# Study on Bending Performance of Tightly Spliced Truss-Reinforced Plate-Honeycomb Flat Beam
## 4 Theoretical Analysis and Design Method  
### The Basic Assumptions  
The holes in the web of honeycomb composite flat beam led to its local weakening, which changes the longitudinal and vertical continuity of the section of steel web, forming a special kind of variable section beam, resulting in the calculation of the bearing capacity of the composite beam in the process of stressing becomes complicated. The honeycomb composite flat beam cross-sectional combination form is different from the common T  
Figure 18: Fitting curve of ultimate bending bearing capacity reduction coefficient. shaped composite beam, and the design formula of the T-shaped composite beam cannot be applied directly. The honeycomb composite flat beam component is formed by a honeycomb steel beam and concrete flange plate together, but the honeycomb composite flat beam can refer to the design calculation method of solid web steel composite flat beam in the calculation process because the concrete flange plate is located on both sides of the web, and the honeycomb hole is basically filled intact. The following assumptions should be met when calculating the flexural load-carrying capacity of the honeycomb composite flat beam:  
1. Honeycomb beam holes, stiffening ribs, and H-beam shear connection keys can ensure that the connection between steel and concrete resists sufficient longitudinal shear to form a synergistic force-bearing whole. 2. The concrete in the tensile zone withdraws from the work after cracking, and the concrete tensile stress is much smaller than its compressive stress, so the concrete in the tensile zone is not involved in the force analysis. Since the concrete flange plate below the bottom part of the concrete is basically in tension, its enhancement of the combined flat beam flexural bearing capacity is not considered. 3. Since the cross-sectional area of the reinforcement in the concrete flange slab is much smaller than the cross-sectional area of the steel beam, the enhancement effect of the reinforcement on the flexural bearing capacity of the combined flat beam specimen is not considered. 4. The steel and reinforcement exhibit ideal elasticity and can reach the strength design value when in tension or compression. 5. The cross-section of the honeycomb composite flat beam specimen can maintain the plane state during the load-bearing process, i.e., the assumption of flat section is satisfied, without considering the uneven distribution of stresses in the concrete flange. 6. Since the concrete is located on both sides of the steel beam to have a stabilizing effect on it, and the steel beam section grade is S1, the overall buckling or local buckling of the specimen is not considered. 7. The effect of the shear connection keys of H-beams on the lower flange of the honeycomb beam and the stiffening ribs is not considered. 8. The concrete flange plate is treated as a whole. 9. In the bending process of the specimen, the concrete compressive part of the stress is actually not rectangular distribution, but for the sake of calculation simplicity, this paper adopts the equivalent rectangular stress method to convert the concrete irregular compressive stress into rectangular stress equivalently. The magnitude of the equivalent rectangular stress should be equal to the magnitude of the actual stress, and the location of the point of action of the joint force should also be the same, then the height of the equivalent compressive zone of concrete \(x=\beta(y_{c}-c)\), the equivalent compressive stress value is \(\alpha f_{c}\).