Capacity Of Columns Research Articles

Experimental and simulation study on seismic performance of steel‐PVA hybrid fiber cementitious composites‐encased CFST

AbstractSix hybrid steel and PVA fiber cementitious composite (S&PFCC)‐encased concrete‐filled steel tube (CFST) columns were designed and fabricated, and the effects of axial compression ratio, core concrete strength grade and steel tube thickness on the seismic performance of composite columns were studied. The test results show that the increase of core concrete strength can obviously improve the bearing capacity and energy dissipation capacity of composite column and can restrain the strain growth rate of steel tube after yielding. Low axial compression ratio and thicker steel tube thickness can improve the overall seismic performance of composite columns. Three calculation methods are modified, and the modified An method can predict the lateral bearing capacity of composite column well. Finally, based on the OpenSees finite element software, the seismic performance of the CFST column wrapped in S&PFCC is simulated to verify the test, and the numerical study shows that the seismic performance of the composite column can be optimized by increasing the steel fiber content, while PVA fiber has a weak effect in the elastic stage, and can effectively improve the ductility of the composite column in the plastic stage.

Axial compressive behavior of spiral stirrup-reinforced concrete-filled cold-formed steel built-up box stub columns

This paper aims to explore the enhancement effect of spiral stirrup on concrete-filled cold-formed steel built-up box (CF-CFB) columns. Herein, four specimens were designed and fabricated to explore the impact of the spiral stirrup and riveted form on the axial compression performance of CF-CFB columns. Then, the finite element model of spiral stirrup-reinforced concrete-filled cold-formed steel built-up box (RCF-CFB) stub columns was established, and a systemic parametric investigation was conducted to explore the impact of geometric and material parameters on the compression performance of RCF-CFB stub columns. Afterwards, the analysis included an assessment of contact stress and stress distribution was conducted to uncover the confining effect. The analysis results revealed that the failure mode of the RCF-CFB column was tube buckling and concrete crush, accompanied by the spliced tube separating at the buckling area. The built-in reinforcement could significantly improve the performance of the built-up column, while riveted forms of spliced steel tubes had little effect. Furthermore, the axial bearing capacity of the RCF-CFB column would increase with the enhancement in steel yield strength, concrete strength, tube thickness, and longitudinal bar diameter. Finally, a calculating method to predict the axial bearing capacity of the RCF-CFB column was proposed, and the applicability of the method was demonstrated by comparison with experimental and FE data.

Compressive and Bonding Performance of GFRP-Reinforced Concrete Columns

The use of glass-fiber-reinforced polymer (GFRP) bars as an alternative to steel bars for reinforcing concrete (RC) structures has gained increasing attention in recent years. GFRP bars offer several advantages over steel bars, such as corrosion resistance, lightweight, high tensile strength, and non-magnetic properties. However, there are also some challenges and uncertainties associated with the behavior and performance of GFRP-reinforced concrete (GFRP-RC) structures, especially under compression and bonding behavior. Therefore, there is a need for comprehensive experimental investigations to validate the effectiveness of GFRP bars in concrete columns. This paper presents a study that aims to address these issues by conducting experimental tests on GFRP-RC columns. The experimental tests examine the mechanical properties of GFRP bars and their bond behavior with concrete, as well as the axial compressive behavior of GFRP-RC columns with different reinforcement configurations, tie spacing, and bar sizes. The findings reveal that GFRP bars demonstrate a comparable, if not superior, compressive capacity to traditional steel bars, significantly contributing to the load-bearing capacity of concrete columns. The study concludes with a set of recommendations for further exploration, underscoring the potential of GFRP bars in revolutionizing the construction industry.

