Analysis Of Steel-concrete Composite Beams Research Articles

Bending Analysis of Steel-Concrete Composite Beams with Porosity

This study investigated the bending behavior of a simply supported pervious composite beam using the finite element method based on cubic order beam theory. The cubic order axial displacement was assumed and solved using shear stress-free conditions on the extreme surfaces of the composite beam. For simplicity, this study considered one-dimensional axial displacement. Three nodded finite elements were assumed, and each node had eight unknowns. Shear locking was eliminated in the present model by numerical integration of the stiffness matrix. A uniform porosity distribution was implemented in the upper layer of the composite beam. The damping ratio was also considered for the bending analysis. The accuracy of the present model makes it robust for the analysis of composite beams.

Performance of steel-concrete composite beams

ABSTRACT Steel-concrete composite construction picked up its utility because of efficient combination of steel and concrete offering high ductility, strength and stiffness to the structure. Loading action is one of the key parameters to understand the behaviour of a structural element. An attempt has been made in this paper to review the structural performance of steel-concrete composite beams under different loading actions. In addition, the results of nonlinear analysis of steel-concrete composite beams subjected to static loading, using commercial finite element software ANSYS, have been included. Numerical investigations have been performed to understand the behaviour of steel-concrete composite beams under static loading criteria. Numerical models of beams have been created and two-point loading was applied. Load versus mid-span deflection has been plotted. Earlier, validation has been done by comparing the analysis results by authors with the experimental results obtained by previous authors available in literature. The results obtained have shown that dimensions of shear connectors used are having influence on ultimate load capacity of steel-concrete composite beams subjected to static loading.

A step-by-step method for time-dependent analysis of composite beams

Composite beams composed of reinforced concrete slab and steel section joined by mechanical connectors. The concrete slab provides compressive strength, fire resistance, and floor surface, whereas the steel section provides high tensile strength. Steel-concrete composite structures are widely used in frame buildings and bridges due to their economic and structural advantages. In the existing literature, a hybrid analytical-numerical procedure is available for service load analysis of steel-concrete composite beams considering cracking, creep, and shrinkage in concrete. The procedure uses an age-adjusted effective modulus method (AEMM) to model creep and shrinkage effects. The AEMM is computationally efficient however, it compromises accuracy owing to the use of the same aging coefficient for creep and shrinkage. Therefore, in this paper, a step-by-step method (SSM) has been proposed for modeling the creep and shrinkage effects. The method takes into account the progressive concrete cracking with time due to creep and shrinkage. The method is computationally efficient for large composite frame buildings compared to the finite element method since no discretization of the member, along the length and/or across the cross-section, is needed. The method has been validated against experimental results available in the literature. It is observed that the SSM has greater accuracy than the AEMM.

Nonlinear analysis of steel-concrete composite beams with flexible shear connectors

Steel-concrete composite beam is a typical construction which is made up of two dissimilar materials such as steel and concrete. It is used mainly for construction of commercial/residential high-rise buildings and bridges. From last few decades steel-concrete composite structure has been utilised in construction industry due to several advantages such as reduced time and cost of major construction and the avoidance of one of the major issues in present era, space scarcity. Shear connector is a basic component through which steel and concrete components are mechanically connected to transfer the load from concrete slab to steel beam in a conventional type of steel-concrete composite beam. Three dimensional numerical models are created using finite element analysis commercial software package ANSYS15 to study the flexural capacity of beam specimens. Earlier, validation has been done with the test results available in the literature and the proposed model is found to be capable of analysing the specimens with acceptable accuracy. Further numerical models are made to understand the behaviour of steel-concrete composite beam which is made up of two different flexible shear connectors such as stud and channel connector under four-point bending. Degree of shear connection, geometry and layout of shear connectors are taken into account as key parameters for this present numerical study. Normal strength of concrete is considered. The associated results such as ultimate load, mid-span deformation, interfacial slip capacity are presented. Diameter along with length of stud connector is found to influence the load carrying capacity of beams. Ultimate load capacity as well as stiffness of beams is found to enhance when channel section is considered with minimal spacing of connector. Thus finding the required degree of shear connection was also proved to be vital for assessing the performance of steel-concrete composite beams.

