Experimental study on the tensile behavior of ultra‐high performance concrete fiber continuous joints

Abstract

The application of ultra‐high performance concrete (UHPC) in the bridge deck effectively increases the strength, ductility, and durability of the deck system, while the problem of fiber discontinuity at the joint‐deck interface remains unsolved. This study proposes an innovative UHPC joint to create steel fiber continuity at the interface and experimentally investigates its tensile behavior. Test parameters include fiber content, fiber length and diameter, fiber shape, and fiber strength. Test results indicate that the joint tensile strength increases with fiber content, fiber length, and fiber strength. The specimen with hooked end fibers also develops higher joint tensile strength compared with the specimen with straight fibers. It is recommended to use fibers with a smaller diameter to increase the interfacial bonding area between the fibers and the matrix. High‐strength fibers are also recommended to achieve the best efficiency in a high‐strength matrix, like UHPC. The tensile performance of the joint with a fiber content of no less than 0.5%, and an embedment length of 15 mm (with a fiber length/diameter ratio of 50), and a diameter of 0.3 mm is similar to the performance of the specimen cast as one piece. Therefore, a properly designed UHPC fiber continuous joint is recommended in engineering practice to improve the integrity of the joint‐deck system.

Experimental and numerical studies on flexural behavior of fiber continuous joints of precast UHPC decks

“…Figure 2 shows the procedure of joint construction for UHPC decks with fiber continuity and lap-spliced rebar, according to the previous literature by authors. 24 The fabrication procedure of tested specimens is as follows:…”

“…Figure 2 shows the procedure of joint construction for UHPC decks with fiber continuity and lap‐spliced rebar, according to the previous literature by authors 24 . The fabrication procedure of tested specimens is as follows: (1) the steel fibers were directionally inserted into a foam board perpendicularly and placed in the middle of the span for UHPC decks.…”

“…Figure 22 shows the typical sectional force and stress profile. It should be noted that the tensile strength of the UHPC joint with directional steel fibers has been previously investigated based on the tensile coupon tests by the authors, 24 considering the influence of fiber content, length, diameter, etc. The measured ultimate tensile strength ( f t ) of the joint with a directional fiber content of 0.2%, 0.3%, 0.4%, and 0.5% was 3.3 MPa, 4.5 MPa, 6.0 MPa, and 7.9 MPa (where the cast‐in‐place coupon is 8.5 MPa), respectively.…”

“…Previously, the authors 24 proposed an innovative fiber continuous joint to connect precast UHPC decks using the directional insertion of steel fibers. The axial tensile tests of dog‐bone coupons were conducted, and similar tensile capacities were obtained for fiber continuous joints and cast‐in‐place specimens.…”

Assessment of fracture energy of strain‐hardening fiber‐reinforced cementitious composite using experiment and machine learning technique

“…Strain-hardening fiber-reinforced cementitious composite (SHFRCC), which exhibits tensile strain-hardening behavior accompanied to the formation of multiple microcracks under tension, is a promising material for many civil structures, such as for bridges, gas tanks, offshore structures, nuclear reactor containment shields, and high-rise building. [1][2][3][4] Two specific types of SHFRCC: high-performance fiber-reinforced cementitious composite (HPFRCC) and ultra-high-performance fiber-reinforced cementitious composite (UHPFRCC) show very high ductility and energy absorption capacity compared to conventional fiber-reinforced cementitious composite (FRCC) and ordinary concrete (NC). 5,6 The secret behind the outstanding performance of SHFRCC is the cooperation of steel fibers which provide crack bridging stresses and ensure a high amount of energy dissipated to pull out the fibers from the cracked sections of SHFRCC.…”