Ghazaleh Laleh, University of Nevada, Las Vegas
IRF: What did you research identify as some of the most promising short-span bridge options available to engineers today?
Ghazaleh Laleh: My research identified a range of both concrete and steel short-span bridge options, giving particular focus to alternatives which can be implemented using accelerated bridge construction. The work attempted to identify both currently implemented systems as well as promising alternatives still under development. Most designers are familiar with the available concrete alternatives: side-by-side box-beam systems, decked bulb tee-girder options, and double-tee girder methods. These systems utilize precast, prestressed elements which lead to considerably decreased on-site time due to concrete forming, casting, and curing operations in an off-site shop environment. However, I think many of the short-span steel options will be new to many engineers. The press-brake-formed steel tub girder system is one of the most recent short-span bridge options which is resulting from extensive research and experimental tests. This bridge modular is composed of cold-bent steel elements and precast, prestressed concrete deck to satisfy demand for rapid bridge construction. Cold bending not only reduces need for welding, required number of bolts and stiffeners, but also maintains the flexural performance of the bridge unit. The steel-concrete composite twin I-girder bridge system is another available steel option which is employed for short and medium bridge span ranges. This system contains a simplified detailing including a concrete deck supported by a twin longitudinal I-girder through welded shear connectors on the top flanges of the steel girders. The system allows bridge owners and designers to increase bridge span by deploying prestressed deck and enlarging the space between the main girders of the unit.
IRF: Conversely, what challenges remain in deploying some of these options with the current state of the art?
Ghazaleh Laleh:Many challenges still remain with a number of the promising available short-span bridge options, especially in regards to serviceability, torsional performance, and seismic behavior. Probably the most challenging aspect for all systems is the longitudinal connection between adjacent modules. Most accelerated bridge alternatives employ modular systems with the deck pre-installed that can be quickly placed using a crane. The decks of the adjacent modules must be connected to ensure continuity and monolithic structural behavior. Unfortunately, degradation and serviceability issues, such as reflective longitudinal cracks on overlay, corrosion of reinforcement due to water penetration, and differential displacement between adjacent units, can occur as a result of connection failure between prefabricated bridge units. Current research seeks to explore a connection detailing to overcome the problems associated with insufficient performance of the longitudinal connections. Constructing longitudinal joints with UHPC materials, and reinforcing system with corrosion-free FRP bars are frequently used innovative methods which decrease life-cycle maintenance costs and increase the continuity between adjacent bridge units. A few other reaming challenges the research identified include exploring methods or configuration to reduce material usage, improve seismic behavior, and enhance the torsional performance of the unit, since the state-of-the-art research implies that poor torsional stiffness may result in weak dynamic characteristic and excessive induced-vibration.
IRF: As a researcher, what is the value of presenting your work at a Conference featuring a wide cross-action of actors from the public, private and academic sector?
Ghazaleh Laleh:Attending professional conferences, presenting data, and exchanging information has tremendous positive effects on the development of a young researcher. Presenting provides real-world experience sharing my work with experts in the field. The wide-range of participants from the public, private, and academic sectors gives a diverse feedback to help improve and advance the research. Each group has a unique and important perspective which must be considered. Gaining such feedback early-on can provide invaluable insight on how to best shape future research endeavors.
One of the greatest benefits to presenting is the opportunity to network with other researchers namely my academic heroes. Interacting with these individuals helps me stay enthusiastic about my research, while keeping me craving for new research sparks. Altogether, I cannot think of a better place to meet other key stakeholders working in the same research topic area, thereby making new connections with other professionals and scholars with similar interest. Ultimately, the conference provides a forum for the scientific panel to create, improve, and advance the state-pf-the-art.
IRF Global R2T Conference & Exhibition: November 19-22, 2019