Health Monitoring of Civil Infrastructures Designed with Pre-stressing Steel

Abstract

Our infrastructure is expanding and the existing infrastructure is aging. Some structures are expensive to maintain and some occasionally fail. Health monitoring of structures has become a hot topic discussed among owners, engineers, contractors and the general public at large. Pre-stressing steel is an important part of the structure where it is installed. Unfortunately there are limited testing methods available to assess the force in the pre-stressing steel. High cost, complicated equipment and limitation of space often prevent these methods from being implemented. DYNA Force sensors have been developed to measure the force in the pre-stressing steel during construction and at any time during the lifetime of the structure. In addition to the long-term monitoring benefit of using the sensor, it may also be used to check the load during stressing to address the safety of the structure. It will eliminate the use of large equipment during lift-off operation. These sensors are manufactured based on the magneto-elastic properties of ferrous material. A readout unit is designed to magnetically energize the steel through the sensor and measure the response of the steel to a direct force reading. The force reading can be collected manually, automatically and also remotely. They can be used for bare, epoxy-coated, galvanized and greased-sheathed steel in bonded, un-bonded, grouted or un-grouted length of the tendon/anchor. It has received attention in terms of accuracy, its performance, ease in installation, durability, and cost effectiveness. It has been used in over seventy projects in various parts of the world. Its application in bridges, buildings, tunnels, retaining walls and dam structures is presented.