Figure 17 - available via license: Creative Commons Attribution 4.0 International
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The variation in the acoustic speed and amplitude of specimens PJ-SMA-ECC and PJ-ECC. (a) The variation in acoustic speed; (b) The variation in amplitude. From Figure17a, compared to Specimen PJ-SMA-ECC, there was a sharp decline of acoustic speed for Specimen PJ-ECC at a target displacement of 2Δy. When the specimens failed (corresponding to measurement number 22), the acoustic speed of Specimens PJ-SMA-ECC and PJ-ECC decreased to 72.2% and 48.9% of the initial acoustic speed, respectively. It indicated that Specimen PJ-ECC suffered greater damage. It may be attributed to
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A novel precast beam–column joint using shape memory alloy fibers-reinforced engineered cementitious composites (SMA-ECC) was proposed in this study to achieve self-repairing of cracks and internal damage after an earthquake. Three large-scale beam–column joints were tested under displacement reversals, including one monolithically cast conventiona...
Citations
... According to the presence or absence of post-cast sections at the joints, the precast concrete BCJs are divided into wet and dry connection forms [2,5]. At present, the investigations on the seismic behavior of PRC structures are still mainly focused on experiments [6][7][8][9], while numerical simulations for their own characteristics are still relatively lacking [10]. The experimental investigations on precast frame joint specimens are focused on the influence of parameters such as the connection methods on the seismic performance of BCJs [5]. ...
Traditional cast-in-place beam–column joints have the defects of high complexity and high construction difficulty, which seriously affect the efficiency and safety of the building construction line, and precast beam–column joints (PBCJs) can greatly improve the construction efficiency and quality. At present, the investigations on the seismic behavior of precast reinforced concrete structures are still mainly focused on experiments, while the numerical simulations for their own characteristics are still relatively lacking. In the present study, the seismic behavior of novel precast beam–column joints with mechanical connections (PBCJs-MCs) is investigated numerically. Based on the available experimental data, fiber models for four PBCJs-MCs are developed. Then, the simulated and experimental seismic behaviors of the prefabricated BCJs are compared and discussed. Finally, the factors influencing the seismic behavior of the PBCJs-MCs are further investigated numerically. The numerical results indicate that the fiber models can consider the effect of the bond–slip relationship of concrete and reinforcement under reciprocating loads. The relative errors of the simulated seismic behavior indexes are about 15%. The bearing capacity and displacement ductility coefficients of the PBCJs-MCs decrease rapidly as the shear-to-span ratio (λ) increases. It is recommended that the optimum λ for PBCJs-MCs is 2.0–2.5. The effect of the axial load ratio on the seismic behavior of PBCJs-MCs can be negligible in the case of the PBCJs-MCs with a moderate value of λ.
... Li et al. gave the definition of the name "Engineered Cementitious Composites", abbreviated as ECCs, which have good ductility, multiple microcracks appearing on the ECC specimens under uniaxial tensile loading with the crack width controlled at 100 µm, and a tensile strain capacity of usually more than 2% [8][9][10]. ECCs have strong fatigue resistance, strong deformation ability, and good durability and crack resistance, which makes them widely used in engineering, such as for jointless pavements [11], structural seismic resistance [12], and bridge deck connection plates [13]. ...
The layer bonding performance of hydraulic engineered cementitious composites (HECCs) plays an important role in their application in hydraulic buildings. This performance encompasses the bonding between layers of HECCs, as well as between HECCs and normal mortar (NM) layers. The influence of various factors on the layer bonding performance of HECCs was investigated. These factors included different pouring intervals (0 min, 20 min, 40 min, 60 min, 2.5 h, 7 days, 14 days, and 28 days), pouring directions (horizontal and vertical), degree of saturation (100%, 70%, 50%, 30%, and 0%), and surface roughness (varying sand-pour roughness). It was found that longer pouring interval times led to a decrease in the layer bonding performance, and the strength of the layer bonding fell below 50% compared to concrete without layers, with the lowest recorded strength being only 1.12 MPa. The layer’s horizontal flexural strength surpassed the vertical flexural strength, but the horizontal compressive strength fell below the vertical compressive strength. Additionally, the bonding performance of the substrate at 0% saturation was 15–20% lower compared to other saturation levels. Notably, roughness significantly enhanced the performance of HECC layers, with improvements reaching a maximum of 180–200%. Furthermore, the layer performance of HECCs and NM experienced an improvement of 20.5–37.5%.
