INFLUENCE OF BI-AXIAL LOADING ON FATIGUESTRENGTH OF MAIN GIRDER WEB CONNECTEDWITH LATERAL GIRDER FLANGE

摘要

A lot of fatigue damage has been reported in various partsrnof I-shaped steel girder bridges. One of them is thernfatigue crack initiated at the weld toe on the main girderrnweb connected with the lateral girder flange. Fatigue strength of this part generally examined through fatiguerntests using web-gusset specimens under uni-axial stressrncondition. However, this part is often subjected to bi-axialrnstresses that are ones on the web and the flange. Thisrnstudy aims at examining the influence of bi-axial loadingrnon fatigue strength of the connection. For this purpose,rnfatigue test system has been developed to conduct fatiguerntest under pure bi-axial stress. Furthermore, fatigue testsrnhave been carried out using the developed test system.rnSpecimens used in fatigue tests and stress measurementrntests simulate the connection between main girder webrnand lateral girder flange. Fatigue tests have beenrnperformed under the condition that stress range on thernweb is kept at 100 N/mm2 and stress range on the flangernis varied from 0 to 150 N/mm2. Fatigue life under bi-axialrnstress condition is significantly decreasing comparedrnwith fatigue life under uni-axial stress condition becausernstress on the web increases due to stress on the flange,rnand stress bi-axiality itself. This fact has been confirmedrnby stress measurement tests and stress analyses.