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Cognitive impairment is common in hemodialysis patients, possibly due to inadequate cerebral blood flow during hemodialysis. No effective non-pharmacological interventions are available. This study investigates the impact of hemodialysis-induced cerebral hypoxia on cognitive decline in hemodialysis patients and the potential of transcutaneous auricular vagus nerve stimulation (taVNS) as a non-pharmacological intervention. A randomized controlled trial with 36 participants showed that cognitive performance and cerebral oxygenation in the dorsolateral prefrontal cortex (DLPFC) significantly declined in the sham group. In contrast, taVNS improved cognitive function by increasing cerebral oxygenation, with significant correlations to reaction times and MoCA scores. The study suggests that Hemodialysis-induced cerebral hypoxia may contribute to persistent cognitive decline in MHD patients. However, taVNS could be an effective intervention to prevent cognitive impairment in hemodialysis patients by alleviating cerebral hypoxia.

Keypoints Fermentation medium with high antagonistic activity of HR10 strain was determined. Antagonistic crude protein of HR10 strain purified by Ion-Exchange Chromatography. Composition of the antagonist protein of HR10 strain was analyzed using LC-MS-MS.

As a result of an ongoing survey of microfungi associated with garden and ornamental plants in Qijing, Yunnan, China, several saprobic fungal taxa were isolated from Magnolia grandiflora. Both morphological and combined SSU, LSU, ITS, tef1, and rpb2 locus phylogenetic analyses (maximum-likelihood and Bayesian analyses) were carried out to identify the fungal taxa. Three new species are introduced in Pleosporales, viz., Lonicericola qujingensis (Parabambusicolaceae), Phragmocamarosporium magnoliae, and Periacma qujingensis (Lentitheciaceae). Botryosphaeria dothidea, Diplodia mutila, and Diplodia seriata (in Botryosphaeriaceae) are reported from Magnolia grandiflora for the first time in China. Angustimassarina populi (Amorosiaceae) is reported for the first time on M. grandiflora from China, and this is the first report of a member of this genus outside Europe. Shearia formosa is also reported for the first time on M. grandiflora from China.

There are complex interactions between mycorrhizal helper bacteria (MHBs) and ectomycorrhizal (ECM) fungi, with MHBs promoting mycorrhizal synthesis and ECM fungi regulating plant rhizobacterial colonization, diversity, and function. In this study, to investigate whether the ECM fungus Hymenochaete sp. Rl affects the survival and colonization of the MHB strain Bacillus pumilus HR10 in the rhizosphere, the biomass of B. pumilus HR10 was measured in the rhizosphere and mycorrhizosphere. In addition, extracts of Hymenochaete sp. Rl and Pinus thunbergii were evaluated for their effect on B. pumilus HR10 colonization (growth, sporulation, biofilm formation, extracellular polysaccharide and extracellular protein contents, flagellar motility, and expression of colonization-related genes). The results showed that inoculation of Hymenochaete sp. Rl significantly increased the biomass of B. pumilus HR10 in the rhizosphere; however, while extracts of Hymenochaete sp. Rl and P. thunbergii did not affect the biomass or spore formation of HR10, they did affect its biofilm formation, extracellular polysaccharide and extracellular protein production, and flagellar motility. Furthermore, the addition of symbiont extracts affected the expression of chemotaxis-related genes in HR10. When the extracts were added separately, the expression of srf genes in HR10 increased; when the extracts were added simultaneously, the expression of the flagellin gene fliG in HR10 increased, but there was no significant effect on the expression of srf genes, consistent with the results on biofilm production. Thus, Hymenochaete sp. Rl and P. thunbergii roots had a positive effect on colonization by B. pumilus HR10 at the rhizosphere level through their secretions.