Parametric analysis of steel-concrete composite beams prestressed with external tendons

The use of external prestressed tendons in steel-concrete composite beams can improve the performance of beams by strengthening their structure, increasing the ultimate moment resistance, and reducing deflections. The present research aims to investigate the behavior of simply supported steel-concrete composite beams, prestressed with external tendons and under positive bending moment through the development of a parametric study. Firstly, for the beam strength determination, an analytical model is discussed. To predict the ultimate increment in tendon stress Chen and Gu method is used. Additionally, a numerical model that can adequately simulate the behavior of prestressed composite beams is developed using the Abaqus software. The accuracy of this model is validated through comparisons between the obtained results and existing experimental tests. Then, a parametric study is carried out to identify the influence of the following variables: positioning and shape of the tendons, initial prestressing force, and tendon and span lengths. The effect of prestressing at the steel-concrete interface is also investigated. The results of the ultimate moment from the finite element models, are compared by applying the analytical procedure. It can be concluded that all the different tendon configurations considered in the parametric study improved the ultimate moment resistance in the composite beams, but some designs are more efficient than others, increasing the resistance even more, and significantly reducing the deflections and cracking in the concrete under service loads. Regarding the analytical procedure, it was found that the method can adequately estimate the strength capacity of the beams.

Elastic Analysis of Steel-Concrete Composite Beams with Partial Interaction

The paper presents an exact analytical method for the elastic analysis of steel-concrete composite beams with partial interaction. Accepting the basic assumptions of the Newmark analytical model and adopting the axial force in the concrete slab as the main unknown, the second order nonhomogeneous differential equation of the steel-concrete composite element with partial interaction is derived. Further, the complete solutions for simply supported and fixed-ended composite beams subjected to concentrated and uniform loads respectively, are developed. The solution of the homogeneous equation is determined by imposing proper Dirichlet or Neumann boundary conditions depending on the static scheme of the element. The particular solutions are then derived for the considered loading conditions. It is shown that the internal axial force in concrete slab associated to composite beams with partial interaction can be expressed as a fraction of the axial force in concrete slab under full interaction through a non-dimensional function f(aL) which takes into account the connection’s stiffness, the mechanical properties and also the length of the element. Moreover, the solutions are included in a flexibility-based approach to derive the force-displacement relations of the beam element with partial interaction. For the resulted 2-noded beam-column element with 6DOF, the stiffness matrix is derived, showing that the partial composite action may be included at the element level by means of a series of correction factors applied to the standard full-interaction stiffness matrix coefficients. A numerical example is provided to demonstrate the accuracy and performance of the proposed method. Within the elastic range, the predicted load-midspan deflection curve is in very good agreement with both experimental and other numerical results retrieved from international literature. A parametric study was conducted to investigate the influence of the shear connection degree on the beam’s midspan deflection and the results were compared with those computed by using code provisions.

Finite Element Analysis on Steel-Concrete Composite Beams Considering the Bond-Slip Effect on the Interface

In order to accurately simulate the bond-slip performance of steel-concrete composite beams, a trilinear stress-strain relation model was adopted to simulate the mechanical properties of steel. A uniaxial stress-strain relation curve was used to study the nonlinear mechanical behaviors of concrete. The resisting shear effects of studs and concrete in the bonding area were equivalent to nonlinear springs. Based on the energy principle, a calculation method of the interfacial bond stiffness of steel-concrete composite beams was proposed and the interfacial bond-slip constitutive relation of steel-concrete composite beams was given. Based on it, the three-dimensional finite element analysis model of steel-concrete composite beams was established by the finite element analysis software ANSYS, and the numerical simulations of existing push-out tests of composite beams were performed. By comparison, it can be seen that the results from finite element analysis in this paper are close to the experimental ones. It indicated that the finite element analysis model can accurately simulate the bond-slip action of the interface, and this model can be applied to the numerical calculation and analysis of steel-concrete composite beams.

