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This study performed an indoor experiment to examine the failure mechanism of a catenary CFST truss arch under a mid-span single-point load. A parametric analysis of a finite element model, validated with literature and experimental data, was conducted, taking into account material strength, rise-span ratio, arch axis coefficient, and steel ratio. A new buckling strength verification formula is proposed, which integrates stability coefficients for pre-buckling deformation and the rise-span ratio, as well as correction coefficients for varying bending moments and axial forces. The results indicate that in-plane failure modes in CFST truss arches typically initiate with the yielding of the web members before the chord tubes, contrasting with truss column failures. The buckling strength showed a direct correlation with material strength, rise-span ratio, and steel ratio, though with diminishing returns. The rise-span ratio and arch axial coefficient had minimal impact. The proposed verification formula, which includes pre-buckling deformation, arch axis coefficient, and the rise-span ratio, provides a precise and conservative method for evaluating the in-plane buckling strength of catenary CFST arches, enhancing engineering design practices. • Large-scale indoor tests were conducted on the buckling strength of catenary concrete-filled steel tube (CFST) truss arches under mid-span single-point loading. • Failure mechanism of catenary CFST truss arches under mid-span load conditions. • Crucial determinants influencing the in-plane buckling strength of catenary CFST truss arches are identified. • A verification equation was formulated for the in-plane buckling strength of catenary CFST truss arches subjected to combined compression and bending. [ABSTRACT FROM AUTHOR]

The massive piling of aluminum tailings waste has led to serious resource wastage and environmental pollution problems. Previous research has mainly focused on the exploitation of aluminum tailings residues (red mud), with little attention paid to the aluminum tailings slurry (ATS) discharged from the washing process. For surveying the feasibility of using ATS as a modifier of asphalt binder, a series of tests and analyses on ATS powder and ATS-modified asphalt have been performed in this study. The results demonstrate that ATS is alkaline and has a coarse surface and fine particle sizes, which make it miscible with asphalt. The ATS-based modification of asphalt is dominated by physical mixing and melting, accompanied by a slight chemical reaction. ATS modifies the microstructure of asphalt, leading to a reduction in the size and quantity of its "bee" structures, which may reduce the self-healing ability of the asphalt to some extent. With the increment in the dosage of ATS, the thermal stability of asphalt is enhanced. When the ATS dosage exceeds 9%, the storage stability of asphalt decreases significantly. Further, the complex modulus (G*), rutting factor (G*/sinδ), and recovery rate (R) increase, whereas the phase angle (δ) and nonrecoverable compliance (J nr) decreases, which indicates that ATS improves the resistance of the asphalt to deformation and elasticity. Furthermore, ATS does not pose any risk of pollution if it is used as the material for road construction on a large scale and provides considerable economic benefits. Therefore, ATS has a wide prospect of being used as a road asphalt modifier from the perspectives of its performance, environmentally-friendly nature, and economical cost. [Display omitted] • Aluminum tailings slurry (ATS) was used as a modifier instead of red mud. • Chemical reactions between ATS and asphalt have been observed. • ATS contributes to the elasticity and stiffness of the asphalt binder. • The application of ATS on roads has no observed risk of contamination. • The amount of ATS asphalt modifier should be limited to 9%. [ABSTRACT FROM AUTHOR]

• The first study of the bond behavior between concrete-filled steel tube and UHPC-encased. • Analyze the influence of each variable parameter on the bond behavior. • Establish the bond strength equation for the interface. This paper examines the bond behavior between steel and ultra-high-performance concrete (UHPC) in members made of UHPC-encased concrete-filled steel tubes (CFST). For the push-out test, a total of ten UHPC-encased CFST specimens, eight normal concrete-encased CFST specimens, and two CFST specimens were designed. The specimen parameters considered for variation include steel fiber content, thickness of the steel tube, anchorage length, thickness of outer concrete, and concrete type. Through experimental observation and measured data, the force failure process and crack development pattern of the specimens were observed, and load-slip curves were obtained for the loading end and the free end. A comprehensive analysis was conducted to examine the influence and mechanism of different parameters on the bonding performance of the specimens. Furthermore, an equation was derived to calculate the bonding strength at the interface between the steel tube and the outer concrete. The findings reveal that both UHPC-encased CFST and normal concrete-encased CFST specimens exhibited bond-anchorage failure, with the load-slip curve exhibiting a sudden change at the peak value, indicating a high degree of brittleness. The bond strength between steel and outer UHPC was found to be twice that between steel and core UHPC, and 1.4 times that between steel and outer normal concrete. Increasing the steel fiber content and the thickness of outer concrete within a certain range effectively improved the bonding performance of the specimens. The thickness of the steel tube did not have a significant effect on the bonding performance of UHPC specimens. Additionally, when the anchorage length reached a certain value, further increases did not significantly enhance the bond strength. Moreover, the influence range of the steel tube's anchorage length and outer UHPC on the bonding performance was smaller compared to outer normal concrete. [ABSTRACT FROM AUTHOR]

• Different epoxy resins to repair the post-fire concrete were studied. • The interface properties of epoxy resin adhesives and post-fire concrete was investigated. • The adhesive-failure constitutive model for epoxy resin adhesive and post-fire concrete was established. In order to investigate the influences of temperature that concrete has undergone on the resin/concrete interface bonding performance for different epoxy resin adhesives, 40 tensile specimens and 24 three-point bending specimens were heated to 200, 300, and 600 ℃, respectively. After natural cooling, resin was injected to form tensile specimens and sandwich specimens, which were subjected to pull-out tests and three-point bending tests, respectively. The interface bond-separation constitutive relationship was obtained to study the influence of fire temperature and different epoxy resin adhesives on the properties of the resin/concrete interface bonding. The results showed that the reinforcement of high-temperature concrete with different permeable epoxy resin adhesives caused the crack initiation load, interface strength, and fracture energy of the concrete/resin interface to increase slightly and then decrease sharply as the temperature of the concrete in the fire increased. When the fire temperature was 200 ℃, the peak value of the bonding performance of high-temperature concrete/resin interface was higher than that at room temperature. [ABSTRACT FROM AUTHOR]

