## 5 Bonded Anchor Tests
### Sustained Load Tests  
Sustained load experiments were carried out on non-reinforced cylindrical concrete specimens. Based on the experimental experience gained in the previous comprehensive experimental campaigns, different sizes were used for the two products. The aim was to avoid potential splitting failure due to the evolution of lateral stresses, while optimizing the weight and ensuring easy manipulation. The final dimensions were: (i) specimens with 450 mm diameter and 200 mm height for Product 1, and (ii) specimens with 300 mm diameter and 200 mm height for Product 2. Figure 3 shows sketches of the selected specimen geometries for each product.  
In this experimental investigation, pull-out tests on post-installed bonded anchors in a so-called \"confined\" configuration were carried out [57; 58]. Contrary to the standard \"unconfined\" configuration [57; 58] where the formation of a concrete cone is almost unrestricted, the confined configuration avoids concrete cone failure and ensures almost exclusive bond failure. Typically, ensuring a sufficiently high steel strength, this leads to the adhesive bond failure localized at the inner (failure on the interface between steel anchor rod and adhesive layer), outer (failure on the interface between adhesive layer and concrete), or a combination of the two failure modes. In the presented study, failure typically occurs due to a crack propagating within the adhesive layer from thread tip to thread tip (inner \"interface\" failure mode), as sketched in Figure 4.  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Product** & **Tests** & \(N_{100\%}\) [**kN**] & **CoV [\%]** \\ \hline Product 1 & 4 & 157.3 & 3.36\% \\ Product 2 & 6 & 111.8 & 7.48\% \\ \hline \hline \end{tabular}
\end{table}
Table 5: Experimentally obtained pull-out load capacities for both products.  
Figure 5 shows the detailed sketch of the set-up used for sustained load tests.  
Figure 4: Occured inner interface failure mode in all tested anchors and for both investigated adhesive products.  
Figure 3: Geometry of concrete specimens used for (**a**) Product 1, and (**b**) Product 2.  
The load was applied using a 700-bar hydraulic system with 12 individually actively controlled jacks, each with a load capacity equal to 22 t. Each hydraulic jack is equipped with a spherical coupling in order to minimize bending moments due to installation and set-up imperfections. Confinement plates of 25 mm thickness with an outer diameters of 250 and 450 mm (the same as concrete cylinders), respectively, were used to ensure a confined configuration following the anchor related codes [57; 58]. The inner diameter of the plate was 28 mm; that corresponds to 1.75 times the anchor diameter (\(1.75\cdot d_{nom}\)). In order to measure the actual system response and creep deformations after the load is applied, the displacement was measured on the top of the anchor relative to the steel confinement plate using linear potentiometers of type LRW2-C-10 with a maximum range of 10 mm and the linearity of \(\pm 0.3\%\). The linear potentiometer was carefully set ensuring alignment with the axis of the anchor. For the short-term tests, calibrated load cells were used in addition to the hydraulic pressure sensors while for the long-term tests only the pressure development was monitored. The corresponding experimental setup for the sustained load tests corresponds to the one shown in Figure 5 but without the load cell.