Flexural behavior of small-sized I-shaped UHPC beams hybrid reinforced with steel plate and BFRP

A new type of small-sized I-shaped ultra-high-performance concrete (UHPC) beam was proposed and tested in this paper. The bottom flange of the I-beam was hybrid reinforced with an embedded steel plate and basalt fiber reinforced polymer (BFRP) sheets. The web was hybrid shear reinforced with embedded steel threaded rods and vertically surface bonded BFRP sheets. The flexural behavior was tested using the four-point loading method, the test parameters include the cross-sectional area of the steel plate, the containing or not of the threaded rods in the web, and the number of the surface bonded BFRP layer. Based on the test data, the calculation and analysis of the cracking, yielding, and ultimate loads of the UHPC beam were conducted. The results showed that the proposed new hybrid beam has excellent mechanical properties. The proposed hybrid reinforcement method can greatly increase the bearing capacity of the UHPC beam from 10.2 kN to 76.6 kN and can increase the ultimate mid-span displacement from a very small 0.52 mm to an astonishing 45.02 mm. Thanks to the ultra-high durability of BFRP and UHPC itself, it has ultra-high durability that ordinary I-steel beams do not have, which has promising application prospects in extremely corrosive environments.