Abstract
Due to increase in the application of glass fibre reinforced polymer (GFRP) beams based structural systems for rehabilitation of existing and construction of new bridges there is a requirement for identification of critical components of these structural systems and the assessment of damage in this sort structural. The application of vibration-based damage detection (VBDD) techniques has been identified as one of the universal technique that is promising in damage assessment in composite beams. The current study aimed at using vibration-based damage detection technique for assessment of damage exhibited by FRP composite beam structure. This thesis addresses the experimental and numerical study of damage assessment of FRP composite beams using vibration data. Dynamic measurements were carried out considering different specified boundary conditions and the effect of supports on the modal parameters and the effect of damage would be obtained. Another set of experiments were conducted on a Fixed-Free beam with unspecified boundary conditions at the free end, where a mass and a spring attached to the free end and beams were tested for different damage scenarios. Triaxial accelerometers were placed at selected locations based on the result of simple FE beam model. The beams were excited in the two (vertical and horizontal) directions by means of a hammer but only the vertical direction was taken into consideration at this point. The responses at different points along the beam were recorded at different levels of damage and fed into an FFT analyzer. Post-processing of data was done with the stochastic subspace identification (SSI) technique. The effect of the damage on the natural frequencies, mode shapes, and damping ratio were determined. Finite element models for the intact, reference and damaged beams were constructed and used to support the dynamic measurements. FE model updating was applied to different five boundary conditions in order to evaluate their effect. Damage assessment techniques based on selected methods such as modal frequency change, direct mode shapes, change in modal curvature, damage index method and model updating methods were developed and applied to the beams. A unique test configuration was introduced by combining fixed-free beam with undefined boundary at the free end. The spring and masses were attached to the free-end, this was implemented for different damage scenarios. The outcome of this implement experiment was discussed and analysed.