This Week's Featured Presentation
Advanced Analysis and Testing Methods for Concrete Bridge Evaluation and Design (ACI Spring 2019 Convention, Québec City, QC, Canada) The Champlain Bridge, opened in 1962, is 3.4 km long and is made up of 50 simply supported spans (about 53 m long) plus an elevated truss structure over the Saint-Lawrence Seaway in Montreal. Corrosion of some of the post-tensioning strands in the girders, as well as structural degradation prompted strengthening measures coupled with instrumentation and monitoring of the bridge. This paper describes the instrumentation and monitoring of the 50 concrete spans and 45 pier caps of that bridge, using optical sensors for recording strains on these elements. Presently, over 330 optical sensors are installed on the bridge to record data continuously at 50Hz. Such data contains invaluable information for monitoring the bridge response and condition after the monthly load tests, which trends can provide an indication of degradation. Furthermore, the daily traffic loading is also analyzed, with the help of a specialized software, to detect any signs of degradation in the girders and pier caps. Trends in the data can then be used to detect structural problems or confirm the impact of structural strengthening. Through these means, among others, The Jacques Cartier and Champlain Bridges Incorporated preventively manages the risks associated with this infrastructure at the end of its service life.
September 21 - 27
Post-Fire Flexural Testing and Rating of Prestressed Concrete Bridge Girders
by Nur Yazdani, University of Texas at Arlington; and Eyosias Beneberu, Bridgefarmer & Associates
Fire and Flood Design, Performance, Mitigation, and Strengthening for Concrete Bridges (ACI Fall 2019 Convention, Cincinnati, OH) Significant investigations have been conducted on the effect of extreme load events, such as earthquake, wind and flood on bridges, as compared to fire hazards, even though fire can cause significant economic and public impacts. To bridge this knowledge gap, a full-scale one span prestressed concrete bridge was tested under a combined hydrocarbon fire and simulated AASHTO live load. The superstructure comprised of three standard I-girders, precast deck panels, cast-in-place deck, and elastomeric bearing pads. One girder was wrapped with carbon fiber reinforced polymer (CFRP), another with CFRP and sprayed fireproofing and a third was without CFRP or fireproofing. The test was conducted for 60 minutes and the fire temperature reached as high as 1131oC. It was found that the fireproofing was helpful in lowering the temperature at the CFRP-concrete interface, thereby preserving the integrity of the CFRP bonding, the concrete substrate, and prestressing steel. Without fireproofing, the CFRP quickly debonded, thereby causing significant concrete spalling and loss of some prestressing strands. Following the fire test, the deck was saw cut and each girder was tested in the laboratory under a three-point bending set-up to determine their residual strengths. The CFRP girder without fireproofing lost 59% of its design flexural capacity, while the one with fireproofing did not experience any reduction in flexural capacity. The results of the load testing and rating of each girder will be presented.