Steel-concrete Composite Elements Research Articles

A simplified method for thermal buckling verification in steel–concrete composite elements

This paper delivers a comprehensive analysis of the thermomechanical behavior of steel–concrete (SC) composite elements under elevated temperatures, up to 200 °C, as these can be encountered in accidental scenarios within nuclear power plant operations. The focus lies on the thermal buckling of external thin steel plates. We undertake an integrated approach, combining an experimental campaign and numerical simulations, to investigate thermal buckling phenomena. Using these findings, along with principles from thermoelasticity and thin plate theory, we establish an analytical model to guide preliminary SC element design. The efficacy of this model is ascertained through rigorous comparisons with experimental and numerical results. The paper concludes by demonstrating the model’s practical utility for thermal buckling verification through a relevant case study.

Analysis of Steel–Concrete Composite Elements Considering the Branson Equation for Cracking Simulation

Analysis of Steel–Concrete Composite Elements Considering the Branson Equation for Cracking Simulation

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.

Analysing the Confinement Effect in Hollow Core Steel-Concrete Composite Columns under Axial Compression.

Spun concrete technology allows manufacturing the reinforced concrete poles, piles, and columns with a circular hollow core. This concreting method ensures higher concrete density and strength than the traditional vibration technique and self-compacting concrete. This technology defines an attractive alternative for producing steel-concrete composite elements, allowing efficient utilisation of the materials due to the confinement effect. This study experimentally investigates the material behaviour of the composite columns subjected to axial compression. The experimental results support the above inference—the test outcomes demonstrate the 1.2–2.1 times increase of the compressive strength of the centrifugal concrete regarding the vibrated counterpart; the experimental resistance of the composite columns 1.25 times exceeds the theoretical load-bearing capacity. The proposed mechanical-geometrical parameter can help to quantify the composite efficiency. The parametric analysis employs the finite element model verified using the test results. It demonstrates a negligible bond model effect on the deformation prediction outcomes, indirectly indicating the steel shell confinement effect and confirming the literature results.

Experimental and numerical investigations of aluminium-timber composite beams with bolted connections

This paper presents an investigation of aluminium-timber composite (ATC) beams subjected to bending. In the proposed ATC beam, a timber slab was connected to an aluminium beam using bolts. ATC beams are a relatively new civil engineering solution and they are still being developed. The authors conducted push-out tests of the bolted connections and bending tests of the ATC beams. The slip moduli k0.4 and k0.6, and the load-carrying capacity of the connection were determined experimentally. Furthermore, the short-term behaviour, load carrying-capacity, mode of failure, load-deflection and load-slip response of the ATC beams with bolted connections were investigated. What is more, the authors used a calculation procedure for steel-concrete composite elements to calculate the load-carrying capacity of the ATC beams. The results from the analytical estimations were compared with the results from the laboratory tests. In addition, two non-linear finite element models of the tested composite beam were developed and verified against the experimental results. In the three-dimensional finite element model, laminated veneer lumber was described as an elastic-perfectly plastic material, and, as a consequence, this model did not need many input parameters. In the two-dimensional finite element model, laminated veneer lumber was described as an orthotropic material and its failure was captured using the Hashin damage model. It was an advanced model which needed many input parameters. The numerical results were similar to the experimental results.

Theoretical Study on Steel Reinforced Concrete Hybrid Walls with Centered and Staggered Openings

Buildings placed in seismic areas are designed to simultaneously ensure strength, ductility and stiffness during earthquakes. In most cases the lateral resisting system is composed by shear walls. Lately for mid and high rise buildings the solution to use steel reinforced concrete shear walls, called hybrid walls, has been used. In most cases, the shear walls provided to limit the lateral displacement of the buildings, need to have openings due to architectural requirements. The existing theoretical and experimental studies presented in the literature refer to the behavior of solid/plain walls and a lack of information was identified for hybrid walls with openings. A theoretical and experimental program was developed at Politehnica University Timisoara, Romania with the aim to study the behavior of hybrid walls with centered and staggered openings. The current paper presents the results of nonlinear finite element analyses using ATENA package performed in order to assess the structural capabilities of the proposed experimental specimens with openings. Using the results obtained in one previous experimental program, consisting in tests on 1:3 scale steel-concrete composite elements, the paper presents a comparative study regarding the behavior of hybrid walls with openings versus solid walls. The study is focused on nonlinear behavior of elements with key parameters being evaluated, i.e. maximum load, deformation capacity and stiffens degradation.

