Steel Reinforced Concrete Columns Research Articles

Eccentric Compression Performance of Core-Steel Tube with T-Shaped Steel Reinforced Concrete Column

This paper introduces a novel steel–concrete composite column referred to as the core-steel tube with T-shaped steel reinforced concrete (CSTRC) column, which is composed of a core steel tube with T-shaped steel embedded in a reinforced concrete column. To investigate the mechanical performance of the CSTRC column under eccentric compressive load, the load–deformation response, stress, and strain distribution of CSTRC columns under eccentric load are analyzed by finite element software. Furthermore, the effects of slenderness ratio, concrete and steel strength on the eccentric compression performance of CSTRC columns are also discussed. Finally, a set of formulas for predicting the ultimate strength of the CSTRC columns is proposed. The study results reveal that: (1) The established finite element model accurately predicts bearing capacity and strain development. (2) When the eccentricity is 0.2, the specimen exhibits characteristics indicative of small eccentricity failure. Conversely, when the eccentricity is 0.8, the specimen demonstrates traits associated with large eccentricity failure. Furthermore, as the eccentricity increases, there is a notable decrease in the bearing capacity of the specimen. (3) The slenderness ratio affects the failure mode of the CSTRC columns, with consideration for second-order effects necessary when the ratio exceeds 22. (4) Increasing the concrete strength, steel strength, and steel ratio significantly enhances the ultimate load values of the CSTRC columns. (5) A comparison between calculated and simulated values demonstrates good agreement, validating the accuracy of the proposed method.

Confinement mechanism of cross-shaped steel reinforced concrete columns

A novel confined concrete constitutive model for steel-reinforced concrete (SRC) columns with cross-shaped steel (CSS) sections is proposed. The model is based on the similar characteristics of descending branches in the stress–strain curves of confined and unconfined concrete (UCC), considering confinement degradation caused by buckling of the steel section or longitudinal reinforcement. The confined region of SRC columns with CSS sections was divided into four parts: highly steel-confined concrete (HSCC), partially steel-confined concrete (PSCC), stirrup-confined concrete (StCC) and UCC. Relevant effective confinement coefficient expressions were also derived. Simulations of existing tests showed that (a) the load–strain curves obtained using the modified stress–strain constitutive model agreed well with the experimental results, with the error in the descending branch less than 5%; (b) the HSCC region for SRC columns with CSS sections in the finite-element model was in good agreement with that in the proposed region division; (c) the simulation of confined concrete region boundaries for SRC columns with CSS sections were determined using plumb lines for improving the calculation efficiency.

Finite element analysis of deterioration of axial compression behavior of corroded steel-reinforced concrete middle-length columns

Abstract The corrosion problem of steel-reinforced concrete (SRC) columns in coastal areas is becoming increasingly severe and needs to be solved urgently. This study established a numerical analysis model for SRC middle-length columns considering corrosion effects. The bond–slip constitutive relationship between corroded steel and concrete was established. It was found that when the rust rate is low, the bonding stress of SRC columns is slightly increased compared to those without corrosion. The ultimate and residual bonding stress will decrease significantly when the rust rate exceeds 1.5%. The comparison between the numerical analysis model and the experimental results shows that the establishment of the model is reasonable. Subsequent parameter analysis showed that for corroded SRC mid-length columns, the larger the slenderness ratio of the component, the faster the decrease in axial compression performance. The rust rate increased from 0 to 30%, and the axial compression performance of SRC columns decreased significantly. When the rust rate exceeded 30%, the axial compression performance of concrete columns tended to stabilize. A formula for calculating SRC middle-length columns’ ultimate bearing capacity considering corrosion effects has been proposed.

