THE EFFECTS OF ADJACENT BRACES ON THE STATIC STRENGTH OF A CORNER YT JOINT

Forty corner YT joints have been manufactured from a tin-lead alloy mo del material. They have been tested in compression, tension, out-of-pl ane and in-plane bending of a single brace or simultaneously of two ad jacent braces. All of the tin-lead alloy models had the same shape; th e T-brace axes were at 90 degrees to the chord axis and the Y-brace ax es were at 45 degrees to the chord axes; the diameter to thickness rat io for the chord was 18.4; the ratio of the brace diameters (all the s ame) to the chord diameter was 0.5; the thicknesses of the braces and chord were the same; the axial spacings between the braces were 0.18 x the chord diameter; the circumferential spacings between the braces w ere 0.26 x the chord diameter. The results of the 12 tests of loading a 90 degrees brace or a 45 degrees brace alone in six loading modes (c ompression, tension and bending towards and away from the two adjacent braces) were compared with the strength of T and Y joints. There were no significant differences except for in-plane bending of a 90 degree s or a 45 degrees brace, away from the other, where the strength was r educed by the presence of the unloaded brace. YT type loading (i.e. si multaneous loading of a 90 degrees brace and 45 degrees brace in the s ame axial plane) of a 90 degrees brace and the adjacent 45 degrees bra ce showed that the load in the adjacent brace could reduce the strengt h by up to 50% or increase it by up to 40%, depending on the ratio of the loads. Corner loading (i.e. simultaneous loading of braces in both axial planes) of two adjacent 90 degrees braces also produces signifi cant changes of strength.