Seismic Behaviour of Composite Steel Fibre Reinforced Concrete Shear Walls

In this paper is presented an experimental study conducted at the “Politehnica” University of Timisoara, Romania. This study provides results from a comprehensive experimental investigation on the behaviour of composite steel fibre reinforced concrete shear walls (CSFRCW) with partially or totally encased profiles. Two experimental composite steel fibre reinforced concrete walls (CSFRCW) and, as a reference specimen, a typical reinforced concrete shear wall (RCW), (without structural reinforcement), were fabricated and tested under constant vertical load and quasi-static reversed cyclic lateral loads, in displacement control. The tests were performed until failure. The tested specimens were designed as 1:3 scale steel-concrete composite elements, representing a three storeys and one bay element from the base of a lateral resisting system made by shear walls. Configuration/arrangement of steel profiles in cross section were varied within the specimens. The main objective of this research consisted in identifying innovative solutions for composite steel-concrete shear walls with enhanced performance, as steel fibre reinforced concrete which was used in order to replace traditional reinforced concrete. A first conclusion was that replacing traditional reinforcement with steel fibre changes the failure mode of the elements, as from a flexural mode, in case of element RCW, to a shear failure mode for CSFRCW. The maximum lateral force had almost similar values but test results indicated an improvement in cracking response, and a decrease in ductility. The addition of steel fibres in the concrete mixture can lead to an increase of the initial cracking force, and can change the sudden opening of a crack in a more stable process.

Modeling of Steel-Concrete Composite Elements under In-Plane and Out-of-Plane Loads

AbstractA nonlinear analysis procedure for steel-concrete (SC) composite structures is presented. The procedure uses smeared crack concrete constitutive modeling done on the basis of the disturbed stress field model and supplemental material models that are used to incorporate response contributions of the steel faceplates comprising SC composite elements. The procedure is implemented within the framework of a thick-shell finite-element analysis program and is verified using experimental data pertaining to SC composite structural elements subjected to exclusively in-plane or exclusively out-of-plane (i.e., through-thickness) loading conditions. Lastly, the shell structure analysis program is used to numerically investigate the performance of SC composite elements subjected to combined in-plane and out-of-plane shear forces, an area directly relevant to SC infrastructure applications, yet one that is limited in the existing database of literature.

Cracking in Concrete near Joints in Steelconcrete Composite Slab / Zarysowanie Płyty Żelbetowej W Strefie Przywęzłowej Stropu Zespolonego

Abstract In this paper results of the experimental tests of four full-scale composite steel-concrete elements are reported. In the steel-concrete composite elements, a steel beam was connected with a slab cast on profiled sheeting, by shear studs. The end-plates were (the thickness of 8 mm, 10 mm and 12 mm) thinner than in ordinary design. Joints between the column and the beams have been designed as semi-rigid, i.e. the deformations of endplates affect the distribution of forces in the adjacent parts of the slab. The paper presents the theory of cracking in reinforced concrete and steel-concrete composite members (according to the codes), view of crack pattern on the surface of the slabs and a comparison of the tests results and the code calculations. It was observed, that some factors influencing on crack widths are not taken in Eurocode 4 (which is based on Eurocode 2 with taking into account the phenomenon called „tension stiffening”).

Experimental testing of wood‐concrete and steel‐concrete composite elements in comparison with numerical testing

AbstractThe paper presents the results of experimental tests with a numerical comparison of some typical composite element systems. Two different kinds of elements were tested: composite steel‐concrete and composite wood‐concrete elements. Deflections at midspan under monotonously increasing static load on simply supported beams were measured. The affects of different types of composite connections on the results were researched. In numerical tests the structure was modeled with two‐dimensional plane elements. The composite surface was modeled with two‐dimensional contact (interface) elements for the continuous connection simulation and modified beam elements for the discrete connection simulation. The applied material models include the most important nonlinear effects of concrete, steel and wood behavior, as well as the nonlinear behavior of the composite surface at the connection. The achieved results of the developed numerical model were compared with the results obtained through the experimental test.

An experimental study on channel type shear connectors

This paper describes an experimental study on European channel shear connectors. While shear studs are widely used in steel–concrete composite elements, the channel connectors are also gaining popularity due to their certain advantages. The channel connectors do not require special equipment and standard welding procedures are adequate for attachment purposes. In addition, this type of connector offers higher amounts of shear resistance due to its high contact area with surrounding concrete. Although first studies date back to 1950s, little work has been done in the past to investigate their behavior. Majority of the work done to date was on channel connectors used in North America with a very limited parameter range. An experimental study consisting of 15 push-out tests was carried out to investigate the behavior of European type channel connectors with various heights and lengths. The ultimate resistance of the connectors obtained from experiments was compared against those predicted by North American steel design specifications. It was observed that the equations presented in American and Canadian specifications are too conservative. Based on a model that represents the typical failure mechanism in push-out tests, a new equation was developed for the ultimate resistance of channel shear connectors. It is shown that the developed equation is capable of predicting the ultimate resistance of channel connectors with reasonable accuracy.

