Developments in the prestressed concrete industry evolved to incorporate innovative design materials and strategies driven towards a more sustainable and durable infrastructure. With steel corrosion being the biggest durability issue for concrete bridges, FRP tendons have been gaining acceptance in modern prestressed technologies, as bonded or unbonded reinforcement, or as part of a “hybrid” system that combines unbonded CFRP tendons and bonded steel strands. Assessments of the efficacy of hybrid-steel beams, combining bonded and unbonded steel tendons. in the construction of segmental bridges and in retrofitting damaged members has been established by several researchers. However, limited research has been conducted on comparable hybrid prestressed beams combining CFRP and steel tendons (hybrid steel-cfrp beams). This paper provides an insight on the flexural behaviour of eighteen prestressed beams tested under third-point loading until failure with the emphasis on the tendon materials (i.e., CFRP and steel) and bonding condition (i.e., bonded, unbonded). In addition, a comprehensive finite element analysis of the beams’ overall behaviour following the trussed-beam methodology is conducted and compared with the experimental results. Results show that hybrid beams, utilizing CFRP as the unbonded element maintained comparable performance when compared to hybrid steel beams. The results presented in this paper aim to expand the use of hybrid tendons and facilitate their incorporation into standard design provisions and guidelines.

The first phase of this work uses experimental evidence to critique some shortcomings of the so-called improved double-lap bond shear tests regarding their limited application to wet layup fiber-reinforced polymer (FRP) and their inapplicability to pultruded FRP laminates. Even in the case of the wet layup FRP, the study provides some evidence of high chances of obtaining undesirable fiber rupture that preclude the use of the results as reliable means for interpreting the FRP-concrete bond-slip models. Further proposed modifications to overcome these challenges are provided by designing a convertible bond tester applicable to both wet layup and pultruded FRP laminates. Apart from the application of the apparatus to FRP-concrete bond assessment under pure double shear, it proved to be applicable to conducting mixed-mode bond tests. The second phase of the work upgrades the so-designed test apparatus to make it convertible to bond testing of other variants (near-surface mounted [NSM] FRP bars/strips, fiber-reinforced cementitious mortar [FRCM], etc.) of strengthening systems without developing a different apparatus for each. The apparatus allows testing the NSM FRP-concrete bond in a novel manner compared to the traditional practice. Also, given the absence of mixed-mode studies for FRCM, the apparatus provides a pioneer means of conducting the same.

The issues related to deformability, strength and ductility of concrete elements reinforced with FRP (Fiber Reinforced Polymer) bars are critically analyzed and discussed in this paper. The analysis is conducted from an experimental point of view by means of bending tests on concrete beams reinforced with Carbon FRP (CFRP) bars with different amounts of reinforcement, and by an analytical approach aiming to evaluate the deflection and cracking phenomenon (number and width of cracks). The experimental results are compared with the analytical predictions and with predictions developed on the basis of the available codes (ACI, EC2, JSCE). The analysis of the results obtained confirms the most relevant issues of the mechanical behavior of FRP bar-reinforced beams, still worthy of research efforts; some technological and construction solutions that can provide significant improvements are also addressed.

Unreinforced masonry buildings (URM) are particularly vulnerable to local out-of-plane failure mechanisms of the walls during earthquakes. This study investigates the effectiveness of a relatively novel class of inorganic composite materials, namely Fibre Reinforced Mortars (FRM), for the out-of-plane strengthening of masonry walls. Experimental tests by using a setup to perform out-of-plane tests on masonry panels, part of an enlarged ongoing testing campaign, are presented herein. Two types of masonry walls are investigated: solid clay brick masonry walls and tuff masonry walls. The specimens are subjected to compressive axial load and out-of-plane horizontal actions according to a “four-point bending test” scheme. Two specimens are reinforced before testing with FRM in double-side configuration, while other two specimens are tested in their bare configuration. Experimental results in terms of capacity curves and deformed shapes are reported and discussed. The preliminary results attest that FRMs are effective in increasing the out-of-plane capacity of masonry walls and in postponing the activation of the out-of-plane failure mechanism.

This paper presents an indeterminate strut-and-tie (IST) method to analyze concrete deep members reinforced with fibre-reinforced polymer (FRP) bars. Because FRP bars are linear-elastic and brittle at failure, the classical ST method based on steel yielding cannot be used to analyze FRP-reinforced concrete deep beams, and current code provisions lack guidance on such designs. Thus, the IST method is proposed for the analysis. This work addresses the details of using the proposed IST method to analyze FRP-reinforced concrete deep beams, including how to size the struts and nodes without assuming steel yielding, how to model the compressive behaviour of concrete struts reasonably, and how to construct and analyze statically indeterminate ST models. Six FRP-reinforced concrete deep beams with stirrups and six beams without stirrups are analyzed in this work, and it is found that the proposed method works well to predict the shear strength of FRP-reinforced concrete deep beams by comparing the analytical results with the test results.