Modeling of IC Debonding of FRP-Strengthened Concrete Flexural Members
The presence of a fiber-reinforced polymer (FRP) strengthening material bonded to the tension face of a reinforced concrete beam will restrict but not prevent the opening of intermediate flexural cracks due to applied loading. Test results indicate that displacements at the toe of flexural cracks create stress concentrations at the interface of the FRP laminate and the beam, leading to the development of localized interface cracks that, typically, propagate, under the effect of the load, to join the original flexural cracks and cause delamination of the FRP system. This type of FRP delamination is commonly termed intermediate crack (IC) debonding. In this paper the analytical models published in the literature are reviewed and it was found that these models do not correlate well with measured experimental results. This paper proposes an analytical model that characterizes the interface shear stress based on two distinct sources: (1) the change in the applied moments along the length of the member and (2) ...
Behavior of FRP Repair/Strengthening Systems for Prestressed Concrete
ROSENBOOM, OWEN ARTHUR. Behavior of FRP Repair/Strengthening Systems for Prestressed Concrete. (Under the direction of Dr. Sami Rizkalla.) This research study examines the behavior of prestressed concrete beams retrofitted with Fiber Reinforced Polymer (FRP) materials. Due to deficiencies in the built environment, engineers may be asked to retrofit or upgrade the capacity of an existing concrete structural member. This could be a result of new demands on the structure, or a repair of damage from an unforeseen event. Retrofits are possible using the traditional building materials of concrete and steel. The cross-section of the structural element can be increased, or steel plates can be bolted or adhesively affixed to the structure to increase capacity. Many of these techniques are costly, and some perform poorly under service conditions. The main benefit for using FRP materials for the strengthening of existing structures is the lightweight nature of the composite material, which makes the use of extensive scaffolding (required in the installation of steel plates) obsolete. The objectives of this research are twofold. First, the overall structural behavior of an FRP strengthened or repaired concrete beam is studied. Two different loading conditions are examined: extreme loading simulated by a monotonic load to failure, and fatigue loading designed to simulate service loads. The structural behavior of the system is evaluated under these different conditions, and an analytical model is presented which predicts the flexural behavior of the system assuming certain failure modes. The second objective of this research is to evaluate the bond behavior of an FRP strengthened reinforced or prestressed concrete flexural member. A database of experimental failures was constructed, and an analytical model is proposed which predicts the bond failure of the FRP strengthening system. BEHAVIOR OF FRP REPAIR/STRENGTHENING SYSTEMS FOR PRESTRESSED CONCRETE
RDF Keyword Search based on Keywords-To-SPARQL Translation
In this paper, we present a summary of our work on RDF keyword search. Given a set of keywords, our method automatically generates a set of candidate SPARQL queries, and their natural language description, to be evaluated on the RDF data graph. We discuss our approach, highlighting current and future directions.