Steel-concrete Composite Columns Research Articles

Study of the fire resistance of partially encased composite steel-concrete columns according to Eurocode 4

In this paper, the behavior of partially encased steel and concrete composite columns without fire protection exposed on four sides to the standard fire and under axial loading was studied using the simplified calculation model of the Eurocode4 (EC4) method. The main objectives of this study are: first to evaluate the temperature of the different components of the column section as well as the variation in the characteristics of the materials constituting them (strengths and Modulus of elasticity); and then analyze the influence of several parameters, such as the section size, the reinforcement rate, the buckling length and the mechanical strengths of the steel and concrete on the ultimate fire resistance. The results show that the dimensions of the section, the reinforcement rate and the buckling length have a significant influence on the fire resistance. On the other hand, the concrete strength, the structural steel grade and the reinforcing steel grade have a moderate influence.

Numerical analysis of flexural behaviour of UHPC-CFTS columns as enclosure supports for electrical substations

Abstract This study establishes a finite element analysis model of ultra-high-performance concrete (UHPC) encased concrete filled steel tube (CFST) composite columns under combined compression and bending. Appropriate constitutive models and element types are selected as the basis. The finite element model simulates the test results of steel-concrete composite columns, and the applicability of the model is verified by comparison with existing test data of UHPC encased CFSTs. On the basis of demonstrating model reliability, the full-range load-deformation curves of UHPC encased CFSTs with different concrete strengths under compression-bending are compared. The failure modes and material stress distributions are analyzed to elucidate the influence mechanism of the UHPC on the flexural performance of UHPC encased CFSTs under combined compression and bending. The results show that compared to normal concrete, UHPC can effectively improve the flexural capacity of UHPC encased CFST columns. Owing to the addition of steel fibers, the failure mode of UHPC encased CFSTs under combined compression and bending is more integral compared to normal concrete. The research results of this study can provide references for the performance evaluation and design of UHPC encased CFSTs in the structural enclosures for electrical equipment in high/low voltage substations.

Behaviour and design of prestressed stayed circular concrete-filled double skin steel tubular (PS-CCFDSST) columns under axial compression

An innovative type of steel-concrete composite column, named the prestressed stayed circular concrete-filled double skin steel tubular (PS-CCFDSST) column, is introduced in this study, aiming to achieve both structural efficiency and economic advantages. Numerical simulation and theoretical analysis on the axial compressive behaviour of PS-CCFDSST columns were carried out, to understand and reveal their fundamental working mechanisms. Nonlinear finite element analysis (FEA) utilising ABAQUS was performed and validated against collected test data of CCFDSST columns and PS columns. Properly designed PS-CCFDSST columns could gain cost savings of over 30 % while maintaining identical load-bearing capacity as prestressed stayed hollow steel tube (PS-HST) columns with the same steel usage. The effects of initial pretension, nominal steel ratio, hollow ratio, column’s slenderness ratio, relative length of struts, column diameter, strut diameter and cable area on the buckling mode and buckling capacity of PS-CCFDSST columns were evaluated via parametric studies. The stiffness ratio β could be used as an index to comprehensively assess the structural efficiency of PS-CCFDSST columns, and a critical threshold of β = 2 corresponds to the transition between symmetric and anti-symmetric buckling modes. Linear calculation formulae for the theoretical buckling capacity and optimal initial pretension of PS-CCFDSST columns were derived. Finally, practical design equations for predicting the column’s buckling capacity were developed, and recommended values for the actual optimal initial pretension and other primary parameters were provided for PS-CCFDSST columns under axial compression. This study, for the first time, provides the fundamental mechanical behaviour, identification of the critical stiffness ratio for buckling mode transition, and design framework for buckling capacity of the PS-CCFDSST column, which is useful for advancing theoretical exploration and informing engineering practices for this new column type.

Seismic Performance of Cross-Shaped Partially Encased Steel–Concrete Composite Columns: Experimental and Numerical Investigations

