## 3 Results of the Field Experiment  
### Static Behavior  
Figure 6 shows the deflection angle calculated from the transducer measurement and image processing approach. In this figure, three loading cases are shown; case 1 (1.57 Tons), case 2 (12.24 Tons), and case 3 (19.66 Tons). The deflection angle calculated from the transducer on Loading case 1 ranged from 0.0004-0.0066 with a difference of 0.01; between R4 and R3, causing a deflection ranging from 0.0030-0.0460 mm. On the other hand, Loading case 2 had a deflection angle ranging from 0.0166-0.0596 with a difference of 0.04 and deformation of 0.1160-0.4160 mm; while Loading case 3 recorded deflections from 0.0278-0.0925 with a residual of 0.06 with deformation of 0.1940-0.6460 mm. A deformation 0 less than 0.1 from Equation (2) was considered reasonable. It meant the structure operated using the concept outlined in Equation (1) (principle of super-position). However, transducers R3 and R4, revealed in Figure 6c,d, exhibited higher deflections from Loading case 2. It was suspected to be due to the calibration and sensitivity of the transducer to higher loads. On the same note, the image processing approach recorded deflections increasing from Loading cases 1-3, that is, Loading case 1--0.0079 (0.0548 mm); Loading case 2--0.0340 (0.2377 mm), and Loading case 3--0.0492 (0.3435 mm), with minimal mean deviation from the transducer measurements of 0.0043, 0.0016 and 0.004 from Loading case 1 in that order, exemplified in Figure 6. Significant \(\Delta\theta\) residuals were observed between the displacement transducer and image processing approach. The Bailey Bridges consist of several panels [27] on each span connected with pins whose tolerances vary. As a result, the pins reset during loading [1], leading to large deflections depending on the spans' side (left or right span). Moreover, the bending moment along the panels does not assume a perfect circular curve because the spans are an assembly of panels having approximately similar rotational angles as opposed to a single continuous beam using the second theorem (\(t_{2/1}=A\overline{x}/EI\)) in Moment area method. Whereas \(t_{2/1}\) tangential deviation, \(A\) area under the curve on a cantilever beam, \(\overline{x}\) centroid, \(EI\) flexural rigidity (\(E\) modulus of elasticity and \(I\) moment of inertia) [26; 27]. Therefore, determining deflection from differentlocations will give rise to varying results, LVDT at 400 mm, and image processing method at 5.905, 10.905, and 15.905 m. Further, the image processing method's targets were on the top chord which experienced compression during loading. On the other hand, the displacement transducer was on the lower chord, which was vulnerable to tension [2, 27]. The phenomena correspondingly affect the profile hereafter presented in Figure 7.  
Figure 7 shows the deformation profiles along the bridge span. From the results, the profile showed symmetry at the center span, increasing with loading cases 1 to 3 on both the transducer measurement and image processing approaches. The deformation at the center span was higher with the transducer (tension members) than with the image processing approach (compression members) [2, 27] with 2.18-14.42 mm. The results show a linear-elastic behavior having approximately similar characteristics in both approaches. Figure 6: Deflection angles calculated from transducer and image processing measurements and FEA at (a) R1. (b) R2. (c) R3. (d) R4. (e) L1. (f) L2. Figure 7: Mean deformation profiles under loading cases 1, 2, and 3 along the five targets on the bridge span. Moreover, the deformation profile indicated an increasing bending moment from the end shears to the center of the span. The phenomena were similar in both spans. In reference to the AASHTO 2010 Bridge design specification, the permissible in-service loading is span/800 [28], translating to a maximum allowable deflection of 39.73 mm under load.