Norbar Torque Tools has been chosen to provide an ultrasonic bolting system for the Izmit Bay Bridge in Turkey, set to be the world’s fourth longest suspension bridge.
The Build Operate Transfer (BOT) project is to construct and then operate a new motorway, including the 3km Izmit Bay Suspension Bridge, between Gebze and Izmir over a 22 year period. Construction and operation of the bridge, was awarded to NOMAYG JV, a joint venture made up of 6 private sector companies; Nurol, Özaltin, Mak-Yol, Astaldi, Yüksel and Göçay.
While the bridge was designed by Danish engineering design firm COWI A/S and architects Dissing+Weitling, Norbar worked directly with Japanese contractor IHI. The business has since been recognised as the only company in the world to manufacture an ultrasonic bolting system; capable of measuring more than ten metre long bolts – used on the steel structures that form the foundations of the North and South towers.
Juan Carlos Casas, sales engineer at Norbar, said: “The Izmit Bay Bridge is an extremely complex project, being built in one of the most seismically active areas in the world, which in turn places additional demands and stresses on the bridge’s design.”
Due to the nature of the application, Norbar has been selected to supply the instrumentation required to measure elongation on tensioned structures of the bridge. In applications like this, factors such as friction or bolt geometry are such that the measurement of applied torque alone will not provide the degree of accuracy necessary.
Casas continued: “Ultrasonic measurement of bolt preload is made possible by introducing a sonic pulse at one end of the fastener and accurately measuring the time of flight required for an echo at the opposite end. The USM-3 converts the time of flight in to an ‘ultrasonic length’, providing data from which future measurements will be made.”
The USM-3 was first used to measure tension on the foundations’ anchor bolts. Upon the completion of the bridge’s construction, the equipment will also be used to measure tension on the structures of the cable ties. It uses state-of-the-art hardware and software to achieve data measurements with maximum automation, and provides a complete system for measurement, recording and control of fastener tension.
The Izmit Bay Bridge, upon completion, will form part of a new extended highway system which links the Turkish cities of Izmir and Istanbul and will be over 2,800m long.