Special-shaped partially encased steel–concrete composite (PEC) columns could not only improve the aesthetic effect and room space use efficiency, but also exhibit good mechanical performance under static load when used in multi-story residential and office buildings. However, research on the seismic performance of special-shaped PEC columns is insufficient and urgently needed. To investigate the seismic performance of cross-shaped partially encased steel–concrete composite (CPEC) columns, three CPEC columns were designed and tested under combined constant axial load and lateral cyclic load. The test results show that the CPEC columns had good load capacity and ductility, and that the columns failed because of concrete crushing and steel flange buckling after the yielding of the steel flange. The plump hysteresis loops indicated that the CPEC column also had good energy dissipation capacity. Due to the constraint of hydraulic jacks, increasing the load ratio would decrease the effective length, thereby increasing the load capacity of the CPEC column and decreasing the ductility. A finite element model was also established to simulate the response of the CPEC columns, and the simulated results agree well with the experimental results. Thereafter, an extensive parametric analysis was performed to study the influences of different parameters on the seismic performance of CPEC columns. For the CPEC column with an ideal hinged boundary condition at the top, its lateral load capacity gradually decreases with the growth of the load ratio and link spacing and increases with the rise of the steel yield strength, concrete compressive strength, flange and web thickness, and sectional aspect ratio. This research could provide a basis for future theoretical analyses and engineering application.

Experimental study on axial compressive behavior of concrete-filled corrugated steel tubular columns

Concrete-filled corrugated steel tubular (CFCST) column is a novel type of steel-concrete composite column, comprising four corrugated steel plates, four square-section steel bars at the corners, and infilled concrete. The transversely placed corrugated steel plates can effectively prevent their premature local buckling, release the axial load, and provide lateral confinement effects on the infilled concrete. This paper investigated the axial compressive behavior of CFCST columns through experimental, numerical, and theoretical approaches. Experiments were conducted on 20 specimens, focusing on their axial load-resistant behavior. The specimens demonstrated excellent axial bearing capacity, ductility, and residual bearing capacity. Besides, the mechanical behavior of corrugated steel plates throughout the loading process was analyzed through the development of the horizontal and vertical strains. Furthermore, a finite element (FE) model was developed to simulate the axial compressive behavior of CFCST columns, which was validated against the experimental data. The FE model was used to analyze the compressive behavior of each part in CFCST columns, revealing that the infilled concrete and steel bars primarily bear the axial load, while the corrugated steel plates mainly provide lateral supports to the infilled concrete. Finally, a simplified method for calculating the critical width of corrugated steel plates and a formula for the axial bearing capacity of CFCST columns were proposed. It was indicated that the limiting width-to-thickness ratio of the corrugated steel plates was larger than that of the steel elements in conventional CFST columns. These formulas were demonstrated to be accurate enough and suitable for the engineering designs.

Fire test and simulation of circular steel tube confined steel-reinforced concrete columns

Steel tube confined steel-reinforced concrete (STCSRC) columns are novel steel-concrete composite columns where the steel tubes are disconnected at beam-column connections. Few researches have been conducted on the fire behaviour of STCSRC columns by now, though there are some relevant studies on the fire performance of steel-reinforced concrete-filled steel tubular (SR-CFST) columns. However, the mechanical behaviour of STCSRC columns under fire exposure differs from that of SR-CFST columns due to the discontinuous external steel tube. It is essential to carry out a study on the fire performance of STCSRC columns. The fire tests of four axially loaded STCSRC columns were carried out in this paper, and the failure mode, distribution of cross-sectional temperature, fire resistance, and lateral deflection were discussed. A finite element model was developed and validated with test results, and then a parametric analysis of the STCSRC stub and slender columns under fire exposure was performed. The load ratio, steel tube strength, the area ratio of steel tube to concrete, and slenderness ratio have an adverse effect on the fire resistance of STCSRC columns, whereas cross-sectional dimension, area ratio of steel section to concrete, and strength of steel section have a favourable impact. Concrete strength has a different influence on the fire resistance of STCSRC stub and slender columns. Finally, based on the specifications JGJ/T 471-2019 and EN 1994-1-2, simplified calculation methods for assessing the fire resistance of STCSRC columns were proposed.

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.

Erratum for “Behavior and Design of Steel-Concrete Composite Columns Subjected to Combined Axial Compression and Biaxial Moment”

Erratum for “Behavior and Design of Steel-Concrete Composite Columns Subjected to Combined Axial Compression and Biaxial Moment”

Experimental investigation and design method of axial compression behavior of T-shaped partially encased steel-concrete composite stub columns

