## 3 Results  
### The First Test: The Bridge at University of Calabria  
The first test was performed on a double deck bridge at the University of Calabria, Italy. The bridge materializes the South-North central axis, that characterizes the campus layout. All the buildings are lined up on the sides of the bridge. The lower deck is intended for pedestrians. The upper one is used occasionally for vehicular traffic. The main structure is a simply supported truss beam, characterized by three longitudinal tubular elements; the lower deck is hung from the upper ones (Figure 3).  
In Figure 4 the cross sections of the simply supported truss beam at the bearings are shown. The red line represents the path followed by the laser scanner during the acquisitions in line-scan mode.  
Figure 5 shows the test layout. The test was performed during the parking of a truck elevator, which weight was about 260 kN (Figure 6). The TLS position was chosen below the deck. In this way it was possible to acquire the points of the upper element of the deck structure, realized with a 3D truss. To minimize the oscillations of the rotation axis, the minimum sampling rate was chosen, equal to 70,000 points per second. The distance between the bearings of the bridge is 40.30 m. Measuring the position of the wheel axles, the center of gravity of the truck was obtained, located 11.07 m from the south support.  
Figure 4: The bridge’s Cross Sections at the bearings: (**a**) transversal; (**b**) longitudinal.  
Figure 3: The bridge at the University of Calabria: (**a**) the pedestrian deck; (**b**) the upper deck.  
RiSCAN PRO(r), the software provided with the TLS, was used for the first processing of data. The coordinates of the scanned points were obtained, with reference to the TLS centre and expressed in meters. The software described in Section 2.3 was then used; the following figures show the results.  
Figure 7a shows, on an arbitrary scale, a view of the entire span and of the lines obtained with the bridge loaded and without loads. The origin of the reference system is the center of TLS. One can observe that the deck has a vertical displacement, with respect to the horizontal direction, of about 134 mm in the middle of the span, with only the dead load. The circles indicate the enlargements shown in Figure 8. Figure 7b shows the deflections due to the truck load, obtained from raw data and the trend-line. In this case, a cubic polynomial, of the type described in Equations (4) and (5), provides an effective fitting line.  
Figure 5: The Layout of the first Test.  
Figure 6: The truck elevator, used as static load.  
Figure 8 shows two enlargements of raw data and interpolation lines. It is possible to observe that the lines obtained with the loading and unloading bridge coincide on the bearing (Figure 8a), while in the central part of the beam there is a difference in height of about 2 mm (Figure 8b). Also in this case the coordinates are referred to the intrinsic reference system of the instrument.  
Using a FEM program developed at the University of Calabria [31], it was obtained an accurate evaluation of vertical displacements. The computed deflection was 1.95 mm, 2.5% less than the value attained by using the proposed methodology. Furthermore, by means of a total station Leica 1201+, a precise measurement was performed. A prism was placed in the middle of the span and was repeatedly monitored from a distance of about 22 m. The automatic target recognition function (ATR) has been activated, which has an accuracy of 1 s; therefore the vertical displacements are obtained with an accuracy of about 0.1 mm. The variation of the bridge deflection thus obtained was 1.9 mm, 5% less than that obtained using the proposed methodology.  
Figure 7: (**a**) The elevation of the bridge and the lines obtained from TLS. The circles indicate the zooms shown in Figure 8; (**b**) The deflections obtained from the row data (blue) and the trendline (red).