## 2 Test Model of Multi-Column Bridge Piers  
### Test Specimens  
Three sets of test specimens were constructed. They were designed to be one-fourth-scale models of the existing two-column piers on Korean highways. The height of prototype is determined to be 12 m to induce flexural failure for transverse direction loading. The diameter of the column section of scale model is 500 mm and the height is 3000 mm. In the case of the scale model, reinforcement with a diameter of 10 mm was used for the longitudinal reinforcement due to the limitations of size of commercial reinforcement bar. Instead, the reinforcement bar ratio was the same for the full-scale model and the one-fourth-scale model as 1.174%. For the lateral reinforcement, a reinforcement bar with a diameter of 4 mm was fabricated. The concrete strength was 24 MPa, which is the same value applied to the prototype model. Therefore, it is judged that the Young's modulus as determined by the concrete strength was similar between the scale model and prototype. However, the geometrical mix design of the concrete could not be properly scaled because of commercial concrete limitations. The properties of the test specimens are summarized in Table 1, and Figure 1 illustrates the geometry of the test specimen. \begin{table}
\begin{tabular}{c} 0.052 \\ 0.052 \(\sigma_{\text{ck}}A_{g}\) \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of the test model. The characteristics of 6 test specimens are described in Table 2. The test specimen was composed of two specimens as a set so that the behavior characteristics in the longitudinal direction and the transverse direction to the superstructure could be investigated. Additionally, 3 different reinforcement details were applied for each specimen set. The first specimen (RH-NS) has the same reinforcement details as existing bridge piers. The second specimen (RH-SL) has different reinforcement bar details. For this specimen, the number of lap-spliced longitudinal reinforcement bars in the plastic hinge region was the half of the total number of longitudinal reinforcement bars, and the transverse reinforcing bar was installed with 1/2 of the amount required by the seismic design regulations. The third specimen used continuous longitudinal reinforcing bars without a lap-splice, and a minimal amount of transverse reinforcing bars was installed to prevent local buckling of the main reinforcing bars. The reinforcement details for each set are shown in Figure 2. Each specimen of the RH-NS set was designed as a prototype without any consideration of seismic performance. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Specimen** & **Loading Direction** & \begin{tabular}{c} **Lap-Splice of** \\ **Longitudinal** \\ **Reinforcement** \\ \end{tabular} & \begin{tabular}{c} **Lap-Splice of** \\ **Longitudinal** \\ **Reinforcement** \\ \end{tabular} & \begin{tabular}{c} **Lateral Reinforcement** \\ **Detail** \\ \end{tabular} & \begin{tabular}{c} **Spacing of Lateral** \\ **Reinforcement** \\ \end{tabular} & \
\begin{tabular}{c} **Volumetric** \\ **Reinforcement** \\ **Ratio** \\ \end{tabular} \\ \hline RH-NS-L & Longitudinal & 100\% in the lower & No consideration of seismic & 37.5 mm & 0.268\% \\ RH-NS-T & Transverse & region & performance & & \\ \hline RH-SL-L & Longitudinal & 50\% in the lower & 50\% of what is required by & 20 mm & 0.503\% \\ RH-SL-T & Transverse & region & AASHTO specifications & & \\ \hline RH-SC-L & Longitudinal & No lap-splice &
\begin{tabular}{c} Preventing local buckling of \\ the longitudinal bar \\ \end{tabular} & 30 mm & 0.335\% \\ RH-SC-T & Transverse & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of the characteristics of each specimen. Figure 1: Geometry of the test specimen (units: mm). For the RH-SL set, the volumetric transverse reinforcement ratio for this set is 50% of what is required by AASHTO (American association of state highway and transportation officials) specifications [28].