The implementation of special shaped Partially Encased Steel-concrete Composite (PEC) columns represents a viable approach to avoid the protruding of PEC columns with conventional cross-sections in tall buildings. Nevertheless, there is a lack of clarity regarding the load-carrying capacity and failure mechanisms associated with special shaped PEC columns. To comprehensively investigate the mechanical behavior of special shaped PEC columns under axial loading, this paper conducts an experimental analysis focusing on the compressive behavior of 9 T-shaped PEC (TPEC) short columns. The study examines the influence of critical design factors, including the content of section steel, spacing between transverse links, aspect ratio of the section, and the strength of concrete, on the axial load-carrying capacity of the members. Subsequently, the failure mode, ultimate load, initial stiffness, strain response, ductility index, and strength characteristic index of TPEC short columns were thoroughly explored. The results show that TPEC short columns exhibited damage patterns characterized by flange buckling, concrete spalling, accompanied by buckling of some transverse links and fracture of connecting joints. The steel ratio and transverse links spacing have substantial influence over the ultimate capacity and ductility of the columns. Notably, an augmentation in the steel ratio leads to an increase in both the ultimate capacity and ductility, while an increase in transverse links spacing results in a decrease in these characteristics. Comparatively, the section aspect ratio and has a relatively minor impact on the capacity and ductility. Additionally, it can be observed that the strength of concrete has a significant influence on the load-bearing capacity of short columns, while its effect on ductile behavior remains relatively insignificant. Finally, the applicability of the current design guidelines (i.e. the ACI318-14, Eurocode 4 and T/CECS719-2010 codes) are evaluated and a new design method for assessing the axial compression resistance of TPEC stub columns based on the constrained partitioning theory and the principle of superposition is proposed. This study can serve as a substantial theoretical foundation for the engineering utilization of TPEC short columns.

Behavior of Two-Chord Steel–Concrete Composite Columns under Axial Compression

Behavior of Two-Chord Steel–Concrete Composite Columns under Axial Compression

Seismic behavior and mechanism of rectangular steel-concrete composite column with three cavities

This paper proposes a rectangular steel-concrete composite column (RSCC) with three cavities, which has a good architectural function. The composite column consists of steel tubes at both ends, steel plates in the middle, and concrete in the cavity. Five RSCC with three cavities were tested to investigate the seismic performance of the column width and headed studs. It was found that the specimens all exhibited flexural damage in the form of flexural tearing of the steel tube/plate and crushing of the concrete in the steel tube cavity. As the column width increases, the load bearing ratio and the percentage of shear displacement in the middle cavity of the specimen increase. The use of headed studs in RSCC with three cavities delay the stiffness degradation of the specimens, and the ductility of the specimens with column width of 400 mm and 500 mm set with headed studs increased by 10.1% and 4.6%, respectively, compared to that of the specimens without headed studs. In addition, a finite element model of the RSCC with three cavities was established, and the finite element analysis results matched well with the experimental hysteresis curves and damage characteristics. A simplified lateral force calculation method was established, and the average error between the predicted values and the corresponding test results for each specimen was 6.1%, which verified the applicability of the calculation model and provided a reference for the engineering application of the RSCC which has good function and performance.

Investigation the influence of geometric parameters on the bearing capacity of partially encased composite columns in fire condition according to Eurocode 4

In this article the method to determine the bearing capacity of composite steel-concrete columns in fire conditions according to Eurocode 4 (EC4) was introduced. Some work examples are presented to clarify the influence of geometric parameters (effective length, axis distance of reinforcement bar) on the bearing capacity of partially encased composite columns in fire condition.

Axial compression behaviour and design of square tubed steel reinforced-concrete stub columns after fire exposure

The tubed steel reinforced-concrete (TSRC) column is an innovative type of steel-concrete composite column, the steel tube of which mainly provides confinement to concrete core without sustaining axial load directly. This paper presents the axial compressive behaviour of square TSRC stub columns after ISO 834 standard fire exposure, experimentally and numerically. Eighteen square TSRC stub columns were heated and cooled and subsequently loaded to failure under axial compression. The influences of heating time, concrete compressive strength and steel tube area ratio on the load vs. displacement response, failure mode, residual capacity and stiffness of the tested columns were investigated. Finite element analysis (FEA) models were then developed and validated against test results. The working mechanism, e.g. confinement effect and axial force distribution within the composite section, was studied via parametric studies. Both the residual ultimate capacity and axial stiffness of square TSRC stub columns decrease significantly with the increase in heating time. The negative effect of fire exposure on residual stiffness is more significant than on the residual capacity. Finally, practical equations for determining the residual ultimate capacity and residual compressive stiffness of square TSRC stub column were proposed, which remain consistent with the ambient-temperature methods given in current design standard.

