# Precast Bridges of Bamboo Reinforced Concrete in Disadvantaged Village Areas in Indonesia
## 4 Discussion
The discretization of the bamboo reinforced concrete bridge frame for the finite element method (FEM) is shown in Figure 31. The Y-direction and X-direction displacement are shown in Figures 32 and 33. The loading stages and Y-direction displacement of the finite element method simulation results are combined with the load vs. displacement laboratory test results [38], and with the field test results as shown in Figure 34. Figure 33 shows displacement in the X-direction; the green color shows the minimum displacement, and the orange and blue colors show the maximum positive and negative displacement, respectively. FEM analysis modeling on the bamboo reinforced concrete frames can be seen in Item 2.3 of the numerical method used. Bridge integrity is the ability of a bridge structure or bridge components to withstand the designed load, preventing structural collapse due to cracks or fractures, deformation, and structural fatigue. Structural integrity is a concept used for the design plan and designing service load. Stiffness is the main parameter of the resistance of a bridge structure to get good bridge integrity [24]. The stiffness of the elements of the bridge structure needs to be controlled to prevent sudden collapse due to cracking and excessive deformation. Stiffness control of the beams and bridge frames was analyzed through a combination of load vs. displacement from the simulation results of the finite element method (FEM), the results of laboratory experiments [22, 38], and the results of field experiments as shown in Figure 34. Control was carried out at the maximum load point of the bamboo reinforced concrete precast frame bridge test in the field, which was 15.5 kN, as shown in Figures 35 and 36. Documentation of the direct test of the bamboo reinforced concrete precast bridges can be seen at the following link: [[https://bit.ly/3](https://bit.ly/3) gzaW30]([https://bit.ly/3](https://bit.ly/3) gzaW30). Calculation of the aerodynamic effects due to wind loads and dynamic analysis on precast concrete bamboo bridges were not carried out. Based on the Earthquake Resistance Standard for Bridges, the SNI SNI-07-SE-2015 [51] dynamic analysis needed to be carried out for bridge types with a complex behavior, one of which was the main span exceeding 200 m. In this study, the bridge width is 2.24 m and the bridge span is 3.20 m, and the ratio of the bridge width to the bridge span of 0.7 is still stable against aerodynamic effects due to wind loads according to [PERSON]'s requirements (\(B\geq L/25\)) and still meets the maximum deflection requirements of AASHTO [48] and RSNI T-12-2004 [49], which is \(\Delta_{max}=\text{L}/800=3.75\) mm. Figure 34: The relationship of load vs. displacement of the bridge frame. Figure 33: The displacement in the X-direction of the bridge frame. The next step was validating the stiffness of the beam and bridge trusses. The main principle is that the bridge must be in a service condition, with a Serviceability Limit State (SLS) load. The elements of the bridge structure should not be subjected to cracks, deflection, or vibrations causing user discomfort. The allowable deflections are those that are elastic deflection and do not cause the crack. Stiffness is the main parameter of structural resistance. Therefore, the stiffness of the field test results needs to be validated by the stiffness of the laboratory test results. Load-displacement relationship diagrams of the experimental results, laboratory results, and FEM analysis results are combined into one graph. The maximum test load of the bridge becomes the stiffness control limit, which is 15.50 kN. Based on the displacement of the laboratory test results, and the displacement of the field experiments results of the bamboo reinforced concrete frame precast bridge at a stop load of 15.50 kN, the displacement ratio of the laboratory test results to the displacement of the field experiment results (\(\Delta_{Exp}/\Delta_{LAB}\)) = 2.6 for the bridge frame and 4.07 for the bridge beam.