Failure analysis of threaded connections in large-scale steel tie rods

Steel tie rods are very important load-carrying components in applications where high levels of pre-stresses are required. The bearing capacity of a steel tie rod is determined not only by the strength of the rod body, but also by the strength of the threaded connection that resists force. Analysis of the strength of the threaded connection and determining the optimal number of turns of thread engagement is critical to ensure structural safety. This paper reports the results of full-scale tensile rupture experiments on two categories of large-scale steel tie rods provided by China JULI Corporation: (i) LG75-00 steel tie rods with triangle threaded connection, and (ii) LG100-00 steel tie rods with trapezoidal threaded connection. The full-scale tensile rupture experiments were carried out to test the maximum allowable axial working load under different numbers of turns of engaged threads. The results of these experiments suggest strong guidelines on the minimum number of turns of thread engagement for preventing the failure of thread teeth of steel tie rods in practical shear and bending applications.