Steel-concrete Composite Research Articles

Finite beam element with 22 DOF for curved composite box girders considering torsion, distortion, and biaxial slip

Experimental and numerical study on the mechanical performance of curved steel–concrete composite box girders is reported in this research. First, this research establishes a theoretical model for curved composite girders with 11° of freedoms (DOFs) for each node. The DOFs include the longitudinal displacement, transverse displacement, deflection, torsion angle, warping angle, and interface biaxial slip between steel and concrete. Based on the virtual work theorem, the equilibrium function, the stiffness matrix, the node displacement matrix and the external load matrix are proposed for the curved composite girders using the FE spatial discretization. Second, the authors conduct an experimental program on three large-scale curved composite girders with various interface shear connectors and central angles. The comparison between the developed finite beam element, the elaborate FE model and the test results indicates the developed finite beam element has an adequate level of accuracy in predicting the deflection, the torsion angle and the axial strain distribution of test specimens. Third, based on the developed finite beam element model, the effect of initial curvature, number of diaphragms, and the interface connector stiffness on the curved composite girder is examined. The simulation results showed that the initial curvature significantly contributes to the displacement and stress of composite girders. Applying more diaphragms can notably reduce the distortion angle and distortion displacement. The interface shear connector stiffness has a significant influence on the curved composite girder. With the increasing shear connector stiffness, the displacement and stress of curved composite girders decrease notably. Based on the parametric analyses, it is recommended to limit the central angle of simply supported composite girder below 45°, to apply an adequate number of diaphragms, and to design curved composite girders as fully shear connection specimens.

Effects of out-of-plane eccentric axial compression on in-plane hysteretic behavior of SC walls

Steel-concrete composite (SC) walls may be subjected to simultaneous in-plane (IP) and out-of-plane (OOP) loads in some civil and industrial buildings. However, there are few studies and no design guideline for SC walls under such load conditions. In this paper, four SC wall specimens were designed and tested to investigate the effects of OOP loading on IP hysteretic behavior. During the experiment, a constant eccentric axial compressive force was applied to the top of the specimen, which generated an OOP bending moment. The variables considered in the experiments were the eccentric distance and the axial compression ratio. All four specimens demonstrated characteristics of the flexural failure mode. The IP bearing capacity and deformation capacity of the specimens were significantly reduced due to the influence of OOP loading. A nonlinear analysis program based on fiber model method was presented to calculate the IP and OOP bearing capacity under different load combinations. An interaction surface, N-Mx-My, and a simplified formula were developed as a simplistic tool to consider simultaneous IP and OOP bending moment.

Numerical modeling of continuous steel concrete composite girders considering cracking of concrete

In continuous steel concrete composite (SCC) girders, the concrete deck is susceptible to cracking because of the negative bending moment, which leads to the redistribution of forces and increases in deformations. The general practice adopted while designing the continuous SCC girder is to ignore the concrete deck in negative moment region and assume the steel girder to resist the entire negative bending moment, which may lead to an uneconomical design. In this regard, a simplified numerical procedure has been proposed, considering concrete cracking effects by aptly modifying the cross-sectional properties of the concrete deck. For this purpose, two different cross-sectional modifiers have been presented. The proposed procedure also incorporates partial shear connection. The proposed simplified numerical procedure is advantageous in terms of flexibility, generality, and the easiness with which it can be adopted in design offices for routine designs of SCC girders. The experimental results available in the literature used to validate the results of the proposed procedure show good agreement. Further, the effectiveness of the proposed procedure is demonstrated with the help of a parametric study. It is observed that a considerable reduction in the negative moment on the steel girder and reduction in deformations of the SCC girder can be achieved by adopting the proposed procedure. An example is solved to illustrate the proposed procedure in the appendix.

Finite Beam Element for Curved Steel-Concrete Composite Box Beams Considering Time-Dependent Effect.

