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59 It is anticipated that several of the following trends will dom- inate the design, construction, and maintenance of stay cables in the next 2 to 5 years. Some of these trends have already taken hold. ⢠Stay cable systems supplied by U.S. manufacturers will finally converge and settle (at least for a time) on a system composed of wedge anchorages, greased-and-sheathed strands (possibly galvanized), and co-extruded HDPE pipe with helical strakes on the surface. Grout will likely not be used in many cases. Strands will be changeable, at least in theory. Issues related to performance of anchor- ages during earthquakes may force a reconsideration of wedge systems in seismically active areas. ⢠Stay cable manufacturers will include additional features and options on their stay systems such as strand force measurements, damper systems that are contained within the guide pipe or in the vicinity of guide pipes, remov- able test strands, and visible or inspectable anchorages and MTEs. ⢠Video monitoring systems for cable vibrations may become available and widely used. ⢠More tools and procedures that would allow inspectors to improve the effectiveness of visual surveys will become available. ⢠Built-in damage monitoring systems may be developed for the anchorage zones (based on magnetic method or guided stress waves), perhaps included as an option on supplierâs systems. ⢠Methods that will likely become common for nonde- structive evaluation of existing grouted/ungrouted cables are acoustic monitoring, vibration-based force measure- ments, ultrasonic testing of anchorages, impulse radar surveys, infrared thermography, and magnetic methods for assessing conditions in the free length of cable. Radiographic methods will also have their place; how- ever, safety and cost issues continue to limit their usage. ⢠Global sensor-based cable damage detection algorithms will be further developed and begin to be used. CHAPTER FIVE FUTURE TRENDS