Abstract
The use of in situ strain measurements to reconstruct the deformed shape of structures is a key technology for real-time monitoring. A particularly promising, versatile and computationally efficient method is the inverse finite element method (iFEM), which can be used to reconstruct the displacement field of beam elements, plate and shell structures from some discrete strain measurements. The iFEM does not require the knowledge of the material properties. Nevertheless, it has always been applied to structures with linear material constitutive behavior. In the present work, advances are proposed to use the method also for concrete structures in civil engineering field such as bridges normally characterized by material nonlinearities due to the behavior of both steel and concrete. The effectiveness of iFEM, for simply supported reinforced concrete beam and continuous beams with load conditions that determine the yielding of reinforcing steel, is studied. In order to assess the influence on displacements and strains reconstructions, different measurement stations and mesh configurations are considered. Hybrid procedures employing iFEM analysis supported by bending moment-curvature relationship are proposed in case of lack of input data in plastic zones. The reliability of the results obtained is tested and commented on to highlight the effectiveness of the approach.
Highlights
The efficiency of civil structures has a crucial role, with economic and social impacts.On the other hand, processes like corrosion, fatigue, erosion and overloads worsen structures’ behavior, making them no longer suitable for the intended use according to the latest safety requirements
A promising, versatile and computationally efficient method is the inverse finite element method, which can be used to reconstruct the displacement field of beam elements, plate and shell structures from some discrete strain measurements
The inverse finite element method (iFEM) does not require the knowledge of the material properties
Summary
The efficiency of civil structures has a crucial role, with economic and social impacts. Existing shape-sensing methods are based on numerical integration of experimental strains, on continuous basis functions that approximate the displacement field, on the use of neural networks or variational principles. None of the numerical or experimental shape and strain sensing applications presented so far consider the material nonlinearities of a reinforced concrete beam To this purpose, the formulation of the iFEM algorithm using the Bernoulli–Euler inverse element described in Savino et al [15] has been adopted. The comparison between reference solutions and iFEM predictions, appropriately extended to the case of nonlinear material behavior, demonstrated the effectiveness of the procedure proposed to reconstruct both displacement and strain fields for reinforced concrete. By introducing constitutive equations, stress-sensing and real-time damage prediction could be enabled
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