Bispec can be used to calculate linear and nonlinear spectra including "Constant Strength", "Constant Ductility" and "Constant Damage" Nonlinear spectra.
It can be used by Engineers, Students and Researchers to:
Bispec supports 7 different ground motion formats, 10 different hysteretic element models, and more than 60 different spectral values. It provides powerful visualization and plotting tools and allows all data to be exported for further analysis.
Perform 1D & 2D dynamic analysis
Calculate Linear Spectra
Calculate 5 types of nonlinear spectra
10 different linear and nonlinear hysteretic models
Over 60 different spectral quantities
Linear and Nonlinear viscous damping
Why Use bispec?
Easy calculation of Linear and Nonlinear Spectra
Multiple nonlinear hysteretic models: Represent multiple types of structures
Easy Parametric Analysis: Amazing Power for Engineering, Educational and Research Work
Powerful Data Analysis and Export: Visualize data using 2D and 3D Plots and Export all data
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Bispec is a nonlinear spectral analysis software program that performs unidirectional and bidirectional dynamic timehistory analysis of a simple dynamic system under earthquake ground motion records. It can also compute several types of Nonlinear Spectra including ConstantStrength, ConstantDuctility and ConstantDamage spectra.
Here are some of Bispec's features:
Time History Analysis Features
Spectral Analysis Features
ForceDeformation Hysteretic Models
The following is the list of 10 hysteretic models available in Bispec. They can be used to model a wide range of structural behavior. See more details on the Nonlinear Hysteretic Models page.
Earthquake Ground Motion Data Formats
Different element models can be used to characterize the hysteretic behavior of the system.
There are 10 different elements that are currently available in Bispec:
1. Elastic Linear Model
2. Bilinear Model with Hardening
3. Bilinear Model with Bidirectional Interaction
4. Clough Bilinear Stiffness Degrading Model
5. Modified Clough Bilinear Stiffness Degrading Model
6. Bilinear OriginOriented Model
7. Bilinear PeakOriented Model
8. Bilinear Elastic Model
9. Bilinear Flag Model
10. Bilinear Slip Model
Bispec computes a large number of spectral quantities that can be plotted and examined in the Spectral Analysis dialog. They can also be exported to text files for further analysis.
In the spectral analysis window, different spectral values can be selected for plotting along the horizontal or vertical axis. This allows any two spectral quantities to be plotted against each other providing a high degree of freedom for the user to explore alternative data plotting and interpretation forms.
In addition to computed spectral quantities, some of the basic input properties can also be plotted such as period, mass and stiffness. This allows for example plotting any quantity vs. period (T) or stiffness (K).
In general, the available quantities are divided into 5 separate groups of related quantities:
Basic Properties: Period (T), frequency (f), Stiffness (K), Damping Ratio (z ), Mass (M), Hardening Stiffness (Kh), Hardening Stiffness Ratio (Kh/K), Postyield period (Tsec), PDelta ratio (P/KL), Damping Coefficient (C), Nonlinear Damping Coefficient (Csup), and nonlinear damping exponent (alpha).
Effective Properties: Effective Period (Teff), Effective Frequency (feff), Effective Stiffness (Keff), Effective Linear Viscous Damping (bIeff), Effective Nonlinear Viscous Damping (bVeff), Total Effective Viscous Damping (bV+Ieff), Effective Hysteretic Damping (bHeff), and Total Effective Damping (bTot_eff).
Kinematics (D, V, A): Sd, Sv, Sar, Sat, PSv, PSa, Dres, Dres/dy, Dres/Sd.
Yielding related quantities: Dyp, Dyn, Gamma (Dinel/Del), Ductility, Pos Ductility, Neg Ductility, YE (Yield Events), Pos YE, Neg YE, Collapse.
Forces: Sfs, Sfd, Sfa, Fyp, Fyn, Cy (Fyp/W), R (Fel/Fyp), Cs (Sfs/W), Eta (Fyp/(M*PGA))
Energy and Power: EI, EK, EE, EH, EHnr, ED, PI, PK, PE, PH, PHnr, PD, and DI_BB (damage index).
The following table lists the 61 spectral quantities and sdof properties that are available for plotting in the spectral results dialog. Each quantity is listed with its symbol, description, dimensional form and physical units. Highlighted text indicates recent changes and additions to Bispec. See the Bispec Help Manual (installed with software) for more details.
Symbol 
Description 
Physical Units 
Unit 
Basic Properties 