In this work, a simple one-step hydrothermal method was employed to prepare the Ce-doped Fe2O3 ordered nanorod arrays (CFT). The Ce doping successfully narrowed the band gap of Fe2O3, which improved the visible light absorption performance. In addition, with the help of Ce doping, the recombination of electron/hole pairs was significantly inhibited. The external voltage will make the performance of the Ce-doped sample better. Therefore, the Ce-doped Fe2O3 has reached superior photoelectrochemical (PEC) performance with a high photocurrent density of 1.47 mA/cm2 at 1.6 V vs. RHE (Reversible Hydrogen Electrode), which is 7.3 times higher than that of pristine Fe2O3 nanorod arrays (FT). The Hydrogen (H2) production from PEC water splitting of Fe2O3 was highly improved by Ce doping to achieve an evolution rate of 21 μmol/cm2/h.

Parkinson's disease (PD) is the second neurodegenerative disease in the world. The pathological characteristics of PD are degeneration, loss and death of dopaminergic neurons in the substantia nigra of the midbrain. At present, most scholars believe that the main pathogenesis of PD is a-synuclein aggregation, oxidative stress, mitochondrial dysfunction and neuroinflammatory reaction. More and more studies have demonstrated that ferroptosis plays an important role in the occurrence and development of PD. Ferroptosis is a new type of cell death that is significantly different from traditional apoptosis, scorching and necrosis. Its main feature is iron-dependent lipid peroxidation. Some studies have found that the efficacy of acupuncture and moxibustion in the treatment of PD may be related to the regulation of ferroptosis. Therefore, this study mainly discusses the occurrence and development mechanism of ferroptosis and its role in PD, and the possible mechanism of acupuncture and moxibustion in the treatment of PD dopaminergic neurons, so as to provide theoretical basis for acupuncture and moxibustion in the treatment of PD. [ABSTRACT FROM AUTHOR]

Abstract Based on the available experimental data, fiber models for four prefabricated fiber-reinforced concrete beam–column joint specimens with grouted sleeve connections are first developed in OpenSees software. Then, the simulated seismic performance of the specimens is compared with the experimental results. Finally, the effects of axial load ratio and shear-to-span ratio on the seismic performance of the specimens are further investigated numerically. The results indicate that Concrete02 material model and Reinforcing Steel material model can accurately simulate the constitutive relationship of concrete and reinforcing steel, respectively; the beam–column joint elements can accurately simulate different damage behaviors of the joint zone. Fiber-reinforced concrete can significantly improve the seismic performance of the specimens. The relative errors of the simulated seismic performance indexes are about 15%. It is recommended that the optimum value of shear-to-span ratio for prefabricated FRC BCJs is 2.0–2.5. The effect of axial load ratio on the seismic behavior of PBCJs-CM is very small, and can be negligible in the case that the prefabricated FRC BCJs has a moderate value of shear-to-span ratio. The fiber model developed in this article can provide a numerical simulation basis for subsequent studies of prefabricated fiber-reinforced concrete beam–column joint specimens with grouted sleeve connections.

In the present study, capric acid and myrisic acid were first selected to prepare a capric acid-myrisic acid eutectic mixture using a compounding method. Then, the thermal properties, structural stability and weight loss of capric acid-myrisic acid eutectic mixtures were analyzed using differential scanning calorimetry, Fourier transform infrared and thermogravimetry. Finally, the activation energy and reaction order of the capric acid-myrisic acid eutectic mixture during solid-liquid transformation were calculated using the phase change kinetic methods of Kissinger and Ozawa. The results indicate that capric acid-myrisic acid eutectic mixtures have good thermal cycle stability and stable energy storage in practical applications. The activation energies of capric acid-myrisic acid eutectic mixtures were calculated using the phase change kinetic methods of Kissinger and Ozawa, with values of 345.6 KJ/mol and 333.3 KJ/mol, respectively, indicating that both phase change kinetic methods have good accuracy.

