Experimental Investigations On Static Behavior Of Uniplanar Gapped K-type Chs Joints Reinforced With Longitudinal Plates

Uniplanar gapped K-type CHS joints as one of the typical tubular joint types，hasbeen widely used in all kinds of industrial and civil architecture. It is easy to find thiskind of joints not only in power transmission tower, pedestrian bridge, but also inairport terminal and large stadium. However, insufficient strength of unstiffened jointsconstantly appear in the engineering design, which have brought about a lot of problemsto the designers. Reinforced with a Longitudinal plate is an effective way to enhance thestatic strength of gapped K-type CHS joints, but deficiency research has been done onthis part, especially research based on experimental tests. Due to few investigations seenat home and abroad papers, and the structure code haven’t given any specific rulesabout it, further research on the ultimate strength and related failure mode of gappedK-type CHS joints reinforced with longitudinal plates is badly in need.This paper based on experimental tests, supplemented with numerical analysis,mainly explores the ultimate strength and related failure mode of gapped K-type CHSjoints reinforced with longitudinal rectangular plates. And also make a comparison withjoints reinforced with two other different ways, one is reinforced with a piece oflongitudinal trapezoidal plate which dierectly welded to branch tubes, the other isreinforced with three pieces of longitudinal trapezoidal plate which also dierectlywelded to branch tubes. Specific details are as follows:(1) In this paper, static tests were carried out on ten uniplanar gapped K-type CHSjoints (including unreinforced joints, joints reinforced with a piece of longitudinalrectangular plate which directly welded to branch tubes，joints reinforced with a piece oflongitudinal trapezoidal plate, joints reinforced with three pieces of longitudinaltrapezoidal plate which directly welded to branch tubes), and then make a deep analysisand comparison of the static ultimate strength and failure modes of different stiffeningways.(2) Based on experimental tests, twenty node solid element Solid95was used inbuilding the FE model, at the same time, the factors of boundary conditions, geometricnonlinearity, material nonlinearity were considered and the influences of welds andresidual stress were ignored. By conducting a fine element meshing, we have accuratelysimulated the ultimate strength and failure mode of these reinforced and unreinforceduniplanar gapped K-type CHS joints. And this in turn fully verifies the accuracy and effective of the ANSYS finite element model.(3) Parameter analysis of joints reinforced with a piece of longitudinal trapezoidalplate and joints reinforced with longitudinal rectangular plates have been conductedrespectively, mainly to investigate the influence of these geometrical parameters onultimate strength and failure mode. These geometrical parameters are the ratio of theheight of stiffening plate to chord diameter η=h/d,ratio of the thickness of stiffeningplate to the thickness of web member τ1=ts/t1,the length of stiffening plate L1, the gap ofweb member g, brace to chord angle θ, brace to chord diameter β, brace to chordthickness τ.