Satin bowerbird optimizer-neural network for approximating the capacity of CFST columns under compression

Concrete-filled steel tube columns (CFSTCs) are important elements in the construction sector and predictive analysis of their behavior is essential. Recent works have revealed the potential of metaheuristic-assisted approximators for this purpose. The main idea of this paper, therefore, is to introduce a novel integrative model for appraising the axial compression capacity (Pu) of CFSTCs. The proposed model represents an artificial neural network (ANN) supervised by satin bowerbird optimizer (SBO). In other words, this metaheuristic algorithm trains the ANN optimally to find the best contribution of input parameters to the Pu. In this sense, column length and the compressive strength of concrete, as well as the characteristics of the steel tube (i.e., diameter, thickness, yield stress, and ultimate stress), are considered input data. The prediction results are compared to five ANNs supervised by backtracking search algorithm (BSA), earthworm optimization algorithm (EWA), social spider algorithm (SOSA), salp swarm algorithm (SSA), and wind-driven optimization. Evaluating various accuracy indicators showed that the proposed model surpassed all of them in both learning and reproducing the Pu pattern. The obtained values of mean absolute percentage error of the SBO-ANN was 2.3082% versus 4.3821%, 17.4724%, 15.7898%, 4.2317%, and 3.6884% for the BSA-ANN, EWA-ANN, SOSA-ANN, SSA-ANN and WDA-ANN, respectively. The higher accuracy of the SBO-ANN against several hybrid models from earlier literature was also deduced. Moreover, the outcomes of principal component analysis on the dataset showed that the yield stress, diameter, and ultimate stress of the steel tube are the three most important factors in Pu prediction. A predictive formula is finally derived from the optimized SBO-ANN by extracting and organizing the weights and biases of the ANN. Owing to the accurate estimation shown by this model, the derived formula can reliably predict the Pu of concrete-filled steel tube columns.

The strain demand of reinforced concrete bridge columns under seismic loading

The steel in reinforced concrete (RC) members that form plastic hinges must possess sufficient strain capacity to dissipate seismic deformation demands. Unfortunately, there is limited information on the seismic strain demands of bridge column plastic hinges. Instead, designers rely on a perception of cyclic strain capacity that is an approximate rule of thumb. A standard methodology needs to be established for quantifying the strain demand on these structural members as a function of the expected seismic hazard. To develop this methodology, 1944 columns were analyzed with nonlinear time-history analyses (NLTHAs) using ground motions from a range of earthquakes. This study evaluates the strain demand on RC bridge columns by defining the relationship between the strain demand and earthquake intensity. The results of the model are defined in terms of the peak tensile strain of the reinforcing bar, [Formula: see text]. The earthquake intensity with the highest correlation to the [Formula: see text] was determined to be the elastic spectral displacement at the optimal period ([Formula: see text]), which is defined as 75% of the effective period. The relationship between [Formula: see text] and [Formula: see text] can be used to predict the strain demand for an RC bridge column at a given geographic location. Results are presented as a probability density function (PDF), representing strain demand, compared to a PDF of the column capacity. The intersection of the capacity curve and demand curve represents the maximum acceptable strain given as a function of [Formula: see text]. This methodology can help understand the demand placed on a structural system given a region’s seismicity.

Experimental study and numerical simulation of a structural concrete column for building heating integration and energy storage

A steel pipe assemblage is integrated into a structurally reinforced precast concrete column to demonstrate thermal energy storage (TES) and space heating capabilities. This thermal energy column is heated via hot water at varying flow conditions. The system is used as a thermal storage medium, as a means of reducing the demands on the building heat pump, and for regulating the thermal comfort of the building interior environment. The thermal performance of the energy column is examined experimentally and numerically in both charging and discharging phases. Two examples are used to demonstrate the improvements in the operation of building thermal equipment and in the building thermal environment offered by either passive or active discharging of the energy column. Following the conclusion of thermal evaluation, the structural performance of the column under axial compression was evaluated by loading the system to failure. The experiment was paused for visual observation at both the service level and nominal capacity milestones. The longitudinally embedded steel pipes developed comparable strains to the column longitudinal steel reinforcing bars. The structural capacity of the energy column can be accurately predicted using standard concrete design approaches that account for the mechanical influence of the embedded steel pipe assemblage. It is demonstrated that the developed concrete energy column provides a viable option for improving the building thermal energy efficiency and maintaining structural performance.

Load-Carrying Capacity of Thin-Walled Composite Columns with Rectangular Cross-Section under Axial Compression.

