# Study on Bending Performance of Tightly Spliced Truss-Reinforced Plate-Honeycomb Flat Beam
## 3 Test Results and Discussions
### Bearing Capacity Analysis
This indicates that the honeycomb beam can increase the cross-sectional moment of inertia while reducing the amount of steel used, improve the use of steel, and increase the flexural capacity of the specimen, and also proves that the honeycomb composite flat beam is a more reasonable structural form than the solid web composite flat beam. The yield load and limit of specimen DTCB1 and DTCB5 are basically the same, but the stiffness of the specimen is slightly increased because the truss reinforcement in specimen DTCB1 can ensure the tight bond between the laminated layer and the cast-in-place layer. The load-deflection curves of the five combined flat beam specimens in the span are shown in Figure 12. All five specimens mainly experienced two main stages, the elastic stage and the plastic deformation. Before the load reaches 0.75 times the ultimate flexural capacity, the specimens are basically in the elastic stage. The load-deflection curve of the honeycomb composite flat beam specimen in this stage shows an approximately linear relationship, the initial stiffness of the specimen is large, and the deflection grows slowly with the increase in load. When the load reaches 0.75 times the ultimate flexural load-carrying capacity, the stiffness of the combined beam decreases and the deflection development accelerates due to the gradual yielding of the upper and lower flanges of the steel beam, which leads to the redistribution of its cross-sectional stress. Except for specimen DTCB2, the deflection of other specimens after yielding keeps growing until it reaches 1/20 of the span, indicating that the honeycomb composite flat beam specimen has good ductility and can be approximated to have formed a plastic hinge at the part of the pure bending section in the span after yielding. The concrete flange plate on both sides of specimen DTCB2 is completely separated from the steel beam web, and there is no other tensile effect except for the bond between the concrete and steel surface, which leads to the detachment of the concrete plate from the steel beam in the late loading period. However, the final deflection of specimen DTCB2 also reached 1/25 of the beam span, and its ductility also met the requirements. From the displacement-load curves of DTCB1, DTCB2, and DTCB3, it can be seen that the initial stiffness and yield load of the three specimens show a decreasing trend with the increase in the honeycomb hole-height ratio in the elastic stage, and the yield displacement increases. After entering the yielding stage, the yield load and ultimate load of the combined beam specimens decreased significantly with the increase in the honeycomb hole, the stiffness of all three specimens decreased significantly compared with the elastic stage, and the slope of the load-displacement curve was basically the same. Comparing the load-displacement curves of specimen DTCB3 with those of specimens DTCB2 and DTCB4, it can be found that filling the honeycomb holes and increasing the section height can increase the initial stiffness of the specimens, and the honeycomb beam has better load-bearing characteristics and coordinated deformation with the concrete under the conditions of similar steel consumption. The deflection-load curves of specimens DTCB1 and DTCB5 show that there is no significant difference between them, the dense truss steel composited plate can achieve the same load capacity as cast-in-place, and the initial stiffness and ultimate flexural load capacity of specimen DTCB1 are slightly higher than those of DTCB5 due to the influence of truss steel in the composited plate.