The present study investigates the seismic behavior of multi-story building using damping devices strategically located within the lateral load resisting elements. It concentrates on a retrofitting strategy with passive energy dissipation device known as Fluid Viscous Damper (FVD) which will be applicable to new design as well as retrofitting existing buildings to ensure seismic safety by fitting damping devices which can transform a wall panel into a damping element. The first study involves analysis of a nine-story model having cut-outs and the use of the dampers of different configuration in these structures. The second study involves the use the diagonal brace configuration dampers provided in the cutout sections of 2D 9, 18, 27 storey structures and 3D 27 storey with core wall structure at three consecutive story levels each. For the second study, the cut out locations is varied depending on their relative positions. The relative position is the ratio of the total height of the structure to the upper edge of the topmost cut-out.
These structures were initially modeled and time history analysis was performed on the structure without FVD and the structure retrofitted with FVD. Three different ground motions were used for the analysis. Results of the un- retrofitted structures are then compared with a retrofitted structure in terms of peak story displacements, roof accelerations, and pseudo-spectral accelerations.
Study shows that there has been a significant reduction in seismic demands for a structure retrofitted with FVD in terms of peak storey displacements, pseudo-spectral accelerations and roof accelerations when the dampers are placed at lower three cut outs i.e. with high relative position. It is also observed that damping coefficient value obtained is least for upper toggle-brace configuration out of the four different damper configurations and with maximum reduction compared to other configurations. For modeling and analysis purpose the software SAP2000® is used.
Through the study it could be concluded that FVD significantly reduces the seismic demands of the structure in terms of peak storey displacements, pseudo-spectral accelerations and roof accelerations. This suggests that FVDs can be efficiently used in retrofitting. Also damping coefficient value obtained is least for upper toggle-brace configuration out of the four different damper configurations suggesting this is the most efficient configuration for retrofitting.
Table of Contents
1. INTRODUCTION
1.1 General
1.2 Modes of failure of Reinforced concrete shear walls
1.3 Different retrofitting techniques for RC shear walls
1.4 Motivation of study
1.5 Objective of work
1.6 Organization of report
2. LITERATURE REVIEW
2.1 Introduction
2.2 Introduction to the project title
2.3 Literature review
2.4 Summarized outcome of the literature review
2.5 Conclusion
3. METHODOLOGY
3.1 Introduction
3.2 Methodology followed
3.3 Model description
4. RESULT ANALYSIS
4.1 Introduction
4.2 Results and discussions for 9 storey structure with different configuration
4.3 Results for 9, 18 and 27,3d core 27 storey structures
5. CONCLUSION AND FUTURE SCOPE OF WORK
5.1 Brief summary of work
5.2 Conclusion
5.3 Future scope of work
Objectives and Research Focus
The primary objective of this research is to investigate the seismic response of multi-storey reinforced concrete buildings retrofitted with Fluid Viscous Dampers (FVDs) strategically placed within shear wall cut-outs. The work aims to provide a practical design procedure for practicing engineers to effectively mitigate seismic demands.
- Analysis of seismic performance for non-retrofitted versus FVD-retrofitted shear wall structures.
- Evaluation and comparison of different damper configurations (diagonal, chevron, upper and lower toggle).
- Assessment of optimal damper placement within building heights (relative positions) for various structure sizes (9, 18, and 27 storeys).
- Reduction of seismic demand parameters including peak storey displacements, roof accelerations, and pseudo spectral accelerations.
Excerpt from the Book
1.2 Modes of failure of Reinforced concrete shear walls
There are several modes of damage/failure of RC shear walls that were observed from post-earthquake events’ reconnaissance or reported from controlled experimental research work. It is important to be able to predict and evaluate the expected response of an existing RC wall in order to be able to choose the most suitable and effective retrofitting technique that meets a target performance. The following subsections identify the most common failure modes of RC shear walls.
1.2.1 Flexural failure
In this mode of failure, considerable flexure cracks appear near the bottom part of the tensile zone of the wall, yielding of tensile steel or compression steel may occur, crushing of concrete in the compression zone could happen at the ultimate stages. The compression steel also might buckle if the concrete cover in the compression zone spalled off. This type of failure occurs when the flexural capacity of the RC wall is lower than its shear capacity, which is usually the case for high-rise walls. Figure 2 shows the crack pattern for a wall failed in a flexure manner (Greifenhagen and Lestuzzi, 2005).
Summary of Chapters
Chapter 1 INTRODUCTION: This chapter introduces the role of RC shear walls in resisting lateral loads and the necessity for seismic retrofitting, while outlining the research motivation and objectives.
Chapter 2 LITERATURE REVIEW: This chapter reviews previous research on retrofitting techniques and damping devices, establishing the research gap regarding FVD application in shear wall cut-outs.
Chapter 3 METHODOLOGY: This chapter details the modeling process, the time history analysis parameters, and the iterative procedure used to determine the damping coefficients for the FVDs.
Chapter 4 RESULT ANALYSIS: This chapter presents the analytical results of the study, evaluating the impact of different damper configurations and placements on the seismic performance of 9, 18, and 27-storey structures.
Chapter 5 CONCLUSION AND FUTURE SCOPE OF WORK: This chapter summarizes the research findings, confirming the effectiveness of FVDs in reducing seismic demands, and suggests future research directions such as exploring non-linear FVD behavior.
Key Terms
Seismic retrofitting, Reinforced Concrete (RC) shear walls, Fluid Viscous Dampers (FVD), Energy dissipation, Seismic mitigation, Toggle-brace configuration, Time history analysis, SAP2000, Peak storey displacement, Pseudo spectral acceleration, Lateral load resisting system, Structural damping, Dynamic excitation, Seismic performance, Multi-storey buildings.
Frequently Asked Questions
What is the primary focus of this research?
The research focuses on the seismic protection of multi-storey buildings by installing Fluid Viscous Dampers (FVDs) within the cut-out sections of reinforced concrete shear walls.
What are the key themes addressed in this report?
The report covers modes of shear wall failure, various retrofitting techniques (such as concrete replacement and steel bracing), the mechanics of FVDs, and optimal damping configurations.
What is the main objective of the work?
The objective is to study the seismic response of structures retrofitted with FVDs and to determine the most efficient damper configuration and placement to reduce seismic demands like displacement and acceleration.
Which methodology is employed in this study?
The study uses linear time history analysis performed via the SAP2000 software to evaluate the structural behavior under various recorded earthquake ground motions.
What is covered in the main body of the report?
The main body includes a thorough literature review, a detailed explanation of the modeling methodology and damper design procedures, and an extensive analysis of results for various building heights and damper configurations.
Which keywords best characterize this work?
Key terms include Seismic retrofitting, RC shear walls, Fluid Viscous Dampers, energy dissipation, and lateral load resistance.
Why are toggle-brace configurations significant?
The study indicates that toggle-brace configurations are particularly efficient because they yield lower damping coefficient values, which can reduce the overall cost of the retrofitting process.
What role does the "relative position" of dampers play?
The research concludes that placing dampers in lower levels (higher relative position) generally achieves the maximum reduction in peak deflection and peak acceleration for the analyzed structures.
- Quote paper
- Sachin Kuckian (Author), 2015, A study on seismic response of reinforced structures retrofitted with fluid viscous dampers in shear walls, Munich, GRIN Verlag, https://www.grin.com/document/496594
