## 2 Experimental Plan
### Loading and Measurement  
The specimens were subjected to three-point bending with a span length of 3800 mm. Two LVDTs of capacity 100 mm were installed at the center of the beam. Five crack gauges of capacity \(\pm 5\) mm were installed such that the gauge length of each one was 430 mm. The gauge length of the original crack gauge device was 100 mm; however, it was extended using a dummy plate. The LVDTs measured the deflection at the front and back of the beam center, and the crack gauges were installed to measure the strain change and curvature of the beam section, as shown in Figure 4.  
The method of computing the curvature from the displacements measured using the crack gauges is expressed by Equation (1):  
\[\varepsilon_{1}=\Delta l_{1}/l_{1},\varepsilon_{2}=\Delta l_{2}/l_{2},\varphi =(\varepsilon_{2}-\varepsilon_{1})/h_{g} \tag{1}\]  
where \(l_{1}\) and \(l_{2}\) are the gauge lengths at the top and bottom crack gauges, respectively; \(\Delta l_{1}\) and \(\Delta l_{2}\) represent the displacements measured at the top and bottom gauges, respectively; \(\varepsilon_{1}\) and \(\varepsilon_{2}\) are the strains in the compression and tension extreme fibers, respectively; \(h_{g}\) is the vertical distance between the two gauges; and \(\varphi\) represents the curvature.  
The steps of the experimental procedure used to simulate the actual rehabilitation and reinforcement of the RC specimens are as follows (see Figure 5):  
Figure 4: Curvature calculation using crack gauges.  
Figure 3: Tensile test results of reinforcements (**left**) and external rods (**right**).  
1. First, bending tests of the unstrengthened control RC beams were carried out to determine their yield strength, ultimate strength, and the corresponding deflections (Figure 5a).
2. The specimens used for strengthening were prepared and the anchor holes at the end of the beam were drilled prior to the loading test rather than prefabricated so as to simulate the real-world condition of the beam (Figure 5b).
3. Preloading was applied to the unstrengthened beam through displacement control. Several repetitive loads were applied until the load exceeded the yield load in order to induce damage to the beam (Figure 5c).
4. The external unbonded member was post-tensioned after reducing the load (i.e., from the load exceeding yield load down to the service load of approximately two-thirds of the ultimate strength; Figure 5d). Since damage to the measuring device and measurement error can occur if the strengthening system were installed during the loading test, the system was prepared prior to the loading test and tensioned after the beam was damaged.
5. Tensioning was applied while monitoring the load-deflection curve and strain of the unbonded steel rod. The post-tensioning (PT) level was set at the first of two strengths: recovery of the deflection at the service load of the unstrengthened beam or attainment of a strain of 2000 \(\mu\varepsilon\) in the steel rod, which is approximately the force converted from torque that two adult men can apply using a wrench. At this time, an actuator was used to maintain the service load level by load control.
6. After the tensioning was completed, the test specimens were subjected to re-loading using the displacement control method until their final failure (Figure 5e).  
Figure 5: Experimental procedure: (**a**) testing of control beam; (**b**) drill hole for anchorage; (**c**) preloading; (**d**) post-tensioning (PT); and (**e**) reloading.