Precast Solutions - September/October 2008 - (Page 12) Jacking Nut Stressing Jack CFCC END ANCHORAGE SYSTEM LAYOUT Temporary Jacking Chair Socket Setting Nut Load Cell transverse unbonded post-tensioned strands has been ongoing. Data have been collected every two hours from vibrating-wire strain gauges, thermistors, deflection transducers and load cells installed within the bridge. This bridge continues to be monitored in order to obtain long-term data for 10 more years based on recently authorized funding by MDOT. The measured concrete strains, deflections and forces in the longitudinal and transverse post-tensioning strands over a period of five-years indicate that the bridge is performing as expected. The measurements also confirm that carbon fiber composite cable strands and their anchorages are intact and effectively serving within environmental conditions at the site. External CFRP post-tensioning strands provide remarkable ductility for bridge beams. Before building the Bridge Street Bridge, ultimate load tests were conducted on double-tee continuous bridge models with externally draped CFRP post-tensioning strands or tendons. Research showed failure in one bridge test model was initiated by crushing of the concrete at the bottom of the webs. For full-scale tests on prototype beams prior to bridge construction, visit http://qbx6.ltu.edu/nabil/. Temporary Stressing Nut Stressing Rod Anchor Socket CFCC Strand Ring Nut Bearing Plate Stuffing Box Wedge Block Permanent Chair Face of Concrete Anchor Block Exit Pipe Unbonded CFCC transverse post-tensioning Research indicates that transverse post-tensioning (TPT) with unbonded carbon fiber composite cable (CFCC) strands can prevent formation and arrest propagation of these longitudinal cracks. Tests (authorized and funded by MDOT) were conducted on a half-scale 31-foot (9.5-meter) span 30degree skew side-by-side box-beam bridge at Lawrence Tech. The bridge model was comprised of four adjacent precast, prestressed concrete box beams integrated with the construction of full-depth shear keys, reinforced composite deck slab, and TPT using unbonded CFCC strands. Results of the study show that the application of high levels of TPT forces effectively enable the bridge system to serve as a monolithic plate and improve load distribution. Transverse post-tensioning with transverse CFCC A close up view of a bridge cable anchor. 12 PRECAST SOLUTIONS | SEPTEMBER/OCTOBER 2008 http://qbx6.ltu.edu/nabil/
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.