# Collapse Potential of an Existing Reinforced Concrete Bridge Structure
## 5 Conclusions  
The following conclusions can be drawn from the results of this study. * No damage has been observed in the longitudinal (traffic) direction of the bridge. Damage was only detected in the transverse direction;
* In the analyses conducted for each earthquake record, it was observed that the performance limits were reached at different spectral acceleration values for each record. However, for the same ground motion, all performance level limits were achieved at the same spectral acceleration level;
* It was observed that the columns reached the specified section damage limits before the elastomeric bearings and shear keys. Consequently, in case of collapse, the main reason is not the probable damage of the shear keys or elastomeric bearings;
* The median and standard deviation values characterizing the fragility curve were found to be 0.33 and 0.31, respectively. * The Turkish Bridge Seismic Design Code requires that this type of bridge must satisfy the Collapse Prevention Performance Level under the effect of an earthquake with a 2% probability of exceedance in 50 years. In such a case, the probability of collapse is expected to be minimal from the point of view of code-compatible design. According to the spectrum provided by the Turkish Bridge Seismic Code for an earthquake with a 2% probability of exceedance in 50 years, the spectral acceleration corresponding to the structural period in a shorter direction (0.24 s) is 1.98 g. The probability of exceeding the Collapse Prevention Performance Level is 100%. In other words, the investigated bridge will collapse at this ground motion level;
* The spectral acceleration value used for the design of the bridge is 1.51 g. This corresponds to the design earthquake with a 10% probability of exceedance in 50 years. Even at this spectral acceleration level, the probability of collapse is 100%, which is already high. Given that the spectral acceleration for an earthquake with a 2% probability of exceedance in 50 years is even higher, the collapse probability will still be 100% in the case of determination of the probability based on the design spectrum;
* The Turkish Bridge Seismic Design Code requires that this type of bridge must meet the Uninterrupted Occupancy Performance Level under the effect of an earthquake with a 50% probability of exceedance in 50 years. According to the Turkish Bridge Seismic Design Code [1], the spectral acceleration value for this level of earthquake is 0.99 g. The probability of exceeding the Uninterrupted Occupancy Performance Level at this spectral acceleration level would still be 100%, even in case of obtaininga fragility curve of this performance level under the effect of ground motion records scaled to this ground motion level;
* No shear failure has been observed in any of the bridge's structural elements. As observed, the bridge does not meet the performance requirements specified by the code. The absence of shear failure in any of the structural elements suggests that the bridge does not exhibit significant deficiencies in ductility or shear strength. The observed damage is primarily attributed to the insufficient lateral stiffness of the piers, which fails to sufficiently prevent excessive lateral displacement. This highlights the importance of ensuring not only adequate strength and ductility but also adequate stiffness in bridge design. Furthermore, the fact that all damage thresholds are reached at the same spectral acceleration level for a given earthquake indicates a lack of redundancy or insufficient reserve capacity in the structural system of the bridge. Methodology, M.S.K. ; Investigation, Z.Y. ; Data curation, Z.Y. ; Writing--original draft, M.S.K. ; Supervision, M.S.K. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The raw data supporting the conclusions of this article will be made available by the authors upon request. The authors declare no conflicts of interest.