## 3 Test Results
### Load-Displacement Curves  
#### 3.2.1. Bending Performance Curves  
The primary test results are displayed in Table 5, where \(N_{y}\) represents the cracking load of the grid beam, \(N_{u}\) represents the ultimate flexural load of the grid beam, and \(\Sigma N_{u}/2\) is the average of the test results for the identical beams.  
Below are the load-displacement curves for the four test beams, two of which are BGC-5 and two BGC-3. To examine the effects of various grid thicknesses on the cracking load and ultimate flexural load of the beams, the BGC-1-a/b group employed grid bars of minimal thickness and exceptionally poor tensile bearing capacity, resulting in the test beams of this group exhibiting behavior that was practically identical to that of plain concrete beams. Consequently, the data was stored, but the load-displacement curves were not graphed.  
The load-displacement relationship of the grid concrete beams exhibits linearity before the occurrence of cracking in the tensile zone of the concrete, as seen in Figure 8. The slopes of the curves for beams made of 3 mm-thick and 5 mm-thick grids are identical. Both sets of test beams exhibit a noticeable decrease in stiffness in their load-displacement curves after the concrete in the tensile zone cracks and leaves the load-bearing area, indicating a considerable fall in the slope of the load-displacement curve during this period.  
It is evident that the BGC-5 group of test beams has noticeably higher slope and peak load values than the BGC-3 group at this point, when the concrete in the tensile zone stops carrying a load and the bottom tensile composite grid takes over. This suggests that the ultimate flexural strength, stiffness, and cracking load of the grid concrete beams are all significantly impacted by an increase in grid thickness. Calculations show that adding 2 mm to the grid thickness increases the composite grid concrete beams' ultimate flexural strength by an average of 61% and their average cracking load by an average of 110%.  
The average maximum deflection of the BGC-5 group is 17.1% higher than that of the BGC-3 group, according to the maximum deflection statistical comparison. The reason for this variation is due to the manufacturing process of the composite grid itself, which leads to unavoidable thickness differences in the 3 mm thick grid bars among different grid  
Figure 7: Experimental phenomenon: (**a**) BGCS-3-a; (**b**) BGC-5-a; (**c**) HBGCS-3.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Specimen Number** & \(N_{y}\) **(kN)** & \(N_{u}\) **(kN)** & \(\Sigma N_{u}\)/2 **(kN)** \\ \hline BGC-5-a & 40.11 & 141.91 & \\ BGC-5-b & 41.26 & 146.63 & 144.27 \\ BGC-3-a & 27.16 & 93.01 & \\ BGC-3-b & 25.21 & 85.22 & 89.12 \\ BGC-1-a & 20.11 & / & \\ BGC-1-b & 21.83 & / & / \\ \hline \hline \end{tabular}
\end{table}
Table 5: Summary of test results of WFST.  
thicknesses. The load-displacement curves for the 3 mm thick and 5 mm thick grid beams were differing at the concrete cracking stage in the tensile zone. This occurred mostly because the preload changed during testing, which caused the load-displacement curves to be different before cracking.