Mechanical Properties of Inclined Steel-Reinforced Concrete Column Structure of Shenzhen Huangmugang Comprehensive Transportation Hub

Mechanical Properties of Inclined Steel-Reinforced Concrete Column Structure of Shenzhen Huangmugang Comprehensive Transportation Hub

Analysis and Research on Load Behavior of H-shaped Steel Concrete

Steel-reinforced concrete (SRC) possesses excellent strength and numerous advantages over traditional concrete, making it extensively used in high-rise buildings and large-span bridge structures. This paper commences with the constitutive relationship of steel reinforcement in SRC, the nominal stress-strain conversion, and real stress-strain transformation. It employs Abaqus for nonlinear finite element analysis to study the stress variations in compressed SRC columns subjected to reciprocating loads and examines load-displacement curves. The paper analyzes the hysteresis loops of SRC columns under reciprocating loads, the trends in skeleton curves, energy dissipation, and stiffness degradation. Consequently, it concludes that the variation of compressive stress along the axis of SRC columns is consistent with the change in bearing capacity. Under reciprocating loads, the stress at the lower end of the SRC column is greater than that at the upper end, suggesting the need for reinforcement in the lower portion. The hysteresis loop of SRC columns exhibits a rich characteristic, with increasing energy absorption as displacement increases.

IMPLEMENTATION OF BUILDING INFORMATION MODELING (BIM) PRINCIPLES AND INFORMATION TECHNOLOGIES FOR STRUCTURAL ANALYSIS IN THE DESIGN OF REINFORCED CONCRETE AND СOMPOSITE STEEL-REINFORCED CONCRETE FRAMED BUILDINGS

The development of Building Information Modeling (BIM) in historical context hasbeen analyzed, including CAD systems for 2D and 3D modeling, considered predecessors of modern BIM systems, parametric 3D modeling systems, the use of information technologies for structural analysis, issues of combined use of BIM systems and information technologies for structural analysis.Using the example of a 20-story frame-monolithic residential building, the sequence of creating a building information model in PC SAPPHIRE, forming a calculation model of the reinforced concrete frame in PC Lira-SAPR through direct integration of the specified software complexes is demonstrated. The issues of preparing a building information model in PC SAPPHIRE for transfer to PCLira-SAPR are discussed, as well as the issues of refining the calculation model in PC Lira-SAPR, including assigning stiffness and load characteristics, and selecting reinforcement for structural elements. Тhe sequence of creating a calculation model of a steel-reinforced concrete frame for three options of steel-reinforced concrete columns is considered: tubular concrete columns; tubular concrete columns with rigid reinforcement by cross steel strips; tubular concrete columns with rigid reinforcement by cross double T-sections.For the selected most loaded columns, mainly on the first floor, operating under the conditions of central or off-center compression, the sequence of forming refined calculation models is demonstratedby modeling these columns and areas of their connection to the floor slabs with 3D finite elements.Equivalent stress iso-surfaces are provided, as well as separate iso-surfaces of equivalent stresses of the steel shell and separately the concrete core of the columns

Post-fire performance of circular steel tube confined steel-reinforced concrete slender columns: Testing, simulation and design

Steel tube confined steel-reinforced concrete (STCSRC) stub columns offer good residual bearing capacity, great ductility, and large stiffness after fire exposure because inner steel profiles are unaffected by exterior temperature. Nonetheless, instability issues exist in STCSRC slender columns, and study into the mechanical characteristics of post-fire slender specimens is critical. At present, no relevant study on the axial performance of STCSRC slender columns after fire exposure has been reported. In this paper, nine circular STCSRC slender columns that had been exposed to fire were tested under axial load. The failure modes, axial load–displacement relationship, and lateral deflections of STCSRC columns were discussed. Furthermore, heat transfer analysis models and mechanical analysis models were established, and the effects of crucial variables on the buckling responses of STCSRC slender columns were explored. Among the parameters studied, sectional diameters and steel profile to concrete area ratio have a significant impact on buckling capacity. To calculate the buckling capacity of the post-fire STCSRC slender column, a simplified calculation method according to JGJ/T 471–2019 was proposed.

