*3.1. Model Building*

In order to verify the effectiveness of the above method, a numerical analysis model of T-beam bridge was established, as shown in Figure 5, the model beam is 3 m in length, 1.175 m in width, 0.21 m in height, the section size is shown in Figure 5a,b. The density of the mode material is 1170 kg/m3, the Poisson's ratio is 0.35. The elastic modulus of 1# beam is *E*1 = 3.25 × 10<sup>4</sup> MPa, and the elastic modulus of 2#~5# beams are *E*2 = 1.02 *E*1, *E*3 = 1.05 *E*1, *E*4 = 1.07 *E*1, *E*5 = 1.1 *E*1, respectively.

Assuming that the vehicle load acting on the bridge was represented by four timevarying forces, its equation can be expressed as below:

$$\begin{cases} P\_{11} = P\_{12} = P(0.2 + 0.025\sin(6.67\pi t)) \\ P\_{21} = P\_{22} = P(0.3 + 0.025\sin(6.67\pi t)) \end{cases} \tag{15}$$

where, *P*11 and *P*12 represented the front wheel loads, *P*21 and *P*22 represented the rear wheel loads, *P* was the total weight of the vehicle. The vehicle wheelbase was 300 mm, the wheel-track was 180 mm, and the vehicle speed was 1 m/s, as shown in Figure 5c.

**Figure 5.** (**a**) Bridge model, (**b**) bridge section size, (**c**) vehicle load (unit: mm).

The vehicle load *P* was divided into three grades, 10 kg, 20 kg, and 30 kg, respectively. The load grade of 10 kg was used to calibrate the strain integral coefficient, and the other load grades were used to test. As shown in Figure 6, the bridge model was divided into three lanes, and the vehicle acted on the left, middle, and right positions of each lane. Thus, the vehicle load position was divided into nine conditions.

**Figure 6.** Vehicle load position.
