Accelerated Bridge Construction
About a quarter of the nation’s bridges require repair, rehabilitation, or replacement. In the past, typically in order for work to be undertaken on a bridge that bridge had to be closed and traffic detoured, the road needed to be re-aligned, a temporary structure needed to be built to maintain traffic, and/or lane closures were required, all for a significant period of time. Accelerated bridge construction (ABC) involves the use of innovative planning, design, materials, and construction methods in order to reduce on-site construction times. The use of ABC reduces the impact on traffic by reducing closure and detour times and can oftentimes produce longer lasting structures with the use of prefabricated elements. Dr. Garber’s work in this area are related to connections between precast elements, full-depth precast concrete deck panels, database development, demolition of bridges, among others.
Ultra-High Performance Concrete
Ultra-high performance concrete (UHPC) is cementitious composite material with high compression strength (greater than 21 ksi), high tensile strength (greater than 1 ksi), and sustained post-cracking tensile strength. Dr. Garber’s work in this area include application of UHPC and development of non-proprietary UHPC mix designs.
Non-Traditional Shear Failures in Prestressed Concrete Girders
The recent trend for prestressed concrete beam design is to create more efficient sections to be used for longer span lengths. These sections have larger bottom flanges (to accommodate additional prestressing strands), thinner webs (enough to handle traditional shear demands without having excess material), and wider top flanges (to ensure lateral stability of girders during fabrication and transportation). In addition to the section optimization, sections are being built with larger prestressing ratios and higher initial compressive stresses. This trend within modern design raises concern, because both of these factors increase the likelihood of nontraditional shear mechanisms (e.g. horizontal shear, shear controlled by bond loss) controlling failure.
Strut-and-Tie Method and Reinforced Concrete Deep Beams
The strut-and-tie method (STM) is a methodology that can be used to design and analyze D-regions in reinforced concrete structures. In STM, the flow of stresses through a structure can be modeled using a series of compression elements (struts) and tension elements (ties) connected by nodes (the intersection of any struts and ties). STM is a lower-bound plasticity approach, so it will always yield a safe design (if used properly). Dr. Garber’s research in this area has included behavior of struts and strut types (bottle-shaped/prismatic versus interior/boundary struts), effect of bonded reinforcement on node strength, and behavior of different deep beam elements (e.g., inverted tee beams and ledges).
Time Effects in Prestressed Concrete Members