## 2 Performance of IWP with Steel Anchor Beam  
### Experimental Program  
The performance of the proposed IWP detail with a steel anchor beam was investigated based on an as-built bridge in China, of which the south and north pylons are 234 m and 232 m high, respectively, with 198.2 m above the deck. A standard segment of the cable-pylon anchorage zone was taken for investigation. The geometries of the anchorage zone of the prototype bridge and the selection of the test zone are illustrated in Figure 2. The test zone was selected near one of the cable anchorages. The small asymmetry in the test area was ignored in the model design. Considering the experimental conditions, the test zone was half-scaled. Figure 1: Proposed IWP structure: (**a**) structural detail; (**b**) IWP with steel anchor beam; (**c**) IWP with steel anchor box. The layout and geometries of the test model are shown in Figure 3. The test model was composed of a concrete part simulating the 1000 mm thick pylon wall and a steel part with a cantilever steel bracket simulating the IWP detail and for load application. After scaling, as shown in Figure 3a, the concrete part was 2200 mm \(\times\) 2800 mm \(\times\) 500 mm, with six circular holes for ground anchors. Other geometric parameters, such as the thickness of the steel plates, the geometries of perfobond connectors, and the diameter and spacing of rebars in the test model were taken as half of the prototype, as summarized in Table 1. Additional rebars were arranged near the anchor holes to prevent local failure. As Figure 3b shows, six narrow perforated side plates and two wide ones were welded on the end plate. Two columns of perfobond connectors, one of which was circular-hole and the other was long-hole, were set on each narrow side plate. For the other two wide ones, four columns of perfobond connectors were set. Perforating bars were set in each long-hole, with a spacing of 150 mm near the anchorage. As for the material characteristics, the values are listed in Table 2. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Plate Thickness**} & \multicolumn{3}{c}{**Perfobond Connector**} & \multicolumn{3}{c}{**Rebar**} \\ \cline{2-9} \cline{5-9} \multicolumn{1}{c}{**End Plate**} & \multicolumn{1}{c}{**Surface Plate**} & \multicolumn{1}{c}{**Side Plate**} & \multicolumn{1}{c}{**Circular Hole**} & \multicolumn{1}{c}{**Long Hole (Long. \(\times\) Trans.)**} & \multicolumn{1}{c}{**Spacing**} & \multicolumn{1}{c}{**Longitudinal Transverse**} \\ \hline Prototype & 30 & 30 & 20 & \(\varphi\)60 & 60 \(\times\) 35 & 300 & \(\Phi\)36@200 & \(\Phi\)28@300 \\ Model & 16 & 16 & 10 & \(\varphi\)30 & 30 \(\times\) 17.5 & 150 & \(\Phi\)18@100 & \(\Phi\)14@150 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Geometries of test model and prototype (unit: mm). \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Concrete**} & \multicolumn{1}{c}{**Steel Plate**} & \multicolumn{1}{c}{**Rebar**} \\ \hline Young’s modulus (MPa) & - & 2.0 \(\times\) 10\({}^{5}\) & 1.95 \(\times\) 10\({}^{5}\) \\ \hline Compressive strength (MPa) & 42.7 & - & - \\ \hline Tensile (yielding) strength (MPa) & 3.92 & 430 & 335 \\ \hline Ultimate tensile strength (MPa) & - & 558 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Material characteristics of test model. Figure 2: Geometries of cable–pylon anchorage zone in prototype bridge and model test zone (unit: mm). The selected segment of the steel anchor beam corresponds to a designed cable force of 9182 kN, with a vertical component of 6434 kN. Based on the law of similarity, the load applied to the specimen P = 6434 \(\times\) 1/4 = 1608 kN. The test setup for the model is shown in Figure 4, which is a self-balancing system. Two 300-ton hydraulic jacks were used to apply horizontal loads to the test model, simulating the vertical force component transferred through the steel anchor beam from the stayed cable.