Analysis and test of modified turn-buckles for measuring tensile force

A turn-buckle inserted between tension members is a device capable of adjusting tensile force. However, the measurement of tensile force is practically difficult, and tensile force is roughly estimated by the experience of field workers. The conventional turn-buckle may be used without any adjustment even though the tensile force has changed with time. Thus, a new measurable turn-buckle was developed to deal with the disadvantages of conventional turn-buckles in this study. The straight elements of a conventional turn-buckle were slightly bent in advance to induce lateral displacement. The change of gap between curved elements due to applied load is measured with a micrometer or vernier calipers in the field construction site. The measured displacement of the gap is then converted to the load of the tension member. A theoretical analysis and FEA were performed to investigate the applicability of the measurable turn-buckle developed in this study. The results of loading and unloading tests showed acceptable linearity and precision of the new turn-buckle for the field application. Additionally, two measurable turn-buckles with different measuring capacity were installed for six-month long-term measurements. The results of this test indicated that the recovery of measuring performance of the measurable turn-buckles was acceptable for long-term usage.