# Retrofitting of a Multi-Span Simply Supported Bridge into a Semi-Integral Bridge
## 6 Summaries and Conclusions  
The retrofitting of the Jinpu Bridge into a semi-integral bridge has successfully addressed critical structural issues and demonstrated measurable improvements in performance and durability. The following points summarize the success of this approach across key components:  
(1) Superstructure Beams:  
* The transformation of simply supported beams into continuous spans reduced the maximum mid-span positive bending moment by 11.1%, improving load distribution and reducing stress concentrations. Shear forces at interior supports increased by 6.4% but remained within allowable limits. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Loading Combination** & \begin{tabular}{c} **Earthquake** \\ **Direction** \\ \end{tabular} & \begin{tabular}{c} \(\Delta_{u}\) \\ **(mm)** \\ \end{tabular} & \begin{tabular}{c} \(\Delta_{limit}\) \\ **(mm)** \\ \end{tabular} \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} Dead load and E1 \\ \end{tabular} } & X & 2.6 & \\ \cline{2-4}  & Y & 1.3 & \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Dead load and E2 \\ \end{tabular} } & X & 7.7 & \\ \cline{2-4}  & Y & 3.9 & \\ \hline \hline \end{tabular}  
Notes: \(\Delta_{u}\) = calculated longitudinal displacements; \(\Delta_{limit}\) = limiting displacement.  
\end{table} 
Table 4: Ultimate displacement and calculated displacement of the pier. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Loading Combination** & \begin{tabular}{c} **Earthquake** \\ **Direction** \\ \end{tabular} & \begin{tabular}{c} \(M_{u}\) \\ **(kN\(\cdot\)m)** \\ \end{tabular} & \begin{tabular}{c} \(M_{r}\) \\ **(kN\(\cdot\)m)** \\ \end{tabular} & \begin{tabular}{c} \(V_{u}\) \\ **(kN)** \\ \end{tabular} & \begin{tabular}{c} \(V_{r}\) \\ **(kN)** \\ \end{tabular} \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} Dead load and E1 \\ \end{tabular} } & X & 508.9 & & 77.5 & \\ \cline{2-4}  & Y & 229.7 & & 106.3 & \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Dead load and E2 \\ \end{tabular} } & X & 984.7 & & 161.8 & \\ \cline{2-4}  & Y & 234.7 & & 312.6 & \\ \hline \hline \end{tabular}  
Notes: \(M_{u}\) = factored applied moments, \(M_{r}\) = resisting ultimate moments, \(V_{u}\) = factored applied shear force, and \(V_{r}\) = resisting ultimate shear forces.  
\end{table} 
Table 3: Ultimate and calculated moments and shear forces of the pier. * The elimination of mid-span expansion joints enhanced durability by removing frequent failure points prone to cracking and water leakage. (2) Semi-Fixed Dowel Joints:
* The use of semi-fixed dowels between the superstructure beams and the substructure, comprising steel bars encased in rubber sleeves, provided controlled flexibility by accommodating some movement while providing continuity. * The longitudinal displacement of the main beam was reduced by 80.1% under dead load and seismic conditions, demonstrating exceptional seismic resilience. * Stress concentrations at piers and abutments were managed efficiently, maintaining structural safety within design limits. (3) Piers and Abutments:
* Existing piers and abutments were successfully integrated into the retrofitted system without additional strengthening, reducing costs. * Maximum bending moments and shear forces on the pier and abutment remained well below their ultimate capacities, ensuring structural safety under all load conditions. * Maximum displacements at the top of the pier (7.7 mm) were well below the allowable limit (52.4 mm), showing a significant seismic safety margin. (4) Approach Slab System:
* The introduction of a new approach slab and transition slab system improved driving comfort and accommodated thermal movements. * Smooth transitions at the roadway interface were ensured by including expansion joints at critical locations, reducing vehicle-induced stresses. (5) Overall Impact:
* This retrofitting approach significantly enhanced the bridge's durability, seismic performance, and service life, while minimizing maintenance demands.