BWBN
Bouc-Wen-Baber-Noori Model
The BWBN
model is an extension of the BoucWen
model with stiffness degradation, strength degradation and pinching effect.
Syntax
material BWBN (1) [2...18]
# (1) int, unique material tag
# [2] double, elastic modulus, default: 2E5
# [3] double, yield stress, default: 4E2
# [4] double, hardening ratio, default: 1E-2
# [5] double, \beta (>0), default: 0.5
# [6] double, exponent n (>0, normally >=1), default: 1.0
# [7] double, initial \nu (>0), default: 1.0
# [8] double, slope of \nu (>0), default: 0.0
# [9] double, initial \eta (>0), default: 1.0
# [10] double, slope of \eta (>0), default: 0.0
# [11] double, initial \phi (>0), default: 1.0
# [12] double, slope of \phi (>0), default: 0.0
# [13] double, \zeta (1>\zeta>0), default: 0.0
# [14] double, slope of A (>0), default: 0.0
# [15] double, p (>0), default: 0.0
# [16] double, q (>0), default: 0.0
# [17] double, \lambda (>0), default: 1.0
# [18] double, density, default: 0.0
History Variable Layout
initial_history(0)
z
Theory
The Wikipedia page contains sufficient information about the formulation of BWBN
model. Some normalizations are carried out compared to the original model.
The evolution of internal displacement is governed by the differential equation,
Then,
For state determination, is solved iteratively by using the Newton method. The evolutions of internal functions rely on the dissipated energy , which is defined to be a normalized quantity.
The trapezoidal rule is used so that
The evolutions are
Parameters
Strength degradation is controlled by . To disable it, set .
Stiffness degradation is controlled by . To disable it, set .
Pinching is controlled by . To disable it, set or .
Examples
Vanilla Model
The default behavior is similar to a bilinear hardening material.
material BWBN 1
materialtest1d 1 4E-4 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 80
Strength degradation
A positive enables strength degradation.
material BWBN 1 2E5 4E2 0 .5 1. 1. 1E0 1. 0. 1. 0. 0. 0. 0. 0. 1. 0.
materialtest1d 1 4E-4 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 80
A positive has the similar effect.
material BWBN 1 2E5 4E2 0 .5 1. 1. 0. 1. 0. 1. 0. 0. 1E0 0. 0. 1. 0.
materialtest1d 1 4E-4 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 80
Stiffness degradation
A positive enables stiffness degradation.
material BWBN 1 2E5 4E2 0 .5 1 1 0 1 1E1 1 0 1 0 1 1 0 0
materialtest1d 1 4E-4 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 80
Pinching Effect
The pinching effect is governed by , , , , and .
material BWBN 1 2E5 4E2 0 .5 1. 1. 0. 1. 0. 1. 1E1 1. 0. 1E1 1E0 1. 0.
materialtest1d 1 1E-3 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 80
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