Experimental investigation on composite beams under combined negative bending and torsional moments

In this study, straight composite steel-concrete beams were tested to investigate their mechanical performance under combined negative bending and torsional moments. Two specimens were used in this study, and different ratios between the applied negative bending and torsional moments were induced. Load and deflection relationships, strain development on the steel main girder and shear connectors (stud), and the slip development on the steel-concrete interface were recorded in the test and reported in this paper. The results indicate that increase of torsional moment will result in the significant decrease of the load-carrying capacities (e.g. yield load and ultimate load) of the specimens. It was also found that the normal strains of stud shear connectors in such beams are very large and non-negligible compared to their shear strains. In addition, the maximum interface slip was found occurring at around the 1/4 span, and the support conditions and serious crack of the concrete were considered to be the main causes. The research results obtained in this study can provide references for the design and analysis of steel-concrete composite beams subjected to the combined negative bending and torsional moments.

GBT Analysis of Steel-Concrete Composite Beams: Recent Developments

This paper reports the most recent developments concerning Generalized Beam Theory (GBT) formulations, and corresponding finite element implementations, for steel-concrete composite beams. These formulations are able to perform the following types of analysis: (i) materially nonlinear analysis, to calculate the beam load-displacement response, up to collapse, including steel plasticity, concrete cracking/crushing and shear lag effects, (ii) bifurcation (linear stability) analysis, to obtain local/distortional bifurcation loads and buckling mode shapes of beams subjected to negative (hogging) bending, accounting for shear lag and concrete cracking effects and (iii) long-term service analysis including creep, cracking and arbitrary cross-section deformation (which includes shear lag) effects. The potential (computational efficiency and accuracy) of the proposed GBT-based finite elements is illustrated through several numerical examples. For comparison purposes, results obtained with standard finite strip and shell/brick finite element models are provided.

GBT-based time-dependent analysis of steel-concrete composite beams including shear lag and concrete cracking effects

Abstract In this paper, a GBT-based finite element previously developed by the authors for steel-concrete composite beams, which incorporates cross-section deformation (including shear lag effects) and concrete creep, is enhanced by including concrete cracking effects. In particular, a fixed smeared crack model with two orthogonal cracks is consistently combined with creep using a strain decomposition approach. As in the previous finite element, creep is modelled using a linear visco-elastic law and a Dirichlet series expansion of the creep function. A set of illustrative numerical examples is presented, to show the capabilities of the proposed element. For comparison purposes, shell finite element model results are provided. It is demonstrated that the proposed element makes it possible to obtain very accurate results with a relatively small number of cross-section deformation modes (cross-section DOFs) and finite elements, thus leading to significant computational savings with respect to shell element models.

Optimized dimensioning of steel-concrete composite beams

Abstract The steel-concrete composite sections are often used in civil building in Brazil and around the world. The connection of the steel profile and the concrete slab increases the performance of the composite structural element due to the use of the advantages of each material. In this article, a bar element is used with an interface element for nonlinear analysis of steel-concrete composite beams with partial interaction. The objective is to develop an algorithm that uses this analysis tool to design steel-concrete composite beams looking for project optimized in terms of material costs. Defined spans, supports, ultimate and service load, an optimization algorithm is used to define the dimensions of the rectangular cross section of the concrete slab, I-shaped steel profile, and the reinforcement bars of the concrete slab, so that the quantity of these materials are the minimum to ensure structural safety, considering the ultimate and service limit states. The design constraints are obtained from building code requirements for concrete, steel and composite structures. The objective function is defined as the cost per unit length of the composite beam, obtained from the unit cost of each material, steel, concrete and reinforcement. In the optimization process, the iterative method sequential linear programming is used, in which the nonlinear problem is approximated by a sequence of linear problems, which has its optimum point defined step by step by the Simplex method. Examples of composite beams with ultimate loads defined in the literature were used to validate the implementations. Other examples were analyzed, being evaluated at each iteration the restrictions and objective function to verify the efficiency of the algorithm.

