Short Columns Research Articles

Influence of GFRP Confinement of Reinforced Concrete Columns Exposed to Sodium Chloride on Microstructure and Hydration Products

This paper explores the effect of sodium chloride (NaCl) on microstructure and hydration products of cylindrical column concrete and compares the results after covering it with Glass Fiber Reinforced Polymer (GFRP). 20 short RC columns were prepared with a single concrete mixture. The specimens have cured in different concentration of NaCl (0, 5%, 10%, 15%), some specimens cured directly in solution and other specimens exposed to wet and dry cycle. These specimens were tested, a first group after 28 days of curing, second group after 56 days, while the third group was repaired by GFRP after 28 day then returned to the cured environment and tested after56 day. In order to determine the main crystalline phase composition of concrete specimens and for phase identification of a crystalline material, scanning electron microscopy (SEM) morphology of microstructure concrete and X-ray diffraction (XRD) have been used. The results revealed denser microstructure with the concentration of NaCl crystalline, existence of binding chloride as free halite, chemical pound as a Friedel’s salt or Physical binding held to the surface of hydration products. In addition, the corrosive compounds were observed, and the hydration product phase decreased due to concentration of curing environment. Furthermore, the results from the samples that were covered with GFRP showed that the value of the hydration products didn't change when compared with the samples that were tested after 28 days, moreover, the voids were found in them when compared with the samples exposed to the environment damage without covering it with GFRP.

Experimental study on the fully encased composite short columns made with high-strength fibre-reinforced concrete

Experimental study on the fully encased composite short columns made with high-strength fibre-reinforced concrete

The influence of basalt fiber on the mechanical performance of concrete-filled steel tube short columns under axial compression

With rapid economic and social development, both concrete-filled steel tube (CFST) composite structures and basalt fiber (BF) have been widely applied in the field of civil engineering. To investigate the laws and characteristics of the influence of chopped BF on the mechanical properties of CFST columns and further promote the application of BF in CFST structures, the axial compressive bearing capacity test of 18 CFST short columns was carried out, and the influence of BF of different lengths on their structural mechanical properties was analyzed. The test results were compared with the theoretical calculation results and the finite element analysis results to verify the reasonableness of the test results. The results reveal that the axial compressive bearing capacity of the CFST short column after adding BF is significantly improved compared to the ordinary CFST short column, in which the bearing capacity and the ductility coefficient are increased by approximately 8.1% and 31.6%, respectively, on average. In addition, changing the length of BF has less effect on the bearing capacity of CFST short columns, the rate of increase in bearing capacity decreases with an increase in the steel ratio of CFST, and the coefficient of ductility increases with the increase in the steel ratio.

Artificial Neural Network Models for Determining the Load-Bearing Capacity of Eccentrically Compressed Short Concrete-Filled Steel Tubular Columns

Artificial neural networks (ANN) have a great promise in predicting the load-bearing capacity of building structures. The purpose of this work was to develop ANN models to determine the ultimate load of eccentrically compressed concrete-filled steel tubular (CFST) columns of circular cross-sections, which operated on the widest possible range of input parameters. Short columns were considered for which the amount of deflection does not affect the bending moment. A feedforward network was selected as the neural network type. The input parameters of the neural networks were the outer diameter of the columns, the thickness of the pipe wall, the yield strength of steel, the compressive strength of concrete and the relative eccentricity. Artificial neural networks were trained on synthetic data generated based on a theoretical model of the limit equilibrium of CFST columns. Two ANN models were created. When training the first model, the ultimate loads were determined at a given eccentricity of the axial force without taking into account additional random eccentricity. When training the second model, additional random eccentricity was taken into account. The total volume of the training dataset was 179,025 samples. Such a large training dataset size has never been used before. The training dataset covers a wide range of changes in the characteristics of the pipe metal and concrete of the core, pipe diameters and wall thicknesses, as well as eccentricities of the axial force. The trained models are characterized by high mean square error (MSE) scores. The correlation coefficients between the predicted and target values are very close to 1. The ANN models were tested on experimental data for 81 eccentrically compressed samples presented in five different works and 265 centrally compressed samples presented in twenty-six papers.

