The loading-deflection curve is bi-linear with a cut-off point corresponding to the cracking of the concrete. It is found that the mechanical characteristics of the GFRP concrete cable duct are similar with that of the concrete cable reinforced with steel bars. The bending tests were conducted for several small and full size specimens of GFRP concrete cable duct and the bearing capacity of bending, deformation and failure characteristics were investigated. The newly developed cable duct is capable of reducing the energy dissipation and can be used to take place of traditional concrete cable duct which is reinforced with steel bars. All right reserved.Ī concrete cable duct reinforced with glass fiber reinforced polymer (GFRP) bars was proposed. © 2018, Editorial Office of Acta Materiae Compositae Sinica. The proposed formula can preferably fulfill the requirements of security and economy for designing or fabricating the concrete cable ducts. The specimens still have relatively high shear bearing capacity under a small reinforcement ratio of longitudinal reinforcement. The effect of stirrup on the shear bearing capacity can be neglected if the stirrup ratio is too small. The experimental results show that the shear bearing capacity increases with the increase of area-stirrup ratio and the longitudinal reinforcement ratio. The crack growth mode, the distributions of the strain on the cross sections and the load-deflection curves were obtained by the shearing test on several small and full size specimens. An appropriate calculation and design method was proposed based on the different countries' design codes. The shear performance of the concrete cable ducts reinforced with glass fiber reinforced polymer (GFRP) bars was investigated. This improvement is dramatically affected by the thickness and deformability of reserved flexible layer. Compared with rigid support structure, pressure and displacement of primary support in tunnels employing flexible layer could achieve a good improvement. It could be found that flexible layer has a good ability to absorb rock deformation. Numerical calculation by use of finite element software Abaqus is carried out to verify the effectiveness and reliability of theoretical analysis. Visco-elastic analytical solutions for displacements and interaction forces in the rock/flexible layer interface and in the flexible layer/primary support interface are provided. For further understanding the effect of flexible layer on mechanical behavior of tunnels, a three-layered model is established to study the mechanical behavior of tunnel where flexible layer is installed between surrounding rock and primary support. The role of flexible layer is to absorb rock deformation due to rock rheology. Installing flexible layer is one kind of supporting techniques to deal with the large deformation in tunnels excavated in viscoelastic rocks. Finally, the evolution trends of the stress and deformation rates of HDPE conduits are recommended for the monitoring indexes and control standards of electrical duct banks. The threshold of the longitudinal curvature radius is determined to be 18000 m. The results suggest 5% and 7.5% as the deformation rate thresholds with respect to the ultimate states of serviceability and bearing capacity, respectively. An analysis of the experiment shows the effective role of HDPE conduits in improving the bending capacity of electrical duct banks. This study examines the bending behaviors of electrical duct banks subjected to monotonic vertical loading in a soil box using an advanced monitoring device to measure the conduit diameter change. The bending capacity of concrete-encased underground electrical duct banks has been the subject of considerable investigation using the load-structure method however, the role of high-density polyethylene (HDPE) conduits and the thresholds of electrical duct banks has not been fully scrutinized.
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