Ferdinando Laudiero

Buckling and Postbuckling Finite-Element Analysis of Pultruded FRP Profiles under Pure Compression

Results of nonlinear finite-element analyses of commercial pultruded fiber-reinforced plastic (PFRP) I-section profiles subjected to pure compression are presented. One narrow flange and four wide flange shapes are analyzed for 10 values of the column slenderness, involving 50 finite-element (FE) models. The imperfection sensitivity is investigated with reference to different imperfection shapes. For wide flange columns, if the imperfection amplitudes are identified with the limiting amplitudes reported by the pultruders, extremely low ultimate axial loads are obtained, associated with unrealistic failure mechanisms and strong interaction between local and global buckling modes. In contrast, reduced imperfection amplitudes reported in the literature lead to well documented failure mechanisms and to a small influence of the buckling mode interaction. As is known, the local buckling of wide flange shapes is triggered by the flange instability. Conversely, the local buckling of narrow flange shapes generally is triggered by the web instability. Because of this property, the paper shows that at equal cross section area, the narrow flange profiles may exhibit higher ultimate loads with respect to the wide flange profiles in a broad range of column slenderness.

Identification of the Short-Term Full-Section Moduli of Pultruded FRP Profiles Using Bending Tests

Three-point and four-point bending tests are traditionally used to estimate the shear and flexural properties of pultruded fiber-reinforced plastic (PFRP) structural shapes. In the framework of Timoshenko’s beam model, the rigidities of beams can simply be obtained from linear combinations of the experimental deflections. However, several measurement uncertainties may affect the parameter identification. To analyze this drawback, a new test configuration was compared with the common three-point and four-point bending test configurations through an extensive experimental program concerning wide-flange commercial profiles. A parametric study was conducted by varying the span length, and, in the case of the four-point bending tests, the relative position of the applied loads. The influence of the load and deflection measurement errors was analyzed and proper uncertainty bands were provided for the computed rigidities.