Experimental study on small eccentric compression performance of RC short columns strengthened by full lightweight ceramsite concrete

Full lightweight ceramsite concrete (FLCC) has a promising future in the field of reinforcement and retrofit, due to its excellent properties of light weight and high strength, especially when structures to be strengthened suffer from a combination of axial and bending forces. Small eccentric compression tests were conducted on RC short columns strengthened by FLCC, and compared with existing columns. Performance indices such as cracking, ultimate bearing capacity, ductility, lateral deflection, and steel bar strain were investigated for both strengthened and existing columns under the influence of load eccentricity. Moreover, the load eccentricity was extended using finite element simulation. The results indicated the following: Compared with the existing columns, cracks in the strengthened columns developed more slowly, and the failure process was significantly delayed. In addition, the old concrete and FLCC were well bonded, and the overall cooperative force was stable. The cracking load, ultimate bearing capacity, and ductility of the strengthened columns were increased by 89.1%–257.9%, 110.9%–195.8%, and 14.9%–17.8%, at different load eccentricities respectively, compared with that of the existing columns. Combining the test results and finite element simulation, an obvious linear decline relationship was obtained between the load eccentricity and the ultimate bearing capacity of the columns. Finally, a formula for calculating the compressive bearing capacity of the strengthened columns was derived, and the calculated theoretical values were in good agreement with the comparison of the tested and simulated values. This study was hoped to provide a theoretical reference in the practical application of RC columns strengthened by lightweight aggregate concrete (LWAC).

Behavior of Axially Loaded Concrete Columns Reinforced with Steel Tubes Infilled with Cementitious Grouting Material

The paper presents a novel method of reinforcing concrete columns using small-diameter steel tubes instead of traditional steel bars. The researchers conducted experimental investigations on twelve mid-scale circular concrete column specimens, which were divided into two groups consisting of six specimens each: short and long columns. Two of the specimens in each group were reinforced with steel bars, while the remaining four were reinforced with steel tubes filled with cementitious grouting material. The study proposed two concepts for cementitious grouted steel-tube reinforcement. The first concept utilized steel tubes with equivalent net areas to the steel bar areas used in the reference column, while the second concept used steel-tube reinforcement with the same diameter as the steel bars in the reference column. Nonlinear Finite Element (FE) analyses were conducted on experimental specimens using ABAQUS software. The results showed that using steel tubes with an area equivalent to that of steel bars instead of conventional columns increased the bearing capacity of reinforced concrete columns by 17%. Moreover, using steel tubes whose area matched 30% of the steel bar area achieved a bearing capacity of about 81% of the conventional concrete columns. The experimental and FE analysis findings indicate that this methodology can increase the bearing capacity of reinforced concrete columns when compared to traditional methods. The axial load-axial displacement curves, axial load-axial strain curves, and failure load of the FE model all demonstrated good convergence with the experimental data. Doi: 10.28991/CEJ-2024-010-02-017 Full Text: PDF

Ultrahigh-Performance Supercritical Fluid Chromatography-Multimodal Ionization-Tandem Mass Spectrometry as a Universal Tool for the Analysis of Small Molecules in Complex Plant Extracts.

Complex analysis of plant extracts usually requires a combination of several analytical approaches. Therefore, in this study, we developed a holistic two-injection approach for plant extract analysis, which is carried out within one instrument without the need for any manual intervention during the analysis. Ultrahigh-performance supercritical fluid chromatography (UHPSFC) was employed for the analysis of 17 volatile terpenes on a porous graphitic carbon column within 7.5 min, followed by analysis on short diol column where flavonoids, phenolic acids, and terpenoic acids were analyzed within 15.5 min. A multimodal ionization source combining electrospray and atmospheric pressure chemical ionization (ESCi) was selected for mass spectrometry detection as a simultaneous ionization of both lipophilic and polar compounds was required. The quantitative aspects of the final UHPSFC-ESI/ESCi-MS/MS two-injection approach were determined, and it was applied to the analysis of Eucalyptus sp. extracts prepared by supercritical fluid extraction. Current methods reported in the literature typically require a labor-intensive combination of liquid and gas chromatography for the complex analysis of plant extracts. We present for the first time a new UHPSFC approach requiring only a single instrument that provides an alternative approach to the analysis of complex plant extracts.

Behavior of Short and Slender RC Columns with BFRP Bars under Axial and Flexural Loads: Experimental and Analytical Investigation

Behavior of Short and Slender RC Columns with BFRP Bars under Axial and Flexural Loads: Experimental and Analytical Investigation

Axial Compression Behavior of Elliptical Concrete-Filled Steel Tube Composite Short Columns with Encased Steel Considering Spherical-Cap Gap