Curved steel–concrete composite box beams are widely used in urban overpasses and ramp bridges. In contrast to straight composite beams, curved composite box beams exhibit complex mechanical behavior with bending–torsion coupling, including constrained torsion, distortion, and interfacial biaxial slip. The shear-lag effect and curvature variation in the radial direction should be taken into account when the beam is sufficiently wide. Additionally, long-term deflection has been observed in curved composite box beams due to the shrinkage and creep effects of the concrete slab. In this paper, an equilibrium equation for a theoretical model of curved composite box beams is proposed according to the virtual work principle. The finite element method is adopted to obtain the element stiffness matrix and nodal load matrix. The age-adjusted effective modulus method is introduced to address the concrete creep effects. This 26-DOF finite beam element model is able to simulate the constrained torsion, distortion, interfacial biaxial slip, shear lag, and time-dependent effects of curved composite box beams and account for curvature variation in the radial direction. An elaborate finite element model of a typical curved composite box beam is established. The correctness and applicability of the proposed finite beam element model is verified by comparing the results from the proposed beam element model to those from the elaborate finite element model. The proposed beam element model is used to analyze the long-term behavior of curved composite box beams. The analysis shows that significant changes in the displacement, stress and shear-lag coefficient occur in the curved composite beams within the first year of loading, after which the variation tendency becomes gradual. Moreover, increases in the central angle and shear connection stiffness both reduce the change rates of displacement and stress with respect to time.

Comparison of various shear connectors for improved structural performance in CFS concrete composite slabs

Composite sections comprising of wisely selected materials has gained popularity in the construction industry, as it may result in utilizing the advantages of two different materials thus resulting in efficient sections, which will not only reduce the dead loads but also provide economical solutions. Cold-formed steel (CFS) concrete composites have been used extensively in building construction, as the inherent weakness of local buckling in the CFS sections under compressive loading is taken care of by the concrete, which has significant compressive strength. This study presents an experimental investigation performed on full-scale simply supported CFS concrete composite slabs under four-point monotonic loading, with an aim to evaluate the effectiveness of the different shear connectors being adopted. The shear connectors were so adopted that they could provide the least possible interaction (for representing the no-interaction condition), partial-interaction and full-interaction between the steel deck sheet and the concrete slab. The performance of the various shear connectors was assessed in terms of strength, stiffness and ductility ratio. Cracking as well as end slippage were also studied. The test results were compared with a conventional RC slab, in terms of structural performance as well as cost and strength-to-weight ratio. The flexural test strengths were compared with the design strength quantified using the Euro Code. The degree of shear interaction was also investigated. It was found that the CFS concrete composite slabs not only performed better structurally but economically as well, in addition to providing significant strength-to-weight ratio, when compared to a conventional RC slab.

Experimental and theoretical study on longitudinal shear behavior of steel-concrete composite beams

Various studies have been performed on the flexural behavior of steel-concrete composite (SCC) beams. The results showed that composite beams have excellent mechanical performance. However, the research on longitudinal shear behavior of composite beams is still few. This paper focuses on an experimental study of the longitudinal shear behavior of SCC beams, including eight SCC beam specimens and six push-out specimens. The investigated parameters were the transverse reinforcement ratio, shear connection degree, longitudinal single-row and double-row studs and stud diameter. The failure modes, concrete slab strains, steel beam strains, load-deflection and load-slip curves were investigated. In addition, the effect of the test parameters on composite beams was also compared and analyzed. Based on the experimental results and open literature, a formula for calculating the longitudinal shear resistance of SCC beams with longitudinal double-row studs was proposed.

Internal force monitoring and estimation of a long‐span ring beam using long‐gauge strain sensing

AbstractThe internal force information of curved beam members is important evidence for the stress state evaluation and design verification of long‐span space structure during construction. Many structural analysis methods for curved beams have been proposed, but most are used to handle the complex geometric shapes. For stress state evaluation of long‐span steel‐concrete composite (SCC) ring beam, this article presents a method that employs a sectional strain distribution model (SSDM) and a fiber model to estimate the internal force distribution depending on the long‐gauge strain. The SSDM of the ring beam used in the article is based on a mechanical model of two‐dimensional (2‐D) plane bending deformation and a three‐dimensional (3‐D) solid finite element model of curved beam members. The application range of the SSDM is defined by the divided different stress areas of ring beam based on the 3‐D solid finite element model. Combined with the established SSDM and the different stress areas, the axial force and bending moment along the span are then identified separately based on the fiber model. In consideration of field monitoring, the influence of different sensor layout on the establishment of SSDM and the result of internal force identification is discussed. The results of the numerical studies show that the proposed methodology can identify the internal force distribution accurately. Internal force of long‐span ring beam from Jiangsu Grand Theater during construction is also identified through the proposed method by using the strain monitoring data.