The aim of the current study was to determine the load capacity of composite columns subjected to axial compressive load. The subjects of the study were two types of columns with a rectangular cross-section, with different edge lengths. The tested columns had a closed cross-section. Four different fiber arrangements were analyzed for both cross-sections studied. The research was realized using interdisciplinary methods to determine the mechanism of damage to the composite material, with particular emphasis on damage initiation and propagation. Experimental tests were realized on a testing machine, the analysis was carried out with an acoustic emission system, and image analysis using visual assessment system of deflections of the walls of the structure. In addition, a number of numerical analyses were realized based on advanced modeling techniques for fiber-reinforced composites. A comparative analysis of both quantitative and qualitative results is presented for both analyses. The innovation of the presented research lies in the development of a custom method for modeling structures made of composite material with special emphasis on the failure phase. This will allow to accurately reflect the modeling of thin-walled structures with closed cross-section subjected to loading in a complex stress state.

Compressive performance of eccentrically double-cell concrete-filled circular steel tubular columns

This paper presents a series of tests conducted on axial compression of concrete-filled steel tubes with double inner circular steel tubes (DIC-CFST) stub columns. The DIC-CFST stub columns are composed of four elements: an outer circular steel tube, two inner hollow circular steel tubes arranged symmetrically along the diameter of the outer tube, and concrete filling the space between the three steel tubes. A total of 27 specimens with varying eccentricity ratio (e), hollow ratio (ψ), and concrete strength (C) were subjected to the tests. The results indicate that under axial compression, noticeable local buckling failures occur in both the inner and outer steel tubes. Concrete failure manifests as vertical through cracks and circumferential crushing zones. The load-deformation curve of the specimens remains essentially the same as that of a full-section concrete-filled steel tube. A general positive correlation exists between the ultimate bearing capacity and the strength of concrete, and the range of eccentricity ratio and hollow ratio significantly influences the relationship between these two parameters and the ultimate bearing capacity of the specimens. As the concrete strength increases, the initial stiffness exhibits a noticeable increase. Conversely, the initial stiffness experiences a significant reduction with an increase in the hollow ratio. The ductility decreases with increasing concrete strength and eccentricity ratio. Furthermore, in comparison to the AISC 360–10 Specification, Eurocode 4, and Han's method, the calculation formula proposed in this paper for determining the ultimate bearing capacity of DIC-CFST stub columns has exhibited superior accuracy.

Finite element analysis and bearing capacity calculation of cross-shaped CFST columns under compressive load

The study investigated the load capacity of cross-shaped concrete-filled steel tubular (CFST) columns under axial and eccentric compression using finite element software ABAQUS. It analyzed six specimens with measured data and an additional 26 specimens with varied parameters, including eccentricity, slenderness ratio, section steel ratio and material properties such as concrete strength and steel yield strength.The objective was to understand how these parameters affect the load capacity of cross-shaped CFST columns. The research findings suggest that as eccentricity and slenderness ratio increase, the ultimate capacity decreases. Conversely, it increases with higher steel content, concrete strength and steel yield strength. Moreover, the bearing capacity deteriorates more rapidly with reduced eccentricity and concrete strength, while it demonstrates a nearly linear increase with greater steel content. Additionally, the study found that enhancing the resilience of the channel steel significantly boosts the load-bearing capacity of the column. Based on these findings, practical design equations were developed to determine the maximum bearing capacity of cross-shaped CFST columns under axial and eccentric compression. These equations are grounded in confined concrete theory and demonstrate robust applicability for practical design purposes.

Axial-compression performance and numerical-simulation analysis of steel tube coal gangue concrete column

Coal gangue is a solid waste produced in the process of coal mining, excessive accumulation will occupy land and pollute the environment. It is one of the most effective means to realize comprehensive utilization of coal gangue by replacing some aggregates in concrete and applying it to engineering structures. In this paper, based on C30 concrete, by changing the replacement rate of coal gangue, slenderness ratio, and steel pipe wall thickness, 17 Coal gangue concrete-filled steel tubular (CGC-FST) columns were designed and made, and the axial compression tests were carried out. The results show that the failure mode of the CGC-FST column is similar to that of CFST, and the annular band shear buckling occurs on the wall of the steel pipe, and the higher the slenderness ratio, the more the number of buckling in the middle. With the increase of coal gangue substitution rate, the ultimate bearing capacity of the CGC-FST column decreases gradually, and the ductility of the specimen decreases slightly. The increase in slenderness ratio reduces the ultimate bearing capacity of the member, the failure form changes from material failure to stable failure, and the material properties are not fully utilized. The most obvious way to improve the bearing capacity and ductility of gangue steel tube members is to increase the steel content. Through the finite element simulation analysis of more working conditions of the CGC-FST column, the calculation formula of the bearing capacity of the CGC-FST column is fitted, which can effectively predict the bearing capacity of the CGC-FST column in a certain range.

