During an extreme event occurring on a reinforced concrete structure, characterized by the loss of a load-bearing element, the remaining resisting members may develop alternate load paths to resist gravity loads. However, it is recognized that reinforced concrete flat slabs are prone to punching shear failure. This issue is particularly relevant for existing reinforced concrete structures where creep, shrinkage, and corrosion effects due to environmental conditions play a fundamental role before the occurrence of the extreme event. In this paper, nonlinear pushdown and dynamic analyses were performed on an existing continuous reinforced concrete flat slab to investigate the structural response in the case of an interior column loss. Firstly, the flexural and membrane action resisting contributions were in-deeply analyzed. Secondly, the crucial effects of creep, shrinkage and corrosion on the dynamic response and punching shear resistance of the system were critically evaluated. Finally, useful insights for the structural robustness assessment of existing RC structures subjected to material deterioration were provided.

This paper presents an investigation of the bond performance of corrosion-free sand-coated glass fiber reinforced polymer bars (GFRP) implanted in two types of fly ash-based eco-friendly concrete. Steel reinforcement is prone to corrosion and is expensive to fix, therefore finding an effective alternative has become a must. One of these alternatives is GFRP bar. On the other hand, conventional concrete (CC) is not issueless, as it significantly affects the environment through its high-intensity CO₂ emissions. Thus, other alternatives have been looked into to mitigate the CO₂ problems. One of these alternatives is partially substituting Portland cement with another CO₂ emission-free material such as fly ash. In this study, two levels (50% and 70%) of high-volume fly ash concrete (HVFAC) were used to investigate their bond performance with GFRP bars. Cylindrical specimens were tested under the effect of pullout load. Furthermore, the bars were investigated chemically and microstructurally to see if the fly ash had some influence on the GFRP bar. For concrete, performance rank analysis was carried out to identify the best concrete mixture in terms of slump, unit weight, cost, and bond strength. In addition, to verify the experimental work, two-dimensional finite element models were built using translator elements to present the bond action between the concrete and its reinforcement. The results of the investigation showed that the bond strength of GFRP bars was less than that of mild steel owing to GFRP bar deformation. In addition, CC resulted in a higher bond strength than HVFAC. The bar analyses did not yield any obvious signs of microstructural deterioration or chemical attack.

The development of rehabilitation strategies for reinforced concrete bridges is a significant concern for civil engineers. Bridges exposed to harsh environmental conditions and subjected to daily fatigue loading are vulnerable to corrosion and accelerated deterioration of their components. Previous studies and field applications have shown that bonding carbon fiber-reinforced polymer (CFRP) to the bridge element surface is an attractive solution for bridge strengthening. This paper aims at reviewing and evaluating the use of externally bonded CFRP for bridge rehabilitation. The article is structured in two main parts. The first part is an experimental and field survey on using CFRP as external reinforcement for concrete bridges. The second part focuses on evaluating the performance of the Original Champlain Bridge (OCB) edge girder strengthened with externally bonded CFRP under live load tests, which were performed by the developers of the bridge. The results of truckload tests on the edge girder of the OCB show that the rehabilitation technique using externally bonded CFRP sheets on the edge girder of the bridge was able to keep the shear strains constant and extend their service life for up to 10 years until deconstruction of the bridge.

Fiber-reinforced polymer (FRP) bars are an alternative solution to traditional steel bars for internal reinforcement of reinforced concrete (RC) structures. The potential reduction of damage in RC structures due to the absence of corrosion and the low weight-to-strength ratio of the FRP bars when compared to steel bars make FRP bars a cost-effective solution when durability is a concern. While a recent ASTM standard (ASTM D7913) has been issued to test the bond of FRP bars, limited work is available in the literature that deals with the determination of the interfacial properties between the FRP bars and concrete and the bond mechanism.

In this paper, experimental results are presented that aim at identifying a suitable setup to study the bond behavior and determining the effect of different bonded lengths on the stress transfer mechanism. Pull-out tests present some advantages to studying the bond mechanism without the complication of flexural stresses. Once the mechanism of the bond is studied at the small scale, and the interfacial cohesive material law is obtained, it is possible to simulate the behavior of full-scale members. The majority of the pull-out tests are performed with a short bonded length, which does not allow to fully establish the stress transfer between the bar and the surrounding concrete. In this paper, bars are embedded in concrete cylinders and pull-out tests are performed in displacement control with four bonded lengths. The first bonded length is equal to 5 times the bar diameter in order to consider the case of ASTM D7913. The other three bonded lengths are equal to 10, 20, and 40 times the diameter of the bar, respectively. Loaded-end displacement is obtained from the measurements of three linear variable displacement transformers (LVDTs). For some specimens, the free-end displacement was measured by two additional LVDTs. The load responses in terms of applied load versus machine stroke, loaded-end slip, and free-end slip are plotted and compared for the different bonded lengths. The results show that the average shear stress calculated according to ASTM D7913 is not constant for the different bonded lengths. In addition, the slip at the free end is activated at a different percentage of the peak load as the bonded length increases, which indicates that the bond phenomenon requires a certain bonded length to be fully established. The experimental peak stress versus bonded length and the stress level in the bar as a function of the embedded (bonded) length, according to ACI 440.1R-15, are compared. The results indicate that for the bar type studied in this paper, the provisions of ACI 440.1R do not match the results of the pull-out tests.

Deep beams are common elements in concrete structures such as bridges, water tanks, and parking garages, which are usually exposed to harsh environments. To mitigate corrosion-induced damage in these structures, steel reinforcement is replaced by fiber-reinforced polymers (FRPs). Several attempts have been made during the last decade to introduce empirical models to estimate the shear strength of FRP-reinforced concrete (RC) deep beams. In this study, the applicability of these models to predict the capacity of simply supported deep beams with and without web reinforcement was assessed. Test results of 54 FRP-RC, 24 steel-fiber-reinforced concrete (FRC), and 7 FRP-FRC deep beams were used to evaluate the available models. In addition, a proposed model to predict the shear strength of FRPFRC deep beams was introduced. The model was calibrated against experiments conducted previously by the authors on FRP-FRC deep beams under gravity load. The model could predict the ultimate capacity with a mean experimental-to-predicted value of 1.04 and a standard deviation of 0.14.