Axial compressive behavior of the PEC slender columns with lightweight aggregate concrete

To greatly facilitate hoisting and assembly of prefabricated partially encased steel-concrete composite (PEC) columns, lightweight aggregate concrete (LAC) is applied into the PEC columns to form the partially encased composite columns with lightweight aggregate concrete (PEC-LAC). This paper reported experimental studies on the axial compressive behavior of PEC-LAC columns with various slenderness ratios. Following this, finite element (FE) modeling methods considering geometrical and residual stress imperfections were developed to reproduce the test responses. FE analysis was carried out to investigate the effect of geometrical and material parameters on PEC-LAC slender columns subjected to axial compression along the minor axis and major axis. It was found from the contact stress analysis that PEC-LAC slender columns with axial loading along the major axis provide a stronger confinement effect than that with axial loading along the minor axis. Based on the comparison of reduction factors between the test/FE and calculated results, the buckling curve of AISC 360 and the buckling curve (b) of T/CECS 719 can economically and conservatively describe the buckling curve of PEC-LAC slender columns regardless of the flexural buckling direction; the buckling curves (b) and (a) of EC4 were recommended to predict buckling curves of PEC-LAC columns with flexural buckling about the major and minor axis, respectively.

Parameter Selection for Concrete Constitutive Models in Finite Element Analysis of Composite Columns

Concrete, as a complex and anisotropic material, poses challenges in accurately simulating its behavior in numerical simulations. This paper focuses on selecting an appropriate constitutive model for simulating the behavior of a steel–concrete composite column using finite element analysis under compression and push-out tests. Two models are analyzed and compared, namely, Drucker–Prager and concrete damage plasticity. The results demonstrate that the concrete damage plasticity model outperforms the Drucker–Prager model in all six test cases, indicating its superior accuracy in capturing the composite column’s behavior. This study enhances the reliability of numerical simulations for steel–concrete composite structures by choosing the most suitable constitutive model, parallel with extensive sensitivity analysis and model calibration. The findings emphasize the significance of meticulous model selection and precise parameter definition for achieving accurate predictions of concrete behavior. This research contributes to advancing the understanding and modeling of concrete’s intricate behavior in structural analyses.

Seismic Evaluation of Building having Steel Concrete Composite Columns and RC Beams

Abstract: Steel concrete composite structures are gaining popularity due to the advantages they offer over the conventional reinforced concrete and steel structures like the ease and speed of construction. In the light of this, it becomes essential to understand the behaviour of this type of structures when used in buildings. This study mainly focuses on the use of building frame consisting of steel-concrete composite column section with the reinforced concrete beams. To achieve this objective, the seismic analysis of the buildings was chosen for evaluating the performances of the buildings designed and analyses using Indian standards. The building selected for the study was rectangular in plan andhad an elevation of 30 meters with no plan or vertical irregularity present. The gravity loads considered for the building are in compliance with the IS 875 Part 1 and IS 875 Part 2. However, the gravity loads used in case of both buildings were kept to be same as the prime focusof the study was seismic analysis. The materials used for the design of the building with respect to Indian standards are E345 grade of steel and M30 grade of concrete. Various codes of practices including IS 456, IS 11384, IS 1893 and IS 13920 have been used throughout the study in case of the building designed and analysed with respect to Indian standards. The assumptions regarding the seismic characteristics of the buildings are also selected of the same nature for both the buildings. A finite element modellingbased software ETABs is used to carry out the design and analysis for the buildings. The buildings were designed with respect to the selected gravity loads and the seismic loads to obtain the section details to be used for seismic analysis. The building with finally obtainedsection sizes is used for carrying out the nonlinear analysis. This includes both the nonlinear static and nonlinear dynamic analysisas they both have their respective advantages in predicting the behaviour of the structure. For carrying out nonlinear analysis both material as well as geometric nonlinearity is considered. In case of the nonlinear dynamic analysis, the ground motions with respect to the guidelines of FEMA P695 and ASCE 7-16 were selected and scaled to perform the analysis. A total of 11 time histories were considered for NLTHA to have a thorough analysis. Various factors such as thecapacity curves, story displacements, base shears and story drifts were considered for evaluation of the seismic performance of both the buildings. The results obtained from the analysis of both thebuildings are represented in the form of tables and graphs, and are compared with each other to study the differences observed. It can be concluded that the buildings designed composite columns offers a better ductility and thus is more earthquake resistant

Axial compressive performance of partially encased steel-concrete composite stub columns filled with lightweight aggregate concrete

