With the development of concrete materials, high strength concrete (HSC) and fiber reinforced concrete (FRC) are more and more used in reinforced concrete frame structures. This paper collected the test results of normal concrete (NC), HSC and reactive power concrete (RPC) beam joints. The performances of different concrete joints were compared and analyzed from two aspects of failure process and characteristics and shear deformation. The results showed that the ratio of through-crack load to shear capacity of NC joints is about 0.75-0.80, while that of RPC joints through-crack is close to shear capacity. The randomly distributed steel fibers of RPC like dispersed steel bars can effectively restrain the development of oblique cracks in the core area of joints. When the ultimate load is reached, the average shear angle of NC joints is much larger than that of RPC and steel fiber reinforced concrete joints. The small deformation of joints ensures the stiffness of RPC and steel fiber reinforced concrete joints. However, because there is no coarse aggregate in RPC, the occlusal interaction between the two sides of oblique cracks in the core area of RPC beam-column joints is obviously lower than that of NC joints.

Ultra-high performance concrete (UHPC) is a type of cementitious composite, and demonstrates very high compressive strength and good ductility. The favorable ductility and energy dissipation capacity of UHPC material make it possible to achieve excellent seismic performance in all kinds of structural members. The paper reviewed the recent progress on the seismic behavior of UHPC members, including flexural members (beams and plates), compressive members (columns and shear walls), joints (beam-column joints and plate-column joints), strengthening (strengthening for columns, shear walls and joints) and connections (bar lap splice and grout). A series of potential future researches on the seismic behavior of UHPC members were finally suggested for promotion of the application of UHPC in civil engineering.

Uniaxial compression tests were carried out on RPC with different steel fiber contents. The mechanical properties of RPC and the compressive-stress-strain curves of RPC with different steel fiber contents were studied. The results show that under the same mixture proportions, compressive strength increase with the increase of steel fiber content. When the steel fiber content is 3.5%, the compressive strength of RPC cubes is the largest; under the same mixture proportions, the compressive strength of RPC cube is approximately linear with the compression strength of prism, and the peak compressive strain and elastic modulus ratio of RPC cubes increase with the increase of steel fiber content. In this paper, the equation of the rising and descending sections of the stress-strain curves of different steel fiber volume admixtures is derived. According to the results of this test, the relationship between rising section, descending section coefficient and steel fiber content is obtained.)

To investigate the crack resistance properties of high-performance fiber-reinforced concrete (HPFRC) beam-column joints, quasi-static tests of twenty-four beam-column joint specimens were performed. Test specimen variables included joint types, size effect, axial compression ratio, stirrup ratio in joint, web reinforcement, and noncorner vertical reinforcement across the joint region. The influences of these factors on the crack properties of HPFRC joints were analyzed. Test results showed that the shear strength at the crack of HPFRC exterior joints with shear failure was closer to the ultimate bearing capacity. The average ratio of the cracking shear force to the peak shear force was 0.631 for the exterior joint with shear failure, and the ratio was 0.527 for the interior joint with the same size. The size effect was observed in HPFRC joint specimens, and the average shear stress at the joint crack decreased with the increase of the joint specimen size. The increase of the axial compression ratio can improve the crack resistance properties (cracking strength and crack width) of HPFRC joints. Web reinforcement and noncorner vertical reinforcement across the joint region have no evident influence on the cracking strength of joints, but they significantly affect the distribution and width of cracks in the joint region. The formulas for calculating the cracking strength and crack width of HPFRC joints were proposed based on the test results.

The developed pullout force formula and the understanding of damage mechanisms are expected to optimize the design of the ultra-high-performance fiber reinforced concrete (UHPFRC) with twisted fibers.