Beam-tendon finite elements for post-tensioned steel-concrete composite beams with partial interaction

Although prestressing is a technique usually linked to reinforced concrete structures, composite steel-concrete beams may improve their mechanical behaviour through post-tensioning tendons. A particular feature of composite beams is the possibility of slip or partial interaction between the components as a result of the shear connection flexibility. This paper describes the development, implementation and test of a one-dimensional finite element formulation for the nonlinear analysis of steel-concrete composite beams prestressed by external tendons, fixed at discrete points along the steel component, taking into account the partial interaction between steel and concrete. Physical and geometrical nonlinearities are considered and a consistent derivation of the tangent stiffness matrix for the tendon is introduced. A recently developed procedure for state determination after prestressing operation is adapted for partially connected composite beams prestressed by external tendons. The accuracy and robustness of the finite element formulation is assessed by means of the comparison with a comprehensive series of experimental results.

A sinus shear deformation model for static analysis of composite steel-concrete beams and twin-girder decks including shear lag and interfacial slip effects

A beam model is developed for the static analysis of composite steel-concrete beams and twin-girder decks which takes into account the effects of shear lag phenomenon as well as the interfacial slip between the concrete slab and steel joists. A sinus distribution is considered for the axial displacements of the concrete slab and steel joists. This kinematic represents the transverse shear strain in the concrete slab and steel joists using a cosine function. The considered kinematic satisfies the boundary conditions of transverse shear stress on the top and bottom surfaces and does not need any shear correction factor. The shear lag effects are introduced by prescribing the warping shape of the slab cross-section and taking its intensity as axial unknowns. A conforming three-nodded 25-dof beam element is derived for numerical simulations. The presented model has been validated by comparing the obtained results with elasticity solutions, 3D finite element results and other analytical and numerical models available in the open literature.

Influence of Shear Connection Distributions on the Behaviour of Continuous Steel-concrete Composite Beams

Background:In this work the behaviour of continuous steel-concrete composite beams with different shear connection distributions obtained from two design methods,i.e. Eurocode 4 and a proposed alternative approach, is analysed.Objective:For this purpose a finite element model specifically developed for the nonlinear analysis of steel-concrete composite beams is adopted. This finite element model includes material nonlinearity of slab concrete, reinforcement steel, beam steel as well as slab-beam nonlinear partial interaction due to the deformable shear connection. The inclusion of the partial interaction in the composite beam model provides information on the slab-beam interface slip and shear force and enables to model the failure of the shear connectors.Results and Conclusion:In this way it is possible to analyse and quantify the effect of shear connector distributions on the global and local response of continuous steel-concrete composite beams, both under service load levels and at collapse. Particular attention is focused on the ductility requirements on the shear connectors when varying the connection design approach and distribution.

Practical nonlinear inelastic analysis method of composite steel-concrete beams with partial composite action

This paper presents an efficient computer method for nonlinear inelastic analysis of composite steel-concrete beams with partial composite action. The proposed formulation is intended to model the combined effects of partial composite action and distributed plasticity using only one 2-noded beam-column element per structural member. Based on elasto-plastic cross-sectional analyses the behaviour model is able to take into account the effects of partial composite action between the concrete slab and the steel beam. Gradual yielding throughout the cross-section is described through basic equilibrium, compatibility, material and shear connection nonlinear constitutive equations. Tangent flexural and axial rigidity of the cross-section are derived and then using the flexibility approach the elasto-plastic tangent stiffness matrix and equivalent nodal loads vector of the beam-column element including the shear deformability of the partially connected composite beam has been developed. The proposed nonlinear analysis formulation has been implemented in a general nonlinear static purpose computer program, NEFCAD. Advanced finite element simulations have been conducted by using the specialized software for nonlinear analysis of structures, ABAQUS. Several computational examples are given to validate the accuracy and efficiency of the proposed method by comparing the results predicted by NEFCAD with those given by the ABAQUS software and other results retrieved from the open literature.

