Behavior Of Beam-columns Research Articles

Experimental study on concrete-filled L-shaped steel tubular columns and beam-columns

Concrete-filled L-shaped steel tube (CFLST) is an efficient structural form for corner columns in high-rise buildings, which avoids column protrusion. This paper presents an experimental and theoretical study on the structural behavior of CFLST columns and beam-columns. A total of nine full-scale specimens (i.e., three stub columns, two slender columns, and four slender beam-columns) was tested under compressive loads and the specimen ends were free to rotate about a geometric axis. Plastic local buckling was observed for the stub columns and the confinement effect was not obvious. Flexural buckling occurred for the slender columns and beam-columns. With the increase in the applied load, the neutral axis shifted to the compressive side of the beam-column. Performance of current design codes, which apply for rectangular CFSTs, on predicting the ultimate capacities of CFLSTs was assessed. The prediction for section capacity was conservative and it was likely caused by the reduction in the design strength of concrete. The buckling curve in design codes for rectangular CFSTs was applicable for CFLST columns whereas the interaction relationship specified in design codes underestimates the ultimate capacities of CFLST beam-columns. Based on fiber element analysis, out-of-plane bending moment was found in the tested CFLST slender members and the values were quantified. A new interaction relationship was proposed for CFLST beam-columns, which exhibited good agreement with experimental and numerical results. Finally, design methods were recommended for CFLST columns and beam-columns.

Out-of-plane behaviour of imperfect beam-column with sinusoidally corrugated web

This paper presents an analytical formula for the second-order normal stresses in flanges of the imperfect I beam-columns with sinusoidal web corrugation. To deduce the analytical expression, the beam is separated into three parts. The flanges are modelled as thin-walled beam-columns and the corrugated web is modelled as a thin equivalent orthotropic plate with uniform thickness. The indispensable elastic critical loads are derived from the total potential strain energy of the imperfect beam-column using an energy method. To assess the accuracy of the proposed analytical formula, full shell finite element models were created in Abaqus software. The result of the benchmark example showed that the derived expression is accurate and applicable for geometrically nonlinear analysis of beam-columns with sinusoidal web corrugation. Based on the proposed analytical expression, the Ayrton-Perry type solutions for corrugated web columns and beams are also presented in this paper.

Simulation of Steel Reinforcement on the Nonlinear Behaviour of Slender Glulam Beam Columns by Using the Newton-Raphson Method

Simulation of Steel Reinforcement on the Nonlinear Behaviour of Slender Glulam Beam Columns by Using the Newton-Raphson Method

Beam-column behavior and design equations for high-strength composite filled tube (CFT) members: Investigating the interaction between section and member slenderness ratio

This paper investigates the influence of the section and member slenderness ratio on the axial-moment interaction behavior for high-strength concrete-filled tube (CFT) members. An extensive parametric study is conducted with the aim of extending the material strength limitations in the AISC 360-22 for composite members and investigating the reduction of strength as the member slenderness increases. A 2D fiber-based model using OpenSees software was developed and calibrated based on experimental studies to conduct an extensive parametric study, which includes; (1) member (global) slenderness; (2) section slenderness; (3) section's aspect ratio; (4) material strength; (5) level of axial loading. The study demonstrates that the unconservative error in the current design equations can be as high as 25 % for high member slenderness, while the conservatism in the high section slenderness can be more than 200 %. The proposed interaction curve and the design equations demonstrate high accuracy in predicting the maximum strength of the CFT members under combined loading conditions for a wide range of parameters, including the conventional strength CFT members. A fundamental insight into behavior is presented along with the results. This paper discusses the potential simplification of these findings into design equations that can be used in everyday practice.

Stability of beam-column by geometrically nonlinear analysis

ABSTRACT Stiffness properties of structural members, such as beam, plate and shell, can change drastically in the presence of axial forces due to geometric effects of the nonlinear strain components. In this paper, the stability behaviour of beam-column is investigated using the governing differential equation and compared with the geometrically nonlinear finite element analysis. The lateral deflection obtained from the theoretical model matches quite accurately with the numerical values for wide range of axial to critical load ratio P/P cr . It is shown that bending stiffness decreases linearly with the axial load. By extending the theory, an expression for the membrane stiffness of the beam-column is presented in this paper. The geometrically nonlinear finite element analysis can capture exactly the parabolic variation of the membrane stiffness as per the derived expression. It increases initially up to P/P cr = 0.35 and decreases rapidly to negligible value near the critical load indicating buckling instability.

