Study on Fretting Fatigue of Prestressing Cable at, Deviator

The followings are summary of what have been obtained in this research.·Fatigue strength of prestressing strand under effect of fretting is apparently smaller than that under ordinary fatigue loading。·Fretting fatigue strength is influenced by stress range，slip range and contacting force。The greater stress range is，and the greater contacting force is，the smaller becomes the fatigue strength。The experimental fact indicates that how slip range influences fretting fatigue strength may depend on magnitude of slip range。Extent of influence of stress range and slip range is greater than that of contacting force.·It is necessary to consider effect of slip range in the direction normal to strand axis besides that in the direction of the strand axis.·Fretting fatigue occurs at contacting point between strands rather than between wires in the same strand.This fact indicates that there is the effect of slip range.·Although contacting force is considered greater at inner contacting points than at outer one at deviator，location of fretting fatigue fracture was found almost evenly。This fact indicates either that with magnitude of contacting force observed in the experiment fretting fatigue strength is hardly affected by change in contacting force，or that actual contacting force in the experiment did not change by the location。·Grouting in protection tube for cable and resin coating of strand can increase fretting fatigue strength，However，it is difficult to prevent fretting fatigue fracture by providing them only。·Restriction of grout movement by taper inside protection tube or spacer of strand for reduction of contacting can prevent fretting fatigue fracture。

The followings are summary of what have been obtained in this research.・ Fatigue strength of prestressing strand under effect of fretting is apparently smaller than that under ordinary fatigue loading.・ Fretting fatigue strength is influenced by stress range, slip range and contacting force. The greater stress range is, and the greater contacting force is, the smaller becomes the fatigue strength. The experimental fact indicates that how slip range influences fretting fatigue strength may depend on magnitude of slip range. Extent of influence of stress range and slip range is greater than that of contacting force.・ It is necessary to consider effect of slip range in the direction normal to strand axis besides that in the direction of the strand axis.・ Fretting fatigue occurs at contacting point between strands rather than between wires in the same strand. This fact indicates that there is the effect of slip range.・ Although contacting force is considered greater at inner contacting points than at outer one at deviator, location of fretting fatigue fracture was found almost evenly. This fact indicates either that with magnitude of contacting force observed in the experiment fretting fatigue strength is hardly affected by change in contacting force, or that actual contacting force in the experiment did not change by the location.・ Grouting in protection tube for cable and resin coating of strand can increase fretting fatigue strength, However, it is difficult to prevent fretting fatigue fracture by providing them only.・ Restriction of grout movement by taper inside protection tube or spacer of strand for reduction of contacting can prevent fretting fatigue fracture.