STRENGTH OF DT TUBULAR JOINTS WITH BRACE AND CHORD COMPRESSION

The effects of chord axial compressive stress on the ultimate strength of a DT joint subjected to brace compression have been studied both e xperimentally and numerically. Three experimental load cases were cons idered, one with brace compression only and the other two with differe nt chord axial stress. Two methods were used in the numerical work to apply the chord and brace loadings: (1) Proportional loading; and (2) nonproportional loading. The former method was adopted in the experime ntal work. The results confirmed that the ultimate strength of DT join ts can be reduced significantly when chord axial stress is present. No nlinear finite-element (FE) analysis on the joints was found to overes timate ultimate loads, especially for high chord loads. A comparison b etween the current results and the API design rules has shown that, ev en with the two safety factors removed, the API equation gives ultimat e brace compression loads that are conservative up to chord utilizatio n values of similar to 0.5.