CREEP BUCKLING OF A NONLINEARLY VISCOELASTIC BEAM-COLUMN.
Interim technical rept.,
CALIFORNIA UNIV BERKELEY STRUCTURAL ENGINEERING LAB
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The stability of an initially crooked, simply-supported, H-section beam-column, subjected to an axial compressive load, is investigated. The material of the column is taken to behave as a general nonlinear viscoelastic solid. It is assumed that the constitutive relation of the material can be represented by a Volterra-Frechet functional polynomial. Conditions sufficient to assure instantaneous, short term and long term i.e., asymptotic stability are established. It is shown that complete knowledge of the material creep functions i.e., the kernels appearing in the functional polynomial representation of the stress-strain relation is not required in order to determine stability conditions. A program of experiments to characterize the material for stability studies is presented. A formal analogy for instantaneous and short term stability conditions is established between the column under consideration and an initially straight, concentrically loaded column fabricated from an imaginary, non-linearly viscoelastic material. The relationship between the actual visco-elastic material under consideration and the imaginary viscoelastic material is explicitly given. A further analogy-this one between the asymptotic stability of the column under consideration and the stability of a fictitious, nonlinearly elastic column - is also established. Author
- Structural Engineering and Building Technology