The efficacy of fiber-reinforced polymer (FRP) confinement as a means of repairing/strengthening reinforced concrete members with nonductile details is explored in this paper with particular emphasis on the interaction between jacket and the embedded longitudinal compression reinforcement at the onset of bar buckling. To this end, a total of 27 short prismatic specimens were tested to failure under concentric compression subsequent to application of FRP jackets; four additional specimens were tested as controls. Specimens had a square cross section and most were detailed according to former practices with the exception of few specimens that contained the minimum transverse reinforcement as specified by modern provisions. Parameters of the experimental study were the extent of initial damage prior to jacketing, the jacket material, and the number of layers. Response variables included ductility at failure, deformation capacity, strength increase, and mode of failure of the repaired/strengthened member. Confinement effectiveness was quantified using the degree of lateral dilation as the primary performance index. Deformation capacity as limited by embedded longitudinal bar buckling and jacket rupture/debonding strains was evaluated from the experimental results and analytical considerations.

The local bond mechanics of glass-fiber reinforced polymer (GFRP) bars in normal strength concrete was investigated through experimental testing and analytical modeling. The experimental program was comprised of 30 direct tension pullout specimens with short anchorages. A novel test setup, specially designed so as to minimize the spurious influence of testing conditions on measured bond properties was adopted in the study. Parameters considered were the bar roughness and diameter, the size effect expressed by the constant cover to bar diameter ratio, and the external confining pressure exerted over the anchorage length by transverse externally bonded FRP sheets. Results of the study were summarized in the form of local bond-slip curves, whereby performance limit states were quantified by the amount of loaded end slip and bond strength. An analytical model of the bond stress-slip response of a GFRP bar was derived from first principles and calibrated against the test data of the present investigation. Using the calibrated model, design values for bond and slip were estimated with reference to the code limit state model for bond.

The distribution of bond on the lateral surface of steel reinforcement embedded in concrete is explored through systematic solution of the governing field equations of the associated mechanical problem. By separating the variables, the state of stress in the concrete surrounding the bar is represented by coupling two independent solutions, each describing attenuation of bond stresses either in the longitudinal direction or in the radial direction of the cover, respectively. Kinematic considerations are used to couple longitudinal slip with the radial translation of the cover, whereas the corresponding stress components developing along the lateral bar surface over the anchorage (radial pressure and bond stress) are related through a frictional relationship. Using the derived solution, various experimentally documented trends and phenomena pertaining to the study of bond, as represented by the international experimental databank, are reproduced analytically and interpreted. These include the proces...

In the Balkan Peninsula, the single-arched stone masonry bridge has served for centuries as an essential part of transportation infrastructure. Being exposed to the natural elements and to aging, several of these structures are in a state of disrepair that is accelerated by neglect. Nevertheless, these are important samples of the built heritage encapsulating historical materials, methods of construction and ancient craftsmanship. Still standing for over half a millennium, such bridges testify the wisdom by which the masons chose the location and form of the arch to span over torrents minimizing the wear from water scouring and floods. Preservation of the bridges that are still standing is a priority. With increasing number of bridge collapses reported in the past years under extreme flood, an immediate need emerges for methods of evaluation of the structural vulnerability and measures to enhance their resilience. Using as a case study a bridge built in fifteenth century in Greece, this paper unfolds the essential attributes of a comprehensive assessment framework that combines non-destructive evaluation techniques to reveal information about technologies and details, with a numerical investigation of the resilience of the structure to floods and seismic hazards in order to identify risks of bridge integrity.