Pushover analysis, also known as non-linear static analysis or pushover load analysis, is a common structural engineering method used to assess the performance of a building or structure under lateral (horizontal) loads, typically seismic or wind loads. The primary goal of pushover analysis is to predict the behavior of a structure as it progressively deforms and reaches its ultimate capacity. It is particularly useful for assessing the capacity and response of structures that are subjected to large lateral displacements and non-linear behavior.
As for laterally loaded piles, pushover analysis helps engineers assess how laterally loaded piles respond to increasing lateral forces. This analysis provides insights into the pile's deformation behavior, yielding points, and ultimate capacities, allowing engineers to understand how the pile will perform under different loading conditions.
For pushover analysis, PileLAT will repeat the runs with different load factor (> 1.0) applied to the loads at the pile head to compute deflections until no convergence can be found. An unstable condition will result in the computer program being unable to converge or converging at extremely large deflection values. The computed deflection should be a reasonable value at and slightly above the factored design loads to ensure that geotechnical strength requirements are satisfied. Some judgement is needs to assess the reasonableness of the computed deflection. For bored piles, a value of 10% of the pile diameter (D) is suggested by Brown et al. (2010).
The figure below shows the input dialog for pushover analysis option. The parameters which the users can input includes: (1) Number of increments, (2) Minimum load factor, (3) Maximum load factor and (4) the load case for which the pushover analysis will be carried out.
In the PileLAT program, the users can view pushover analysis results if this option is selected, and the analysis is successfully completed. The dialog for the results can be opened by clicking the "Pushover Analysis Results" option under "Tools" menu as shown in the figure below.
The figure below shows the typical dialog of pushover analysis results. The dialog includes the following results from pushover analysis:
Top Deflection versus Load Factor
Max Bending Moment versus Top Deflection
Max Shear Force versus Top Deflection
The detailed results are tabulated in the table on the right side of the dialog.
Pushover analysis tool provided in the PileLAT program offers the following benefits for laterally loaded piles:
Assessment of Structural Performance: Pushover analysis helps engineers assess how laterally loaded piles respond to increasing lateral forces. This analysis provides insights into the pile's deformation behavior, yielding points, and ultimate capacities, allowing engineers to understand how the pile will perform under different loading conditions.
Identification of Critical Sections: By analyzing the distribution of internal forces and moments within the pile, pushover analysis can identify critical sections along the pile length where the stresses are highest. This information is essential for designing pile reinforcement or selecting appropriate pile types to ensure that the pile can safely carry the applied lateral loads.
Optimization of Pile Design: Engineers can use pushover analysis to optimize the design of laterally loaded piles. It helps in selecting the right pile dimensions, materials, and construction methods to achieve the desired level of lateral load resistance while minimizing material usage and construction costs.
Retrofitting Existing Structures: Pushover analysis is useful for assessing the capacity of existing piles in retrofitting projects. Engineers can determine if the current piles can withstand increased lateral loads or if additional piles or strengthening measures are required to enhance the structure's lateral load resistance.
Safety Evaluation: Pushover analysis allows for a comprehensive safety evaluation of laterally loaded piles. Engineers can compare the calculated pile response to safety criteria and design standards to ensure that the piles meet the required safety and deformation limits. This ensures the safety and stability of structures.
Mitigation of Lateral Displacement: Understanding the pile's lateral displacement behavior through pushover analysis helps in designing systems to limit excessive lateral movement during seismic events or other lateral loading conditions. This is crucial for preventing structural damage and ensuring occupant safety.
Performance-Based Design: Pushover analysis is often used in performance-based design approaches, where the structural performance is directly linked to engineering goals and criteria. This allows for more flexibility in design and a focus on achieving specific performance objectives.
Cost Savings: By accurately assessing the behavior of laterally loaded piles, pushover analysis can lead to cost savings by avoiding overdesign or identifying more efficient foundation solutions. It can also prevent costly failures and repairs by ensuring the integrity of the foundation system.
In summary, pushover analysis for laterally loaded piles provides valuable insights into the behavior and capacity of these foundation elements under lateral loads. It aids in the design process, safety assessment, and optimization of pile systems, contributing to the overall performance and reliability of structures.