## 3 Test Results
### Load-Displacement Curves
#### 3.2.4 Discussion of Bending Performance  
In summary, the analysis of the shear behavior of composite material grid-reinforced concrete beams may be derived from the experimental results and load-displacement curves obtained from the preceding two sections.  
(1) Crack Development:  
Based on the test findings of different beams, it was found that the pure bending portion of the beams for the BGCS-3-a and BGCS-3-b groups had vertical cracks. Both beams experienced diagonal cracks along the loading points to the support end, occurring at 186 kN and 170 kN, respectively. The first diagonal crack was surrounded by parallel diagonal cracks as the load rose, and the vertical cracks in the pure bending portion stayed at a constant height until collapse. In contrast, BGCS-5-a/b and HBGCS-3/5 exhibited a  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen** & **Cracking Load** & **Ultimate Load** & & \\
**Number** & **(kN)** & **(kN)** & **Deflection (mm)** & **Shear Span Ratio** \\ \hline BGCS-3-a & 83.3 & 230.13 & 14.25 & 0.8 \\ BGCS-3-b & 60.2 & 193.25 & 14.40 & 1.16 \\ BGCS-5-a & 79.1 & 251.93 & 15.59 & 0.8 \\ BGCS-5-b & 80.2 & 224.07 & 14.48 & 1.16 \\ HBGCS-3 & 210 & 220.24 & 13.90 & 0.8 \\ HBGCS-5 & 285 & 291.78 & 15.52 & 0.8 \\ \hline \hline \end{tabular}
\end{table}
Table 6: The crack distribution of BFRP-grid beams.  
different crack development pattern. Initially, no obvious cracks appeared, and there were no significant vertical cracks in the pure bending section. The initial rigidity of these beams was higher, and the strain on the hydraulic machine grew quickly. Later, diagonal cracks that ran from the loading point to the support end started to show. Dense parallel diagonal cracks around the original diagonal crack appeared with further loading.  
(2) Influence of Side Grid Thickness on Shear Capacity:  
Comparing the results, BGCS-5-a had a 28% higher ultimate shear capacity compared to BGCS-3-a, BGCS-5-b had a 35% higher ultimate shear capacity compared to BGCS-3-b, and HBGCS-5 had a 32% higher ultimate shear capacity compared to HBGCS-3.  
(3) Influence of Shear Span Ratio on Ultimate Shear Capacity:  
To compare the impact of shear span ratio, under the same side grid thickness conditions, when comparing BGCS-3-a and BGCS-5-b, the former had a 19.9% greater ultimate shear capacity, and the latter had a 12.4% higher ultimate shear capacity. The findings showed that the composite grid-reinforced concrete beams' ultimate shear capacity decreases as the shear span ratio increases.  
(4) Comparison of Bottom Tensile Part with Steel Reinforcement:  
The bottom part of HBGCS was made of HRB400 steel bars, and the grid material for BGCS was basalt fiber composite. The tests showed that when the side grid thickness and shear span ratio were kept the same, BGCS-3-a and HBGCS-3 had ultimate shear capacities of 231.71 kN and 219.89 kN, respectively. BGCS-5-a and HBGCS-5 had ultimate shear capacities of 251.93 kN and 291.90 kN, respectively. The side grid thickness had a more pronounced effect on ultimate shear capacity compared to the material used in the bottom tensile part.  
As a result, these observations and comparisons provide valuable insights into the behavior and performance of composite material grid-reinforced concrete beams under shear loading. The shear performance of these beams is influenced by the presence of vertical and diagonal cracks, the thickness of the side grid, the shear span ratio, and the role of the bottom tensile component (composite grid or steel reinforcement).