Behavior of Concrete-Filled Steel Tube Columns with Multiple Chambers and Round-Ended Cross-Sections under Axial Loading

Concrete-filled round-ended steel tubes (CFRTs) are a unique type of composite stub columns, which have the advantage of aesthetics and a well-distributed major–minor axis. Thus, the structure has been widely employed as piers and columns in bridges. To improve the mechanical performance of CFRTs with a large length–width ratio and to enhance the restraint effect of steel tubes on concrete, this study investigates the compressive property of multi-chamber, concrete-filled, round-ended steel tubular (M-CFRT) stub columns using a combination of experimental and numerical analyses. A detailed compression test on eight specimens is conducted to examine the compressive property of M-CFRT stub columns. The study focuses on understanding the influence of some key parameters on ultimate bearing capacity, failure stage, damage modes, and ductility. Additionally, the accuracy of the finite element modeling method in simulating the ultimate bearing capacity of the structure is verified. Finally, the calculating formula for the ultimate bearing capacity of M-CFRT stub columns is proposed on the basis of the experimental and numerical findings. Results of the formula calculation are consistent with the experimental data. These research findings serve as a valuable reference for designing similar structures in engineering practice.

Axial compressive behaviors of multi-cavity concrete-filled double-skin tubular stub columns

The axial compressive behaviors of multi-cavity concrete-filled double-skin steel tubular (MCFDST) stub columns are investigated using experimental and numerical methods in this study. The MCFDST columns comprise two concentric steel tubes (circular hollow section (CHS) inner and square hollow section (SHS) outer), sandwiched concrete filled between them, and four strips connecting outer and inner tubes. Fourteen MCFDST stub columns and two concrete-filled double-skin steel tubular (CFDST) (CHS inner and SHS outer) stub columns are fabricated and tested. Experimental results are used to validate the accuracy of finite element models of MCFDST and CFDST stub columns, and based on which, extensive parameter analyses are conducted. The analysis results show that the strips delay the local buckling and change the buckling mode of outer steel tube, as well as improve the bearing capacity and ductility of stub columns. Observed failure modes are controlled by the local buckling of the outer tube associated with the crushing of filled concrete. In addition, the axial compressive performance of MCFDST stub columns can be improved by reducing the width-to-thickness ratio of outer tube, increasing the steel yield strength of outer tube and concrete strength, and adding strips. The hollow ratio has a negligible effect on the axial compressive behaviors when it ranges from 0.26 to 0.56. Furthermore, the predicted results by European, Japanese, British, and Chinese codes are compared with the experimental and FE results, suggesting that the formula in the European code has the best accuracy when predicting the load-bearing capacity of MCFDST stub columns.

Experimental study on axial compression behavior of square pultruded GFRP tubular stub column

To investigate the influence of aspect ratio and width-to-thickness ratio on the axial compression behavior of square pultruded glass fiber-reinforced polymer (GFRP) tubular stub columns, axial compression tests were conducted on 12 GFRP tubular columns. The mechanical properties of the GFRP tubular columns, including load-bearing capacity, initial stiffness, compressive toughness, and ductility coefficient, were analyzed. The test results reveal that all GFRP tubular columns exhibit crushing failure, with specific failure modes, including mid-section fracture and longitudinal tearing along the corners of the columns. The load-bearing capacity is negatively correlated with the aspect ratio and width-to-thickness ratio. The initial stiffness negatively correlates with the aspect ratio, and the compressive toughness negatively correlates with the width-to-thickness ratio. The Hashin damage criteria for the C3D8R solid element was developed by utilizing the explicit finite element subroutine ABAQUS-VUMAT to analyze the axial compression behavior of GFRP tubular columns. Through parameter analysis, the relationship between the load-bearing capacity and fiber orientation was obtained, and an empirical equation for predicting the load-bearing capacity of the GFRP tubular column was proposed.

