Last Updated August 17, 2017

Built-In Structural Components

Element Types

  • Frame element for beams, columns and braces.
  • Wall element for shear walls.
  • Slab element for floors.
  • Bar elements (with only axial stiffness) of various types
  • Buckling restrained brace.
  • Gap elements.
  • Seismic isolators of rubber and friction pendulum type
  • Fluid damper, with nonlinear relationship between force and deformation rate.
  • Connection panel zone, to model shear deformation in beam-to-column connections.
  • Infill panel, with only shear strength and stiffness.
  • Deformation “gages” of various types. These elements have no stiffness. They are used for calculating deformations, and hence deformation demand/capacity ratios.

Components

In PERFORM-3D, most elements are made up of a number of components. For example, a beam element might consist of several components.

Components Properties

All inelastic components have essentially the same force-deformation relationship. This is a basic tri-linear relationship, with optional strength loss that can be captured in PERFORM-3D.

Hysteresis Loops

The hysteresis loop for an inelastic component can be varied to account for stiffness degradation. The loop can be plotted to check that it has the expected shape.

Demand/Capacity Ratios

PERFORM-3D includes a large number of components, both inelastic and elastic. During an analysis, D/C ratios are calculated as follows:

  • Deformation D/C ratios are calculated for inelastic components.
  • Hence, components that are allowed to become inelastic can be checked to make sure they have sufficient ductility.
  • Strength D/C ratios are calculated for elastic components.
  • Hence, components that are required to remain essentially elastic can be checked to make sure they have sufficient strength.

Deformation Capacities

Deformation capacities can be specified for inelastic components, for calculating deformation demand/capacity ratios. Deformation capacities can be specified for up to 5 performance levels.

The number of components with D/C ratios can be very large. To simplify decision making, components that have similar D/C measures can be grouped into Limit States. An example D/C measure is the concrete tension strain in a shear wall. Each limit state has a “usage ratio”, which is the maximum D/C ratio for any component in the limit state. For a structure to satisfy the performance requirements, the usage ratios for all limit states should not exceed 1.0.

Frame Structures

Simple frame structures consist of beam and column elements. Beam and column elements can be made up of a variety of components, and may be elastic or inelastic. P-delta effects can be considered or ignored.

Shear Wall Structures

Shear walls are modeled using plane wall elements. Complex shear cores are made up of plane elements. Wall elements can have inelastic behavior in bending and shear. Coupling beams are usually modeled using beam elements, with inelastic behavior in either bending or shear.