T 
Period 
T 
s 
f 
Frequency 
F 
Hz 
K 
Stiffness 
F/L 
Kip/in 
Damping % 
Damping 
 
% 
M 
Mass 
M 
Kip*s2/in 
Kh 
Hardening Stiffness 
F/L 
Kip/in 
Kh/K 
Hardening Stiffness Ratio 
 
 
Tsec 
Postyield period, corresponding to Kh 
T 
s 
PDelta ratio 
PDelta Ratio = P/KL , (where L is the effective height) 
 
 
C 
Damping Coefficient for Linear Viscous Damping (LVD) 
F.t/L 
Kip.s/in 
Csup 
Damping Coefficient for Nonlinear Viscous Damping (NLVD) 
F.(t/L)α 
Kip.(s/in)α 
Alpha (α) 
Exponent coefficient for Nonlinear Viscoud Damping (NLVD) 
 
 
Effective Properties 

Teff 
Effective Period 
T 
s 
feff 
Effective Frequency 
F 
Hz 
Keff 
Effective Stiffness 
F/L 
Kip/in 
βIeff % 
Effective Inherent (Linear) Viscous Damping (LVD) 
 
% 
βVeff % 
Effective Supplemental (Nonlinear) Viscous Damping (LVD) 
 
% 
βV+Ieff % 
Total Effective Viscous Damping (LVD+NLVD) 
 
% 
βHeff % 
Effective Hysteretic Damping 
 
% 
βTot_eff % 
Total Effective Damping (Hysteretic + Viscous) 
 
% 
Kinematics (D, V, A) 

Sd 
Spectral Displacement 
L 
in 
Sv 
Spectral Velocity 
L/t 
in/s 
Sar 
Spectral Acceleration (Relative) 
L/t 2 
in/s 2 
Sat 
Spectral Acceleration (Absolute) 
L/t 2 
in/s 2 
PSv 
PseudoSpectral Velocity = Sd*(2 π /T) 
L/t 
in/s 
PSa 
PseudoSpectral Acceleration = Sd*(2 π /T) 2 
L/t 2 
in/s 2 
Dres 
Residual Displacement at end of record (Absolute) 
L 
in 
Dres/Dyp 
Residual ductility 
 
 
Dres/Sd 
Dres/Sd ratio 
 
 
Yielding 

Dyp 
Positive yield displacement 
L 
in 
Dyn 
Negative yield displacement (Signed) 
L 
in 
Gamma (γ) 
Dinel/Del: Ratio of inelastic Sd to elastic Sd 
 
 
Ductility 
Peak Ratio inelastic displacement to yield displacement,

 
 
Pos Ductility 
Positive Ductility (Dmax/Dyp) 
 
 
Neg Ductility 
Negative Ductility (Dmin/Dyn) 
 
 
YE 
Number of yielding events 
 
 
Pos YE 
Number of positive yield events 
 
 
Neg YE 
Number of negative yield events 
 
 
Collapse 
Collapse indicator (1: Collapse, 0: No Collapse) 
 
 
Forces 

Sfs 
Hysteretic Force = max(fs) 
F 
Kip 
Sfd 
Damping Force = max(fd) 
F 
Kip 
Sfa 
Inertia Force = M*Sat, also equal to max(fs+fd) 
F 
Kip 
Fyp 
Positive yield force 
F 
Kip 
Fyn 
Negative yield force, (Signed) 
F 
Kip 
Cy (Fyp/W) 
Normalized Yield Capacity 
 