Nonlinear analysis of frame structural systems based on closed form solutions of thin beam-columns with multiple strong axial and rotation embedded discontinuities

A new thin beam-column element with capability to model multiple embedded discontinuities is developed, in which the mechanical failure process is simulated, leading to nonlinear analysis of frame structural systems. The physical and mathematical principles are based on a Lagrangian variational formulation of the mechanical behavior of thin beam-columns with multiple strong axial and rotation embedded discontinuities adapted to represent strain localization. These strong embedded discontinuities represent the material failure process as hinges for beams and cracking or crushing for bars. The developed variational formulation is derived from a decomposed continuous incremental plasticity model with hardening, softening and elastoplastic behavior, from which the strong embedded discontinuities, that represent the strain concentration at non-predetermined localization zone, are naturally obtained. The boundary value problem, which is valid throughout the domain of the structural member, is obtained. Closed form solutions for bars and thin beams with multiple strong embedded discontinuities for any boundary condition are obtained by solving the proposed variational formulation. Closed form solutions are particularized to a basic system without rigid-body displacement modes, which naturally leads to a symmetric flexibility matrix and thus a symmetric stiffness matrix of the thin beam-column element with capability to model multiple embedded discontinuities with arbitrary locations. This matrix is more efficient than those developed with the finite element method, since it is naturally condensed, its coefficients are defined values, not in terms of integrals, and any type of loads are modelled. Representative examples of beams and frames validate the capability of the formulated thin beam-column element for modelling damage. In these examples, the load-displacement curves are in agreement with those reported in the literature.

Analytical Study of the Behavior of Steel Beam-Columns with Different Shapes of Web Opening at Different Location

Analytical Study of the Behavior of Steel Beam-Columns with Different Shapes of Web Opening at Different Location

Inelastic Behaviour and Strength of Steel Beam-Columns with Applied Torsion

Abstract: This dissertation presents the outcome of an experimental and theoretical study o f the inelastic behavior and strength of steel beam-columns with applied torsion. Although the international steel design specifications contain interaction relations for biaxially loaded beam-columns, the influence of applied torsion on such members has been completely ignored in the past. A series of hollow square section steel members are tested using an apparatus specially designed to apply torsion in the presence of an axial load and biaxial bending. The theoretical analysis involves formulation of a system of materially nonlinear differential equations and their solution based on a finite integral formulation. The predicted member response agreed quite well with the experiments. A set of new yield limit and strength interaction expressions are then developed which include the influence of applied torsion. In addition, beam-column interaction relations used in Australia, Canada, China, Great Britain, Japan, Russia, the U.S. and Eurocode are modified to account for applied torsion. Finally, this dissertation presents new load-moment-torsion interaction relations for possible adoption in the international steel design specifications.

Structural behaviour of cold-formed steel built-up closed section beam–columns

In order to examine the beam–column behaviour of cold-formed steel (CFS) built-up closed sections, a numerical study was performed and is presented in this paper. The finite element model with careful considerations of material nonlinearity and initial geometric imperfections was established for the thin-walled section components under eccentric compression and verified against the existing experimental results. Then, the calibrated finite element model was adopted to obtain the numerical predictions of additional 280 beam–columns over an extensive scope of sectional geometries and initial loading eccentricities. Underpinned by the newly generated numerical predictions of 280 members and the existing test results of 30 specimens, the design approaches using codified interaction formulae and a bi-linear interaction expression proposed in the recent research for CFS built-up open section beam–columns together with the nominal compressive and flexural resistances determined by direct strength method (DSM) were assessed for thin-walled built-up closed section members under combined loading. Based on the nominal resistances determined by DSM, the interaction formulae in the ANSI/AISC 360 and EN 1993-1-3 as well as the available bi-linear interaction expression were overall unconservative for the design of built-up closed section beam–columns, while the interaction curve specified in the AISI S100 generally offered slightly conservative strength predictions. Furthermore, it was revealed that the interaction relationship in the AS/NZS 4600 and the bi-linear interaction expression modified in this study could provide accurate predictions for the CFS built-up closed section beam–columns, whereas the predictions obtained by the modified bi-linear interaction expression were overall less scattered.

