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The tests have been developed in two steps
2012-07-29 08:25:49

Moreover, the orthotropic constitutive relationships of the material bring to the forefront local buckling of the section components, flanges and web, where the bidimensional behavior comes in.
Even though these mechanical characteristics of FRP profiles clearly point out that specific design rules are needed, the standard shapes of the profile section are actually very similar to steel ones, and the subject is still being investigated with experimental and theoretical studies.
Global buckling in particular has been the subject of various works ; in many experimental results obtained in the last 30 years have been summarized and discussed, as well as new experimental tests pointing out the meaningful aspects of the problem. The tests have been developed in two steps. In the first one the elastic constants of the profiles considered have been evaluated, and it is clear that: they change with the profiles’ dimensions, the coefficient of variation of specimens from the same section also reaches 15%, their average value is different between flanges and web by up to 11%. The necessity of suitable experimental procedures, not only on the material but also on the entire element, is clearly confirmed, but probably an even more detailed quality control of the producers is necessary.
In the second part the compression tests are presented and the experimental critical loads are compared with the theoretical ones obtained by the authors’ model, taking into account the shear strain, that could be important for FRP materials which have a large ratio of the Young’s modulus to the shear one.
Another approach for evaluating the critical load has been introduced in ; based on many experimental results and numerical simulations with a finite element model, for cases where a local and/or global buckling mode occurred, a single expression for developing the buckling curve is proposed in which a coefficient takes into account the mode-interaction. Comparison with the experimental results considered in the study proves that when the local mode governs the structural behavior, the proposed curve is not always safe or is sometimes much too conservative.

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