Grant: Discovery Grants Program - Individual

Bridges are aging and often taken for granted despite their critical role in our transportation networks. Their health has a significant impact on the economy and public safety. Indeed, the timing of bridge replacement or rehabilitation is critical. Catastrophe may occur if this is delayed, while unnecessary disruptions and costs are incurred if this is rushed. A key consideration in bridge performance is cyclic loading due to moving traffic, which causes reduction in stiffness with time and potentially fatigue failure. Current methods examining these phenomena apply stationary "pulsating" loading to simulate traffic (i.e. loading and unloading vertically, repeatedly, at the same spot). This practice is fundamentally different from actual "rolling" loads, which are constantly applied but travel horizontally. The latter generates stress reversals in shear (e.g. in bridge decks) and in bending (e.g. continuous girders), whch are more aggressive conditions than those experienced under pulsating loading. It also causes a wider spread of damage and cracking. All this is anticipated to produce larger deformations and a shorter fatigue life than using pulsating loading, which is not conservative. For the first time, damage and deterioration mechanisms leading to bridge failure will be studied rigorously at full scale under realistic rolling load conditions. We seek to create a paradigm shift towards a more robust understanding of bridge behavior, which will impact the research and design communities. The proposed program will answer important questions: What is the correlation between fatigue life under rolling and pulsating loads? How do rolling loads affect interfacial bond in decks retrofitted with overlay? What are the synergistic effects of steel corrosion and fatigue? Does the share of load of a girder (lateral distribution) vary with time as stiffness degrades? How does stress reversal affects shear and flexural strengths of girders? How do `clean' versus `clogged' expansion joints respond to rolling loads? Can rolling load tests combined with hybrid simulation examine dynamic behavior of bridges with different surface conditions? Different bridge building technologies and materials will be examined in this research using a unique facility at Queen's University, namely Canada's first and only Loading Load Simulator (ROLLS), capable of large scale bridge testing, up to 18m x 4m. The wealth of knowledge to be gained from this program will enable making design and construction recommendations for bridge authorities, designers and contractors, and improve the protocols governing bridge management, bridge rating and scheduled maintenance. Six doctoral, 5 master's and 5 undergraduate students will be trained in the project. Training involves critical thinking, problem solving, hands on experience, laboratory testing, data analysis, computer modeling, technical writing, presenting in conferences, team work and mentoring by industry partners.