ETABS - 28 Nonlinear Static Procedures - Pushover Analysis: Watch & Learn

Summary

The tutorial on ETABS explores nonlinear static procedures (NSPs) for seismic evaluation of buildings, focusing on pushover analysis and capacity spectrum methods. It details the application of hinges, load patterns, and analysis verification for a two-story structure. The capacity spectrum method and displacement coefficient method are compared to estimate maximum global displacement during an earthquake. The session illustrates how to analyze hinge behavior, plot pushover curves, and evaluate member forces, ultimately emphasizing the importance of local collapse checks alongside global structural adequacy.

Takeaways

• 🏗️ NSPs (Non-Linear Static Procedures) provide valuable insights into the seismic behavior of buildings with less computational effort.
• 📊 NSPs consist of pushover analysis and ground response spectrum to estimate maximum global displacements.
• 🔍 The Capacity Spectrum Method (CSM) converts pushover curves into capacity spectra to determine performance points.
• 📈 The Displacement Coefficient Method (DCM) modifies elastic displacements to estimate target displacements.
• 🏢 The example structure analyzed is a two-story building with specific steel column and beam sections.
• ⚖️ It's crucial to verify that structures have adequate capacity for gravity loads before conducting pushover analyses.
• 🔧 Assigning appropriate hinges to structural elements is essential for accurate pushover analysis results.
• 📉 The performance point indicates the maximum displacement estimated during pushover analysis.
• 📍 Local collapse checks are vital even if global capacity appears sufficient during analyses.
• 📊 Reports on non-linear static procedures can provide detailed member forces for maximum earthquake scenarios.

Q & A

What are non-linear static procedures (NSPs) used for in ETABS?

NSPs are used for the seismic evaluation of existing and new buildings, providing insights into global behavior and possible failure modes with less computational effort than non-linear time history analysis.

What are the two main components of a non-linear static procedure?

The two main components of an NSP are pushover analysis and a site response spectrum.

What is the capacity spectrum method (CSM)?

CSM is an approach that converts a pushover curve into a capacity spectrum using equivalent linearization, which allows for the estimation of maximum global displacement.

How does the displacement coefficient method (DCM) determine target displacement?

DCM applies modifying coefficients to the peak elastic displacement based on the pushover curve to calculate the target displacement.

What structure was analyzed in the example provided?

The analyzed structure was a two-story building with specific column and beam sections, designed to assess its capacity under seismic loads.

What steps are taken before performing a pushover analysis?

Before the pushover analysis, the structure's capacity for gravity loads is verified using defined load patterns.

Why is it important to check local collapse during the pushover analysis?

Checking for local collapse is crucial even if the structure appears to have adequate global capacity, as local failures can still occur under seismic loads.

What does the performance point represent in the capacity spectrum method?

The performance point is where the capacity spectrum intersects with the demand spectrum, providing an estimate of the maximum displacement expected during an earthquake.

What values were set for the spectral response in the example?

The values set for the spectral response were Ss = 2.302 and S1 = 0.956, specific to the location of Berkeley.

How does the DCM compare to the CSM in estimating maximum displacement?

The DCM provides a slightly higher target displacement than the CSM, with both methods indicating no local collapse should occur for the given levels of earthquake load.