Low Cycle Fatigue Research on Welded Joint of Beam-Column Conection

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The low-cycle fatigue strength of welded joints steel beam-column connection which were subjected repeated stresses by wind and/or earthquake loads were investigated experimentaly. Test specimens was T type connection consiste of the perimeter column and beam. The column was a rectangular hollow section ( □ -200x200x9, STKR400), and the beam was H-section (H-200x100x5.5x8, SS400). Test parameters were 1) scallop and/or non-scallop, 2) backing bar and/or non-backing bar. Tested specimens were total 24 pieces by combination of these parameters.The results of low-cycle fatigue test of welded joints of beam to column were as follows,1. The facture of non-scallop specimens were the full wide failure of the beam flange by the crack propagation from (1) the groove weld between the diaphragm and the beam flange in case of non-backing bar, (2) the fillete welds between backing bar and the beam flange when the displacement-amplitude was under 1.25 △ィイD2pィエD2, (3) the groove weld between the diaphragm and the beam flange when over 1.0 △ィイD2pィエD2 in case of with backing bar.2. The fracture of with scallop specimens were also the full wide failure of the beam flange by the crack propagation from (4) the groove weld between the diaphragm and the beam flange when the displacement-amplitude was under 0.87△ィイD2pィエD2, (5) the bottom of the scallop when over 1.0 △ィイD2pィエD2 in case of non-backing bar, and (6) the fillet welds between the backing bar and the beam flange in case of with backing bar.3. The fatigue life of with scallop specimens deteriorated to about 20% to 50% of the fatigue life of the non-scallop specimens in case of non-backing bar, and deteriorated to about 10% to 30% of these in case of with backing bar.