Last Updated August 17, 2017

Overview

Traditionally, earthquake-resistant design has been strength-based, using linear elastic analysis. Since inelastic behavior is usually allowed for strong earthquakes, this is not entirely rational. Strength-based design considers inelastic behavior only implicitly. Displacement-based (or deformation-based) design considers inelastic behavior explicitly, using nonlinear inelastic analysis. Displacement-based design recognizes that in a strong earthquake, inelastic deformation (or ductility) can be more important than strength. PERFORM-3D allows you to use displacement-based design.

Procedures for displacement-based design using inelastic analysis are specified in ASCE 41, “Seismic Rehabilitation of Existing Buildings”. ASCE 41 applies to the retrofit of existing buildings, but the procedures can be applied to the design of new buildings. PERFORM-3D implements the procedures in ASCE 41. However, PERFORM-3D is a general tool for implementing displacement-based design. It is not limited to ASCE 41.

The response of a structure to earthquake ground motion, whether elastic or inelastic, is highly uncertain. Capacity design is a rational way to improve the response of a structure in a strong earthquake, by deliberately controlling its behavior. Capacity design controls the inelastic behavior of a structure, by allowing inelastic behavior only in locations chosen by the designer. In these locations the structural components are designed to be ductile. The rest of the structure remains essentially elastic, and can be less ductile. Controlling the behavior in this way improves reliability, reduces the amount of damage, and can reduce construction costs. PERFORM-3D allows you to apply capacity design principles.

PERFORM-3D has powerful capabilities for inelastic analysis, but it is not intended for general purpose nonlinear analysis. If you have no idea how your structure will behave when it becomes inelastic in a strong earthquake, PERFORM-3D can probably help you to identify the weak points, and hence can guide you in improving the design. However, PERFORM-3D is not intended for “design by analysis”, where the engineer expects the analysis to determine exactly how a structure will behave. PERFORM-3D is a powerful tool for implementing displacement-based design and capacity design. It will help you to produce better designs, but it will not do the engineering for you.

Why PERFORM3D

The new way of earthquake engineering!

Performance-Based Design (PBD) is a major shift from traditional structural design concepts and represents the future of earthquake engineering. These new procedures help assure that the design will reliably meet a desired level of performance during a given earthquake.

Displacement-based design and Capacity-based design

PERFORM-3D allows you to use displacement-based design and capacity-based design principles in assessing resistance of your structure to earthquake loads.

Save structural cost!

Traditional strength-based design for earthquake loadings using linear elastic analysis could be costly and not entirely rational. Performance-Based Design allows inelastic behavior explicitly in the analysis of selected members under earthquake loadings using nonlinear inelastic analysis. Therefore, giving users deliberate control on the structure’s behavior and improve its response in a strong earthquake.

It’s the right tool for seismic rehabilitation of existing buildings

PERFORM-3D with its powerful capabilities for inelastic analysis will help users to identify weak points in existing structures under seismic loading, and hence providing guidance on improving design for retrofits.

Many tools for performance assessments

PERFORM-3D includes powerful tools that assess the performance of a structure, and hence support design. These tools are as follows:

  • Target displacement calculation for push-over analysis
  • Usage ratio plots for single load cases. As the drift increases in a push-over analysis, or time increases in a response history analysis, the usage ratios for the limit states progressively increase. A usage ratio plot shows how the usage ratios vary for user-selected groups of limit states.
  • Usage ratio plots for load combinations. It is common practice to run response history analyses for several earthquakes (often 7 or more), and to assess performance based the mean values of the usage ratios. The tool implements this procedure.
  • Deflected shapes with color coding based on D/C ratio.