| Summary: | 碩士 === 國立交通大學 === 土木工程系 === 87 === The test of the research attempts mainly to investigate the dynamic behavior and failure mechanism after anchorage of the Drop-In Type Expansion Anchors of different sizes in concrete slabs, to be separately applied with pullout force solely, shear force solely, or compound stress. It shall include load and position deviation, final limit failure value and failure mode. In the test, it is also studied, under the influence of anchorage span,the final limit failure value attenuation situation and final failure mode of being applied with pullout force solely, shear force solely, or compound stress.
The concrete failure cone to concrete caused to expansion anchors while being applied with pullout force solely and level surface generally shows a 30°angle. While conducting test result regression analysis, the effective projection area of a 30°cone failure surface can be considered as the stress influence area, then the recommendation formula of tolerance pullout force of this type of expansion bolt in shallow embedding is P = 0.479×f'c1/2×Ac(kgf), while single pull safe edge span can be set to be about 2 times of anchorage depth, and ideal anchorage span can be set to be about 4 times of the anchorage depth.
As an expansion anchor is applied solely with shear force, as the anchorage edge span is larger than or equals to 1.5 times of anchorage depth, the failure mode shall be anchor bolt shank cut off, therefore, the tolerable shear of expansion anchor is directly related to the externally connected bolt shank nature of an expansion anchor, with the value as V1= 0.577×fy (kgf）, while anchorage edge span is less than 1.5 times of anchorage depth, the failure mode turns to concrete side to collapse, with the tolerable shear recommended to be calculated by V2 = 0.355×f'c1/2×Ac(kgf).
As the expansion anchor undertakes compound stress to be under influence of edge span, the attenuation of shear applied first to pullout force applied later shall be larger than the attenuation of pullout force applied first to shear applied later ; its failure mode also tends to the failure mode under shear. The safe edge span of an anchorage bolt with tooth diameter at 5/16" in undertaking compound stress can be set to be 1.5 times of anchorage depth, while the safe edge span of anchorage bolts with tooth diameters at 1/2" and 3/8" can be set to be 2 times of anchorage depth.
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