# Dynamic Performance of a New-Type PSC I-girder for Railway Bridge Application
###### Abstract  
This study intends to verify analytically and experimentally the performance of a new type of prestressed concrete (PSC) I-girder for its application as railway bridge. Since the girder-type railway bridge develops relatively low torsional rigidity, there is risk for the dynamic responses to amplify due to the superposition of the torsional mode and flexural mode. The superposition of the torsional and flexural modes as well as the dynamic stability of the railway bridge were examined through dynamic analysis. Three-dimensional modelling was built to be suitable for carrying out moving load analysis. Four different span lengths of 30, 35, 40 and 45 m adopted considering the most applied span length currently and future lengthening of the span length. Moreover, a full-scale girder specimen with span length of 35 m was fabricated and subjected to dynamic loading. The measured dynamic responses were then compared to the analytic values. Finally, the ultimate bearing capacity of the specimen was verified by static loading test. P 3020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020220202020202020202020202020220202020202020202020202020220202020 Table 1 classifies the 34,297 roadway bridges according to the type of their structure and superstructure [1]. The most preferred superstructure types are the reinforced concrete (RC) slab bridge followed successively by the rahmen (rigid-frame) bridge, the prestressed concrete (PSC) I-girder bridge and the steel box girder bridge with rates of occupancy of 24.1%, 23.6%, 22.6% and 13.7%, respectively. These four types of superstructure account for 84% of the bridge stock. According to [PERSON] et al. [3], most of the bridge superstructures applied the RC slab and the RC T-girder in the 1950s, and the PSC I-girder became the preponderant type of superstructure after a peak in the 1960s owing to its low cost and shortened construction period. Figure 2a shows the domestic bridge market share of the PSC I-girder since 1970 and reveals that this share increased by an average of 36.2% between 2014 and 2018. Figure 2b presents the change in the distribution of the span length for the PSC I-girder since its first introduction in the early 1960s. It can be observed that the PSC I-girder is currently preferred for medium span lengths between 30 m and 40 m. Apart from special long-span bridges, the application of the PSC I-girder as superstructure is now common in Korea for its aesthetics and economy for usual span lengths [4; 5]. For the roadway bridges, the stiffness of the girder is a primary factor determining the structural stability. Besides, securing the dynamic stability under large live loads and repeated loading is the primary factor in the case of railway bridges. Accordingly, studies have been conducted recently on the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Bridge Type** & \begin{tabular}{c} **Number of** \\ **Bridges** \\ \end{tabular} & \begin{tabular}{c} **Total Span** \\ **(km)** \\ \end{tabular} & \begin{tabular}{c} **Superstructure** \\ **Type** \\ \end{tabular} & \
\begin{tabular}{c} **Number of** \\ **Bridges** \\ \end{tabular} &
\begin{tabular}{c} **Total Span** \\ **(km)** \\ \end{tabular} \\ \hline Suspension & 9 & 21.3 & RC slab & 8271 & 348.1 \\ \hline Cable-stayed & 69 & 74.3 & RC hollow slab & 238 & 22.1 \\ \hline Extradosed & 22 & 14.1 & RC box girder & 211 & 9.4 \\ \hline Truss & 17 & 8.9 & RC T-girder & 751 & 36.0 \\ \hline Internal & 8092 & 173.6 & PSC slab & 491 & 41.1 \\ \hline Arch & 226 & 40.7 & PSC hollow slab & 40 & 7.8 \\ \hline Steel plate girder & 307 & 61.2 & PSC box girder & 625 & 336.8 \\ \hline Steel box girder & 4705 & 1051.7 & PSC I-girder & 7768 & 1009.3 \\ \hline Steel I-girder & 201 & 23.1 & Preflex girder & 1362 & 88.4 \\ \hline Others & 892 & 83.6 & Total & 34,297 & 3451.5 \\ \hline \hline \end{tabular}
\end{table}