## 5 Conclusions  
In this study, six scaled models of two-column piers were constructed and tested to investigate their behavior when seismic load is applied. Test specimens having three different reinforcement details were loaded in the longitudinal direction and the transverse directions.  
Initially, bond failure was expected according to lap-splice reinforcement detail. If the longitudinal reinforcements are lap-spliced to enough length and the transverse reinforcement is appropriate, the flexural failure can be expected. Multi-column piers have a smaller cross-sectional size than single-column piers, and the fact that the plastic hinge length is small may be why there was no bond failure at the lap-splice. Accordingly, the effect of the lap-splice resulted in the reduction of the curvature of the corresponding height because the longitudinal reinforcement bar ratio was increased.  
The behaviors of two-column piers in the transverse direction is different from the behavior in the longitudinal direction. For the transverse direction, high ductility was produced due to multiple plastic hinges. The ultimate failure occurs due to the bending failure of the top of the column connected to the cap beam, so the ductility is affected by the seismic reinforcement detail of this part.  
In this study, lap-splicing did not have a significant effect. However, it should be noted that if there is a lap-splice in the longitudinal reinforcement of an actual pier, bond failure may occur depending on the seismic detail. In particular, since it is a result of a small-scale test, the size effect needs to be additionally considered. Nevertheless, piers with non-seismic details can withstand earthquakes to some extent if adequate details are supported.  
Experiment, J.H.K.; supervision, I.-H.K.; writing--review and editing J.H.L. All authors have read and agreed to the published version of the manuscript.  
Figure 17: Energy absorption with respect to displacement ductility factor.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **RH-NS-L** & **RH-SL-L** & **RH-SC-L** & **RH-NS-T** & **RH-SL-T** & **RH-SC-T** \\ \hline Yield displacement \(\Delta_{y}\) (mm) & & 43.67 & & & 19.21 & \\ \hline Maximum lateral force, \(P_{m}\) (kN) & 117.72 & 118.13 & 116.06 & 287.93 & 294.06 & 277.06 \\ Displacement at \(P_{m}\) (mm) & 118.34 & 132.94 & 153.30 & 56.25 & 70.27 & 63.58 \\ Displacement at failure (mm) & & 171.47 & 193.46 & 93.68 & 101.69 & 96.73 \\ Drift ratio at failure & & 4.45\% & 5.02\% & 3.12\% & 3.39\% & 3.22\% \\ Displacement ductility at failure & & 3.92 & 4.43 & 4.87 & 5.29 & 5.03 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of failure displacement and ductility.  
**Funding:** This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (No. 20181510102410) and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2019R1I1A3A01058812).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.