Slenderness limit for GFRP reinforced concrete columns based on axial force ratio

Concrete columns reinforced with fiber-reinforced polymer (FRP) bars have been of great interest in recent years. The distinct properties of FRP bars, such as linear stress–strain behavior and low modulus of elasticity in comparison to steel bars, make the study of FRP reinforced concrete (FRP-RC) columns of importance, especially with regard to the effect of slenderness. This work presents a numerical method for second-order analysis and examines the slenderness limit of glass FRP bars reinforced concrete (GFRP-RC) columns based on two criteria: a reduction in moment capacity at constant load and a reduction in load capacity at constant eccentricity. In the literature, only limited contributions have been made on the slenderness limit of FRP-RC columns, usually based on the latter criterion, whereas there is a lack of literature regarding the slenderness limit of FRP-RC columns based on the former criterion, which is also the slenderness limit criterion of Eurocode 2 (EC2-04) for steel-reinforced concrete (steel-RC) columns. This work may assist in the development of Eurocode provisions, national annexures and guidelines for the design of GFRP-RC concrete columns. A detailed sensitivity analysis was conducted with parameters including the modulus of elasticity of the GFRP bar, percentage of reinforcement, compressive strength of concrete and axial force ratio to examine the variation of slenderness limit for GFRP-RC columns. The axial force ratio is observed to be an important parameter to estimate the slenderness limit from the sensitivity analysis. Variation of slenderness limit for GFRP-RC columns with axial force ratio is observed to be different and the value of slenderness limit is lower compared to the steel-RC columns. Two Equations, which take into account the variation due to the axial force ratio, are proposed to estimate the slenderness limit for GFRP-RC columns.

Evaluation on the static and seismic performance of steel reinforced concrete composite columns with high strength materials

High strength steel and concrete have gained acceptance in heavily loaded structures due to the self-weight reduction and capacity enhancement. However, current design codes restrict the application of high strength materials in Steel Reinforced Concrete (SRC) composite columns. In order to give a comprehensive evaluation of the structural performance of High Strength SRC (HS-SRC) columns and form the basis of future design guidelines, this paper performs theoretical and statistical analysis of HS-SRC columns subjected to both static and seismic actions. Based on the literature scan, three databases were gathered and categorized into concentrically-compressed HS-SRC columns, eccentrically-compressed HS-SRC columns and cyclically-loaded HS-SRC columns according to the loading schemes. The failure mechanism, load-carrying capacity and ductility coefficient of HS-SRC columns were analyzed in detail, and the key issues concerned with high strength materials were highlighted and discussed. Based on the experimental and analytical results, recommendations are proposed to support the codification of future design guide and promote the application of HS-SRC columns in engineering practice.

Finite element modeling and design equations of partially steel-reinforced concrete beam-to-steel tube column joint

Steel reinforced concrete beams are increasingly used as novel transfer structures in high-rise buildings. In this paper, numerical and theoretical studies were carried out on a novel joint of steel-reinforced concrete beam and steel tube column, in which the beam was reinforced by a short steel beam with partial length. Based on the previous experimental studies, finite element modeling was performed to consider the evolution of the concrete damage and to investigate the effects of the main design parameters on the seismic performance of the new joint. It was found that the length of the steel shape, the thickness of the concrete cover, and the concrete compressive strength have significant effects on the initial stiffness and peak capacity of the new joint, while changing those parameters may not change the failure mode of the joint. A theoretical analysis was performed to establish an analytical model for the shear capacity of the new connection that takes into account the contributions of the steel web, stirrups, and concrete. The model was verified against the database of experimental and numerical analysis results. Design equations and recommendations for checking the flexural and shear strength of the embedded steel shape, the composite beam and the RC part of the beam were also provided.