As a result of an ongoing survey of microfungi associated with garden and ornamental plants in Qijing, Yunnan, China, several saprobic fungal taxa were isolated from Magnolia grandiflora. Both morphological and combined SSU, LSU, ITS, tef1, and rpb2 locus phylogenetic analyses (maximum-likelihood and Bayesian analyses) were carried out to identify the fungal taxa. Three new species are introduced in Pleosporales, viz., Lonicericola qujingensis (Parabambusicolaceae), Phragmocamarosporium magnoliae, and Periacma qujingensis (Lentitheciaceae). Botryosphaeria dothidea, Diplodia mutila, and Diplodia seriata (in Botryosphaeriaceae) are reported from Magnolia grandiflora for the first time in China. Angustimassarina populi (Amorosiaceae) is reported for the first time on M. grandiflora from China, and this is the first report of a member of this genus outside Europe. Shearia formosa is also reported for the first time on M. grandiflora from China. [ABSTRACT FROM AUTHOR]

Widening existing bridges is an important way to meet the surge in traffic demand, which is often carried out in a way that does not interrupt traffic. To investigate the effect of traffic vibration on the compressive strength of high-strength concrete and the splitting strength of new-to-old concrete interfaces, the initial to final set time of high-strength concrete C60 was first investigated in this article. Then, the traffic disturbance parameters were determined. Later, the compressive strength of C60 concrete at different stages under traffic disturbance parameters was carried out. Finally, the splitting tensile strength of new-to-old concrete specimens at different stages with different loading modes was tested. The test results indicated that the compressive strength of the specimens vibrated for 3 h and cured for 3, 7, and 28 days was increased by 4.3%, 5.7%, and 11.9%, respectively; those of the specimens vibrated for 7 h and cured for 3, 7, and 28 days was decreased by 13.7%, 20.4%, and 19.9%, respectively; the effect traffic vibration on the compressive strength of the specimens vibrated for 5 h was not obvious. When loaded along the old and new concrete joint, the specimens cracked along the joint; the splitting tensile strengths of the specimen at different disturbed stages were significantly decreased. When loaded perpendicular to the joint, the specimens cured for 3 and 7 days still cracked along the joint, and the splitting tensile strengths of the specimen at different disturbed stages were significantly decreased; while the specimens cured for 28 days cracked in the direction perpendicular to the joint, the tensile strengths of the specimens at different disturbed stages were significantly decreased. This study can promote the widening and improvement of existing concrete highways and bridges, which can save resources and improve land use.

Concrete structures in high-altitude environments face many challenges. Establishing concrete crack control methods in high-altitude environments is crucial for enhancing the service capacity of concrete structures. In this study, a multi-field (hydration-temperature–humidity-constraint) coupling model was used to quantitatively assess the cracking risk of pier bodies at high altitude. On-site crack control tests were conducted on pier bodies using a micro-expansion anti-cracking agent to demonstrate the effectiveness of deformation shrinkage compensation in crack control at high altitudes. The results indicated that there was a risk of cracking in the pier body at high-altitude conditions, especially within 0.3 m from the pile cap and ±2.5 m from the center of the pier side surface. Compared with conventional piers, the micro-expansion anti-cracking agent approximately doubled the unit expansion deflection of piers at high temperatures while reducing the unit shrinkage deflection of piers by 11% to 12% at low temperatures. The concrete in conventional pier bodies was in a tension state after long-term hardening, while the concrete treated with the micro-expansive anti-cracking agent was in compression. Therefore, the deformation compensation effect of the micro-expansive anti-cracking agent was significant and reduced the risk of concrete cracking. In addition, early freezing had a significant impact on concrete strength, underscoring the importance of effective temperature control during the early stages of concrete placement in high-altitude environments.