• Based on the change of fiber strain, the dynamic instability criterion of CFST arch space curvature difference is proposed. • The accuracy of the critical curvature difference of instability failure is verified by the comparison with instability failure tests. • The proposed critical curvature difference can accurately assess the dynamic stability of CFST arch structure. With the rapid development of the construction technology of concrete-filled steel tube (CFST) arch bridges, the width-span and width-to-height ratios continue to increase, which cause stability problems, especially for the dynamic stability. The current Budiansky-Roth criterion (B-R criterion) and the energy criterion are hard to use and cannot be quantitatively described. Therefore, a CFST arch dynamic instability criterion by the difference in spatial curvature based on the changes in fiber strains is proposed in this paper. Firstly, the critical spatial curvature difference is derived based on the structural characteristics of CFST arches and is the threshold value of the dynamic stability discrimination. Then, the calculation format of the CFST arches' dynamic instability criterion is established by the central difference method, and the calculation procedure is programmed. Furtherly, the accuracy of the proposed critical curvature difference method is validated by the instability-induced failure experiments. In addition, the discrimination results of instability-induced failure experiments are also obtained by B-R criterion as well as the energy criterion. The discrimination result of the proposed critical curvature difference method is consistent with those of B-R criterion and energy criterion. Moreover, the method proposed quantifies the critical load of dynamic instability into the threshold index by the critical curvature difference and has easy-to-measure parameters as well as easy to operate, which are more suitable for the engineering applications compared with other methods. [ABSTRACT FROM AUTHOR]

Piezoelectric strain and its temperature stability of KNN-based ceramics sintered in reducing atmosphere are improved simultaneously via defects design of Mn doping. MnO and MnO 2 as raw materials have an impact on defects in KNN-based ceramics. When the dopant changes from MnO to MnO 2 , the defects (Mn Nb ′ ′ ′ , Mn K · , Mn Na ·) concentration decrease and defects (Mn Nb ′) increase. Defect dipoles (Mn K · - V K ′ , Mn Na · - V Na ′ , Mn Nb ′ ′ ′ - V o ··) in poled and aged 0.94 K 0.48 Na 0.52 Nb 0.96 Ta 0.04 O 3 -0.06BaZrO 3 + 0.08MnO ceramics form a strong restoring force for domain switching, which enhances the reversibility of the non-180° domains switching and then significantly improves piezoelectric strain. The stable defect dipoles (Mn K · - V K ′ , Mn Na · - V Na ′) form so that the reversibility of the non-180° domains switching can be preserved to high temperature. This defect dipoles design provides a general method to achieve large piezoelectric strain (582 pm/V@20 kV/cm) and excellent temperature stability (T 90 =210 °C). [ABSTRACT FROM AUTHOR]

Self-sensing cementitious composites containing nano carbon fillers have extensive application prospects in structural health monitoring (SHM) due to their excellent intrinsic piezoresistivity, good mechanical performances, high compatibility and durability. However, the piezoresistivity is prone to be affected by environmental factors, such as water content. Therefore, it is urgent to study the influence of water content on piezoresistivity to avoid unwanted effect. In the present study, piezoresistivity of self-sensing cementitious composites containing nano carbon fillers under cyclic compression with different water contents is investigated. Moreover, mechanisms are also explored comprehensively. The results indicate that the sensitivity, repeatability and stability of the piezoresistivity deteriorate with decreasing of water content. The maximum FCR and stress/strain sensitivity are decreased from 14.3 % to 4.5 % and 0.72 %·MPa−1/124–0.23 %·MPa−1/39, respectively, when water content decreases from 3.53 % to nearly 0 %. Variation of electrical conductivity pathways and networks caused by enclosed water film on surface of electrical conductive fillers take responsible for the changeable of piezoresistivity with different water content. The outcomes offered validity of self-sensing cementitious composites implementation in SHM withstand variation of water content. [Display omitted] • Piezoresistivity of nano fillers cementitious composites is investigated. • Mechanisms of water content effects on piezoresistivity are explored. • The piezoresistivity deteriorates with decreasing of water content. [ABSTRACT FROM AUTHOR]

The pure mode-II fracture behavior of an adhesively bonded glass fiber reinforced polymer (GFRP)/steel joint was experimentally investigated using a four-point end-notched flexure (4ENF) test. Cracking of the 4ENF specimen initiated and propagated in the adhesive-steel surface. The dominant failure mode observed in all specimens was adhesive-steel interface failure. The compliance of the 4ENF specimen was determined with the rigid joint model and finite element method. The extended global method was employed to obtain a simple analytical solution of the mode-II energy release rate, and the corresponding results were compared with that determined by the virtual crack closure technique (VCCT). The full R-curve for the pure mode-II fracture behavior of an adhesively bonded pultruded GFRP/steel joint was obtained. Then, the VCCT was used to determine the load–displacement curves of the 4ENF specimens for validating the accuracy and applicability of the pure mode-II fracture criteria of the adhesively bonded pultruded GFRP/steel joint. • Mode-II fracture behavior of adhesive GFRP/steel joint was experimentally investigated using 4ENF specimen. • Full R-curve for mode-II fracture behavior of adhesive GFRP/steel joint was obtained from 4ENF test. • Load–displacement response of 4ENF specimen was predicted based on the mode-II fracture criteria and virtual crack closure technique. [ABSTRACT FROM AUTHOR]