The accuracy of the Born Approximation as a forward model of elastic wave scattering in the context of simulating
Impact Echo tests of reinforced of concrete is investigated in this paper. The ability of a forward model to realistically
simulate the physics of a system can be important when such a model is used as part of an inverse solution. Synthetic
data of scattering by air void defects that are typically present in damaged civil engineering structures is generated by a
two-dimensional Finite Difference in Time Domain (FDTD) model for elastic wave propagation in an infinite,
homogeneous and isotropic concrete medium. Horizontal elongated cracks and air voids with compact shapes are
considered in this study for comparison between the synthetic and the Born approximated data. It is observed that the
Born Approximation simulates a compact air void better than a horizontal elongated one. This knowledge provides
insight on Born Approximation as part of an inverse solution towards imaging of air voids of various shapes in a
damaged civil engineering structure.
In this work, the shape control of curved beams using symmetric surface bonded piezoelectric actuators, excited out of phase, is studied. To predict the deflections accurately, a finite element model using a three-noded isoparametric curved beam element has been implemented. To model the piezoelectric layers, coupled finite element equations have been used and solved using iterative approach. Closed form expression for deflection has also been derived and compared with FEM and experimental results. The closed form solution based on linear strain variation is used for the static shape control of curved beams. Shape control is achieved by minimizing an objective function, which takes into account the error between actual and desired shapes as well as energy consumed by the actuators.