System and method for automatically stressing mono-strand tendons

Abstract

A system and method for stressing tendons includes a hydraulically actuated puller configured to pull a tendon extending from a structure and a user input configured to receive a user-desired stressing parameter indicating at least one of a desired stressing magnitude and desired stressing distance. A processor is included that is configured to receive the user-desired stressing parameter from the user input and control the hydraulically actuated puller to apply at least one of the desired stressing magnitude and the desired stressing distance to the tendon.

1 . A system for stressing a tendon comprising:
 a hydraulically actuated puller configured to grip a tendon extending from a structure;   a user input configured to receive a user-desired stressing parameter indicating at least one of a desired stressing magnitude and a desired stressing distance;   a processor configured to receive the user-desired stressing parameter from the user input and control actuation of the hydraulically actuated puller to apply at least one of the desired stressing magnitude and the desired stressing distance to the tendon.   
   
   
       2 . The system of  claim 1  further comprising a tendon sensor configured to monitor at least one of an actual stressing magnitude and an actual stressing distance of the tendon and wherein the processor is further configured to compare at least one of the actual stressing magnitude to the desired stressing magnitude and the actual stressing distance to the desired stressing distance to determine when the tendon has been stressed according to the user-desired stressing parameter. 
   
   
       3 . The system of  claim 2  further comprising a hydraulic jack having a pump and a pump sensor configured to monitor a pressure applied at the pump and wherein the processor is further configured to receive feedback from the pump sensor prior to stressing the tendon and control the hydraulically actuated puller to remove slack in the tendon. 
   
   
       4 . The system of  claim 3  wherein the processor is further configured to reset the tendon sensor after determining slack in the tendon has been removed. 
   
   
       5 . The system of  claim 2  wherein the processor is further configured to determine when the tendon has been stressed beyond the user-desired stressing parameter and control the hydraulically actuated puller to retract to match a stress applied to the tendon to the user-desired stressing parameter. 
   
   
       6 . The system of  claim 1  wherein the user input includes a digital interface configured to receive the user-desired stressing parameter and a liquid crystal display (LCD) screen configured to display the user-desired stressing parameter as a numerical value. 
   
   
       7 . The system of  claim 1  wherein the desired stressing magnitude includes a stressing pressure and the and the desired stressing distance includes an elongation measurement. 
   
   
       8 . A hydraulic stressing system comprising:
 a gripper configured to engage a tendon extending from a structure;   a hydraulically actuated puller configured to pull the gripper to elongate the tendon during a stressing process;   a sensor configured to determine an actual elongation of the tendon during the stressing process;   a user input configured to accept a user-selected stressing parameter indicating a desired elongation of the tendon to be achieved during the stressing process;   a processor configured to control the hydraulic stressing system; and   a storage medium having stored thereon a program that, when executed by the processor, causes the processor to:
 receive the user-selected stressing parameter indicating the desired elongation of the tendon from the user input; 
 receive feedback from the sensor indicating the actual elongation of the tendon; and 
 control the stressing process to match the actual elongation of the tendon to the desired elongation of the tendon. 
   
   
   
       9 . The system of  claim 8  wherein the user-selected stressing parameter includes a desired pressure and wherein the processor is further caused to determine the desired elongation from the desired pressure. 
   
   
       10 . The system of  claim 8  further comprising a display configured to display at least one of the user-selected stressing parameter, the actual elongation of the tendon, and the desired elongation of the tendon. 
   
   
       11 . The system of  claim 8  wherein the tendon includes multiple wires forming a mono-strand post. 
   
   
       12 . The system of  claim 8  wherein the structure includes a concrete beam. 
   
   
       13 . A hydraulic stressing system comprising:
 a gripper configured to engage a tendon extending from a structure;   a hydraulic jack configured to pull the gripper to elongate the tendon during a stressing process;   a pump configured to provide a fluid to the hydraulic jack to cause the hydraulic jack to pull the gripper;   a pump sensor configured to monitor an actual pressure applied at the pump;   a position sensor configured to monitor an actual elongation of the tendon during the stressing process;   a processor configured to control the hydraulic stressing system; and   a storage medium having stored thereon a program that, when executed by the processor, causes the processor to:
 control the pump to increase the fluid provided to the hydraulic jack according to a desired pump pressure; 
 receive feedback from the pump sensor indicating the actual pump pressure of the pump; 
 receive feedback from the position sensor indicating the actual elongation of the tendon resulting from the actual pump pressure; and 
 calculate whether any slack in the tendon has been removed using the desired pump pressure, the actual pump pressure, and the actual elongation of the tendon. 
   
   
   
       14 . The system of  claim 13  wherein the processor is further caused to:
 control the pump to incrementally increase the fluid provided to the hydraulic jack; and   after each increment, calculate whether any slack in the tendon has been removed using the desired pump pressure, the actual pump pressure, and the actual elongation of the tendon.   
   
   
       15 . The system of  claim 14  wherein the processor is caused to reset the position sensor configured to monitor the actual elongation of the tendon during the stressing process after any slack in the tendon has been removed. 
   
   
       16 . The system of  claim 13  wherein the processor is further caused to postpone the stressing process until any slack in the tendon has been removed. 
   
   
       17 . The system of  claim 13  further comprising:
 a user input configured to accept a user-selected stressing parameter indicating a desired elongation of the tendon to be achieved during the stressing process;   wherein the processor is further caused to:
 receive the user-selected stressing parameter indicating the desired elongation of the tendon from the user input; and 
 after any slack in the tendon has been removed, reset the actual elongation monitored by the sensor and initiate the stressing process by controlling the pump to deliver fluid to the hydraulic jack to match the actual elongation of the tendon to the desired elongation of the tendon.