In the traditional mass concrete temperature field calculation, the accuracy of the thermal parameters is extremely important. However, the actual thermal parameters of mass concrete may have some errors with the laboratory-measured values or specification values due to the site ambient temperature, concrete surface insulation measures, cooling water flow, etc. Therefore, it can be combined with the measured temperature of the field temperature sensors using the sparrow search algorithm (SSA) for the inverse analysis of thermal parameters. Firstly, to address the problem that SSA has low convergence accuracy and easily falls into local optimum, a mixed strategy was adopted to improve the algorithm, including Logistic Chaos mapping initialization of the population, the introduction of adaptive weighting factors, and the use of the Cauchy mutation strategy. Then, the performance test was carried out to compare the performance of the algorithm with three different intelligent algorithms and reflect the superiority of the SSA that was improved by mixed strategies (SSAIMSs). Finally, the proposed method was applied to the thermal parameter inversion of a mass concrete pile cap. The inversion results demonstrated that SSAIMSs can improve the accuracy and speed of thermal parameter inversion, and the calculated results of the thermal parameters and temperatures obtained using the SSAIMSs matched well with the measured results in the field, which can meet the accuracy requirements of the actual engineering.

Abstract The temperature stress in mass concrete structure is relatively high during construction, which usually leads to temperature cracks. To solve this problem, concrete blocks are usually placed by setting wide slots. Connecting the truncated steel bars at the position of the wide slots by welding or extruding sleeves has many disadvantages. To solve the problem of temperature-induced stress loss, a new type of slightly curved arc HRB400 (SCAHRB400) steel bars was proposed without cutting off the steel bars in this article. Tensile tests and numerical simulations were performed for five types of SCAHRB400 steel bars considering geometric and material nonlinearity. Based on the test results and numerical simulation results, the equivalent stress–strain relationships of SCAHRB400 steel bars were established, and the emergence of the plastic zone of SCAHRB400 steel bars in the tensile process were observed, the tensile properties of SCAHRB400 steel bars were analyzed and discussed. The test results indicate that SCAHRB400 steel bars are prone to local yielding near the crown of large arches and at the connection of horizontal and arc sections. The numerical simulation equivalent stress–strain curves have good regularity. The equivalent stress–strain curves of slightly curved arc HRB400 and HRB335 steel bars have the similar changing law. When the stress is small, the tensile stiffness and compressive axial stiffness of slightly curved arc HRB400 and HRB335 steel bars are similar; when the stress is large, the axial stiffness of SCAHRB400 steel bars is greater than that of slight curved arc HRB335 steel bars. Through test and numerical simulation studies, the theoretical basis can be established for the engineering application of new slightly curved arc steel bars in mass concrete.

In the present study, first, the environmental challenges and cracking characteristics during the construction of plateau concrete on the Sichuan–Tibet route were revealed. Then, using a multi-field coupled shrinkage model with hydration temperature humidity constraints, the early and long-term cracking risks in the core of plateau pier bodies were investigated. Later, the effects of tensile strength, pouring interval age and adiabatic temperature rise on the cracking risk were analyzed. Finally, various control measures for high-altitude concrete cracking were proposed. The results indicated that the complex environment of the plateau led to different forms of cracks in the pier body, especially vertical cracks in the straight sections. The long-term risk of core cracking in the plateau pier body is significantly greater than the risk of early cracking. This risk was strongly influenced by factors such as the concrete tensile strength, pouring interval age and adiabatic temperature rise, which should be given more attention. Deformation compensation can significantly enhance the peak and residual deformation capacities of plateau concrete, with peak values greater than 900 με and residual deformation greater than 200 με at day 60, as well as its resistance to cracking. Strategies such as adopting radiant cooling techniques, improving construction techniques and implementing effective management measures can all play a vital role in improving the cracking resistance of highland concrete.

