## 2 Performance of IWP with Steel Anchor Beam
### Experimental Results
#### 2.2.4 Comparison Between IWP Specim and PBL Specim  
The experimental results of the IWP specimen were compared with the PBL specimen reported in the literature ([PERSON] et al., 2024) ([PERSON] et al., 2024). The geometries and loading scheme were identical with the IWP specimen, except for the anchorage detail. It can be observed that the stress distribution patterns on the steel plates are similar under both structural forms. Taking plate A as an example, the Mises stress increases from measurement point A-1 to A-3, and then exhibited a very similar stress distribution from A-3 to A-7.  
Figure 12a compares the stress measurements at the same positions on the perforated plates of the two specimens. The Mises stress values on the measurement points of the PBL specimen begin to decrease after the load exceeds 1.9P. For the IWP specimen, the Mises stress curve at measurement point A-3 shows a plateau when the load reaches 1.7P and then begins to increase after the load reaches about 2.4P. The Mises stress at measurement point A-3 increases linearly in two segments, with the slope change occurring around 0.9P. After 1.9P, the stress on the IWP specimen remains unchanged or continues to increase, demonstrating higher load-bearing capacity compared to the PBL specimen.  
Figure 12b shows the relationship of axial stress with load at measurement point V-3 on the main reinforcing bars between the plates of the two specimens. It can be observed  
Figure 11: Steel–concrete displacement: (**a**) slip; (**b**) separation.  
Figure 12: Stress at the same position of PBL specimen and IWP specimen: (**a**) Mises stress at plate A, B, and D; (**b**) stress at V-3.  
that for the PBL specimen, the slope of the curve starts to increase after the load exceeds 0.8P, indicating that the proportion of force borne by the reinforcing bars is increasing, and the concrete near the measurement point has started to exhibit non-linear behavior. In contrast, the slope of the curve for the IWP specimen only starts to increase after the load exceeds 1.2P. Moreover, when the load exceeds 1.7P, there is a sudden increase in the stress value at the measurement point on the PBL specimen, indicating that cracks perpendicular to the strain measurement direction have appeared near the measurement point in the concrete. However, this phenomenon is not observed at the measurement points on the IWP specimen.  
Figure 13a compares the relative slip between the end plate and concrete for the two specimens. In the initial loading phase, both specimens have almost identical shear stiffness, and the steel-concrete relative slip is also quite similar. However, at load levels of 1.6P and 1.9P, the slope of the curve for the PBL specimen increases significantly twice, indicating a notable change in structural stiffness. This results in the steel-concrete relative slip of the PBL specimen being significantly greater than that of IWP specimen. Figure 13b compares the separation between the end plate and concrete for the two specimens. The slope of the separation curve for the PBL specimen is greater, indicating that the IWP specimen has higher pull-out stiffness than the PBL specimen. The slope of the separation curve for the IWP specimen increases more gradually, whereas the corresponding curve for the PBL specimen shows noticeable increases in slope at 1.7P and 2.7P.