This study explored the axial compression behavior of elliptical concrete-filled steel tubes with encased steel considering spherical-cap gap (GSECFST) composite short columns. We designed 25 composite column specimens by varying the steel tube yield strength (fty), steel skeleton yield strength (fsy), concrete cubic compression strength (fcu), steel tube thickness (t), steel skeleton sectional area (As), the long and short half-axis ratio (a/b), the gap ratio (Xsg), and the slenderness ratio (λ). Based on the nonlinear constitutive models of the materials and the nonlinear contact effect among materials, the ABAQUS 6.20 finite element software established the refined finite element models of these composite short columns. Also, the rationality of the finite element modeling with a spherical-cap gap was verified by comparing it with the existing experimental results. The influence regularity of various parameters on the load (N)-displacement (Δ) curves, bearing capacity, initial stiffness, and ductility of the composite short columns was obtained. In addition, the failure modes, N-Δ process, sectional strain distribution, and gap feature index of the constraint partition model for GSECFST axial compression short columns were revealed. The results showed a weakened interaction between the elliptical steel tube and concrete. Also, the axial compression bearing capacity, initial stiffness, and core concrete ductility were reduced because of the spherical-cap gap. As fty, fsy, fc, and Asy increased, the axial bearing capacity, initial stiffness, and ductility of GSECFST composite short columns improved significantly but decreased with increasing of a/b, Xsg, and λ. When the gap ratio of the spherical crown was less than 4%, the outer steel tubes in the mid-span area of the GSECFST composite short columns buckled in the direction of the elliptical short axis under axial compression, and the concrete expanded outward and crushed. The failures were similar to those of the specimens without the spherical-cap gap. Based on the sectional constraint partition model, we propose the calculation formula of axial compression bearing capacity for GSECFST composite short columns. Consequently, this study is a reference for the elastic-plastic analysis of frame systems with similar composite columns.

Adeno-associated virus analysis by size exclusion chromatography within 3 minutes using short bio-inert columns made with 3 µm particles operated at high flowrates

Adeno-associated virus (AAV) analytical characterization is crucial to the well-defined and reproducible production of human gene therapies utilizing the AAV vector modality. The establishment of analytical methods based upon technology platforms currently widely used by bio-therapeutic manufacturers, namely HPLC, will assist efforts to produce high quality AAV reproducibly and decrease chemical manufacturing and control challenges in method portability and reliability. AAV analysis by size exclusion chromatography (SEC) is currently practiced with columns and mobile phase conditions traditional to SEC of proteins. Here, an improved method to measure multiple AVV critical quality attributes (CQA) rapidly by SEC is explored. The use of short columns made with small particles at high flow rates resulted in up to 80 % reduction in analysis time and 66 % in sample consumption while maintaining reliable quantitation of AAV aggregate or high molecular weight (HMW) content. These results were demonstrated across four different AAV serotypes. Furthermore, critical AAV sample handling learnings are shared.

Analytical Study on Capacity and Ductility for Composite Column Under Different Areas Loading

the main purpose of this research is to study analytically the CFT columns using the finite element method. ANSYS computer program is employed, in order to evaluate the behavior of the CFT short columns. 3-D finite element model is presented and calibrated successfully in order to predict the performance of the CFT columns under axial static loading. This paper presents the results of analytically study on the performance of axially loaded concrete-filled steel box columns subjected to different loading cases. The study investigates the effect of these loads on both axial capacity and ductility of CFT columns for different loading cases. The study investigates the effect of these loads on both axial capacity and ductility of CFT columns for different loading cases. This effect is studied for each type of loading individually. From the results it is obvious that in case CFT columns with load acting on total area of steel and concrete increasing both stiffness and strength can be attributed to the composite action between the steel tube and the concrete infill. Therefore, the composite action between the steel tube and the concrete not only The steel tube work as longitudinal reinforcing bars to resist the loads as ties or spirals to confine the concrete infill but also both strength and ductility of the concrete are enhanced.

Stress–strain characteristics of FRP–PVC confined spontaneous combustion gangue concrete columns

A total of 40 fiber reinforced polymer (FRP) and polyvinyl chloride (PVC) confined spontaneous combustion gangue coarse-aggregate concrete (SAC) specimens were subjected to axial compression tests and theoretical studies. The main analysis focused on the impact of the replacement rate of spontaneous combustion gangue (SCG), the type of CFRP confinement, and the number of CFRP layers on the axial compression performance of CFRP–PVC confined SAC (CFRP–PVC–SAC). The results show that CFRP–PVC confinement can effectively enhance the axial compressive capacity, axial deformation, and lateral deformation of the components. The increase in strength ranges from 1.68 to 3.48 times, while the increase in strain ranges from 5.21 to 11.98 times. The crack patterns and expansive behavior of the coal gangue concrete under confinement exhibit significant differences compared to ordinary concrete. In addition, based on the framework of the existing FRP-confined plain concrete model, a modified model is established to facilitate prediction of stress–strain relationships for short columns of CFRP–PVC–SAC, with the calculated results in good agreement with experimental values.

