ATTEN: Manager Liu
ADD: Longhua Development Zone, Jing County, Hengshui City, Hebei Province
By comparing the skeleton curves of the two joints in Fig. 4, it can be seen that the hysteretic curve of SP1-2 joints is "inverse S-shaped", and there is no strengthening section in the skeleton curve. When the bearing capacity of the joints reaches a certain value, it transits to the descending section without strengthening, and the bearing capacity of the descending section decreases rapidly. The peak value of the bearing capacity during the whole loading process is about + 130kN, - 180 kN, while that of SP1-1 joints. The joint skeleton curve has complete strengthening section and descending section, the peak bearing capacity is 80 kN, which is 3 times the bearing capacity of SP1-2 specimen. The experimental results and analysis of 32Sp13 box-column defective joints show that the inter-story displacement angle is between 0.00375 rad and 0.01rad, the joint is in the stage of elastic loading, and the bearing capacity of the joint reaches 250 kN; when the inter-story displacement angle reaches 0.015 ra; At d, the joints begin to yield. When the end of the beam is loaded forward to the second cycle, the beams bulge up (Fig. 5 (a). Then the bearing plate of the joints deforms (Fig. 5 (b). The bearing capacity of the joints reaches 356 kN. When the displacement angle between layers reaches 0.04 rad, the dog bone of the upper flange weakens the deepest buckling becomes obvious, and the web also undergoes slight buckling (Fig. 5 (C). At this time, the bearing capacity of the joints occurs. After further loading, the weld cracks at the connection between the upper flange of the beam and the flange of the column. With the increase of the interlayer displacement angle, the flange of the beam and the surface of the column gradually detached (as shown in Fig. 5 (d). After checking, it was found that the inner diaphragm of the box column was not aligned with the upper flange of the beam, which led to this phenomenon.
(c) 0.04 rad22 hysteresis curve and skeleton curve Fig. 6 sP1-3 hysteresis curve and skeleton curve Fig. 6 are the hysteresis curve and skeleton curve obtained from the test. From the hysteretic curve and skeleton curve, it can be seen that the hysteretic curve of the joints is obviously "shuttle" after yielding and before the cracking of the weld, and the ultimate bearing capacity has been increasing. When the weld cracks at the upper flange-column connection, the bearing capacity decreases directly from 348.07 kN to 119.11 kN, and then the web bears only the bearing capacity under forward loading. In the process of picking up test phenomena, when the interlayer displacement angle reaches 0.0lrad and is loaded forward to 227kN, but when the reverse loading reaches the maximum, a huge sound will occur, and the weld cracks at the lower flange of the beam end will occur (as shown in Figure 7 (a)); continue loading, the interlayer displacement angle will occur. When the load reaches 0.015 rad, the yield of the rising flange specimen will no longer occur; when the displacement angle is 0.02 rad inch, the upper flange weld cracks (fig. 7 (b)) when the forward loading reaches the maximum; when the interlayer displacement angle reaches o3rad, the upper and lower flange weld cracks will continue to deepen, and when the positive loading reaches the maximum, the column at the lower flange and column connection will be pulled up; When O.4rad is reached, the upper and lower flange welds are completely destroyed, and the rigid joints become articulated; when 0.05rad is used, the lower flange is torn apart when the cylindrical surface is torn apart from the upper and lower flanges, as shown in Figure 7 (the hysteretic curve 332 and skeleton curve 332 and skeleton curvature curve at the end of 7sP1-4 test show that the elastic-plastic stress of the joints does not occur as high as 0.1). 5 rad, due to the lower flange of the beam.
The cracking of the weld makes the bearing capacity of the beam decrease from 961 kN to 187 kN, and the bearing capacity of the joint loses. In the subsequent loading process, the bearing capacity of the joint continues to decline. The ductility of the whole failure process is low.