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