*4.1. Experimental Setup*

To test the feasibility of the proposed method, a series of bridge model experiments were conducted. The experimental platform was made of an acceleration platform, test bridge, and deceleration platform, which is shown in Figure 12a. The model bridge was made according to the size of the numerical simulation bridge, as shown in Figure 5, the material of the model bridge is polymethyl methacrylate (as shown in Figure 12b), and its density is 1170 kg/m3, the Poisson's ratio is 0.35, and the elastic modulus is 3.25 × 10<sup>4</sup> MPa.

The experimental vehicle models were divided into two-axle and three-axle vehicles, as shown in Figure 13, and the way to change the vehicle weight was to add counterweight in the vehicle. In addition, the long-gauge FBG strain sensors were used to collect and analyze the data in the experiment [1]. Based on the influence line method considering the load transverse distribution, five FBG strain sensors were arranged in the mid-span of each beam bottom, as shown in Figure 12b.

(**a**) (**b**)

**Figure 12.** (**a**) Experimental platform, (**b**) model bridge.

**Figure 13.** Vehicle model in the experiment: (**a**) Two-axle vehicle, (**b**) three-axle vehicle.

*4.2. Analysis of Experiment Results*

The MOI's S130 model acquisition instrument was used to collect the data of FBG sensors in the experiment, and the measured data were used for load identification. When the vehicle drives in the second lane with the speed of 1.33 m/s, the typical long-gauge strain time history curve of each beam bottom is shown in Figure 14.

**Figure 14.** Measured strain time history curve.