Seismic behaviour of stainless-clad bimetallic steel welded box-section beam-columns

The stainless-clad (SC) bimetallic steel is an advanced high-performance steel with high strength and outstanding corrosion-resistant performance. It is especially competitive in the application of structures with demands of high corrosion resistance. However, the current research on SC bimetallic steels mainly focuses on the material level rather than the structural level, and it is not clear whether the excellent performance of materials can be reflected in the seismic behaviours of members. Thus, cyclic behaviours of SC bimetallic steel members need to be thoroughly investigated to fill the research gap and expand the application fields of this steel in the seismic region. To this end, this paper aims to study the cyclic behaviour of SC bimetallic steel box-section beam-columns subjected to combined constant axial load and low-cycle reciprocating lateral load through full-scale tests and finite element (FE) models. Four specimens were tested, and the influence of the width-to-thickness ratio of component plates was clarified through comparative research on the test processes, buckling details, hysteresis curves, strain curves, energy dissipation and ductility performance. Moreover, a refined FE model adopted single-layered modelling or double-layered modelling was developed respectively; and then, the model validation, the shear stress distribution at the bonding interface and parametric analyses were carried out. Research showed that the SC bimetallic steel beam-columns exhibit good energy dissipation and seismic behaviour under cyclic loadings; the smaller width-to-thickness ratio or axial load ratio could result in the plumper hysteresis curves, more sufficient energy dissipation and superior ductility performance; the ductility performance of SC bimetallic steel column was significantly improved; the ductility-based design approach proposed herein could approximately quantify the ductility performance of SC bimetallic steel box-section column, which could provide a reference for the seismic design.

Experimental and theoretical study on concrete-filled T-shaped steel tubular columns under uniaxial eccentric compression

This paper presents an experimental and theoretical study on concrete-filled T-shape steel tubular (CFTST) beam-columns. Four full-scale slender beam-columns with slenderness ratio of 33.7–39.1 were tested under uniaxial eccentric compressive loads. In addition, three stub columns with the same cross-sections were axially compressed to investigate the confinement effect. Failure mode, axial displacement, lateral deflection, axial strain and hoop strain were obtained to understand the structural behavior of CFTST beam-columns. For beam-columns bended about the symmetric axis, torsion was not observed but a slight rotation of the neutral axis that was no longer parallel to the centroid axis was found by analyzing the experimental results. A fiber element model for CFTST beam-columns was developed and verified for parametrical analysis. The effects of key parameters, such as material properties, cross-section dimensions, loading angle and slenderness ratio, on the behavior of stub and slender beam-columns were investigated. Finally, theoretical models were proposed to estimate the interaction curve and the load-carrying capacity of CFTST beam-columns. The prediction matches well with the experimental results.

In-plane structural response and design of steel I-section beam-columns at elevated temperatures

In this paper, the behaviour and design of steel I-section beam-columns in fire are explored. Finite element models capable of mimicking the behaviour of steel beam-columns in fire are developed. Results from fire experiments on steel I-section beam-columns from the literature are utilised for the validation of the finite element models. Extensive structural performance data are generated on the response of steel I-section beam-columns through numerical simulations, considering different cross-section shapes, elevated temperature levels, member slendernesses and loading conditions. The accuracy and safety of the beam-column design methods provided in the current European structural steel fire design standard EN 1993-1-2 and its upcoming version prEN 1993-1-2 are explored. A new fire design method for steel beam-columns that is compatible with the room temperature beam-column design method provided in the European room temperature structural steel design standard EN 1993-1-1 is put forward. The proposed design rules enable the establishment of a consistency between the beam-column design methods of the European structural steel room temperature and fire design standards (i.e.EN 1993-1-1 and EN 1993-1-2), which is currently lacking. The higher accuracy, safety and reliability of the proposed fire design rules for steel beam-columns relative to those given in EN 1993-1-2 and prEN1993-1-2 are verified.

Artificial neural network and regressed beam-column connection explicit mathematical moment-rotation expressions