Seismic behavior of Q620 high-strength steel welded Box-section columns: Experimental tests, analysis, and model

This study experimentally and numerically investigates the seismic behavior of high-strength steel (HSS) welded Box-section columns. The HSS structures have made rapid development in various types of building structures. However, the high yield-to-tensile ratio of HSS limits its application in seismic design. To address this gap, a new type of HSS called Q620 has been developed by Hebei Iron and Steel Co., Ltd. (HISCO). A total of three specimens were designed by this seismic-resistant Q620 HSS material and tested under cyclic load. The main failure modes included local buckling of the bottom section of the column, and obvious flexural deformation led to fracture of the specimen. Additionally, the nonlinear kinematic hardening model was utilized to accurately establish the finite element (FE) model for the HSS welded Box-section columns. Based on the validated FE model, an extensive parametric analysis (e.g., width-to-thickness ratio, axial compression ratio, and slenderness ratio) was conducted to evaluate the seismic behavior of the Q620 HSS welded Box-section columns. The results indicated that the Box-section columns exhibited favorable hysteretic behavior and notable plastic deformation capacity. A higher width-to-thickness ratio resulted in a faster decline in stiffness and a more pronounced advancement of damage. The ductility and energy dissipation capacity of Box-section columns were generally decreased with increasing axial compression ratio or slenderness ratio. A newly simplified hysteretic model was proposed, which was in good agreement with the experimental results.

Stability bearing capacity of equal-leg angle steel columns with end connection joints

This study investigated the stability bearing capacity of Q355 equal-leg angle steel columns with end connection joints for transmission towers and proposed a new design method for stable bearing capacity. A total of 39 structural tests were conducted considering the connection joints. The test results, including the failure modes and load-response histories, were reported. The numerical simulations were conducted and validated using multiple comparisons. An extensive parametric study based on a calibrated finite-element model was conducted to investigate several influential parameters. The critical elastic buckling load of a three-span continuous beam with rigid or elastic supports was derived, and the relationship between the effective length coefficients and the support stiffness was obtained. Based on the experimental and numerical simulation results, a stable bearing capacity design method applicable to equal-leg angle steel columns with end connection joints was proposed. It is shown that the proposed design method improves the consistency and reliability of the prediction of the ultimate strength.

Experimental study on performance of reinforced concrete short columns repaired and strengthened with Basalt fiber ultra-high-performance concrete (BF-UHPC)

To explore the reinforcement effectiveness of basalt fiber UHPC repair materials on concrete structures, this study designed four types of wrapping materials for C40 concrete short columns (inner columns), and formed four types of composite short columns. Axial compression tests were conducted on these specimens to analyze the effects of wrapping material type, wrapping material thickness, and protective layer thickness on bearing capacity. Additionally, a model for axial compressive bearing capacity of short column specimens, based on the Mander model and relevant parameter modifications, was established. The results show that: (1) All designed short column specimens showed brittle failure in the experiment, and the brittle failure phenomenon during the experiment is like that of ordinary concrete short columns constrained by stirrups. (2) The type of wrapping material and the thickness of the wrapping layer are important factors affecting the axial compressive bearing capacity of the entire short column. (3) Adding an appropriate amount of basalt fiber and nano-silica significantly enhances the reinforcing and repairing capabilities of the repair material, thereby improving the load-bearing capacity of the repaired concrete columns. (4) Based on the Mander model and the correction of correlation coefficients, a model for axial compressive bearing capacity of short column specimens was established.

Potential removal of arsenite from contaminated water using a fixed bed column packed with TiO2-impregnated pomegranate peel powder

A dynamic biosorption of arsenite in a fixed bed column packed with TiO2 impregnated pomegranate peel (PP@TiO2) has been investigated in this work, which is important to identify the effectiveness and affordability of an adsorbent in actual practice. To create an active adsorption site for As (III) ions, pomegranate peel powder (PP) was impregnated with TiO2. Under various operating parameters, the performance of a column packed with PP@TiO2 for adsorbing As (III) ions was evaluated. Breakthrough curve modelling showed that the bed depth service time (BDST) and Thomas models agreed well with the experimental data. The maximum column capacity of PP@TiO2 using the Thomas model was found to have resembled experimental value with high values of coefficient of determination. Therefore from these results, we may anticipate that PP@TiO2 can be a strong contender for the treatment of wastewater that has traces amount of the As (III) ion in a fixed bed system.

