Structural Parameter Estimation Using Modal Responses and Incorporating Boundary Conditions

Masoud Sanayei
    Associate Professor, Tufts University

Sara Wadia-Fascetti
    Assistant Professor, Northeastern University

Jennifer A. S. McClain
    Structural Engineer, Weidlinger Assoc.

Inna Gornshteyn
    Structural Engineer, Ammann & Whitney Consulting Engineers

Erin M. Santini
    Graduate Student, Tufts University
 
 

ABSTRACT

A new method is introduced to use natural frequencies and associated mode shapes measured at a selected subset of degrees of freedom (DOF) for stiffness and mass parameter estimation at the component level.  Structural modeling errors can not be completely avoided in any analytical procedure that relies on finite element models (FEM).  However, some errors may be controlled.  Two new elements are proposed to capture more accurately the behavior of the structure at complex interfaces, thus reducing error.  The first new element is the soil-substructure super-element and is created to capture all aspects of the elements' interface for both stiffness and mass. The second new element is the partially restrained frame element.  This element is introduced to expand connections from being modeled as fixed or pinned to include partially restrained joints in the finite element model.  Changes in these stiffness values can be used for model updating and to establish a baseline for future condition assessment.  To examine the capability of the proposed parameter estimation algorithm, these two new elements are incorporated in a parameter estimation example using simulated modal data.  In this example, parameter estimates successfully converged to the “true” parameter values with a high degree of accuracy.  Such parameter estimates can be used for model updating and condition assessments.
 

Contact Information:

Prof. S. Wadia-Fascetti (swf@neu.edu)
Dept. of Civil & Env. Engineering
Northeastern University
Boston, MA  02115

Reference:

Sanayei, M, Wadia-Fascetti, S., McClain†, J. A. S., Gornshteyn†, I., Santini†, E. M., (1998) "Structural Parameter Estimation Using Modal Responses and Incorporating Boundary Conditions."  Paper Number T118-2.  World Structures Congress, San Francisco, CA, July 1998.
 

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