Steel flush endplate beam-column connections behavior is commonly described by the moment-rotation, M -φ, relationship, which is characterized by two essential terms; resistant moment, M j, Rd , and initial rotational stiffness , S j, init . A great amount of concerted effort has been invested worldwide to either experimentally or analytically describe these properties due to geometrical and material variations. However, these methods are either costly, laborious, or time-consuming. Therefore, acknowledging the wealth of literature information, this paper formulates a set of practically convenient mathematical M -φ expressions by means of artificial neural network (ANN) and multi-linear regression (MLR) approaches utilizing the MATLAB software. Differing from most existing machine learning variants, the paper offers explicit expressions for maximum moment, M max , and S j, init , which can be characterized through a simplistic insertion of input parameters in terms of beam depth, beam width, thickness of beam flange , thickness of beam web, column depth, column width, endplate depth, endplate thickness, and bolt capacity. The computed M max and S j, init can then be adopted to express the currently defined continuous M -φ relationship. By statistical evaluation, it is witnessed that the mean-absolute-percentage error (MAPE) and correlation coefficient ( R 2 ) of both ANN and MLR methods are of remarkable prediction vitality. Also, ANN outperforms slightly MLR model in the prediction of both M max and S j, init although both approaches agree closely with the source data. Therefore, both approaches are of high reliability in predicting M max and S j, init as well as in characterizing the M -φ relationship of the flush endplate beam-column connections for further engineering analysis and design purposes. • Equation for continual M-φ relation for flush endplate beam-column behavior. • Continuous M-φ relation is produced simply by plugging in connection properties. • M-φ relation is defined only by maximum moment M max & stiffness S j,init . • M max & S j,init are defined by connection geometrical & material expressions. • Proposed ANN & regression models predict statistically well the observed M-φ curve.

Residual behavior of recycled aggregate concrete beam and column after elevated temperatures

This paper presents the results of an experimental study on the residual behavior of reinforced recycled aggregate concrete (RRAC) beam-columns after exposure to elevated temperatures. Two parameters were considered in this test: (a) recycled coarse aggregate (RCA) replacement percentages (i.e. 0, 30, 50, 70 and 100%); (b) high temperatures (i.e. 20, 200, 400, 600, and 800℃). A total of 25 RRAC short columns and 32 RRAC beams were conducted and subjected to different high temperatures for 1 h. After cooling down to ambient temperature, the following basic physical and mechanical properties were then tested and discussed: (a) surface change and mass loss ratio; (b) strength of recycled aggregate concrete (RAC) and steel subjected to elevated temperatures; (c) bearing capacity of beam-columns; (d) load-deformation curve. According to the test results, the law of performance degradation of RRAC beam-columns after exposure to high temperatures is analyzed. Finally, introducing the influence coefficient of RCA replacement percentage and high temperatures, respectively, to correct the calculation formulas of bearing capacity of beam-columns in Chinese Standard, and then the residual bearing capacity of RRAC beam-columns subjected elevated temperatures is calculated according to the modified formulas, the calculated results are in good agreement with the experimental results.

Beam-column joints made of self-compacting concrete containing recycled coarse aggregates and nano-silica

This research focuses on the analysis of beam-column joints prepared using self-compacting concrete (SCC) incorporated with nano-silica (NS) and recycled coarse aggregates (RCA). For this purpose, beam-column joint behaviour of normal concrete, SCC incorporating RCA and NS was examined under static loading condition. Analysis of the experimental results indicates that the performance of the joints made with RCA is comparable with that of normal concrete in terms of cracking and ultimate load-carrying capacity. This study also depicts that compressive strength (CS) of SCC made with 100% RCA is somewhat higher than that of SCC made with normal aggregates. Moreover, enhancement in CS can be obtained with the introduction of NS in SCC containing 100% RCA.

Analysis of uniaxially loaded short round-ended concrete-filled steel tubular beam-columns

Round-ended concrete-filled steel tubular (RCFST) columns exhibit low resistance to running water, strong y-axis bending strength and aesthetic appearance for their use in bridge piers. However, the behavior of RCFST beam-columns under uniaxial loading has not been studied numerically. This paper describes the computational simulation and design of uniaxially compressed short RCFST beam-columns. The nonlinear simulation is based on the numerical fiber-based methodology. The flange local and post-local stability in terms of outward buckling of the flat plate and circular-rectangular concrete confinement are considered in the fiber-based simulation. The simulation procedures for generating the load-strain responses, moment-curvature curves, and nonlinear strength envelopes are described. The computed axial capacity, ultimate bending strength and load-strain performance of short RCFST beam-columns are assessed against the independent experimental results. The statistical results reveal the accuracy of the fiber-based simulation for exploring the compression and bending behavior of short RCFST beam-columns. The parametric analysis is conducted using the fiber-based model to examine the local buckling, bending axis, aspect ratio, and material strength influence on the performance of uniaxially compressed RCFST short beam-columns. The design of eccentrically loaded short beam-columns based on Eurocode 4 provisions is described.

