Study on the Mechanical Properties of Stay Cable HDPE Sheathing Fatigue in Dynamic Bridge Environments
As the main force-bearing component of a cable-stayed bridge, a durable stay cable is paramount to the safety and durability of the entire bridge. High-density polyethylene (HDPE) sheathing is the main protective component of a stay cable and is the key to insuring cable durability. To address the issue of HDPE sheathing fracture on service, strain level data for in-service, HDPE bridge cable sheathing was used in this study as the basis for HDPE material aging and fatigue testing. A fatigue yield phenomenon with a yield platform on the hysteresis curve of the fatigue cycles is observed by the fatigue test. The parameters to describe this phenomenon are proposed and defined in this paper. A preliminary examination of the relationship between these parameters and the factors, such as the number of cycles, the strain amplitude, and strain rate, are presented. Based on the results obtained, it is suggested that the condition of fatigue yield of HDPE sheathing be defined as the fatigue durability limit state for the purposes of durability design, assessment, and protection of cable-stayed bridges.
Fatigue assessment for the floating collar of a fish cage using the deterministic method in waves
Abstract Fish farms have moved into the open sea in recent years and the failure risk of fish cages has increased in the harsher environmental conditions. Fatigue failure is an important limit state for the floating system of the fish cage under the long-term action of waves. A fatigue analysis of the high-density polyethylene (HDPE) floating system in waves is presented in this study based on the deterministic method and finite element analysis combined with a hydrodynamic model. As the basis of the fatigue assessment, a stress analysis of the floating pipes is first performed based on the joint use of the finite element model and the hydrodynamic model. The fatigue lifetime is then calculated using the Palmgren – Miner cumulative damage theory together with the deterministic method in which the stochastic sea state is decomposed into a reasonably high number of individual wave scatter diagrams. The results show that the recommended replacement period of the HDPE floating pipes is 20 years and that the fatigue lifetime of the floating pipes is more sensitive to the wave period than to the wave height. In addition, the effects of mooring line arrangements, wave incident angle and typhoons are also investigated. Comparisons of the fatigue lifetimes of the floating pipes for different mooring line arrangements indicate that the fatigue lifetime increases dramatically with increasing number of mooring lines. For a symmetrically arranged four-point mooring fish cage, the most unfavourable wave loading angle is 45°. Typhoons lead to a significant decrease in the fatigue lifetime of the floating pipes despite the short durations of the typhoons.
Frequency selective surface design for blinds applications
In this paper, the reconfigurable blind structure with frequency selective surfaces(FSS) for the building applications are presented. Frequency transmission characteristics for different angles of the proposed blind-FSSs are investigated and verified through simulation and measurement. The simulation results show that we can implement the reconfigurable blind-FSS for multiband wireless applications. To verify the proposed paper, two kinds of blind-FSSs, crossed dipole FSS and circular ring FSS are fabricated and measurements are performed for different angles. The proposed structure in this paper which is very simple, can be easily applied to any planar surface for wireless security applications at low cost.