## 4 Experiment Verification  
### Experiment Design and Arrangement  
An indoor simply supported the composite-box-beam experiment under moving load was designed to validate the accuracy of full-field temporal-spatial structural displacement measurement with STMM. In the experiment, the beam is 5.77 m long, with a cross section of 160 mm in width, 40 mm in height, and 2 mm in thickness, shown in Figure 10.  
On the simply supported beam, the dynamic load \(F\) was applied with an 8 kg toy truck, traveling from the right support end to the left at a constant speed, as shown in Figure 11. The total image sequence was taken in 8 s, and the toy truck started 1.8 s after the shooting began. Then, the truck traveled to the middle span point at 4.2 s, arriving the left end at 6.6 s and stopped until the shot was over.  
Theoretically, the beam deflection curve, under concentrated force \(F\), can be formulated according to the differential equation in mechanics of materials.  
\[w(x)=\begin{cases}\frac{Fbx}{6 EL_{z}l}(l^{2}-x^{2}-b^{2})&0\leq x\leq a\\ \frac{Fb}{6 EL_{z}l}[\frac{l}{b}(x-a)^{2}+(l^{2}-b^{2})x-x^{3}]&a\leq x\leq l \end{cases} \tag{4}\]  
where \(w\) is the deflection of beam, \(a\) and \(b\) are the distance between concentrated force and the two supports end, respectively, shown in Figure 11, and \(EL_{z}\) is the flexural rigidity of the beam.  
In the experiment, the image sequence was captured orthogonally by a SONY video camera, and the dynamic displacement-time history curve in the mid-span of the beam were measured with a laser ranger, and the parameters of the camera and laser ranger are listed in Table 1.  
In the image, the number of pixels along test beam length direction is 3770 pixels, and the spatial measurement resolution of the system is 1.53 mm/pixel. Research showed  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Experiment Device** & **Model** & **Technical Parameters** \\ \hline Video Camera & SONY/FDR-AX40 & Resolution 3840 px \(\times\) 2160 px \\ Laser Ranger & RIFTEK/R603 & 9600 Baud \\ \hline \hline \end{tabular}
\end{table}
Table 1: Parameters of experiment devices.  
Figure 11: Diagram of a simply supported composite box beam experiment.  
Figure 10: Cross section of the composite box beam.  
that high reflection coefficient material [20] could help to improve the accuracy of machine vision measurement. A 1.5 cm reflective strip in height was stuck on the beam surface, shown in Figure 12, to improve the distinguishability between structural surface and the environment.  
The setup of the simple supported composite box beam experiment under moving toy truck load is shown in Figure 13.  
Following the procedure in Figure 9, the mask and transversed region are selected in each column of 1-D image, as shown of the \(i\)th column in Figure 14, and slice template matching model was set up column by column. Totally the entire beam region was segmented into 3770 columns, and 3770 1-D slice template matching models were setup to track the full-field temporal-spatial deflection of the simply supported beam.  
The dynamic response of the beam is recorded at the speed of 25 frames per second when the toy truck travels from the right end to the left end, and a total of 94,250 displacement data can be calculated per second for all 3770 monitoring points along the beam.  
Figure 14: Mask selection and transversal region of 1-D image in the \(i\)th column.  
Figure 12: Reflective stripe on beam surface.  
Figure 13: Front view of simply supported composite box beam.