## 3 Test Results and Analysis
### Mechanical Properties  
The test results of the two groups of irregular concrete deep beam specimens are shown in Table 2. P\({}_{\mathrm{c}}\) is the cracking load of the specimen; P\({}_{\mathrm{d}}\) is the design load of the specimen; P\({}_{\mathrm{u}}\) is the ultimate  
Figure 16: Failure patterns of the Group B irregular concrete deep beams: (**a**) specimen B-01; (**b**) specimen B-02; (**c**) specimen B-03; (**d**) specimen B-04  
load-carrying capacity of the specimen; Cw is the maximum crack width of the specimen under the design load; \(\Delta_{\text{d}}\) is the midspan deflection of the bottom of the beam specimen under the design load; and \(\Delta_{\text{u}}\) is the deflection of the specimen when its ultimate load-carrying capacity is reached. The load-deflection curves are shown in Figure 17.  
Table 2 and Figure 17 show that except for the plain concrete specimens A-01 and B-01, all specimens had an ultimate load-carrying capacity that exceeded the corresponding design load, verifying the effectiveness of the STM design method. In the Group A irregular concrete deep beam specimens, specimen A-04 had the largest cracking load and ultimate load-carrying capacity, and its midspan deflection at the bottom of the beam under the design load was the smallest. Specim A-03 had the smallest ultimate load-carrying capacity, and its midspan deflection at the bottom of the beam at the time of failure was the smallest. Specim A-02 had the largest midspan deflection at the bottom of the beam at the time of failure, followed by specimen A-04. The Pq/Pd of specimen A-04 was 10% and 35% larger than that of specimens A-02 and A-03, respectively. In the Group B irregular concrete deep beams, specimen B-04 had the largest cracking load (95 kN) and ultimate load-carrying capacity (141 kN), followed by specimen B-03. Additionally, specimen B-04 had the smallest crack width under the design load, and its midspan deflection at the bottom of the beam was between those of specimens B-02 and B-03. The Pu/Pd of specimen B-04 was 21% and 5% larger than that of specimens B-02 and B-03, respectively.  
The variation trends of the load-deflection curves of the irregular concrete deep beam specimens in the two groups are essentially the same. The load-deflection curves of specimens A-02 and A-04 are closer, as are load-deflection curves of specimens B-02 and B-04. At the initial stage of loading, that is, from the beginning of loading to the time when cracks occurred in the specimens, the concrete resisted most of the load, resulting in essentially the same load-deflection curves of different specimens. However, for concrete deep beams in the elastic stage, due to the large shear deformation and  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Specimen** & **P\({}_{\text{c}}\) (kN)** & **P\({}_{\text{d}}\) (kN)** & **P\({}_{\text{u}}\) (kN)** & **C\({}_{\text{w}}\) (mm)** & \(\Delta_{\text{d}}\) (mm)** & \(\Delta_{\text{u}}\) (mm) & **P\({}_{\text  
coexistence of the beam action and arch action, the stress in the concrete compression zone also exhibited a nonlinear distribution. With the generation and development of cracks, the stress in the specimen was redistributed, and the rebar stress gradually increased, forming a \"tie\", which together with the concrete softfit between the loading point and the supports at both ends constituted a \"tied arch\" system. The difference in the load-deflection curves of different specimens was caused by the different reinforcement designs guided by different STMs.