Improving durability of joints of precast decks

点击翻译按钮获取中文摘要

The poor state of North American infrastructure has received considerable attention over the last several years. Many of the bridges in Manitoba were built in the 1950s to 1970s. These bridges are approaching the end of their service lives and will need to be replaced or rehabilitated in the near future. The American Society of Civil Engineers reports that 200 million trips in the United States are taken daily across bridges that are deteriorating and may need replacing or strengthening. The cost of replacement or rehabilitation is impacted by the length of time required to complete the upgrade. As a result, Accelerated Bridge Construction (ABC) practices have been developed in recent years. This research proposal focuses on prefabrication of bridge elements, a type of ABC that will further accelerate construction while improving structural safety and durability.Besides accelerating construction, precast bridge deck construction has the advantage of achieving high quality production with tight tolerances. Precast construction increases the long-term durability of concrete as a result of its low permeability, and reduces shrinkage strains thanks to the controlled environment of a precast plant. High performance concrete (HPC) can be used to join the precast panels to shorten the curing time. Therefore, the use of HPC in construction joints is increasing and is often an integral part of ABC.This research will focus on the use of innovative reinforcement methods to produce durable joints for precast bridge deck panels. The current methods of joining precast bridge decks in negative moment regions requires external post-tensioning, in order to prevent cracking of the joint. My research proposes innovative methods to solve the problem. Fibre-reinforced polymer (FRP) prestressed concrete prisms (PCP) will be used to introduce small levels of compression into the joints. This will improve the service load performance by delaying and minimizing cracking, and also will result in much smaller crack widths. FRPs are non-corrosive, therefore the joints will last longer. FRP tendons have been reported to fail without warning during prestressing. To mitigate possible workplace injuries in precast plants using this material, my research will focus on developing of acoustic emission monitoring technique to detect failures of FRP bars during stressing. The warning system will be used for long-term monitoring of stresses in FRP bars, and improving worker safety during stressing operations by detecting and preventing FRP bar rupture due to overstressing and providing warning before FRP bar failure. The practical findings of this research will be useful for bridge engineers, infrastructure owners, and precast contractors. The development of FRP failure warning system has a large potential for improving safety of FRP-reinforced and prestressed structures. The research will provide data for accelerating bridge construction using FRP and prestressed concrete prisms. Accelerated construction reduces traffic interruptions, and the overall cost of construction while improving durability and structural integrity.