# Study on Bending Performance of Tightly Spliced Truss-Reinforced Plate-Honeycomb Flat Beam
## 3 Test Results and Discussions
### Bearing Capacity Analysis  
In this paper, the spanwise bending moment at cracking of concrete flange slab \(M_{bt}\), spanwise bending moment at cracking of composited plate joints \(M_{ct}\), spanwise bending moment at yielding of specimen \(M_{y}\), spanwise bending moment at the end of loading of specimen \(M_{u}\), spanwise deflection at yielding of specimen \(\delta_{y}\), spanwise deflection at the end of loading of specimen \(\delta_{u}\), measured in the test procedure of five specimens with two concentrated forces are detailed in Table 3.  
The yield moment and yield displacement of the specimen are obtained by the tangent method, i.e., the horizontal coordinate of the intersection of the initial tangent line of the load-deflection curve of the specimen and the horizontal line passing through the ultimate \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Eigenvalue** & **Unit** & **DTCB1** & **DTCB2** & **DTCB3** & **DTCB4** & **DTCB5** \\ \hline \(M_{bt}\) & kN\(\cdot\)m & 45 & 50 & 45 & 50 & 55 \\ \(M_{ct}\) & kN\(\cdot\)m & 55 & 55 & 55 & 50 & — \\ \(M_{y}\) & kN\(\cdot\)m & 81.3 & 83.1 & 75.7 & 86.4 & 82.6 \\ \(M_{u}\) & kN\(\cdot\)m & 107.5 & 110 & 100 & 115 & 105 \\ \(\delta_{y}\) & mm & 17.1 & 14.1 & 18.0 & 14.6 & 21.3 \\ \(\delta_{u}\) & mm & 141.05 & 115.71 & 143.01 & 143.72 & 143.88 \\ \(M_{y}\)/\(M_{u}\) & / & 75.63\% & 75.55\% & 75.70\% & 75.13\% & 78.67\% \\ \(\delta_{u}\)/\(\delta_{y}\) & / & 8.25 & 8.21 & 7.95 & 9.84 & 6.75 \\ \(M_{y}\)/\(\delta_{y}\) & / & 4.75 & 5.89 & 4.21 & 5.92 & 3.88 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Main characteristic loads of honeycomb composite flat beams. load point of the specimen is the yield displacement of the specimen, and the corresponding load obtained by the linear interpolation method is the yield load of the specimen. Since the stiffness of the specimen remains basically unchanged in the elastic stage, the initial tangent of the load-deflection curve is obtained by taking the data of the first cracking of the bottom surface of the concrete flange of the specimen in order to prevent the accidental error of the first few loading levels of the specimen from being too large. Comparing the four specimens with the composited plate composite flat beam, the cracking load of the concrete flange slab in the middle of the span and the cracking load of the splice are basically the same. All four specimens have the concrete flange cracking in the middle of the span earlier than the cracking at the splice, which indicates that the splice reinforcement measures and the splice arrangement of the composited plate can avoid premature damage at the splice better. The cracking load at the bottom of the cast-in-place slab specimen DTCB5 is slightly larger than the other four specimens, the crack distribution at the bottom of the slab is more uniform, and the crack width is smaller than that of the combined flat beam of the composited plate. This is due to the localization of horizontal cracks along the intersection of the composited plate and the cast-in-place layer (such as at the place without truss reinforcement or at the place where the cast-in-place layer is not filled), which affects the transfer of stress between the concrete on both sides and leads to the uneven stress inside the composited plate. As can be seen from Table 3, when the bending moment of the specimen reaches 0.75 times the ultimate flexural load bearing capacity around the honeycomb composite flat beam specimen begins to yield, the specimen deflection can reach 8.2 times the yield displacement on average at the time of damage, and the ductility of the specimen has a good performance. It is found that the flexural load capacity and flexural stiffness of the specimens slightly decrease with the increase in the hole-height ratio of the honeycomb holes in the web of the steel beam, and the amount of steel used in DTCB2 is 1.05 times that of DTCB4, but the yield moment and ultimate bending moment of DTCB4 are 4.0% and 4.5% higher than that of DTCB2, respectively.