Effect of heating rate on crystallisation and properties of R2O–CaO–MgO–CuO–Al2O3–SiO2 glass-ceramics

R2O–CaO–MgO–CuO–Al2O3–SiO2 (RNa, K) glass-ceramics were fabricated using the melt-quenching method and the effect of heating rate on the microstructure and properties of the glass-ceramics was investigated. The results demonstrated that the main crystal phase of the samples was clinoenstatite, and the secondary crystal phases were forsterite and diopside. With an increase in heating rate, the diffraction peak intensity of clinoenstatite gradually increased, and the morphology of the particles changed from short columns to long needles. When the heating rate was 1 °C/min, the sample exhibited flexural strength and Vickers hardness of 7.38 GPa and 84.33 MPa, respectively. When the heating rate was 10 °C/min, the Cu+ content in the sample reached the maximum of 2.1 wt%, which is 1.4 times of Cu+ in the brown sample obtained by heat-treatment at 1 °C/min. The colour of the sample intensified as the heating rate was increased from 1 °C/min to 20 °C/min, and the sample heated at 10 °C/min was brownish-red. The heating rate has a significant effect on the colour of glass-ceramics with the same CuO content, providing a new approach for regulating the colour of glass-ceramics. Further, this study has significant prospects in enriching the colour of glass-ceramics for architectural decoration and reducing production costs.

Experimental and theoretical study on seismic behavior of a new UHPFRC sandwich wall and wall-wall joint

A new type of precast ultra-high performance concrete (UHPFRC) sandwich wall is proposed in this study. The proposed UHPFRC sandwich wall is composed of the UHPFRC layers, extruded polystyrene foam (XPS) board layer, and short UHPFRC columns connecting the UHPFRC layers. Compared with the traditional reinforced concrete wall, the UHPFRC sandwich wall possesses lower self-weight, less reinforcement, and higher strength. In addition, two types of wall-wall vertical joint connection methods, flexible cable connection and embedded steel plate welding connection, are proposed. The pseudo-static tests on five UHPFRC sandwich wall specimens were conducted to study the effects of UHPFRC layer thickness, reinforcement ratio, and width of edge solid area on the seismic behavior of the wall. Then, the seismic performance of different connection methods was studied by pseudo-static tests on two T-shaped UHPFRC sandwich wall-wall joint specimens. Test results demonstrate that the unreinforced UHPFRC sandwich wall, with 20–30 mm UHPFRC thickness and 150 mm edge solid area, showed excellent cracking resistance and seismic behavior. The cracking loads are more than 50% of the peak loads, and the bottom shear capacity to self-weight ratios are generally more than 35. The seismic behavior of the wall-wall joints connected by the flexible cable and embedded steel plate welding are both reliable. Finally, formulas for cracking and peak load of the UHPFRC sandwich wall are proposed and the fiber model is developed for analysis of the wall-wall joint, which is verified by the test results to be accurate and reasonable.

Axial compression behavior of STCLAC short columns

In this paper, the axial compression behavior of steel tube confined lightweight aggregate concrete (STCLAC) columns is studied by combining test research, finite element analysis (FEA), and theoretical derivation. The experimental parameters include the diameter-to-thickness (D/t) ratio, yield strength, and the contact materials. The results revealed that when the D/t ratio equals or exceeds 19.0, it affects the axial compression performance of STCLAC columns; conversely, the effect can be ignored. The yield strength also notably influences the ultimate capacity of STCLAC columns. Furthermore, the longitudinal forces of steel tubes in STCLAC columns, which use polytetrafluoroethylene (PTFE) and polyvinyl chloride (PVC), are later than those columns using oil, resulting in decreased specimen stiffness. Then, a three-dimensional FEA model for STCLAC columns was established and confirmed its accuracy. The influence of D/t ratios, LAC compressive strength, and friction coefficients on the bearing capacity of STCLAC columns is studied through parameter analysis. Finally, formulas are presented for calculating the transverse and longitudinal stresses in the steel tube of STCLAC columns at ultimate loads and predicting the ultimate load-bearing capacity.

Numerical Analysis of Sectional Shape Effect on Behavior of Short Concrete Columns

Numerical Analysis of Sectional Shape Effect on Behavior of Short Concrete Columns

A simple and rapid preparation of smooth muscle myosin 2 for the electron microscopic analysis.

