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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 93
Edited by: B.H.V. Topping, J.M. Adam, F.J. Pallarés, R. Bru and M.L. Romero
Paper 62

Evaluation of Structural Damage in Beam Structures using the Strain Energy Method

I. Štimac Grandic and D. Grandic

Faculty of Civil Engineering, University of Rijeka, Croatia

Full Bibliographic Reference for this paper
I. Štimac Grandic, D. Grandic, "Evaluation of Structural Damage in Beam Structures using the Strain Energy Method", in B.H.V. Topping, J.M. Adam, F.J. Pallarés, R. Bru, M.L. Romero, (Editors), "Proceedings of the Tenth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 62, 2010. doi:10.4203/ccp.93.62
Keywords: damage evaluation, curvature, deflection influence line, strain energy.

In this paper the problem of using displacement influence lines to detect, locate and evaluate the degree of damage in beam structures is investigated. The main problem in many research papers arises from a limited number of measurement instruments. This problem is overcome in methods presented in papers [1,2,3] by using displacement influence lines.

Theoretically, displacement influence line can be obtained from measurements at only one point in the structure therefore this method avoids the need for many measurement points. Measurements conducted on site confirm the efficiency of constructing the displacement influence line from one measurement point [1,3,4]. According to Stimac et al. [1,2] one measurement point at each span in the beam structure enables the location of the damage reliably by using the displacement influence line curvature method. But the mentioned curvature method is not always reliable for damage evaluation. Changes in the displacement influence line curvatures are caused by changes in the bending moment and the bending stiffness. In static undetermined systems, theoretically, the change in the bending stiffness causes changes in the bending moment as well. Therefore, the strain energy method has been applied to evaluate the rate of damage in the damaged section.

The numerical analysis has been carried out for a two-span continuous beam. The displacement influence line curvature method has been employed to locate the damaged sub-region(s). The curvature damage method is based on computed differences in curvatures of the two displacement influence lines (for pre-damaged and damaged state). Once the damage is located, the strain energy method is used to evaluate the rate of the damage. The strain energy damage evaluation theory assumes that the damage is primarily located at a single sub-region [5,6]. In this paper, the combination of two damage detection methods is proposed, namely the displacement influence line curvature method and the strain energy method. It is shown through numerical examples that even if there are more then one damaged section the proposed algorithm is quite suitable for engineering purposes. The main advantage of the method presented is a need for only a few measuring points in the structure.

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