Modelling of the flexural stiffness of concrete-steel beams under negative moment

Composite concrete–steel sections are widely used in flooring and decking systems in buildings and bridges. Concrete decks form cracks at negative moment regions and remain uncracked at the positive ones. Finite-element (FE) analyses of beams composed of concrete–steel sections must take the change in the composite section properties into consideration on the basis of the level of cracks in the concrete deck. Commercial FE software packages use linear elastic analysis for calculating the moment and shear force distributions in beams loaded with gravitational loads, with no consideration of the level of cracking in the concrete slab at the negative moment regions. A FE modelling technique for beams with concrete–steel sections was developed by using FE software packages to estimate the internal loadings necessary for the design process. The results from the proposed FE technique were compared with experimental data on continuous and simply supported beams reported by other researchers. It was found that consideration of the concrete deck longitudinal reinforcement in the modelling of a composite section over negative moment regions is necessary for identifying flexural properties, resulting in better accuracy of the structural analysis outcomes. The proposed modelling technique estimated deflection in the tested beams with only 7% error with respect to the experimentally measured deflection.

The main directions taken by road bridges in Germany in the twentieth century

Using the example of German bridge construction and its international connections, this paper describes how the successful refurbishment and strengthening of road bridges benefits from a knowledge of construction history. The author focuses on the knowledge about chains of development for prestressed concrete, steel–concrete composites and steel and divides these into an innovation phase before World War II and a post-war establishment phase. It is shown that the key progress took place in prestressing and in the construction of continuous superstructure cross-sections irrespective of the material. It therefore becomes clear how, in Germany, prestressed concrete bridges came to prevail for common spans and how a related form of construction, cable-stayed bridges, became the favourite for large bridges in the country.

Shear Strengthening of Composite Concrete Steel Plate Girders with Web Openings Using Steel Strips

The study aims to investigate behaviour plus influence on the final load resistance of strengthen girders containing openings in web which were 40% of web height. This paper presents an experimental study of applying of five steel-concrete composite plate girder specimens that were loaded in shear predominantly. Three of those girders were considered as control girders, without web openings, containing circular web holes, and containing square web holes, respectively. Other two girders were strengthen girders. The slab reinforcement, dimensions of girders and compressive strength of concrete slabs were constant. Strengthening was made by using steel rings and strips which were welded to webs of strengthen girders to investigate influence of strengthening plan by steel welding on behaviour and final load strength for these girders. Findings illustrate increasing in final load strength of strengthen girders with circular and square web holes with about 57.38% and 43.75%, respectively in comparing to that for control girders. Moreover, the final shear capacity for the tested girders was also compared with that predicted by von Mises stresses.

Retraction Note to: Potential of soft computing approach for evaluating the factors affecting the capacity of steel–concrete composite beam

Evaluation of the parameters affecting the shear strength and ductility of steel–concrete composite beam is the goal of this study. This study focuses on predicting the future output of beam’s strength and ductility based on relative inputs using a soft computing scheme, extreme learning machine (ELM). Estimation and prediction results of the ELM models were compared with genetic programming (GP) and artificial neural networks (ANNs) models. Referring to the experimental results, as opposed to the GP and ANN methods, the ELM approach enhanced generalization ability and predictive accuracy. Moreover, achieved results indicated that the developed ELM models can be used with confidence for further work on formulating novel model predictive strategy in shear strength and ductility of steel concrete composite. Furthermore, the experimental results indicate that on the whole, the newflanged algorithm creates good generalization presentation. In comparison to the other widely used conventional learning algorithms, the ELM has a much faster learning ability.

Retrofitting seismically damaged steel sections encased concrete composite walls using externally bonded CFRP strips

Concrete shear wall encased with steel sections were widely used in high rise buildings due to its high lateral stiffness, ductility, and energy dissipation capacity. However, to date, little studies were conducted on retrofitting seismically damaged steel-concrete composite (SCC) walls to recover their lateral load resisting capacity. One of the possible retrofitting methods is to use Carbon Fiber Reinforced Polymers (CFRP) strips to retrofit SCC walls after earthquake. However, its efficiency was unclear. For this purpose, four SCC walls were first tested to failure under cyclic lateral loads with subsequently repairmen and re-testing aiming to investigate the efficiency of this retrofitting technique. The load causing the first crack, crack pattern, yield load, and peak load were measured and compared. It was found that replacing buckled rebar and applying proper CFRP repairing scheme could fully recover the seismic resistance of damaged SCC walls. However, purely rely on CFRP repairing schemes without buckled rebar replacement will not achieve full recover of the capacity of the SCC walls. However, specimens retrofitted by CFRP schemes alone can delay the process of strength and stiffness degradation than that of counterpart without retrofitting, which resulted in enhancement of relatively larger drift ratio.

