A review on seismic behavior of ultra-high performance concrete members

A novel type of traditional composite member-unbonded prestressed I-shaped steel encased in a UHPC (PSRUHPC) beam is proposed to reduce the brittleness of UHPC beams and improve their bearing capacity. A PSRUHPC beam, an unbonded prestressed UHPC (PRUHPC) beam, and an I-shape steel UHPC (SRUHPC) beam were manufactured, and their flexural static performances were assessed using a flexural comparison test. The test results reveal that the flexural process of the PSRUHPC beam is similar to that of ordinary reinforced concrete beams, and UHPC crushing in the compression zone is a sign of failure. Due to the bridge coupling effect of steel fiber, the crushed concrete still maintains good integrity without bursting, the UHPC in the tension zone remains functional after cracking, and the cracking inflection point of the load–deflection curve was not obvious. The PSRUHPC beam showed a significantly improved bearing capacity and flexural stiffness, its load–deflection curve exhibited significantly more energy consumption, and its bending ductility performance was improved, with better deformation properties. Compared with PRUHPC beams, PSRUHPC beams show a bearing capacity increase of 55.3%, a cracking load increase of 11.9%, and a displacement ductility coefficient increase of 76.2%. Compared with SRUHPC beams, PSRUHPC beams show a 15.4% increase in bearing capacity, a 50.2% increase in cracking load, and a 12.1% increase in displacement ductility coefficient. The application of prestress can significantly improve the stiffness of the beam prior to cracking. The cracking loads of prestressed ordinary concrete beams and steel-reinforced concrete beams account for 20–30% of their ultimate loads, which value was 40–50% for the tested beams. The change trend of strain in the section steel and UHPC is roughly the same at the same height, and the strains of the two deviated after most of the section steel yielded under tension, but they can generally work together. When the tested beams were cracked, multiple cracks appeared, which were fine and dense. The magnetic flux sensor cable force-monitoring system can better monitor the strand stress increment of unbonded prestressed steel UHPC beams, where the prestressed strand did not yield tension under the final state; the load–strand stress increment curve was basically the same as the load–deflection curve, and the stress increment of the unbonded steel strand positively correlated with the midspan deflection. Finite element simulation was used to verify the test results, and we determined the reinforcement ratios for non-prestressed and prestressed reinforcement, as well as the ratio of a steel-containing section, the effective prestress, the height of prestressed reinforcement, the position and strength of I-shaped steel, and whether or not the prestressed reinforcement was bonded. The effects of these parameters on the bearing capacity and displacement ductility coefficient of PSRUHPC beams were studied. The results can provide a reference for subsequent theoretical design calculations.

Section: Influence Of Resistance To Ductility (1) Reinforcement Ratio...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Study on the Flexural Behaviors of Unbonded Prestressed I-Shaped Steel Encased in Ultra-High-Performance Concrete Beams

Deng,

Duan

et al. 2023

“…Reinforced concrete (RC) shear wall (SW) is a common anti-lateral force component in high-rise buildings that has been widely used in high-frequent earthquake-prone areas [1][2][3][4][5]. The observation from recent earthquake reconnaissance indicated that the main reason why the RC SW was seriously damaged and even collapsed was its inadequate ductility and energy dissipation [6][7][8]. There are many problems that need to be solved urgently in the existing ordinary reinforced concrete SW located in high-intensity earthquake areas.…”

Section: Introductionmentioning

confidence: 99%

Shear Bearing Capacity of Steel-Fiber-Reinforced Concrete Shear Wall under Low-Cycle Repeated Loading Based on the Softened Strut-and-Tie Model

You,

Zhang,

Wang

et al. 2023

In this paper, the loading mechanism of steel-fiber-reinforced concrete (SFRC) shear wall (SW) under low-cycle repeated loading is analyzed, and the softened strut-and-tie model (SSTM) of SFRC SW composed of horizontal and vertical resistant members and diagonal strut is proposed, in which the contributions of distributed web reinforcement, concrete, and steel fiber (SF) to the shear bearing capacity (SBC) of SFRC SW is identified. Furthermore, a new algorithm to obtain the SBC of SFRC SW is established, and then it is validated by using the test results of steel-fiber-reinforced high-strength concrete (SFHSC) SW and SFRC SW under low-cycle repeated loading. The results show that the calculated values are in good agreement with the experimental values for the 11 SFRC SWs, and the average strength ratio between calculated and experimental values (Vjh,t/Vjh,c) is 0.958. Therefore, the proposed calculation method is scientific and accurate for analyzing and predicting the SBC of SFRC SW. In addition, the proposed calculation method can scientifically and accurately analyze and predict the SBC of SFRC SW.

“…Research on fiber-reinforced concrete (FRC) underscores the advantageous characteristics fibers confer, depending on the fiber type and loading conditions. This encompasses topics such as the flexural behavior of FRC beams using single and hybrid steel fibers [6][7][8][9][10], shear behavior [11][12][13], performance under cryogenic temperatures [14,15], seismic response [16], effects of age [17], and more. The addition of fibers, especially steel ones, enhances not only tensile strength but also other crucial parameters in concrete behavior, such as compressive, shear, and flexural strength, corrosion resistance, and freeze-thaw resilience.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Shear Behavior in High-Strength Concrete Beams Reinforced with Hooked-End Steel Fibers and High-Strength Steel Rebars

Alizadeh,

Moradi Shaghaghi,

Pourbaba

et al. 2023

Shear failure is an unfavorable phenomenon as it is a brittle type of failure; however, adding rebars and fibers to a concrete beam can minimize its detrimental effects. The objective of this study was to experimentally investigate the shear behavior of high-strength concrete (HC) beams reinforced with hooked-end (H) steel fibers and high-strength steel (HS) rebars under three-point bending tests. For this purpose, nine HC beams (300 × 250 × 1150 mm in dimension) were cast with 0%, 1%, and 2% H fibers by volume in three longitudinal rebar ratios (i.e., 1.5%, 2.0%, and 3.1%) and compared with beams without fibers. Furthermore, numerical analyses were performed to validate the experimental results and compare them with design codes. The results showed that, irrespective of the fiber content or longitudinal rebar ratio, the beams failed in shear. Increasing the rebar ratio and fiber content increased the shear capacity to as high as 100% (for the specimen with 3% rebar and 2% fiber compared to its counterpart with 1% rebar and 2% fiber). In addition, the research-based equations proposed in the literature either overestimated or underestimated the shear capacity of fibrous HC beams significantly. The level of overestimation or underestimation was closely related to the sensitivity of the proposed model to the shear span ratio and the fiber content. Rebars proved to be more beneficial in contributing to the shear capacity, but the rate of this positive contribution decreased as the fiber ratio increased. Finally, the inverse analysis approach adopted herein proved to be an efficient tool in estimating the shear response of fiber-reinforced beams failing in shear (margin of error: less than 10%).