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In order to study the effect of basalt fiber on the flexural properties of ultra-high performance concrete (UHPC) slabs, basalt fiber UHPC containing coarse aggregate was prepared. The basic mechanical properties of basalt fiber UHPC were tested, and the bending test of four-sided simply supported two-way slabs was carried out. The effects of different fiber types, steel mesh, waterborne epoxy, and their mixture on the toughness and flexural strength of UHPC slabs were studied. The results show that the basalt fiber can significantly improve the basic mechanical properties of UHPC; Comparing the UHPC plates mixed with different types of basalt fiber, Compared to the plain UHPC plates, UHPC with higher tensile strength and shorter length exhibit higher bending resistance, The peak load increased by 154.7% and 196.6%, respectively, The maximum deflection increased by 38.1% and 326.2%, respectively; The ductility of the UHPC plate mixed with basalt fiber and steel wire mesh has been significantly improved, The maximum increase is 48.9%; Based on the assumption theory, the bidirectional theory is calculated and compared with the test value, and the results agree well.

The top and bottom shells of fused deposition 3D-printed PLA models are exposed to the highest stresses. To improve the bending performance of PLA models under three-point bending conditions, the models were strengthened by a selective enhancement method. Several sets of PLA models were fabricated using FDM technology, and three-point bending experiments were conducted to compare the bending strength of PLA models when the layer height, top/bottom shell thickness, and extrusion rate were varied. The bending strength of the PLA models increased as the layer height of the top/bottom shell decreased, the thickness increased, and the extrusion rate increased. The average bending strength of the PLA models after selective enhancement was 84.4 MPa, and the average bending modulus of elasticity was 0.816 GPa, which were higher than the average bending strength of 68.6 MPa and the average bending modulus of elasticity of 0.736 GPa of the conventional groups. These results indicated that the selective enhancement method improved the bending performance of 3D-printed PLA models, and it also provided a reference for the improvement of the mechanical properties of the 3D-printed models with cellulose composite reinforced materials.

The existing research primarily focuses on wood-concrete composite beams, with limited studies on the bending performance and effective width of wood-concrete composite slabs. A full-scale composite slab with screw connections was constructed and subjected to static load testing. The study extensively investigated the ultimate bearing capacity, load-deflection curves, interface slips, strain distributions of cross-section and effective width of the wood-concrete composite slab. It was found that the failure mechanism of the composite slab involved both bending and tensile failure of the wood beams. As the applied load intensified, a marked augmentation in the longitudinal strain of the concrete slab was observed; along the width direction, the longitudinal strain of concrete slab manifested a curved distribution. The precise determination of the effective width of the concrete slab within the composite floor could be accurately achieved via the utilization of a simplified computational approach. In order to simplify the analysis, the M-shaped section of composite slab was approximated as T-section composite beams when evaluating the bending behavior. The linear-elastic model was shown to be accurate in predicting the bending stiffness and load-carrying capacity of composite slabs.

The top and bottom shells of fused deposition 3D-printed PLA models are exposed to the highest stresses. To improve the bending performance of PLA models under three-point bending conditions, the models were strengthened by a selective enhancement method. Several sets of PLA models were fabricated using FDM technology, and three-point bending experiments were conducted to compare the bending strength of PLA models when the layer height, top/bottom shell thickness, and extrusion rate were varied. The bending strength of the PLA models increased as the layer height of the top/bottom shell decreased, the thickness increased, and the extrusion rate increased. The average bending strength of the PLA models after selective enhancement was 84.4 MPa, and the average bending modulus of elasticity was 0.816 GPa, which were higher than the average bending strength of 68.6 MPa and the average bending modulus of elasticity of 0.736 GPa of the conventional groups. These results indicated that the selective enhancement method improved the bending performance of 3D-printed PLA models, and it also provided a reference for the improvement of the mechanical properties of the 3D-printed models with cellulose composite reinforced materials.

Combining the advantages of cast-in-place hollow slabs and prefabricated reinforced truss composite concrete slabs, a novel hollow composite slab is proposed, characterized by the inclusion of hollow thin-walled boxes without reinforcement at the edges, referred to as the hollow composite slab. To further investigate the flexural performance and critical design parameters of the hollow composite slab, numerical simulations were conducted using the finite element software ABAQUS. Based on the actual specimen fabrication and test results, the rationality of the finite element modeling was validated. Using the finite element model, a parametric analysis of key parameters for the specimens was conducted. The results showed that the finite element model could effectively simulate the crack distribution, flexural performance, and deformation characteristics of hollow composite slabs. The influence of concrete strength and the longitudinal dimension of hollow thin-walled boxes on the flexural performance of hollow composite slabs was minimal, with ultimate bearing capacities changing by only 4.63% and 0.91%, respectively. In contrast, changes in slab thickness and span had a significant impact on the flexural performance, with ultimate bearing capacities changing by 20.46% and 42.09%, respectively. The bearing capacity of hollow composite slabs increased significantly with increasing slab thickness but decreased markedly with increasing span.

