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| Experimental Researchonthe Fatigue Properties of High – strengthBars |
| XU Sheng - qiao，LIN Hui |
| (China Railway Engineering Consulting Group Co. Ltd，Beijing 100055，China) |
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Abstract Abstract ：Research purposes： Current Chinese design specifications lack of fatigue design parameters of high - strengtli bars， which is not conducive to popularization and application of high - strengtli bars in the railway engineering. To
implement the national industrial policy，realize high - strength bars technical and economic performance and provide technical support for standards， railway engineering application of high - strengthi bars was studied. Two production processes( micro - alloyed and fine - grained)，two levels of intensity(400 MPa and 500 MPa)，four diameters(16 mm， 20 mm，25 mm and 32 mm) high - strength bars were studied. Fatigue performance test of high - strength bars base material and connecting joints was carried out，as the number of fatigue test for cycles 10= times.
Research conclusions ：( 1) After the dynamic calibration measures，comparative tests of base material and connecting joints showthat there was no significant difference between the high - frequency fatigue testing machine test results and the low - frequency fatigue testing machine test results，high - frequency fatigue testing machine could be used to test high - strength bars. (2) The gripping end processing method of high - strength bars base material and connecting joints was mastered which solved the technical problems of high - strength bars fatigue specimen grij) end easily broken ；avoided custom high - strength bars fatigue specimens ； achieved a random sample of high - strength bars fatigue specimens. (3 ) By a large number of test data statistical analysis ； research presented p - " - ： curve equation and fatigue resistance of high strength bars base material and flash butt welding，arc welding，straight thread connecting joints ； stress cycles was taken as 10 times. It provided the basis for the use of the high - strength bars. (4) According to the characteristics of 10 high fatigue life region，double logarithmic bilinear methods for data analysis，and considering the confidence，guaranteed rate and other factors curves for diferent sample conditions， statistics reflect the characteristics of high - strengtli bars fatigue specimens，to sum up the high - strengtli bars fatigue resistance test results provide a theoretical basis. (5 ) Study proposed railway projects of high - strengtli bars concrete structure design requirements. High - strengthi bars fatigue bearing capacity calculation methiod take into account thie effect of stress ratio， diameter， strength level，fatigue damage，fatigue type of construction details. Stress amplitude was calculated in the form of specifications consistent wit!i the international mainstream. (6 ) The research results will be widely used in the design of concrete structures.
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Received: 21 July 2016
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2016, Vol. 33 