Numerical investigation on cyclic behavior of Q690 high strength steel beam-columns

It has been well-recognized that high strength steels possess worse ductility and deformability compared to normal strength steels, leading to greater risk of low-cycle failure. In addition, high strength steels generally exhibit prominent cyclic softening behavior rather than cyclic hardening behavior. These characteristics should be properly implemented into finite element model to gain exclusive numerical simulation on cyclic behavior of high strength steel beam columns. In this paper, finite element models which not only consider the initial imperfection but also incorporate the ductile fracture behavior as well as cyclic softening behavior were established and used to simulate cyclic loading experiments on high strength steel beam-columns bending about strong axis. The simulation results including hysteretic curves and failure modes both provide good agreement with experimental results, verifying the capability of finite element models proposed. Accordingly, a parametric study was conducted to investigate the effects of axial load ratio, flange width-to-thickness ratio and web height-to-thickness ratio on cyclic behaviors of Q690 high strength steel beam-columns. It can be concluded that the increase in flange width-to-thickness ratio and axial load ratio will change the damage mechanism and consequently present different cyclic deterioration characteristics. Furthermore, the increase in flange and web slenderness and axial load ratio results in decrease in deformability and sectional plasticity development ability.

Behaviour of Beam-Column Subjected to Reversed Lateral Loading

This paper presents an experimental investigation on the behaviour of Concrete Filled Double Skin Tubular (CFDST) column connected to Concrete Filled Steel Tubular (CFST) beam under reversed lateral loading. The CFDST column consists of two concentric cold-formed steel tubes with concrete sandwiched between them and the CFST member consist of cold-formed steel hollow section completely filled with concrete. The specimen in this study consists of a hollow square tube as the outer skin for both CFDST and CFST members. The inner skin of the CFDST column is a circular steel tube and M30 grade concrete having 40% cement replaced with fly ash was filled in between the tubes. The connection between the beams and the columns were provided using through bolts and angle plates. A pair of specimens considered as the control specimens having CFST members for both beam and column were also tested for comparison. All the four specimens were subjected to a constant axial load and reversed lateral loading which simulates the earthquake forces. The seismic characteristics like hysteretic behavior, peak load displacement, ductility, stiffness degradation and energy dissipation of CFDST beam-column were compared with that of the CFST beam-column. The beam-column specimens with CFDST columns exhibited favorable seismic behaviour with reduced self-weight and hence a better choice than CFST columns in regions of seismic risk.

Full slenderness range DSM approach for stainless steel hollow cross-section columns and beam-columns

The behaviour of austenitic, ferritic and duplex stainless steel Rectangular and Square Hollow Section members subjected to compression and combined loading is investigated in this paper. A full slenderness range Direct Strength Method (DSM) approach is proposed based on experimental results and numerical strengths obtained from FE parametric studies. The method accounts for local buckling effects and enhanced material properties are also incorporated for those members stable enough to allow partial yielding of the cross-sections. The proposed method is based on strength curves previously provided for cross-sections although additional limitations have been adopted. The DSM approach for columns is based on existing buckling curves and provides accurate resistance predictions for slender and stocky cross-sections. The proposed DSM approach for beam-columns also improves capacity predictions for stocky and slender cross-sections obtained from the traditional methods for different bending moment distributions. This is attributed to the fact that the beam-column behaviour is directly calculated with a unique strength curve, considering the member and section slendernesses based on the elastic instabilities of the section subjected to the actual stress distribution instead of calculating the compressive and flexural strengths independently and combining these through an interaction equation, as is the traditional uncoupled approach. Finally, a reliability study of the full slenderness range DSM approach is presented to determine resistance factors for the different stainless steel grades columns and beam-columns.

On the behaviour and Eurocode design of T-section columns, beams and beam-columns with slender webs

This paper summarizes the authors' work on the buckling behaviour of T-section beam-columns, and describes an extensive numerical study, as well as comparisons with and discussions of the current Eurocode 3 design rules. The study highlights the significance of defining appropriate buckling reduction factors for the basic local and global torsional and lateral-torsional buckling modes. In the case of bending moments, the significance of the sign of the bending diagram is highlighted. The relevance of the centroid shift anticipated by the Eurocode 3 (EC3) effective section approach to local buckling is discussed, as well as the influence of bending moments – and their sign – on the buckling strength of beam-columns. The importance of classification for the Eurocode design rules for beam-columns is discussed. Finally, a proposal for a simplification and improvement of the EC3 rules is made, followed by an outlook on possible code amendments and needed future research.