## 4 Cases Study
### Czech Republic Grider Bridge Case Study  
This Case Study looks at a Grider Bridge in Dob, Czech Republic, built in 1983, specifically its asphalt roadway and steel barrier rails (Figure 12). The average daily traffic on the bridge is 20,306 cars and 3868 trucks in Dob, where the bridge connects rail D4 and local route III/10226. It is unavailable to approach the concrete foundations or abutments, and the two portions of the superstructure (one for each direction of traffic) comprise ten girders made of precast and prestressed I73 concrete. The drainage system is on the side.  
Figure 11: Case Study Methodology for Establishing a Quality Control Procedure (_source: COST Action TU1406_).  
According to an available Finite Element analysis, the following are the estimated load capacities: Normal capacity for an unlimited number of vehicles: 24 tons; capacity for a single vehicle on the bridge: 53 tons; exceptional capacity for special heavy transport: 292 tons. What matters is the lateral beam's bending capacity. The Czech method uses a scale from I (excellent) to VII (emergency), with ratings ranging from bad and satisfactory for the superstructure and substructure, respectively. The availability level is 2, meaning it is \"available with limitations\" (1 is available until 5 for unavailable).  
Inspecting the bridge shows that the concrete is deteriorating and the reinforcement is eroding in both abutments, the main girders, the expansion joints, the waterproofing, bearings and concrete parapets. Possible failure areas have been found, such as (a) the failure from the outermost girder resulting from substantial degradation and rust of the support, which affects the prestressing cables and prestressing bolts and causes the girder to fail. Be aware that it is probably going to happen because leaks within the anchoring location can cause rust of the prestressing support nearby to the anchorage; (b) The failure from the bearings caused by heavy corrosion, nevertheless it will require a long time, and the results won't be wrong; (c) If the abutment loses stability within its outer bearing, local pressure on the deteriorating concrete will cause a local girder to break; if the girder slips, the failure will cause a significant deformation, not a global fall. Different materials used to test girders show the alkali-silica reaction as well as the range of compression strength of concrete. The carbonation depth on the main girders is 8.6 mm; on the support, it is 26.7 mm, and on the parapet is 36.7 mm. The superstructure can withstand 75 freeze-thaw cycles, while the concrete on the asset can only withstand 25 cycles.  
Key performance indicators are developed using information on leading methods utilized by the Czech Republic (see Table 1). For the pre-stressed concrete and reinforced  
Figure 12: Czech Republic’s girder bridge (_source: COST Action TU1406_).  
concrete, a combination of material tests are performed for the KPI evaluation, including compressive concrete strength, alkali-silica reaction, carbonation and freezing resistance tests. On the other hand, for the other type of structures, the estimated failure time is assumed according to the experience from the research team with the concrete structures in Czech Republic, and then estimating the defect progress. It can be considered as the safe assumption under severe condition.  
Despite being conservative under extreme exposure conditions, the anticipated failure period has been established upon the Czech Republic's previous work using concrete structures as well as the evolution of the flaws. The dead load's project estimated reliability index (8) was 4.1%; the corresponding value at the live load was 3.0%, considering the appropriate materials, loading, and model uncertainties. Careful deliberation led to selecting this lower value to reflect the overall bridge condition concerning the identified concerns.