International Concrete Abstracts Portal

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.

The load bearing behaviour of fibre reinforced UHPC members in shear has not yet been investigated sufficiently. Therefore, an experimental campaign was conducted, investigating the behaviour of I-shaped beams made of Ultra-High Performance Concrete (UHPC) subjected to shear loading. The height of the beams was 350 mm, and the single span length 3.00 m. The main parameters were the fibre content (up to 2% by volume) and the degree of stirrup reinforcement (no stirrups or diameter 10 mm bars, spacing 125 to 300 mm). A total of 20 tests were performed, all of them ending up in typical shear failure: pronounced shear cracks formed along the web between support and load introduction at a level of 60-70% of the ultimate load. The cracking process was monitored by a digital image correlation (DIC) measurement system. A decisive effect of the fibres was observed: the addition of 1% to 2% fibres by volume led to a more distributed crack pattern as well as a significant increase of the ultimate load. The enhancement of the shear load capacity was not proportional to the fibre content, but corresponded quite well with the UHPFRC’s residual tensile strength in the post-cracking stage. The interaction with varying degrees of stirrup reinforcement was assessed as well.

This paper presents an experimental study on shear performance of concrete I-beams with fiber reinforced polymers (FRP) as internal reinforcement. A total of four beam tests were conducted, including one test without shear reinforcement and three tests with glass fiber reinforced polymers (GFRP) stirrups. In all specimens, GFRP bars were used as flexural reinforcement. The test variable was the ratio of shear reinforcement. In the test without stirrups, diagonal tension failure occurred. Failure due to rupture of the GFRP stirrups rupture was observed in the test with a shear reinforcement ratio of pw = 0.75% and web crushing failure occurred in the beam tests with pw = 1.26% and pw = 2.26% respectively. The experimentally obtained shear strengths were then compared to calculated design values using equations provided in the modified Eurocode 2, ACI 440.1R06, and CSAS806-2.

The simple-supported concrete beams reinforced with aramid FRP (AFRP) rods and carbon FRP (CFRP) sheets were tested to failure using a symmetric two-point concentrated static loading system. AFRP rods were used instead of steel reinforcing bars, and CFRP sheets were epoxy bonded to the tension face of the concrete beams to enhance their flexural strength. Moreover, a 5-cm wide strip of CFRP sheet in some places were wrapped around the web (hereafter, called “U-jacket”) after the CFRP sheets were bonded. The strain distributions on AFRP rods and CFRP sheets, and flexural behavior of the beams with AFRP rods and CFRP sheets were examined experimentally. The results showed that; 1) peeling of CFRP sheets occurred near the maximum flexural moment region, 2) ultimate load and deflection of the beam with U-jackets were higher, and 3) the U-jacket was a significant factor affecting the ductile behavior of beams with CFRP sheets.

The method of transversely reinforcing columns and beam-to-column connections with bellows square steel tubes was devised to develop a construction method necessary to realize reinforced concrete frame highrise buildings which are easy to design and execute in zones where high earthquake resisting performance is required. To secure a ductile seismic behavior for columns subjected to heavy load, strong shear reinforcement and transverse reinforcement are necessary to prevent brittle failure, such as shear failure, bond split failure along the longitudinal bars, and failure of the compressed extreme fiber of concrete, or to change it into ductile failure. It was manifested by concentric compression tests of 1/4 scale columns, combined compression, bending and shear tests of 1/3 scale columns, seismic load tests of 1/3 scale and 1/4 scale beam-column subassemblages, and bond tests of main bars embedded in 1/4 scale columns that no dangerous collapse of the building is likely to occur even if shear forces of some of the columns and/or beam-to-column connections in the same story reach the loading capacity, because the mechanical behavior of the columns and beam-to-column connections is very ductile even when the webs of their tube yield in shear. Field execution tests of this structure have been conducted.