A method for monitoring a civil engineering structure comprising at least a first metal reinforcement contributing to the mechanical strength of said structure, and an electric cable consisting of at least one pair of electrical conductors having a first electrically accessible end, the method comprising the following steps: a) measurement, by a network analyser, of the impedance reflection coefficient of the electric cable as a function of frequency; b) processing (TRAIT) the recovered reflection coefficients S11 to derive the characteristic impedance Zc of the electric cable as a function of distance comprising the following steps: b1) extrapolate the reflection coefficients S11 to a zero frequency to form a signal S11*; b2) apply an anti-aliasing low-pass filter to the signal 511*; b3) calculate an inverse Fourier transform of the filtered signal S11* considering that the signal S11* exists only for times greater than or equal to 0 and that a solution of the calculation of the inverse Fourier transform of the signal S11* is real, so as to obtain an impulse response of the electric cable: h ( t) = TF - 1 ( S11 ∗ ( f) × FiltrePB ( f))with TF -1 the inverse Fourier transform and FiltrePB(f) the low-pass filter; b4) integrating the impulse response, to obtain a step response u ( t) = ∫ 0 t h τ dτ; and b5) apply an affine conversion to the step response to transform the step response into an impedance: Z c t = Z VNA 1 + u t 1 − u t with Z VNA an internal impedance of the network analyser; c) comparison (COMP) of the characteristic impedance with a reference impedance Z0 corresponding to a reference state of the electric cable so as to deduce an impedance variation Δ Z along the electric cable as a function of a characteristic physical quantity of the cable. a) measurement, by a network analyser, of the impedance reflection coefficient of the electric cable as a function of frequency; b) processing (TRAIT) the recovered reflection coefficients S11 to derive the characteristic impedance Zc of the electric cable as a function of distance comprising the following steps: b1) extrapolate the reflection coefficients S11 to a zero frequency to form a signal S11*; b2) apply an anti-aliasing low-pass filter to the signal 511*; b3) calculate an inverse Fourier transform of the filtered signal S11* considering that the signal S11* exists only for times greater than or equal to 0 and that a solution of the calculation of the inverse Fourier transform of the signal S11* is real, so as to obtain an impulse response of the electric cable: h ( t) = TF - 1 ( S11 ∗ ( f) × FiltrePB ( f))with TF -1 the inverse Fourier transform and FiltrePB(f) the low-pass filter; b4) integrating the impulse response, to obtain a step response u ( t) = ∫ 0 t h τ dτ; and b5) apply an affine conversion to the step response to transform the step response into an impedance: Z c t = Z VNA 1 + u t 1 − u t with Z VNA an internal impedance of the network analyser; b1) extrapolate the reflection coefficients S11 to a zero frequency to form a signal S11*; b2) apply an anti-aliasing low-pass filter to the signal 511*; b3) calculate an inverse Fourier transform of the filtered signal S11* considering that the signal S11* exists only for times greater than or equal to 0 and that a solution of the calculation of the inverse Fourier transform of the signal S11* is real, so as to obtain an impulse response of the electric cable: h ( t) = TF - 1 ( S11 ∗ ( f) × FiltrePB ( f))with TF -1 the inverse Fourier transform and FiltrePB(f) the low-pass filter; b4) integrating the impulse response, to obtain a step response u ( t) = ∫ 0 t h τ dτ; and b5) apply an affine conversion to the step response to transform the step response into an impedance: Z c t = Z VNA 1 + u t 1 − u t with Z VNA an internal impedance of the network analyser; c) comparison (COMP) of the characteristic impedance with a reference impedance Z0 corresponding to a reference state of the electric cable so as to deduce an impedance variation Δ Z along the electric cable as a function of a characteristic physical quantity of the cable.