## 2 Test Program
### Test Setup and Loading Procedure  
The beam tip was subjected to a cyclic load as the column was subjected to a constant compressive load. A schematic of the test setup is provided in Figure 3. The bottom and top of the column formed a hinged support, which was simulated by solid steel circular shafts placed between the hole of two steel connectors. The compressive load of the column end was applied by a 2000 kN hydraulic jack. The cyclic load of the beam tips was applied by two electro-hydraulic servo actuators. According to the Chinese code [16], the seismic loading scheme consisted of two phases, namely the load-controlled and displacement-controlled phases. At the beginning of the test, the specimens were under reverse cyclic loading with load control, in which only one cycle of each load level was applied. When the specimen experienced cracking in the joint core or the longitudinal reinforcements in the beam reached their yield strain, the process was switched to displacement control. The corresponding displacement of the beam tip is defined as \(\Delta_{y}\). During the displacement-controlled phase, three cycles were applied  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Material** & **Cement** & **Silica** & **0.16-0.315** & **0.315-0.63** & **0.63-1.25** & **Steel** & **Super-Plasticizer** & **Water** \\  & **Fume** & **Sam** & **mm Quartz** & **mm Quartz** & **Sim** & **Sand** & **Fiber** & **Super-Plasticizer** & **Water** \\ \hline Mass (kg) & 756.7 & 227.0 & 169.6 & 370.8 & 737.7 & 105.8 & 20.4 & 216.4 \\ \hline \hline \end{tabular}
\end{table}
Table 2: UHPFRC mixture proportions (per m\({}^{3}\)).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of** & **Application** & **Effective** & **Yield** & **Ultimate** & **Elastic** \\
**Reinforcement** & **Application** & **Diameter** & **Strength** & **Strength** & **Modulus** \\  & & **(mm)** & **(MPa)** & **(MPa)** & **(MPa)** & **(MPa)** \\ \hline HPB300 & Transverse stirrup & 6 & 353.56 & 398.30 & 210 \\ HPB300 & Longitudinal bars & 9.5 & 360.6 & 522.2 & 201 \\ HRB400 & Longitudinal bars & 14 & 423.40 & 632.40 & 200 \\ HRB400 & Longitudinal bars & 20 & 441.90 & 588.60 & 200 \\ HRB600 & Longitudinal bars & 14 & 651.00 & 861.67 & 195 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Material parameters of reinforcement.  
Figure 2: The typical stress-strain curves of HRB400 and HRB600 grade steel bars.  
for each displacement level, and the displacement amplitude was \(\Delta_{y}\). The test was terminated when the load-carrying capacity of specimens dropped to less than 85% of the maximum load or eventually failed. For interior UHPFRC beam-column joint specimens, the left and right beam tips are subjected to reverse loading simultaneously, with an equal loading rate.  
The instrumentation was designed to monitor the overall specimen response and load resistance mechanism in the beam, column, and joint. The vertical load and displacement of the beam tip were measured by load and displacement sensors. The strains in the longitudinal reinforcement bar and stirrups were monitored by strain gauges. The UHPFRC strain in the joint regions was measured by gauges attached to surfaces of these regions. The shear distortions of joints were measured by two displacement sensors installed in the joint regions. The joint shear deformation angle was calculated by [17]:  
\[\gamma=\frac{\sqrt{a^{2}+b^{2}}}{2 ab}(\Delta_{1}+\Delta_{2}+\Delta_{3}+\Delta _{4}) \tag{1}\]  
in which \(\gamma\) is average joint shear deformation angle; \(a\) and \(b\) are the horizontal and vertical distances between the end points of the diagonal, respectively; and \((\Delta_{1}+\Delta_{2})\) and \((\Delta_{3}+\Delta_{4})\) are the changes in diagonal lengths.