Machine learning-based prediction of shear strength of steel reinforced concrete columns subjected to axial compressive load and seismic lateral load

The shear strength of steel reinforced concrete (SRC) columns is a crucial basis in their seismic design and evaluation of structural performance. Most of the existing research predicts the lateral load carrying capacity based on regression equations, but lacks accuracy. To this end, in this study, Gaussian process regression (GPR), Least Squares Boosting (LSBoosting), Support Vector Regression (SVR), Feedforward Neural Network (FNN) and other machine learning (ML) algorithms were employed to develop the shear strength model of SRC columns subjected to axial compressive load and seismic lateral load. A large experimental database with 395 samples was established to train 11 input features. The original database was divided into 5 datasets based on the mixed, flexural, flexural-shear, shear, and bond failure modes. The failure mechanism factors were introduced for better evaluation. Specifically, an effective data splitting strategy-bootstrapping was used to train the models, and Bayesian optimization was attempted to improve the prediction accuracy. Results demonstrate that GPR has the highest prediction accuracy with the most failure modes, and the factors affecting the shear strength are explained reasonably by correlation analysis and Partial Dependence Plot. Through comprehensive comparison, the GPR model developed in this paper is advanced in predicting the shear strength of SRC columns.

EXPERIMENTAL STUDY ON AXIAL STRENGTH AND PURE BENDING RESPONSE OF FWSCT-JACKETED SRC CIRCULAR COLUMNS

A novel composite shell system called FWSCT (FRP-wrapped steel corrugated tube) is composed of steel corrugated tube and fiber reinforced polymer (FRP). A series of experiments have been conducted to investigate the mechanical performance of FWSCT applied to steel-reinforced concrete (SRC) circular columns. This paper introduces the development of FWSCT, and the experimental programs on the FWSCT-jacketed SRC circular columns under uniaxial compression and pure bending. A total of 48 small-size FWSCT-jacketed SRC column cylinders were loaded axially, and the other five large-size circular column specimens were tested under four-point bending. Test parameters include the type of shaped steel, steel tube confinement, and the FWSCTs with various FRP layers and orientations. The experimental results were used to identify the mechanical contribution of various FWSCTs to the column strength and as the database for model development and numerical simulation for FWSCT-jacketed columns. Test results have validated the confinement effect and failure mechanism of the FWSCT applied on SRC columns.

Axial compressive performances of thin-walled steel tube confined steel-reinforced concrete columns after fire exposure

The thin-walled steel tube confined steel-reinforced concrete (STCSRC) column can efficiently utilise the confinement effect of steel tube on concrete. The local buckling of external thin-walled steel tubes can be delayed or avoided owing to their discontinuity at beam–column joints, thus, the structural performances of thin-walled STCSRC columns are improved. To date, the behaviour of thin-walled STCSRC columns after fire exposure under axial load has not been reported. Experimental and theoretical studies of axially-loaded circular thin-walled STCSRC stub columns were conducted in this paper, exploring mechanical performance indexes and mechanisms after fire exposure. A total of eighteen thin-walled STCSRC stub columns were designed, considering the parameters of the steel tube to concrete area ratio, heating time, and strength of the concrete. To better comprehend the behaviours of thin-walled STCSRC stub columns after fire exposure, detailed discussions in terms of the temperature distribution, failure modes, load–axial strain response, stresses of steel tubes, and load proportion of each component are presented. The heating test results reveal that the maximum temperature is lower and the time to reach the peak temperature is longer when measuring points are closer to the centre of the cross-section. The thin-walled STCSRC stub column after fire exposure presents shear failure under axial compression. The longer the heating time, the earlier the shear slippage line appears. Compared with the specimen at room temperature, the residual compressive resistance and stiffness reduce with increasing heating time. The ductility of the thin-walled STCSRC stub column improves when increasing the heating time. In addition, the diameter of the cross-section, H-shaped steel to concrete area ratio, and concrete strength have beneficial effects on residual axial load capacities and stiffnesses. Moreover, simplified calculation methods were assessed to predict the residual axial load capacities and stiffnesses of thin-walled STCSRC stub columns.