 
R 
Fel/Fyp: Ratio of elastic Sfs to Fyp 
 
 
Cs (Sfs/W) 
Normalized Peak Force 
 
 
Eta (η) 
Normalized yield strength = Fyp/(M*PGA) 
 
 
Energy & Power 

EI 
Input Energy 
F.L 
Kip.in 
EK 
Kinetic Energy 
F.L 
Kip.in 
EE 
Elastic Energy 
F.L 
Kip.in 
EH 
Hysteretic Energy 
F.L 
Kip.in 
EHnr 
Hysteretic NonRecoverable Energy 
F.L 
Kip.in 
ED 
Damping Energy 
F.L 
Kip.in 
PI 
Input Power 
F.L/t 
Kip.in/s 
PK 
Kinetic Power 
F.L/t 
Kip.in/s 
PE 
Elastic Power 
F.L/t 
Kip.in/s 
PH 
Hysteretic Power 
F.L/t 
Kip.in/s 
PHnr 
Hysteretic NonRecoverable Power 
F.L/t 
Kip.in/s 
PD 
Damping Power 
F.L/t 
Kip.in/s 
DI_BB 
Damage index (Bozorgnia and Bertero) 
 
 
Bispec is available in three different editions: Standard, Professional, and Advanced. Please see the description below for the various features supported by each edition.

Bispec Student 
Bispec Professional 
Bispec Advanced 
Open/Save Functionality 
Yes 
Yes 
Yes 
Single Dynamic Analysis 
Yes 
Yes 
Yes 
Linear Spectra 
Yes 
Yes 
Yes 
Nonlinear Spectra 
Yes 
Yes 
Yes 
Maximum Number of Records in Spectral Analysis 
7 
100 
Unlimited* 
Number of Available Hysteretic Models 
6 
10 
10 
Supported Hysteretic Models 
1. Linear 2. Bilnear 3. 2D Bilinear Coupled 4. Clough 5. Modified Clough 6. Bilinear Elastic 
1. Linear 2. Bilnear 3. 2D Bilinear Coupled 4. Clough 5. Modified Clough 6. Bilinear Elastic 7. OriginOriented
8. PeakOriented
9. Bilinear Flag
10. Bilinear Slip

1. Linear 2. Bilnear 3. 2D Bilinear Coupled 4. Clough 5. Modified Clough 6. Bilinear Elastic 7. OriginOriented8. PeakOriented 9. Bilinear Flag 10. Bilinear Slip 
Parallel Processing Number of Processors 
4 
8 
Unlimited* 
Parametric Analysis Capability 
Good 
Better 
Excellent 
Export Resutls for Processing 
Yes 
Yes 
Yes 
Ground Motion Formats 
7 
7 
7 
Export of Results to Text File 
Yes 
Yes 
Yes 
Export all spectral analysis results to a single file (databaselike format)  No  No  Yes 
Constant Strength Spectra 
Yes 
Yes 
Yes 
Constant Normalized Strength Spectra 
Yes 
Yes 
Yes 
Constant R Spectra 
Yes 
Yes 
Yes 
Constant Ductility Spectra 
Yes 
Yes 
Yes 
Constant Damage Spectra 
Yes 
Yes 
Yes 
Bidirectional Spectra (Maximum Rotated Spectra) Compute Resultant Compute Resultant Angle Compute SRSS Compute Geomean 
Yes Yes No No 
Yes Yes No No 
Yes Yes Yes Yes 
Supported Spectral Quantities 
61 
61 
61 




Interactive Hysteretic Model Testing 
5 
10 
10 
PDelta Effects 
Yes 
Yes 
Yes 
2D & 3D Dispaly of Spectral Results 
Yes 
Yes 
Yes 
Animation of Dynamic Analysis Results 
Yes 
Yes 
Yes 
New Detailed Help Documentation 
Yes 
Yes 
Yes 