| Summary: | 碩士 === 中華大學 === 土木工程學系碩士在職專班 === 102 === prestressed ground anchors are widely applied in earth retaining structure of mountain areas roads. For bearing prestressing force for a long time, and subject to factors such as geological conditions and construction, it causes losses to anchorage prestressing force. At present, anchor load is usually drawn to test remaining anchor prestressing force in practice, then, the anchor prestressing force is reinforced by a gasket made of structural steel. However, there is still a probability that the prestressing force went down after reinforcement if there exists a creep problem between anchorage segment and bed boundary to cause reduction of anchorage force. Provided that the anchorage force could be grasped before reinforcing anchor prestressing force, it can prejudge whether the prestressing force needs reinforcement, or skid resistance requirements of side slope are met by increasing anchor quantity.
This research conducted lift-off test method to obtain residual load as the initial load of creep test, and exerts tension by 1.25 times of design load. This research explored creep limit load through displacement at each stage within holding up time, studies and judges function of anchorage segment to learn whether the present creep limit load meet the requirements of prestressing force reinforcement, to search proper reinforcement method and budget.
This research should studied and obtained judge function of the free segment, further exerted tension and set the holding up time through cyclic load of employment and suitability test. To maximize the permanent reinforcement of anchor prestressing force, friction loss load, creep limit load, steel key performance, and gripping force of a clamping piece should be considered. Provided that steel strand is rusted in mild degree, the lift-off test can still exert tension by 1.25 times of design load, although the residual load is low, it can still carry out passive and stable function. The creep limit load is not able to meet the requirements of design load, thus there is still a probability that the anchorage segment might produce a relative displacement after the reinforcement of anchor prestressing force. The change of the creep limit load decides whether the anchor prestressing force is reinforced or not. Through comparison of budgets, the expenditure of anchor pulling reinforcement is lower than that of adding anchors.
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