A stacking-CRRL fusion model for predicting the bearing capacity of a steel-reinforced concrete column constrained by carbon fiber-reinforced polymer

In a two-level stacking algorithm framework, a fusion model (stacking-CRRL) of categorical boosting (Catboost), random forest regression (RFR), ridge regression (RR), and Least absolute shrinkage and selection operator (LASSO) is proposed and shown to accurately predict the load capacity in axial compression of steel-reinforced concrete columns (SRCCs) clad in carbon fiber-reinforced polymer (CFRP). Sparse initial data were extended by synthetic minority oversampling in the model-building process, and 12 model input features were identified after eliminating redundant features using Spearman correlation coefficients. The prediction performance of five boosting models, two bagging models, and three traditional machine learning (ML) models were compared. The Catboost, RFR, and RR models were selected as the base learners, and LASSO regression was chosen for the meta-learner. The prediction performance of different algorithmic models before and after synthetic minority oversampling technique (SMOTE) processing is compared, and the stacking-CRRL fusion model established is compared with that of established prediction techniques. The Shapley additive explanations technique was applied and discussed the impact of input features on the bearing capacity of SRCCs. The results demonstrate that the prediction performance of the proposed stacking-CRRL fusion model surpasses that of the alternative models tested, that of a published prediction equation, and that of an Abaqus simulation.

Compressive behavior of FRP-confined cruciform steel-reinforced normal- and high-strength concrete columns

Fiber-reinforced polymer (FRP)-confined steel-reinforced concrete column (FCSRC), which consists of an external FRP tube and a steel-reinforced concrete (SRC) core, have been proposed to avoid the brittleness of SRCs. Capitalizing on the benefits of FRP-confine concrete, it is expected that full strength capacities of high-strength materials (i.e., high-strength concrete and high-strength steel) in FCSRCs can be exploited. Axial compression tests on FCSRCs with different strengths of concrete and steel were conducted in this study. A cruciform steel was adopted in FCSRCs. The parameters investigated in this study included the concrete strength, the steel strength and the FRP tube thickness. The test results demonstrated that the excellent performance of FCSRCs. Compared with normal-strength cross-shaped steel, the high-strength cruciform steel delays the development of hoop strains in the FRP tube for FCSRCs with normal-strength concrete. Additionally, the ultimate axial load of FCSRCs is generally larger than the direct summation of those of the steel section and FRP-confined concrete section (i.e., CFFT), demonstrating that the interaction between the three components (concrete, steel profile and FRP tube) in FCSRCs are in a benificial manner.

Seismic performance of steel-reinforced reactive powder concrete columns

The seismic performance of the innovative steel-reinforced reactive powder concrete (SRRPC) composite columns was evaluated via the cyclic experiments considering the steel shape ratio, axial compression ratio and the stirrup ratio. The SRRPC columns generally exhibited appreciable seismic behavior, great crack-resistance and excellent anti-spalling property. It was found that increasing the steel shape ratio from 4.20% to 5.35% can significantly enhance the ductility and the energy dissipation capacity. As the axial compression ratio increased from 0.1 to 0.3, the peak lateral load increased but the ductility significantly decreased. Increasing the stirrup ratio from 1.57% to 2.52% was not helpful for seismic performance in the pre-peak zone but was beneficial to the strength and ductility in the post-peak zone. Moreover, the average strength loss of the SRRPC columns with low axial compression ratio at the 4.5% drift ratio was less than 12.5%, satisfying the modern seismic drift criteria. Two coefficients, βtu and k, for predicting the equivalent tensile strength were identified and compared to the suggested values from the specifications JGJ/T 465-2019 and T/CCPA 35-2022, respectively. An analytical model was successfully developed to predict the lateral load-bearing capacity. Good agreements were found between the experimental and analytical results.

Investigation of Circular Hollow Concrete Columns Reinforced with GFRP Bars and Spirals

