Influence of Ballast Track on Vertical Response of Multi-span SS Bridges
3
2.2 Numerical Model
In a first approach, the numerical model described in what follows is used. Only half
of the deck is represented as two successive Bernoulli-Euler (B-E) beams resting on
elastic supports, accounting for the neoprene bearings vertical stiffness. The two rails
are simulated as an equivalent single B-E beam as well. A three layer discrete track
model (see Fig. 3) as the one proposed by Zhai [9] is implemented, where the damping
and stiffness of rail pads, ballast and subgrade are included at the sleepers positions.
Fig. 2. Old Guadiana Bridge cross-section
Fig. 3. Numerical track-bridge interaction model
In order to simulate the axle vertical forces, a constant moving load model is selected,
therefore neglecting vehicle-structure interaction effects in a first approach. The model,
as described above, is generated using Finite Elements in Ansys software. Then, the
equations of motion of the complete system are integrated in the time domain applying
Newmark-Betta constant acceleration algorithm programmed in Matlab.
3
2.2 Numerical Model
In a first approach, the numerical model described in what follows is used. Only half
of the deck is represented as two successive Bernoulli-Euler (B-E) beams resting on
elastic supports, accounting for the neoprene bearings vertical stiffness. The two rails
are simulated as an equivalent single B-E beam as well. A three layer discrete track
model (see Fig. 3) as the one proposed by Zhai [9] is implemented, where the damping
and stiffness of rail pads, ballast and subgrade are included at the sleepers positions.
Fig. 2. Old Guadiana Bridge cross-section
Fig. 3. Numerical track-bridge interaction model
In order to simulate the axle vertical forces, a constant moving load model is selected,
therefore neglecting vehicle-structure interaction effects in a first approach. The model,
as described above, is generated using Finite Elements in Ansys software. Then, the
equations of motion of the complete system are integrated in the time domain applying
Newmark-Betta constant acceleration algorithm programmed in Matlab.