Precast, pretensioned concrete girders are extensively used in bridge engineering to prevent damage to concrete girders, such as the loss of prestress and the corrosion of strands. Existing studies of the mechanical performance and failure characteristics of bridge girders had shortcomings, resulting in potential safety hazards. This study conducted a full-scale model experiment and theoretical analysis of the bending performance of a 35-m long precast, pretensioned concrete I-girder with pretensioned double broken strands. The cracks and bending damage were investigated. The results showed that the maximum vertical displacement of the composite girder was much lower than the required standard value, with a crack factor and bearing capacity factor of 1.31 and 1.54, respectively. The bending stiffness of the composite girder decreased by 70%. Many cracks occurred in the concrete, resulting in excess stress of the steel bars and prestressed strands. The crack width during loading was much smaller than the theoretical one in the Specifications for Highway Reinforced Concrete Prestressed Concrete Bridge Culverts ( JTG 3362–2018 ). Therefore, the girder exhibited optimum bending stiffness, sufficient crack resistance, acceptable ultimate bending capacity, and ductile failure performance. The mechanical behavior and failure mechanism during loading were investigated. This study provides recommendations for the design, maintenance, and damage assessment of this bridge type to improve the service lives of bridges.

To expand the potential of cork composite wood flooring as an interior material, this study investigated the bending performance of sandwich-structured cork composite wood flooring. The cork composite wood flooring was composed of temperate and tropical wood species as face layer and a cork board reinforced with metal, glass fiber, or carbon fiber placed between two cork boards as the core layer. The MOE value of wood flooring with merbau (M) had the highest value (6.71 GPa) and that of larch (La) had the lowest value (5.40 GPa). Overall, the MOE value of wood flooring with tropical wood species had higher value than those with temperate wood species, which had lower densities. According to the core reinforcements, the CM (cork board-metal) type showed a higher MOE value than the CG (cork board-glass fiber) and CC (cork board-carbon fiber) types. However, within the specific MOE, the order was CG > CC > CM. The ratio measured to calculated MOE ranged from 1.0 to 1.1, it showed a similar or slightly higher value than the measured MOE. The MOR of wood flooring had the highest value (51.0 MPa) in that with teak (T) and had the lowest value (34.9 MPa) in that with larch (La). The specific MOR of the wood floorings with cork board reinforced with glass fiber and carbon fiber was 20 to 40% higher than those reinforced with metal. Stable fracture behavior was observed for the cork composite wood flooring reinforced with metal, glass fiber, or carbon fiber.

In order to explore the flexural behavior of a concrete sandwich panel under concentrated boundary conditions, based on Kirachhoff’s elastic thin plate theory in this paper, the geometric deformation, physical conditions, and equilibrium relationship of a sandwich panel are deduced by constructing the layered analysis model of the sandwich panel, the basic differential equation of the flexural deformation of the concrete sandwich thin plate is obtained, and the mathematical expression of the internal force and displacement under the boundary condition of concentrated support is given. Combined with an engineering example, the proposed calculation method is verified. The results show that, in the arrangement of reliable connectors for concrete sandwich panels, the concrete wythes bear the load while the contribution of the core layer to the bending capacity of the structure can be ignored. When subjected to a laterally distributed load, the sandwich panel mainly experiences out-of-plane bending deformation, and the bending normal stress in the concrete panel layer shows a linear non-uniform distribution along the thickness direction of the panel. The bending deformation performance and bearing efficiency of a concrete sandwich slab with the change in concentrated support position have significant effects, and the load transfer efficiency can be improved by optimizing the arrangement of supports. Except for small local areas near the supports, the bending stress distribution and deformation behavior of the concrete sandwich panel can be accurately analyzed by the calculation method established in this paper.

A separable glued-laminated timber (GLT, Larix kaempferi Carr.)-steel beam system is presented in this work for easy recycling at the time of disposal. The minimum thickness of steel required to induce compressive GLT failure was assembled with GLT by inclined screws. In a total of 8 GLTs, 3 GLTs were not reinforced (control group), and 5 GLTs were reinforced with steel plates (comparison group). In the GLT in the comparison group, a steel plate (SPHC, yield strength: 227 MPa, modulus of elasticity 166.33 GPa) was installed with screws (∅9x160mm, 45°). The deflection and load of specimens were measured by a third-point bending test to derive their bending stiffness and load-carrying capacities. All specimens in the control group showed brittle tensile failure, but all specimens in the comparison group showed ductile behavior and maintained a load-carrying capacity of about 30 kN. After the compression failure of the GLT, there was no damage to the screw connection, while the steel plate was extended. Based on the behavior of the steel, a GLT-steel beam prediction model was developed, similar to the structural design method for reinforced concrete.

In order to solve the problems of high production cost and complex control of the inverted arch of an unsupported prestressed concrete composite slab, a flange truss high-ductility concrete composite slab floor is proposed to change the structure and pouring material to meet the requirements of no support during construction. The crack distribution and bending performance of the flange truss high-ductile concrete composite slab floor (CRHDCS) under different structures are clarified through the test and numerical analysis of four different rib plate structure floors. According to the analysis results, the calculation formulas of the cracking moment and short-term stiffness before cracking are modified, and the equivalent short-term stiffness formula of a single web member of the “V” truss to this kind of bottom plate is established. The results show that, unlike the short-term stiffness-change law of typical concrete composite slabs after cracking, the short-term stiffness of the designed bottom plate in this paper includes a short-term increase stage. The numerical simulation results are the same as the experimental ones; the maximum error is 10%. The maximum errors between the modified cracking moment and the short-term stiffness calculation formula are 6% and 8%, respectively. The influence rates of removing flange plate, truss-inverted binding, and adding rib plate on the cracking bending moment of foundation structure are −81.5%, 11.0%, and 22.2% respectively, and the influence rates on short-term stiffness are −87.6%, −1.5%, and 37.5% respectively.