Measurement of tension in securing members

A method to determine an unknown, current pre-tension in a pre-tensioned securing member having an exposed portion, comprising:

• coupling a pulling member to the exposed portion of the pre-tensioned securing member;
• generating pulling forces with the pulling member on the pre-tensioned securing member;
• measuring pulling force displacements of the pre-tensioned securing member in response to at least two lower applied pulling forces that are different from each other;
• determining a first relationship between the pulling force displacements for the lower applied pulling forces;
• measuring pulling force displacements of the pre-tensioned securing member in response to at least two higher applied pulling forces that are different from each other until it is determined that a second relationship different from the first relationship is defined;
• determining the current pre-tension in the pre-tensioned securing member by setting the first relationship and the second relationship equal to each other.

A device to determine an unknown current pre-tension in a pre-tensioned securing member having an exposed portion, comprising:

• a memory;
• a processor connected to the memory and having a pre-tension calculator, wherein the pre-tension calculator:
• receives first and second pulling force displacements of the pre-tensioned securing member corresponding to first and second pulling forces applied to the securing member that are different from each other;
• stores the first pulling force displacement and the first pulling force in association with each other;
• stores the second pulling force displacement and the second pulling force in association with each other;
• receives third and fourth pulling force displacements of the pre-tensioned securing member corresponding to third and fourth pulling forces applied to the securing member that are different from each other;
• stores the third pulling force displacement and the third pulling force in association with each other;
• stores the fourth pulling force displacement and the fourth pulling force in association with each other;
• determines a first relationship between the first and second pulling force displacements;
• determines a second relationship between the third and fourth pulling force displacements;
• and
• determines the current pre-tension in the pre-tensioned securing member by setting the first relationship and the second relationship equal to each other.

A computer-readable medium having stored thereon program code, the program code executable by a computer to perform operations comprising:

• receiving first and second pulling force displacements of the pre-tensioned securing member corresponding to first and second pulling forces applied to the securing member that are different from each other;
• storing the first pulling force displacement and the first pulling force in association with each other;
• storing the second pulling force displacement and the second pulling force in association with each other;
• receiving third and fourth pulling force displacements of the pre-tensioned securing member corresponding to third and fourth pulling forces applied to the securing member that are different from each other;
• storing the third pulling force displacement and the third pulling force in association with each other;
• storing the fourth pulling force displacement and the fourth pulling force in association with each other;
• determining a first relationship between the first and second pulling force displacements;
• determining a second relationship between the third and fourth pulling force displacements;
• and
• determining the current pre-tension in the pre-tensioned securing member by setting the first relationship and the second relationship equal to each other.