Mechanically connected precast piles are a type of precast piles that utilise snap-type mechanical connectors to restrain the pile ends of two identical or different precast piles at the top and bottom so as to quickly realise the purpose of the connection. However, the gap problem in the connectors of mechanically connected piles can lead to uneven and uniform deformation of the piles under horizontal loading, resulting in additional displacements and rotation angles of the piles at the connection. Solving the problem of calculating the internal force response of discontinuous deformed piles is a prerequisite for promoting and applying mechanically connected precast piles. Firstly, the theoretical derivation of mechanically connected piles with fixed constraints at the pile bottom is carried out. Secondly, the pile response equations of mechanically connected piles are established, and the theoretical solutions of pile displacement and internal force response of mechanically connected piles under horizontal loading are derived. Thirdly, the pile-soil model of the test pile is established using ABAQUS software (ABAQUS 2016) in combination with the design data of the test pile. The numerical simulation displacements and angles of rotation are compared with the test results. Finally, the theoretical and numerical simulation displacements and internal forces of the ordinary pile and the mechanically connected pile are compared. The relative errors of the displacements and angles of rotation of the established pile-soil model are less than 10%, indicating that the established model has good accuracy. The relative errors of the theoretical and numerical simulation displacements and internal forces of the mechanically connected pile are less than 10%, proving the correctness of the theoretical calculation by the m-method. This study can provide effective theoretical support and methodological guidance for the displacement and internal force response of discontinuous piles.

In the present study, effect of ultrasonic impact treatment (UIT) on the microstructural characterization and mechanical properties of 316L stainless steel (hereinafter referred to as 316L) was investigated experimentally. The fatigue fracture mechanism of 316L before and after UIT was revealed. The experimental results indicated that the martensitic grain size induced at the impact edge was about 2.00 Å. The surface modified 316L formed a gradient nanostructure and induced a martensitic phase transformation. The hardness of the surface layer of the modified 316L was twice the hardness of its matrix. The tensile strengths of 316L before and after UIT were 576 MPa and 703 MPa, respectively. The stretching stripes of 316L were more disordered after UIT. The fatigue strengths of 316L before and after UIT were 267 MPa and 327 MPa, respectively. The fatigue cracking of 316L started from the austenite grain boundaries. The fatigue fracture surface was relatively rough. The fatigue crack sources of the modified 316L came from internal inclusions. The inclusions were oxides dominated by SiO2. As the stress range increased, the crack initiation site migrated to the interior and the fatigue fracture surface became flatter.

Abstract This study presents experimental and numerical methods to reveal concrete structures’ crack propagation and intersection laws under static and dynamic loads. Firstly, a numerical simulation method was established using the user-defined material subroutines to solve the free crack surface contact problem of concrete structures. Secondly, three-point bending tests of concrete beams containing double cracks of different approaching angles were carried out based on the digital image correlation (DIC) technology to study the intersection and propagation of cracks. Finally, the fracture processes of double-crack concrete beams and concrete gravity dams with and without a longitudinal crack were simulated and analyzed under static and dynamic loads. The numerical results were compared with the test results to verify the effectiveness and accuracy of the proposed method in simulating crack intersection and propagation in concrete structures. Results indicate that the crack intersection affects the fracture path of concrete structures, weakens their bearing capacity, and accelerates the failure of the structures. The proposed simulation method provides an effective technical approach for crack propagation prediction and safety evaluation of engineering structures.

Steel–UHPC composite bridge decking made of ultra-high performance concrete (UHPC) has been progressively employed to reinforce historic steel bridges. The coordinated force and deformation between the steel deck and UHPC are therefore greatly influenced by the shear stud connectors at the shear interface. Four fatigue push-out specimens of ultra-short studs with an aspect ratio of 1.84 in UHPC were examined to investigate the fatigue properties of ultra-short studs with an aspect ratio below 2.0 utilized in UHPC reinforcing aged steel bridges. The test results indicated that three failure modes—fracture surface at stud shank, fracture surface at steel flange, and fracture surface at stud cap—were noted for ultra-short studs in UHPC under various load ranges. The fatigue life decreased from 1287.3 × 104 to 24.4 × 104 as the shear stress range of the stud increased from 88.2 MPa to 158.8 MPa. The UHPC can ensure that the failure mode of the specimens was stud shank failure. Based on the test and literature results, a fatigue strength design S–N curve for short studs in UHPC was proposed, and calculation models for stiffness degradation and plastic slip accumulation of short studs in UHPC were established. The employment of ultra-short studs in the field of UHPC reinforcing aging steel bridges can be supported by the research findings.

