# Studies on Seismic Performance of Precast Concrete Columns with Ground Splice Sleeve
## 3 Test Results and Discussion
### Discussion on Test Results
#### 3.2.5. Ductility  
Ductility refers to the ability of a section to deform beyond its yield point without a significant strength loss, which is one of the essential indexes that reflect the inelastic deformation capacity of structures, members, and materials, and that evaluates the structural seismic performance. If a structure or a member has a strong inelastic deformation ability after yielding, it has a good ductility and ductile failure mode, but if not, brittle failure may happen more easily.  
According to the deformation types that ductility represents, ductility is mainly categorized into the following four classifications: strain ductility, curvature ductility, rotation ductility, and displacement ductility. For displacement ductility, it is defined as the ratio of the ultimate displacement to the yield displacement. This paper utilizes the displacement ductility of the column end for analysis, denoted as \(\mu_{\Delta}\), which is expressed as follows:  
\[\mu_{\Delta}=\frac{\Delta_{u}}{\Delta_{y}} \tag{4}\]  
where \(\Delta_{u}\) denotes the effective horizontal displacement of the column when the horizontal loads imposed on the specimens begin to decline while the horizontal displacement continuously increases; \(\Delta_{y}\) denotes the effective horizontal displacement of the column when the specimens yield. The effective horizontal displacement is obtained from the displacement at the top of column minus the displacement of the pedestal.  
Based on Table 7, it is shown that all of the four prefabricated columns have a displacement ductility coefficient of the column end larger than 3.2, which satisfies the general regulation that the displacement ductility coefficient of the frame column should be larger than 2.0 [43], indicating that the prefabricated columns possess good ductility.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen** & **1** & **3** & **34** & **133** \\ \hline
1\# (cast in situ) & 0.153 & 0.123 & 0.049 & 0.011 \\
2\# & 0.183 & 0.164 & 0.073 & 0.059 \\
3\# & 0.145 & 0.128 & 0.039 & 0.024 \\
5\# & 0.249 & 0.171 & 0.067 & 0.047 \\
6\# (cast in situ) & 0.188 & 0.168 & 0.016 & 0.045 \\
7\# & 0.191 & 0.230 & 0.027 & 0.047 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Viscous damping coefficient \(h_{e}\) of the specimens.  
In conclusion, the prefabricated columns not only have high load-carrying capability but also have good ductility and energy-dissipating capacity, which meets the earthquake-resistant requirements. Through the experimental study, some important conclusions can be drawn as follows:  
1. According to the hysteresis loops of the specimens, the hysteresis curves of both the cast-in-situ columns and prefabricated columns have changed from plump shuttle shapes to reversed S shapes with the reduced pinch phenomenon.
2. As for the load-carrying capability and stiffness, the cracking load of the prefabricated columns is almost identical with that of the cast-in-situ columns. Take the fully grouted specimen 5# for example; its yield load and ultimate load are slightly less than that of the cast-in-situ columns. Furthermore, the stiffness of the prefabricated columns degrades slower than that of the cast-in-situ columns.
3. Based on the viscous damping coefficient and displacement ductility, the behavior of energy dissipation of the prefabricated columns is close to that of the cast-in-situ columns, indicating that the prefabricated columns have satisfactory energy-dissipating capacity.
4. The ultimate displacement angle of the prefabricated columns is between 1/104 and 1/54, which satisfies the requirements of the code for seismic design on columns under rare earthquake [44].