building located in a seismic zone and equipped with a variety of bracings. The work being done right now is on a multi-story structure that is situated in Zone V, and it is being done on three distinct stories: 12, 20, and 30. The research was carried out using X, K, V, and O bracings, as well as X-O, V-O, and K-O bracings for each individual tale. FEM uses SAP 2000 to perform a non-linear time history analysis to complete the research. In addition, we established a number of factors, such as tale displacement and story drift. When compared to other sorts of combinations of bracing and individual bracings, it has been shown that the K-O bracing combination results in 12% less narrative displacement and 11% less story drift.

Introduction

Earthquakes cause thousands of deaths annually, making seismic engineering critical to reduce loss of life and damage. Buildings in seismic zones commonly use frame structures designed to withstand lateral forces caused by earthquakes. An earthquake is viewed as an energy exchange between the ground and structure; thus, earthquake-resistant design focuses on safely storing and dissipating seismic energy to prevent collapse.

2. Need for the Study

• Bracing systems are essential for resisting lateral loads like wind and earthquakes, especially in multi-story buildings.

• Steel bracings provide high stiffness with minimal added weight, improving lateral displacement control and reducing bending moments.

• Conventional bracings (e.g., K-braces) have limitations, especially in high seismic zones.

• Combining different bracing types can yield more effective, economical solutions.

• This study proposes and evaluates a new bracing system along with combinations of bracing types.

3. Objectives

• Analyze seismic response of regular reinforced concrete (RCC) buildings using nonlinear time history analysis (NLTHA).

• Identify the most effective bracing types among O-grid, X-grid, inverted V-grid, K-grid, and combinations (O-X, O-K, O-V) that minimize lateral displacement, story drift, and increase shear capacity.

• Compare roof displacement and time periods across different bracing systems.

4. Scope

• Focus on symmetric high-rise RCC buildings of 12, 20, and 30 stories.

• Analyze buildings designed per IS-1893:2016 seismic code using SAP 2000 software.

• Study bracing effects on lateral stiffness and seismic performance for multiple configurations.

5. Methodology

• Models with 5x5 bays (each 6m) and uniform 3m story height.

• Eight building models analyzed:

  1. No brace (normal)

  2. K-brace

  3. O-brace

  4. X-brace

  5. V-brace

  6. Combination X-O brace

  7. Combination K-O brace

  8. Combination V-O brace

• Nonlinear dynamic Time History Analysis performed to obtain story displacement data.

6. Results and Discussion

• Story displacement was calculated and compared for the 30-story building under different bracing systems.

• O-bracing alone showed higher displacement compared to others.

• Combination bracings (e.g., K-O, V-O, X-O) demonstrated better performance, reducing lateral displacements more effectively.

• Combination bracing also offers a more economical solution than using individual brace types alone.

Conclusion

Based on the observations and the results obtained during this study, the following conclusions can be arrived: 1) As per the results obtained from the analysis of different bracing method, K brace (65.8 mm) are less effective when compared with X (58.5 mm) and V (58.13mm) brace, as displacement due to K brace is 1.2 times of the displacement due to V brace. 2) K-O brace combination is effective as the displacement is less compared to other combination as V-O brace system. 3) Based on above results, it is concluded that concentrically braced frames had high ductility performance. Concentrically bracing system can easily retrofit with framed structures and can effectively control the various responses of the buildings such as story drift, displacement etc 4) Story displacement is also reduced to a great level such as X bracing reduces up to 58 mm, V bracing reduces up to 58 mm, K bracing reduces up to 65 mm , when compared to un braced structure with 82 mm. X bracing and V bracing are found to be more effective to control the story displacements 5) This study proposed new type of bracing system O-Grid bracing system, a braced frame with a circular brace attached to a moment-resistant frame (MRF) with a joint connection to resist lateral forces. O-Grid braces, unlike other braces, have a structure and form that allows them to be employed in any portion of the structure without sacrificing architectural space or architectural form. The O-Grid bracing system is ductile and rigid. 6) Story drift in the MRF model is more than other systems, and the x-bracing model is less than other systems. The combination of the k-O model has 11% lower story drift (0.00047) than other models, and in all models story drift is within the limit as per code. Providing the combination of K-O grid is more effective and economical compared to other combinations and also individual O grid is not much effective compared to combinations of bracings

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Copyright

Copyright © 2025 Jakki Vishakha , Lakshmi . 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.