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.

Abstract HTRB630 steel bar is a new type of high-strength steel bars. To study the seismic performance and promote the application of concrete columns reinforced with HTRB630 high-strength steel bars, the pseudo-static test of 10 concrete columns reinforced with HTRB630 high-strength steel bars and 3 concrete columns reinforced with HRB400 was carried out. Test specimens were divided into five categories according to concrete grade, reinforcement strength, and degree of confinement. The effect of concrete strength (C45 and C60), axial load ratio (0.1 and 0.25), equal strength substitution of longitudinal reinforcements (HTRB630 and HRB400), equal strength and volume substitution of stirrups (HTRB630 and HRB400), equal strength substitution of confined reinforcements (HTRB630 and HRB400) on the seismic performance are analyzed and discussed from the failure mode, hysteresis loops, skeleton curves, lateral strength, ductility, energy dissipation capacity, stiffness and strength degradation. The failure mode of each specimen was bending failure. Reducing of the axial lo ratio or increasing the strength of reinforcements, the seismic performance of the specimen could be improved. C60 concrete can improve the seismic performance of HTRB630 reinforced columns. The lateral strength of the concrete column specimen with HTRB630 reinforcements was slightly increased, and the ductility and energy dissipation capacity were reduced, the stiffness degradation was more gradual, the strength degradation coefficient was greater than 0.94, but still met the requirements of the code for seismic design of buildings (GB50011-2010).

To investigate the restoring force model (RFM) for a novel type of precast beam-to-column joints using a mechanical connection (PBCJ-MCs), the low-cycle cyclic loading test of three PBCJ-MCs was first performed in this article. Subsequently, combined with the shape of the test hysteresis curves and skeleton curves, three key characteristic points of cracking point, yield point, peak point and a key parameter at the strength degradation stage, stiffness were defined in the theoretical skeleton model. Using the regression approach, a four-line skeleton curve model for PBCJ-MCs was fitted by the dimensionless test skeleton curve data. Then, a mathematical model for strength degradation of PBCJ-MCs at the same loading displacement was established based on the damage index. By the analysis of the hysteresis path, the hysteresis rules applicable to PBCJ-MCs were formulated. The RFM for PBCJ-MCs considering the slipping and pinching effect was determined by fitting and properly defining the inflection point, pinching point, unloading stiffness and reload stiffness of the hysteresis curve in the unloading-reloading path. Finally, the theoretical skeleton curves, hysteresis curves and energy dissipation capacity were compared with test results. The results illustrated that the proposed RFM for PBCJ-MCs can better consider the pinching effect of PBCJ-MCs. The theoretical hysteresis curves of the proposed RFM considering the damage effect were more consistent with the test hysteresis curves, which can be used for further theoretical analysis and engineering applications.

The pore structure characteristics and thermal conductivity of foamed concrete (FC) reinforced with glass fibers (GF), polyvinyl alcohol fibers (PVAF) and polypropylene fibers (PPF) were investigated experimentally in this article. Firstly, GF, PVAF or PPF with different mass fractions (0%, 1%, 1.5% and 2%) were added to the Portland cement, fly ash and plant protein foaming agent to prepare the FC. Then, SEM tests, dry density tests, porosity tests, and thermal conductivity tests were carried out on FRFC. Later, the adhesion of GF, PVAF and FFF with different mass fractions to the cementitious base was investigated by SEM images of FRFC. The pore size distribution, shape factor and porosity of FRFC were analyzed using Photoshop software and Image Pro Plus (IPP) software. Finally, the effects of different mass fractions and lengths of three types of fibers on the thermal conductivity of FRFC were discussed. The results indicated that proper fiber mass fraction can play a role of refining small pores and separating large pores, improving the structural compactness, reducing the pore collapse phenomenon and optimizing the pore structure of FRFC. The three types of fibers can promote the optimization of cellular roundness and increase the proportion of pores with diameters below 400 μm. The FC with larger porosity had smaller dry density. As the fiber mass fraction increased, the thermal conductivity performed a phenomenon of first decrease and then increase. The three types of fibers with 1% mass fraction achieved relatively low thermal conductivity. Compared with the FC without fibers, the thermal conductivities of GF reinforced FC, PVAF reinforced FC and PPF reinforced FC with 1% mass fraction were decreased by 20.73%, 18.23% and 7.00%, respectively.

