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>> Bispec 2.20 (Released 6/16/2012) - See new version updates
Bispec is a nonlinear spectral analysis software program that performs unidirectional and bidirectional dynamic time-history analysis of a simple dynamic system under earthquake ground motion records. It can also compute several types of Nonlinear Spectra including Constant-Strength, Constant-Ductility and Constant-Damage spectra.
Here are some of Bispec's features:
  • Perform a single dynamic analysis of one system, or
  • Generate ground motion spectra (through a series of single dynamic analyses),
  • Generate "Linear Spectra" which are used for seismic design.
  • Generate 5 types of nonlinear spectra (Constant strength, constant normalized strength, constant R, constant ductility, constant damage index)
  • 10 different linear and nonlinear hysteretic models that model realistic nonlinear beahvior, for investigating various types of structural behavior.
  • Linear viscous damping, and nonlinear viscous damping, ideal for analyzing structures with supplemental damping.
  • Computation of effective period, stiffness, and several measure of equivalent effective damping (hysteretic, linear and nonlinear viscous damping, total damping).
  • Fast analysis of base-isolated structures.
  • A unique feature of Bispec is the ability to generate "Bidirectional Spectra", by analyzing the motion in two directions and reporting the maximum resultant or maximum rotated response (also called MaxRot or RotD100). Bispec can also calculate the angle of maximum response, as well as bidirectional SRSS and Geometric mean (Geomean) response.
  • Compute spectra for multiple ground motion records for convenience or for performing parametric studies.
  • Extremely fast with many productivity features, which helps the user save hours of work.
  • Even faster now with Parallel processing support: Running spectral analysis in Bispec is now even much faster with support for multiple processors and multiple cores. For example, with two quad-core processors, spectral analysis can run close to 8 times faster, which can be paritcularly useful when analyzing multiple ground motions.


>> Bispec Overview

Bispec offers great flexibility for modifying and controlling the dynamic properties of the dynamic system (mass, stiffness, damping etc.), and the nonlinear properties of the nonlinear element (yield strength, etc.). The program currently supports 10 different hysteretic element models (see below). These models can be configured to model the structural response of a large variety of structures (building, bridges, tower, tanks, etc.), as well as the seismic response of many different seismic systems (steel moment frame and braced systems, reinforced concrete moment frames and shear walls, precast, prestressed and post-tensioned concrete systems, base isolation devices, energy dissipation devices, etc.).
Bispec can compute linear spectra for specified ranges of frequencies and damping ratios. It can also compute nonlinear "Constant Strength", "Constant Ductility" and "Constant Damage" spectra. 7 different ground motion formats can be easily and automatically imported and analyzed (see bottom of page).
Bispec can be used as an educational tool to teach students about dynamic behavior, as well as an engineering tool that allows engineers to compute response spectra of design ground motions and investigate the sensitivity of structural response to various structural properties such as strength, stiffness, and shape of the hysteretic force-displacement curve. It is also a very effective research tool that can be used to perform parametric analyses of large numbers of ground motion records. With 10 different hysteretic models, and about 61 different spectral quantities that can be reported ranging from spectral displacement and acceleration, to system forces and ductilities, and including various energy and power spectral values, it provides unlimited options for research and investigation of the dynamic response under ground motion records.
>> Time History Analysis Features

  • Unidirectional and bidirectional dynamic time history analysis 
  • Plotting of all computed quantities (displacement, velocity, acceleration, forces, energy, power, and others...) 
  • Linear and nonlinear models both for single dynamic analysis and spectral analysis 
  • All results can be exported to text files for further processing
  • 3D Animation of unidirectional
     and bidirectional response.






>> Spectral Analysis Features

  • Unidirectional and bidirectional spectra
  • Types of nonlinear spectra: Constant Ductility, Constant Strength (Normalized or Absolute), Constant R (Felastic/Fy) and Constant Damage Index.
  • Nonlinear Spectra can have two different variables:
      Period (frequency), and 
    • Strength, ductility or damage index
  • Spectra can be computed for any number of earthquake records. Spectra are then plotted for an individual record or statistics for all records can be shown (mean, standard deviation, ...)
  •  Spectra can be plotted in 2D charts, in which any quantity can be shown on either the x-axis or y-axis
  •  Spectra with two variables can also be shown in 3D charts (for example Spectral Displacement Vs. Period and Strength)
  •  Point-click feature of the spectra plot. Click any point on any spectra, and see the time history response corresponding to that point in a separate window
  •  All results can be exported to text files for further processing


>> Force-Deformation 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.
  1. Linear Elastic Model
  2. Bilinear Plastic Model
  3. Clough Bilinear Stiffness Degrading Model
  4. Modified Clough Bilinear Stiffness Degrading Model
  5. Origin-Oriented Bilinear Model
  6. Peak-Oriented Bilinear Model
  7. Bilinear Elastic Model
  8. B
    ilinear Flag Model
  9. Bilinear Slip Model
  10. Bilinear Plasticity Model with Bidirectional Coupling


 >> Earthquake Ground Motion Data Formats

  • Import from several different earthquake data formats (SAC, PEER/NGA, SMC/USGS, CSMIP/CDMG and USC) or use a User-defined format option. An automatic feature allows files having one of the formats listed above to be imported without having to specify the format.
  • Define a group of ground motions (unlimited number) for spectral analysis. The group can be saved for later use.
  • Plot the acceleration time history of the record, as well as the integrated velocity and displacement records
  • Modify the records by scaling their magnitude, or changing the timestep or duration