Nonlinear behavior of composite shear walls with vertical steel encased profiles

Research on seismic engineering of buildings using composite steel–concrete structural systems has increased in the past decade. One horizontal resisting system for buildings, placed in seismic areas, is the composite steel–concrete structural shear wall with steel encased profiles (CSRCW). The benefits of this structural system, relative to more common systems, include the performance characteristics when subjected to service or ultimate loads. The present paper summarizes the experimental results of recent research made on six experimental steel–concrete composite elements 1:3 scale, tested in laboratory under cyclic lateral loads. The experimental elements differ by the arrangement of the steel shapes embedded in the cross section of the wall and by the cross section type of the steel encased profiles. All specimens were tested under constant vertical load and cyclically increasing horizontal (lateral) loads. The tests were performed until failure. Using the recorded data during the tests, the following parameters are presented and discussed: maximum load capacity, stress and strain distribution in structural components (reinforcements, structural steel and on concrete surface), interstory drifts, cracking patterns, deformation and degradation capacity.

Theoretical and experimental study on composite steel–concrete shear walls with vertical steel encased profiles

The present work describes the theoretical study and the experimental tests on composite steel–concrete shear walls with steel encased profiles (CSRCW), performed at Politehnica University of Timişoara, Romania. The composite steel–concrete structural shear walls with steel encased profiles can be used as horizontal resisting systems for buildings that require considerable large horizontal load capacity. The study consists in numerical analysis and tests on 1:3 scale experimental steel–concrete composite elements. The experimental elements differ by the arrangement of the steel shapes embedded in the cross section of the wall and by the cross section type of the steel encased element. Headed steel studs are provided to ensure the connection between the steel profiles and the concrete. The aim of this study is to analyze the nonlinear behavior of elements, focused on the connection between the steel profiles and the concrete respectively, to compare the behavior of shear walls with different steel shape encased profiles with typical reinforced concrete shear walls. Using the tests performed until failure, the maximum load, the deformation capacity and the dissipated energy were evaluated.

A steel-concrete composite beam element with material nonlinearities and partial shear interaction

This paper presents the formulation of a novel force-based 1D steel-concrete composite element that captures material nonlinearities and partial shear interaction between the steel profile and the reinforced concrete slab. By decomposing the material total strain into its elastic and inelastic components, a total secant solution strategy based on a direct iterative scheme is introduced and the corresponding solution strategy is outlined. A composite Simpson integration scheme, together with piecewise interpolation of the slip strain along the element axis, is employed to calculate the slip forces along the element axis consistently. The accuracy and efficiency of the formulation are verified by some numerical examples reported elsewhere in the literature, and it is shown that the formulation with just one element can lead to virtually closed form analytical results as long as the integrals in the formulation are calculated accurately.

Behavior of Composite Steel-Concrete Girders in Fire Condition

Fires have a highly destructive effect on steel structures. Steel-concrete composite elements have better fire resistance than bare steel, but the composite behavior differs a lot in fire than at normal conditions. This paper studies the flexural behavior of steel-concrete composite simply supported girders in fire condition. A three dimensional nonlinear thermalstructural finite element model has been established using COSMOSM software package to evaluate both girder structural and thermal responses in fire condition. Temperature distribution, mid-span deflection, and stresses in both steel beam and concrete slab have been introduced as functions of time. Results of the finite element model have been verified against experimental work and analytical models found in the available literature. The proposed model proved an accepted correlation with the available experimental work. A parametric study based on the outputs of this model has been performed to study effects of variations in various structural parameters on the behavior of composite girders. Practical conclusions about fire endurance, recommended load ratios, and best composite configurations have been extracted.

FRP strengthening of steel and steel-concrete composite structures: an analytical approach

A recent technique for strengthening steel and steel-concrete composite structures by the use of externally bonded Fiber Reinforced Polymer (FRP) sheets, to increase the flexural capacity of the structural element, is described. Several researches developed FRP strengthening of reinforced concrete and masonry structures, but few experimental studies about steel and steel-concrete composite elements are available. Some examples of guidelines for the design and construction of externally bonded FRP systems for strengthening existing metal structures are available, but the method used to predict the flexural behaviour of FRP strengthened elements is usually based on the hypothesis of elastic behaviour of materials and FRP laminate is mainly considered only under the tensile flange. In this paper, an analytical procedure to predict the flexural behaviour of FRP strengthened steel and steel-concrete composite elements, based on cross-sectional behaviour and taking into account the non-linear behaviour of the materials with any configuration of FRP reinforcement, is given. Analytical predictions are compared with some experimental results available in the literature on the flexural behaviour of FRP strengthened steel and steel-concrete composite elements, showing good agreement of the results, even in the non-linear phase, until failure.

Trends in Steel-Concrete Composite Bridges in Japan

Bridges in Japan are exposed to extreme natural forces in the form of earthquakes, typhoons, floods, tidal and wave actions, ground subsidence and landslides, in addition to heavy vehicle loads. The use of steel-concrete composite elements is widespread in Japanese bridges today. Numerous new types of steel-concrete composite bridge structures are being investigated and developed in order to benefit from the structural integrity and performance, ductility and economy of construction offered by steel-concrete composite bridge decks and piers. This paper presents the steel-concrete composite bridge trends in Japan, focusing mainly on composite girders, slabs and columns.