Discrimination of plastic waste pyrolysis oil feedstocks using supercritical fluid chromatography

Advanced chemical recycling techniques provide new avenues for handling and recycling mixed plastic waste; pyrolysis is a prominent approach involving heating plastic waste in an oxygen-free environment to create pyrolysis oils. Pyrolysis oils must be thoroughly characterized before being refined into fuels and chemical feedstocks. Here, a method based on supercritical fluid chromatography with ultraviolet detection was developed to analyze plastic waste pyrolysis oils. Multiple stationary phases were examined, and 2-ethyl pyridine was chosen as the best stationary phase for resolving pyrolysis oil components. Different standards and different plastic waste pyrolysis oils were compared across the different stationary phases. Up to three columns were serially coupled to increase efficiency and column capacity. It was found that a general method using ethanol as a modifier and two 2-ethyl pyridine columns could effectively resolve plastic waste pyrolysis oils. The potential for differentiating polyethylene and polypropylene feedstocks was demonstrated using principal component analysis.

Cyclic behaviour of circular CFT-SG columns under axial tension-compression: Novel FE modelling and design methods

The ultra-high concrete-filled steel tubular (CFT) power transmission tower is popularly applied in engineering practice, which may be under a typical cyclic axial tension-compression loading condition due to the dynamic wind load. Nonetheless, the CFT columns of the tower may be accompanied by significant gap defects due to the influence of structural feature, material property, and service environment. Hence, to figure out the performance of circular CFT columns with spherical-cap gaps (CFT-SG) subjected to cyclic axial tension-compression, this paper investigates a constitutive relationship for the gapped core concrete, which is verified by several existing experiments. A novel numerical modelling approach for simulating the irregular cross-section of the circular CFT-SG columns under cyclic axial load was following established based on the triangulation method and code programming. The influence of important parameters such as gap ratio, material strength, and diameter to thickness ratio on the hysteresis characteristics, load-bearing capacity, elastic stiffness, energy dissipation and ductility of circular CFT-SG columns under cyclic axial tension-compression force is studied. Moreover, the restoring force model of the circular CFT-SG columns under cyclic axial tension-compression is finally presented. Research results declare that the compressive bearing capacity, stiffness, ductility, and energy dissipation of circular CFT-SG columns under cyclic axial tension-compression are gradually weakened with the increment in the gap ratio. The numerical modelling approach and restoring force model proposed in this article can accurately evaluate the hysteresis performance of circular CFT-SG columns subjected to cyclic axial tension-compression.

Influence of Variation in Tie Reinforcement Diameter on the Ductility of Reinforced Concrete Columns

Reinforced concrete columns are crucial structural elements in ensuring the strength and stability of buildings. Column ductility, which is the ability to absorb energy and undergo deformation before failure, is a primary concern in structural engineering, especially in extreme external loading situations such as earthquakes. This study aims to evaluate the influence of variation in Tie reinforcement diameter on the ductility of reinforced concrete columns using Xtract software. The research method involves creating column structure models with specified dimensions and specifications, followed by the gradual application of axial loads to each model. Three models were created with varying Tie reinforcement diameters, namely 10 mm, 12 mm, and 14 mm. Structural analysis was conducted to examine the structure's response to the applied axial and moment loads, including evaluation of stresses, deformations, and column capacities. The analysis results show differences in ductility levels among the models. The model with a 10 mm Tie reinforcement diameter achieves higher ductility levels at low axial loads but fails to meet the requirements at higher axial loads according to the SNI 1726:2019 standard. However, models with Tie reinforcement diameters of 12 mm and 14 mm also exhibit a similar pattern, with good ductility at low axial loads but failing to meet the requirements at higher axial loads. In conclusion, variations in Tie reinforcement diameter affect the ductility of reinforced concrete columns. To ensure full ductility under various axial load conditions, adjustments to the design or specifications of the reinforced concrete column structure are necessary. This research contributes to understanding the factors influencing the ductility of reinforced concrete columns and can serve as a basis for the development of more effective design methods in the future.