Abstract
The vibration screening efficiency of a curved, inclined, open trench is investigated in this paper. An elastic, transversely isotropic half-space with hysteretic damping, acted upon by a harmonic vertical excitation, is assumed. Equations of motion with absorbing boundary conditions are presented and numerically integrated using FlexPDE software, based on the finite element method. The barrier efficiency is analysed in terms of the reduction of the vertical and horizontal components of the ground surface vibration. The results are presented for trenches with different geometric features based on the non-dimensional amplitude reduction factor. The trench inclination angle, the shape of the trench surface and the distance between the source of vibration and an obstacle are investigated as factors that can improve the trench reduction ability. It is demonstrated that a better attenuation of vibration is achieved with the proposed inclined trench than with its vertical counterpart. Moreover, the vibration mitigation effect is more significant in the case of a more horizontally located trench than for its vertical counterpart (even up to 5 times smaller displacement amplitudes for the vertical displacement component). Additionally, assuming the same trench depth, the vibration reduction effect is better in the case of a smaller number of rings used. The vibration attenuation efficiency is more visible if the trench is located closer to the vibration source.
Highlights
Approaches for preventing the failure of structures due to seismic, wind or man-induced vibrations can generally be divided into two groups: the use of excitation-resistant structures and joints based on passive, active or semi-active vibration mitigation techniques [1,2] and the use of barriers in the ground to prevent the transmission of surface wave energy
The results are presented in the form of the amplitude mitigation factor (AMF), defined according to Woods [10] as the ratio between the maximum absolute value of the vertical (AMFy) or horizontal (AMFx) displacement observed after using the trench (v, u) (Figs 2 and 3) and the maximum displacement for the same points without the trench (Fig 4)
A similar definition can be introduced for the horizontal displacement component (AMFx)
Summary
Approaches for preventing the failure of structures due to seismic, wind or man-induced vibrations can generally be divided into two groups: the use of excitation-resistant structures and joints based on passive, active or semi-active vibration mitigation techniques [1,2] and the use of barriers in the ground to prevent the transmission of surface wave energy. The approach proposed in this paper, based on an inclined, curved, open trench, belongs to the second group. Vibration screening allows for the possibility of preventing energy from reaching sensitive zones. The idea is simple, and if required screening geometry criteria are met, a reliable solution can be obtained. The majority of the energy that affects nearby structures is carried by a Rayleigh wave travelling on a ground
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