The Earthquake Engineering Online Archive

BISPEC: Bidirectional linear and non-linear spectra of earthquakes

Hachem, Mahmoud M.

Department of Civil Engineering, University of California, Berkeley, 2004,

BISPEC is a user-friendly program that computes linear and nonlinear spectra of earthquake records. Bispec can also be used to analyze a single SDOF system under any ground acceleration record, and plot the displacement or force response over time. You can even watch an animation of the shaking in real time! Since real earthquakes are not Unidirectional, each earthquake in Bispec can have either one or two components, which makes it easy to generate spectra for two directions (Bidirectional), as well as spectra for the 2D resultant of the two directions (Planar Spectra). The program offers great flexibility for changing the dynamic properties of the SDOF system, such as Mass, Stiffness, Period and Damping. In addition to elastic response, the nonlinear response of the structure can be specified by selecting one of several hysteretic models. The program currently has three nonlinear models. The current nonlinear models are: 1) Bilinear model, 2) Bilinear with Stiffness Degradation, and 3) A Plasticity-Based Bilinear Coupled Element with Bi-directional interaction. Linear spectral analysis can be performed by specifying multiple frequencies. Ranges of strengths could also be specified in nonlinear analysis which results in Constant Strength Spectra. The program can also perform target searches for ductility resulting in Constant Ductility Spectra.

Available online: http://www.ce.berkeley.edu/~hachem/bispec/index.html