| The flange-plate reinforced connection and the cover-plate reinforced connection studied by this paper are both a typical node beam enhanced form. Through welding flange-plate or cover-plate at the beam-end to improve the modulus of the beam section, the plastic hinge has been remote away from the beam-column weld which is brittle and suffered complex stress to achieve the purpose of improving the ductility and preventing brittle fracture.Five beam-column T-joints of steel moment-resisting frame were designed at 1/2 scale in this paper, of which were one ordinary bolt-welding connection specimen, two flange-plate reinforced connection specimens and two cover-plate connection reinforced connection specimens, Q235B steel and E43 series welding rod were used. The specimens were designed with our country's code and referenced the USA FEMA350 design method and construction requirements. The beam and column flanges of FPS were not directly connected but used flange-plate for transition, which the flange-plate was first welded to beam flange with filled welds and then connected to column flange with groove welds. In CPS specimens, the beam flange and the cover-plate were welded to column flange by the same groove. In this test, the two reinforced plates of rectangle plate and trapezoid plate were used for each reinforced connection.By exerting the low-cycle reciprocating load on the specimens, can obtain the joint damage model and the development of plastic hinge of each specimen, load-displacement hysteresis curve, skeleton curve, moment-plastic rotation hysteresis curves, the equivalent viscosity coefficient, ductility coefficient and so on. The tests show that: the plastic hinges were formed in FPS specimens at the location which was far from the flange-plate 1/4 department of the beam, shift away the column flange surface to protect the weld of the joints. In the CPS specimens the weld which connects the top cover-plate with the column flange has been cracking during the test process. But they could continue to resist the load because of the good groove weld between the beam flange and the column flange. The plastic hinges were formed at the location which was far from the cover-plate 1/4 department of the beam, like the FPS specimens. The ordinary bolt-welding specimen has taken place brittle failure, can not form plastic hinge, which the bottom flange of the beam was pulled off at the weld access hole. The test results show that: the ultimate bearing capacity of the reinforced connections as compared with ordinary bolt-welding connection has greatly improved, and the FPS-1 specimen's increased the largest of about 14.6%. The reinforced connections' plastic rotation angel range of 4.47%rad～4.72%rad, the total rotation angel range of 5.08%rad～5.32%rad, ductility coefficient range of 3.11～3.31, the equivalent viscous coefficient range of 0.477～0.564, satisfying the minimum standard of seismic performance, which was 3%rad plastic rotation angel, 5%rad total rotation angel and 3 ductility coefficient. The flange-plate reinforced connection and the cover-plate reinforced connection could be adopted and promoted at the meizoseismal area. By comparing these reinforced specimens, the trapezoidal flange-plate specimen (FPS-2) has the best seismic performance, which was significantly better than the ordinary bolt-welding connection specimen... |
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