Pushover analysis is a widely used method in structural engineering to assess the performance of masonry structures, especially during strong seismic events. This analysis technique allows engineers to evaluate the capacity and behavior of a masonry structure under increasing levels of applied forces, simulating the effects of lateral loads. In order to perform pushover analysis for masonry structures using ETABS software, several crucial steps need to be followed. These include defining material properties, establishing the structural model, applying lateral loads, and analyzing the results.
How Do You Perform a Pushover Analysis?
Performing a pushover analysis involves a two-step process that aids in understanding the behavior and response of a structure. The first step is known as the pushover or “Capacity Curve” determination. This involves subjecting a model of the structure to incremental static loads, which gradually increases the applied load until the structure reaches it’s limit of non-linear behavior. By doing this, the capacity curve is derived, which demonstrates the capacity of the structure to resist displacement under increasing loads.
To carry out a pushover analysis, various software programs are available that employ numerical methods to simulate the behavior of the structure. These programs utilize finite element analysis techniques, considering the material properties, loads, and boundary conditions to accurately model the structures response. The analysis can consider different failure modes or limit states, such as global collapse or local damage, providing a comprehensive understanding of the structures behavior under extreme conditions.
During the pushover analysis, it’s essential to consider the selection of ground motion records for the input analysis. These records should represent a range of potential earthquake scenarios that may affect the structure. The utilization of appropriate ground motion records ensures that the analysis provides accurate results, reflecting the actual behavior of the structure under different seismic conditions.
Overall, pushover analysis is a valuable tool used in structural engineering to assess the seismic performance of a structure. It provides insights into the capacity and vulnerability of the structure, allowing engineers to evaluate and enhance the design to meet desired performance criteria. By considering the capacity curve and demand tools, engineers can make informed decisions regarding the structural design, retrofitting, and evaluating potential modifications to ensure the safety and resilience of the structure.
Pushover Analysis for Different Types of Structures (e.g., Buildings, Bridges)
- Introduction to pushover analysis
- Importance of pushover analysis in structural design
- Pushover analysis for buildings
- Methodology and procedures
- Response spectrum analysis
- Collapse mechanisms
- Limitations and challenges
- Pushover analysis for bridges
- Comparison with traditional analysis methods
- Load redistribution
- Influence of different loading conditions
- Seismic vulnerability assessment
- Factors influencing pushover analysis results
- Structural material properties
- Geometric configurations
- Boundary conditions
- Earthquake ground motions
- Applications and benefits of pushover analysis
- Optimization of structural design
- Enhanced seismic performance
- Retrofitting and strengthening strategies
- Code development and standardization
- Conclusion
Once in the Pushover Curve menu, enter the desired damping ratio and click on the “Find Performance Point” button. The software will then calculate the intersection of the Capacity Spectrum and Demand Spectrum, providing the sought-after Performance Point. This crucial step allows engineers to accurately assess the structure’s maximum inelastic capacity and effectively analyze it’s overall performance.
How Do You Find the Performance Point in Pushover Analysis?
In the Pushover Curve dialog box, choose the Load Pattern and select the pushover analysis options. Specify the Target Displacement or Drift and the number of steps in the analysis. It’s important to input accurate information for the structural properties, such as material properties, section sizes, and boundary conditions. Once all the necessary parameters have been set, click OK to generate the pushover curve.
The pushover curve represents the relationship between the applied lateral force and the corresponding displacement or drift of the structure. This curve is obtained by incrementally applying lateral loads to the structure and recording the displacements or drifts at each step. The analysis continues until the target displacement or drift is reached.
To find the performance point on the pushover curve, the Capacity Spectrum and Demand Spectrum need to be plotted on the same graph. The Capacity Spectrum represents the inelastic capacity of the structure, while the Demand Spectrum represents the demand or load that the structure is subjected to. These spectra are obtained from seismic design codes or other reliable sources.
By comparing the Capacity and Demand Spectra, the performance point can be determined. The performance point is the intersection of the Capacity Spectrum and Demand Spectrum curves. It represents the state at which the structure is in maximum inelastic capacity, meaning it’s reached it’s ultimate strength and deformation capacity.
The Structural Engineer can then assess the performance point and evaluate if the structure meets the desired performance objectives. If the performance point is within the acceptable range, the structure is deemed to perform adequately under the given seismic loads. However, if the performance point is outside the acceptable range, additional strengthening or retrofitting measures may be required to ensure the structures performance and safety.
Steps to Generate a Pushover Curve
- Step 1: Collect the required data points for the pushover curve.
- Step 2: Plot a graph with the displacements on the x-axis and the base shear on the y-axis.
- Step 3: Identify the initial linear range of the curve.
- Step 4: Determine the yield point, where the curve starts to deviate from linearity.
- Step 5: Identify the post-yield range and the ultimate point of the pushover curve.
- Step 6: Calculate the area under the pushover curve up to the ultimate point.
- Step 7: Assess the building’s response by comparing the area under the pushover curve with predefined performance criteria.
- Step 8: Analyze the results and make necessary design improvements if required.
Conclusion
It allows engineers to assess the ductility, strength, and deformation characteristics of these structures, guiding necessary design modifications to enhance their seismic resistance.