Glass fiber-reinforced polymer (GFRP) reinforcements are useful alternatives to traditional steel bars in concrete structures, particularly in vertical structural elements such as columns, as they are less prone to corrosion, and impart increasing strength and endurance of buildings. There is limited research on the finite element analysis (FEA) of the structural behavior of hollow glass fiber-reinforced polymer reinforced concrete (GFRPRC) columns. The hollow portion can be used for the service duct and for reducing the self-weight of the members. Numerical analysis of the compressive response of circular hollow concrete columns reinforced with GFRP bars and spirals is performed in this study. This article aims to investigate the axial behavior of hollow GFRP concrete columns and compare it with that of solid steel reinforced concrete (RC) columns as well as hollow steel RC columns. The Abaqus software is used to construct finite element models. After calibration of modeling using an experimental test result as a control model, a parametric study is conducted. The columns with the same geometry, loading, and boundary conditions are analyzed in the parametric study. It is resulted that the hollow GFRP concrete columns provide a greater confinement effect than the solid steel RC columns. The average variation in the ultimate axial load-carrying capacities of the experimental results, from that of the FEA values, is noted to be only 3.87%, while the average difference in the corresponding deformations is 7.08%. Moreover, the hollow GFRP concrete columns possess greater axial load and deformation capacities compared with the solid steel RC columns.

Effect of Entrance Frame on Crack Development around Prefabricated Subway Station Openings

The openings at the sidewalls of subway station entrances generally reduce the localized load-bearing capacity of the sidewalls and lead to concentrated stress around the openings. In this study, to strengthen the sidewalls with openings in a newly-developed prefabricated subway station, a prefabricated steel-reinforced concrete (SRC) frame around the entrance was developed. To further investigate the effect of the developed entrance frame on the mechanical behavior of the sidewalls, a monotonic static test and finite element analysis were performed on a 1/2 scale station entrance substructure, including the proposed entrance frame and the adjacent top slab, bottom slab, and sidewalls. It was found that the developed entrance frame could effectively prevent stress concentration in the adjacent sidewall region. The most severe crack development was concentrated at the corner of the opening, which could be attributed to the torsional moment at the SRC beam end. The ratio of the torque shared by the beam to the total bending moment of the slab end varied from 21.2% to 26.8% in the elastic stage of all cases. In addition, both the improvement in the torsional bearing capacity of the SRC beam and the out-of-plane flexural capacity of the SRC column could positively contribute to controlling the crack development around the opening.

Behavior and design of eccentrically-loaded slender tubed steel-reinforced high-strength concrete columns

This study experimentally and numerically investigated the behavior of eccentrically-loaded slender circular tubed steel-reinforced concrete (CTSRC) columns filled with high-strength concrete (HSC). Six specimens with the HSC of 81.4 MPa were tested considering the length-to-diameter ratio and load eccentricity; and their effects on the failure phenomenon, bearing capacity, and ductility were evaluated. A three-dimensional finite element model was established and validated for further investigating the column behavior. The study results indicate that all specimens fail in a flexural failure mode and show good ductility; and the shear studs and circular steel tube are found to ensure the composite behavior of CTSRC columns. Besides, increasing the tube thickness contributes more to the improvement of column ductility than the load capacity and the steel shape yields before the peak load, indicating the full utilization of steel strength. Based on the parametric study, a design method considering the second-order effect and the influence of unequal load eccentricities at both column ends is proposed to assist designers to determine the load capacity of slender CTSRC columns.

Mechanical Behavior of Special-Shaped Double-Web Steel-Reinforced Concrete Column Joints

In this paper, five new joints of special-shaped double-web steel-reinforced concrete (SDSRC) columns connected with steel beams are designed. The load-displacement curves, joint yield states and damage forms of the beam ends of the five joints under monotonic loading with the same axial pressure ratio are investigated. Additionally, the hysteresis performance, strength and stiffness degradation under cyclic loading are studied. The results show that the bearing capacity of joints with studs can increase by approximately 10%. Since the arrangement of multiple rows of studs at the connection between the beam web and the column has better force transfer performance and concrete synergy behavior, the failure modes of these joints are plastic hinge formation at the end of the beam, satisfying strong column-weak beam requirements. Moreover, these joints exhibit good ductility and energy dissipation capacity under cyclic loading, and their strength and stiffness gradually decrease. In contrast, joints with single-row studs or without studs at the connection between beam web and column exhibit beam flange buckling rather than full-section plastic hinge formation at the beam end, and tensile deformation of column web is larger. Although these joints exhibit good ductility performance, their energy dissipation capacity is weaker than that of joints with multiple rows of studs at the beam web-column connection.