... The semi-dog bone specimens were made for a cyclic pull-out test which found that knotted SMA fibers were better able to bond. Chen et al. [45][46][47] added SMA fibers to ECC to make a composite material. With the increase in SMA content, the self-healing ability increased, but the self-healing ability did not change after 0.7%. ...
In order to research the flexural behavior of shape memory alloy (SMA)-reinforced seawater sea-sand concrete (SWSSC) beams and improve their self-healing ability, three SMA SWSSC beams and one anti-corrosive steel bar SWSSC beam were designed. The influence of the reinforcement ratio, strength grade of SWSSC and type of reinforcement on the flexural performance of the beam were considered. The failure process, maximum crack width, mid-span deflection, displacement ductility and stiffness degradation of beams were studied by cyclic loading tests. The test results showed that the number of cracks in SMA-reinforced beams were significantly smaller than that in anti-corrosive-reinforced beams, and the crack width and mid-span deflection recovery effect were better after unloading. However, the effect of increasing the SMA reinforcement ratio on crack recovery was not obvious. The increase in SMA reinforcement ratio and the strength grade of SWSSC can significantly improve the bearing capacity of the beam and the stiffness, but the stiffness degradation rate decreased. Moreover, the ductility of concrete beams with SMA bars was significantly increased.
Shape memory alloys (SMAs) have unique characteristics, such as the shape memory effect, which allows them to recover their initial shape after being deformed when stimulated, and pseudoelasticity, which enables them to accommodate large deformation without residual strains after being unloaded. SMAs may be used as short fibers in fiber-reinforced concrete (FRC) composites to pre-stress, heal fractures, and re-center themselves. As a result, SMA-FRC is a potential alternative to conventional construction materials in a wide range of applications. SMA-FRC composite application and modeling may present challenges, such as computational modeling complexities, practical constraints regarding fiber volume fraction, fiber-to-concrete adhesion strength, and the complex temperature-based activation of SMA fibers embedded in concrete. Despite these challenges and difficulties, significant work toward resolution is being made, making SMA-FRC an innovative technology with many potential research and development alternatives. This article presents an overview of experimental testing, computational methods, limitations, and future research potential for SMA-FRC composite materials. The study also looks at practical applications of SMA fibers in concrete composites including beam–column junctions, pre-stressing, and self-healing, as well as major developments and implications. The advantages and limits of several computational strategies for studying SMA-FRCs are discussed. The research suggests multiscale modeling as an effective approach for analyzing SMA-FRC, and a unique example of SMA-FRC multiscale modeling is briefly demonstrated. In conclusion, this research emphasizes the significant potential of SMA-FRC composites as novel construction materials with prospective practical applications, as well as the importance of multiscale modeling in SMA-FRC computational modeling.
By using high-ductile matrix material instead of just adding more reinforcement, Engineered Cementitious Composites (ECC) offers an alternate method of improving the ductility of structural components. The evolution of ECC over the years is outlined in this article through a critical review. To adequately assess the properties of ECC to perform identical functions of an earthquake resistance device, in particular, the Base Isolator (BI), ECC and BI were examined along with their most widely used types and fundamental characteristics. Engineers and researchers interested in employing ECC for seismic isolation in structures will find this paper valuable. This paper's abundance of knowledge could support the development of innovative applications and enhance the safety and longevity of building structures. In addition, the challenges for both ECC and BI were compiled as a guide for future research. The vast amount of valuable data presented in this paper can help with the future seismic isolation use of ECC.