There has been an increase in the demand for purified protein as a result of recent developments in the structural biology of myosin 2. Although promising, current practices in myosin purification are usually time-consuming and cumbersome. The reported increased actin to myosin ratio in smooth muscles adds to the complexity of the purification process. Present study outlines a streamlined approach to isolate smooth muscle myosin 2 molecules from actomyosin suspension of chicken gizzard tissues. The procedure entails treating actomyosin for a brief period with actin-binding peptide phalloidin, followed by co-sedimentation and short column size exclusion chromatography. Typical myosin molecule with heavy and light chains and approximately 95% purity was examined using gel electrophoresis. Negative staining electron microscopy and image processing showed intact 10S myosin 2 molecules, proving that phalloidin is effective at eliminating majority of actin in the form of F-actin without dramatic alteration in the structure of myosin. The entire purification discussed here can be completed in a few hours, and further analysis can be done the same day. Thus, by offering quick and fresh supplies of native myosin molecules suited for structural research, specially cryo-electron microscopy, this innovative approach can be adapted to get around the drawbacks of time-intensive myosin purifying processes.

CatBoost algorithms to predict the load-bearing capacity of centrally compressed short CFST columns of circular cross-section

The article investigates the use of regression models, GradientBoostingRegressor and RandomForestRegressor, to predict the load-bearing capacity of centrally compressed short concrete filled steel tubular columns. The work is based on experimental data covering a wide range of column geometric characteristics and material strength characteristics. An important part of the analysis was to deter-mine the influence of various parameters on the model predictions. The importance of features, assessment of the quality of models (MSE, MAE, MAPE) were considered , and visualization of actual and predicted values was carried out to compare the results. The results showed that both models success-fully cope with the task of predicting the load-bearing capacity of structures under given conditions. Analysis of the importance of features revealed the most significant parameters affecting the load-bearing capacity of columns. Visualization of forecasts and analysis of residuals confirmed the adequacy of the models. Additionally, a process of tuning model parameters using cross-validation was carried out to optimize their performance. The results of the study can be used in engineering applications such as the design of reinforced concrete structures to predict load-bearing capacity.

Axial compressive behavior of CFRP reinforced concrete filled steel tube short columns with a circumferential gap

Carbon fiber reinforced polymer (Carbon Reinforced Polymer Plastic) can effectively use its own tensile properties to provide stronger restraint for concrete, and can delay the buckling of steel pipes after yielding, and has been widely used in engineering repair and reinforcement. For the CFST composite structure with annular void defects, whether the reinforcement of CFRP can make up for a series of problems caused by void defects is still a fog. In order to explore the axial compression performance of CFRP (carbon fiber cloth) reinforced concrete-filled steel tubular short columns with circumferential void defects, 12 CFRP-reinforced CFRP short columns with circumferential void defects were proposed to be reinforced with a void ratio of 1.1-2.2%. The axial compression performance test was carried out to analyze the influence of parameters such as void ratio and the number of reinforcement layers on the axial compression performance, and a corresponding finite element model was established to assist in analyzing its working mechanism. The test results show that with the increase of the void ratio, the ultimate bearing capacity and the corresponding displacement of the components show a downward trend, and the deformation capacity is also greatly weakened. The ductility of the empty specimen is significantly improved, and the ductility of the specimen is also strengthened. With the increase of the number of reinforcement layers, the buckling deformation restraint effect of CFRP on the steel pipe becomes more and more significant, and it also provides better hoop restraint for the core concrete. To a certain extent, CFRP can reduce the effect of annular voiding defects.

Optimization of non-bearing splice connection in GFRP short columns by manual testing and finite element analysis

Connection designs are established to ensure the stability of joined cut sections, the joints so designed should be based on the optimal performance as per the requirements. The connection joints so established should not be based on just strength but reliability and durability as well. This study focuses on tackling one of the major issues faced when using Glass Fibre Reinforced Polymers (GFRPs) as construction materials, which is based on the abrupt failure of the material under critical or maximum loading. Connection designs are established in GFRP short column H-sections based on Bolted Splicing connections by Eurocode 3 for steel splicing connections. A total of seven Connection designs are established using bearing and non-bearing splicing connections. A total of five models for each connection is established for manual testing and Finite Element Analysis (FEA) is used to simulate and analyze these connection designs. Parameters such as ultimate load, displacement at ultimate load, stiffness, compressive strength, failure mode, load versus displacement behavior graph, and percentage compressive strength compared to the un-cut section are provided in this study. The strongest specimen in this study displaced 128% and 127.7% compressive strength compared to an un-cut GFRP H-section when tested using manual testing and FEA accordingly.