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SFE- Modelling of dynamic and static properties of R/C Beams in progressive damage

The application of systematic inspection and maintenance of civil engineering structures has increased enormously during the last decades. Dynamic testing for damage assessment as non-destructive method has attracted growing interest. The applicability of the dynamic investigation does not depend on the building material. It is also possible to detect damage at unobserved locations. Dynamic in situ testing can be a fast method with relatively low cost. The increasing speed of personal computers and data acquisition systems opens new dimensions for dynamic investigations. The accumulation of damage in a structure causes a change in dynamic properties such as natural frequencies, mode shapes and damping. The occurrence of a crack in a R/C or in a steel structure changes the local stiffness and so the modal properties. In general, the natural frequency decreases, the damping capacity changes up and down and the mode shapes shift slightly. Only a few studies so far focus on relations between progressive structural damage and changes of dynamic structural behavior. Most of these investigations concentrate on beam structures. Investigations with R/C beams can be found e.g. in Dieterle & Bachmann;1979, Jahn; 1996, Owens et al.; 1999, De Roeck et al.; 1999, for steel beams in Rytter et al.; 2000. Studies of plate structures can be found in Meinhold et al.; 1996; Ebert et al.; 1999. Structures have time-independent randomly varying material parameters. These properties influence the state of an undamaged structure and the damage evolution. Therefore, the dynamic properties are not only a function of the damage state of a structure, but also of these varying parameters. For understanding and for assessing the actual damage state, it becomes mandatory to investigate the influence of stochastic properties. In this context static and dynamic experiments with three R/C beams were performed. A Stochastic Finite Element (SFE) Model is developed to investigate numerically the nonlinear behavior of the beams by using correlated random fields for different material and physical properties. Thus, different damage histories are investigated.