This paper applied lightweight aggregate concrete (LWAC) in the partially encased steel-concrete composite (PEC) stub columns to achieve the advantages of lightweight and easy assembly. A total of 8 axial-loaded specimens were tested to explore the effect of concrete type, concrete strength, link spacing, longitudinal rebars, and height-to-width ratio on the compressive behavior of the partially encased steel-concrete composite stub columns with lightweight aggregate concrete (PEC-LC). Then, the finite element models of PEC-LC columns were established to conduct a systemic parametric investigation. The results demonstrated that the PEC-LC column experienced failure due to concrete crushing and local buckling of flanges, similar to the PEC column. Compared to the PEC column, the PEC-LC column exhibited a similar load-bearing capacity but poorer post-peak compressive performance, which could be improved by closer link spacing. Consequently, applying LWAC to reduce the self-weight of prefabricated members is a feasible option. Besides, the contact stress and the stress distribution at typical cross-sections were analyzed to reveal the confinement effect of H-shaped steel and links on the filled LWAC. Finally, A calculation method for estimating the axial compression capacity of the PEC-LC column was proposed, taking into account the reduction in flange strength and enhancement of core concrete. The accuracy of the calculation method was verified by comparison with experimental and numerical data. Overall, this research serves as a valuable reference for promoting the adoption of the PEC-LC column in assembled structures.

Experimental and Numerical Investigations of Laced Built-Up Lightweight Concrete Encased Columns Subjected to Cyclic Axial Load

The steel-concrete composite column comprises a steel core and surrounding concrete. The purpose of the system is to provide analysis and design techniques for a newly invented class of laced steel-concrete composite short columns for cyclic axial loads. To minimize the increasing density issues associated with nominal strength concrete and in consideration of the depletion of natural resources required to produce concrete, factory-obtained lightweight sintered fly ash aggregates with and without basalt fiber are employed. The normal-weight concrete containing basalt fiber is shown to be more ductile than any other column. The axial deformation of columns LNA and LSA at failure was found to be 3.5 mm, whereas columns LNAF and LSAF reached an axial shortening of 4.5 mm at failure. The column LSAF was found to have 5.3% more energy absorption than the LSA and 11.5% less than the column LNAF. It was observed that the rigidity of these fabricated components had been enhanced. It was found that the section configuration with a lacing system had improved confinement effects and ductility. Comparing the finite element analysis to the experimental data revealed a strong connection with numerical modeling, with a variance of around 8.77%.

Effectiveness of Stiffeners in CFDST Columns: Comparative Study

Concrete-filled double-skin tube (CFDST) columns are considered one of most efficient forms of steel-concrete composite columns, which provide higher axial strength and better ductility compared with their counterpart concrete-filled tube (CFT) columns. This paper aims to numerically investigate and compare the performance of axially loaded circular CFDST short columns provided with stiffeners in inner tubes and outer tubes. Circular steel hollow sections have been adopted for inner as well as outer tubes, and rectangular steel stiffeners were fixed in inner and outer tubes to check the effectiveness of stiffeners in stiffened CFDST columns. These CFDST columns were investigated numerically by using a verified finite-element (FE) model from commercially available software. Behavior of 36 unstiffened, inner-tube stiffened, and outer-tube stiffened CFDST columns (12 each) was studied. The FE results were verified by comparing them with previous test results. The FE analysis study has exhibited an increase in peak load (load-carrying capacity) up to 26% and 15% in outer-tube stiffened CFDST columns compared with unstiffened and inner-tube stiffened CFDST columns, respectively. Also, enhanced ductility has been observed in case of these stiffened CFDST columns.

Experimental study on the axial compressive behaviour of steel reinforced concrete composite columns with stay-in-place ECC jacket

Steel Reinforced Concrete (SRC) column made with high strength materials features excellent load-carrying capacity and energy dissipation capacity, but the compromised ductility issue hinders the widespread application in seismic-prone areas. To overcome this weakness, this paper proposes a novel type of steel-concrete composite column by employing Engineered Cementitious Composites (ECC) as the permanent formwork of conventional SRC column. An experimental program was conducted by subjecting seven stub columns to monotonic axial compressive loading. The test variables in this study include the presence of ECC jacket, the presence of embedded structural steel, stirrup spacing and stirrup configuration. The axial performance were carefully analyzed in terms of load-carrying capacity, initial stiffness, post-peak ductility, damage pattern, as well as the full range load-deformation response. The physical tests confirm the potential of ECC jacket to be used as the permanent formwork of SRC columns as to improve both the construction efficiency and structural performance, and the comparison between the test results and analytical predictions demonstrates the applicability of design equation in EN 1994-1-1 and JGJ 138–2016 to predict the axial capacity of ECC-SRC columns.