Reduced stiffness of composite beams considering slip and shear deformation of steel

In this paper, a theory is developed for analysis of steel-concrete composite beams with interfacial slip and shear deformation in steel considered. Closed-form solutions are derived for simply supported composite beam under uniform and mid-span concentrated load respectively. Examples are given to compute various quantities of beams. Comparing the results calculated by closed-form solutions with those by ANSYS, good agreements are found. Finally, an explicit formula for the equivalent bending stiffness of the composite beams is found by which the deflections of the composite beams can be calculated as if they were common Bernoulli beams.

Analysis of composite steel-concrete beams using a refined high-order beam theory

A finite element model is presented for the analysis of composite steel-concrete beams based on a refined high-order theory. The employed theory satisfies all the kinematic and stress continuity conditions at the layer interfaces and considers effects of the transverse normal stress and transverse flexibility. The global displacement components, described by polynomial or combinations of polynomial and exponential expressions, are superposed on local ones chosen based on the layerwise or discrete-layer concepts. The present finite model does not need the incorporating any shear correction factor. Moreover, in the present C¹-continuous finite element model, the number of unknowns is independent of the number of layers. The proposed finite element model is validated by comparing the present results with those obtained from the three-dimensional (3D) finite element analysis. In addition to correctly predicting the distribution of all stress components of the composite steel-concrete beams, the proposed finite element model is computationally economic.

Time dependent finite element analysis of steel-concrete composite beams considering partial interaction

A finite element computer code for short-term analysis of steel-concrete composite structures is extended to study long-term effects under service loads, in the present work. Long-term effects are important in engineering design because they influence stress and strain distribution of the structural system and therefore contribute to the increment of deflections in these structures. For creep analysis, a rheological model based on a Kelvin chain, with elements placed in series, was employed. The parameters of the Kelvin chain were obtained using Dirichlet series. Creep and shrinkage models, proposed by the CEB FIP 90, were used. The shear-lag phenomenon that takes place at the concrete slab is usually neglected or not properly taken into account in the formulation of beam-column finite elements. Therefore, in this work, a three-dimensional numerical model based on the assemblage of shell finite elements for representing the steel beam and the concrete slab is used. Stud shear connectors are represented for special beam-column elements to simulate the partial interaction at the slab-beam interface. The two-dimensional representation of the concrete slab permits to capture the non-uniform shear stress distribution in the horizontal plane of the slab due to shear-lag phenomenon. The model is validated with experimental results of two full-scale continuous composite beams previously studied by other authors. Results are given in terms of displacements, bending moments and cracking patterns in order to shown the influence of long-term effects in the structural response and also the potentiality of the present numerical code.

Analysis of Composite Steel-concrete Beams Exposed to Fire using OpenSees

OpenSees is an open-source object-oriented software framework developed at UC Berekeley. The OpenSees framework has been recently extended to deal with structural behaviour under fire conditions. This paper summaries the key work done for this extension and focuses on the validation and application of the developed OpenSees to study the behaviour of composite steel-concrete beams under fire conditions. The performance of the developed OpenSees are verified by four mechanical tests and two fire tests on simply supported composite beams. A parametric study is carried out using OpenSees to study the influence of boundary condition as well as composite effect of slab on the behavior of composite beams exposed to fire. The stress and strain along the beam section is output and compared with yield stress limit at elevated temperature to explain these influences in detail. The results show that the stress distribution in the web of the steel beam is more complex due to the support effects.

Dynamic stiffness analysis of steel-concrete composite beams

An exact dynamic stiffness method is introduced for investigating the free vibration characteristics of the steel-concrete composite beams consisting of a reinforced concrete slab and a steel beam which are connected by using the stud connectors. The elementary beam theory is used to define the dynamic behaviors of the two beams and the relative transverse deformation of the connectors is included in the formulation. The dynamic stiffness matrix is formulated from the exact analytical solutions of the governing differential equations of the composite beams in undamped free vibration. The application of the derived dynamic stiffness matrix is illustrated to predict the natural frequencies and mode shapes of the steel-concrete composite beams with seven boundary conditions. The present results are compared to the available solutions in the literature whenever possible.