Heat-treated ribbed bar 630 (HTRB630) is a new type of the main 630 MPa reinforcing steel produced in China. To explore the possibility of using HTRB630 high-strength steel bars to replace HRB400 steel bars in reinforced concrete structures, experimental and numerical investigations on seismic performance of HTRB630 high-strength steel bars and HRB400 steel bars reinforced concrete columns are presented in this article. Firstly, the pseudo-static experiment of HTRB630 and HRB400 steel bars reinforced concrete columns is carried out. Secondly, an efficient modeling method is proposed to simulate and analyze the seismic performance of reinforced concrete columns on OpenSees platform based on the measured mechanical properties. ConcreteCM model and Reinforcing Steel model are applied to accurately simulate the uniaxial constitutive relationship of concrete and steel bars respectively. The constitutive parameters of confined concrete of specimens are calculated using the iterative algorithm method to effectively consider the degree of improvement of concrete performance in the core area by transverse steel reinforcements. Considering the bond-slip effect and shear deformation of reinforcements, a rotation spring element and a shear spring element are introduced on the fiber model. Finally, the applicability and accuracy of the numerical simulation results are verified by the experiment results on the hysteresis curves, normalized skeleton curves, bearing capacity, displacement ductility, energy dissipation capacity and degradation of stiffness. The experimental results indicate that the failure modes of the reinforced concrete column specimens are all bending failure. Hysteresis loops of the specimens reinforced HTRB630 and HRB400 steel bars are all bow-shaped. After the equal strength of HTRB630 steel bars, the shape of the hysteresis curve is not changed significantly. HTRB630 high-strength steel bars reinforced concrete columns can achieve good seismic performance under the premise of reasonable reinforcements. The numerical results indicate that the finite element model has a good simulation effect on most seismic performance indicators. For specimens with relatively low axial pressure and insignificant pinching, the error of the simulated hysteresis curve is larger; for specimens with relatively high axial pressure and obvious pinching, the error of the simulated hysteresis curve is smaller. The simulation errors of those seismic performance indicators are about 10%.

Within the context of the performance-based seismic design (PBSD), it is crucial to determine the drift ratio limits of PVA-FRCs under different performance levels. In this article, seven PVA fibers and high strength steel bars reinforced concrete columns were designed, and the quasi-static test was carried out to investigate their failure models and hysteretic loops. The calculated damage indexes using the Kunnath damage model were compared with the measured damage index ranges. The results indicated that the Kunnath damage model could accurately calculate the damage indexes of PVA-FRCs. According to the failure process of columns, the cracking point, yield point, peak point and ultimate point were used as the performance level control points of PVA-FRCs. Based on the idea of PBSD, the seismic performance levels of PVA-FRCs were divided into normal operation performance level, temporary operation performance level, reparable operation performance level, life safety performance level and collapse prevention performance level. Combined with the fiber concrete column test data in the references, the relative frequency statistics of the drift ratios of 38 PVA-FRCs at each feature point were carried out. The drift ratio limits under different performance levels and the corresponding damage indexes for PVA fiber reinforced concrete columns were established. Through the statistical analysis of relative frequency, the drift ratio limits of PVA-FRCs under different performance levels with more than 85% safety assurance rate were obtained, which were 1/300, 1/150, 1/80, 1/55 and 1/40, respectively. The performance level, damage state, lateral drift ratio limit and damage index were combined to form a relatively complete system to provide a reference for the anti-seismic repair of PVA fiber reinforced concrete structures.