Reliability Assessment of Steel‐Concrete Composite Beams considering Metal Corrosion Effects

Steel‐concrete composite (SCC) beams have been widely used in civil engineering and industrial structures. This kind of structure has some advantages such as fast fabrication time and optimized weight. However, designers are often concerned about the initial reliability, while over time the structural reliability will be reduced, especially due to metal corrosion. The objective of the paper is to assess the structural reliability of corroded SCC beams, in which the input parameters are considered as random variables. The SCC beam has been designed according to Eurocode‐4 (EC‐4), in which input parameters consist of cross‐sectional dimensions of the beam, material properties, and applied loads. The effects of the random input variables on the reliability of structures are evaluated by sensitivity analyses, which are calculated by the global sensitivity analysis using Sobol’s method and Monte Carlo simulation. The developed reliability analysis algorithm in this study is verified with previous studies, highlighting the capability of the used method. Four different corrosion levels, which are pristine, 10‐year, 20‐year, and 50‐year, are considered in the sensitivity analyses of the SCC beam. Finally, a series of first‐order and total‐order Sobol’s indices are obtained for measuring the sensitivity of input parameters with four corrosion levels.

Strain rate effect of steel-concrete composite panel indented by a hemispherical rigid body

This paper presents numerical and theoretical investigations on the strain rate in steel-concrete composite (SC) panels under low-velocity impact of a hemispherical rigid body. Finite element analyses were performed on five specimens with different loading rates. The impact energy was kept constant to eliminate its influence by simultaneously altering the velocity and mass of the projectile. Results show that the strain rate in most parts of the specimens was low and its influence on bearing capacity and energy dissipation was limited in an average sense of space and time. Therefore, the strain rate effect can be ignored for the analyses of global deformation. However, the strain rate effect should be considered in local contact problems. Equations of the local strain and strain rate were theoretically derived.

Numerical study on the deformation behavior of steel concrete composite girders considering partial shear interaction

The present paper focuses on the study of deformation behavior of steel concrete composite (SCC) girders with partial shear interaction. The main objective of this work is to bring out the relative significance of the partial shear interaction with respect to full interaction, which has been addressed with the help of parametric study considering various influencing parameters such as, degree of shear connection, span length, type of loading, distribution of shear stud connectors, geometry of steel girder, yield strength of structural steel and concrete grade. The parametric study has been carried out using a simplified numerical modelling technique with the help of commercially available finite element software SAP2000. The numerical modelling involves simulation of composite action between the concrete deck and the steel girder in the SCC girder, which has been carried out by using various elements such as, beam elements, rigid link elements and spring elements. Further, a comparative study has been carried out to study the accuracy of numerical model with the available analytical models. The results of the numerical model are also compared with the results of the equations given in several national codes to calculate deflections, to study the efficacy of the codal provisions. It is seen that the various aforementioned parameters have considerable influence on the deformations of SCC girders. It is also seen that the change in distribution type of shear stud connectors considerably reduce their number without significantly affecting the deformations of SCC girder.

Shear characterisation of pultruded superstructural FRP-concrete push-outs

In this paper, an investigation aimed at characterising the behaviour of headed shear studs in push-out testing is presented. The study aims to contribute to the limited knowledge of Pultruded Fibre Reinforced Polymer (PFRP)-concrete composites, highlighting the predominant failure mode and the underlying variables relevant for predictive analytical equations. Two phases of experimental push-out tests were carried out on composite slabs comprising of normal density concrete (NWC), and PFRP connected using steel headed studs. Phase one focused on studying the effects of headed shear stud configuration on the load capacity of the composite slabs, adopting 19 mm diameter studs. Phase two of the study was aimed at characterising the behaviour of the composite slab by varying the headed stud diameters. Two push-out test specimens adopted 12 mm diameter studs, and a third specimen within this phase adopted the 16 mm stud diameter. The dominant failure mode was bearing, net tension and shear out failures of the FRP plates. These modes of failure were distinctly different from those prevalent in the conventional steel-concrete composite, which is either stud shank failure or concrete pull out. The test investigation suggested a successive increase in shear capacity with increased stud sizes. Specimen with stud size of 16 mm attained higher shear strength per stud, approximately 29.4% in comparison to those with 12 mm diameter studs. The study observed that PFRP-concrete composites could mobilise between 40 and 50% shear resistances to that of their steel-concrete counterpart’s. However, the intensity of bearing failure increases with increase in stud size, thereby compromising the ductility of shear connection.

Full scale experiments on splitting behaviour of concrete slabs in steel concrete composite beams with shear stud connection

This paper presents the results of 15 push-off tests to determine, with a high degree of precision, the longitudinal splitting characteristics of a concrete slab in a novel steel-concrete composite beam with headed shear stud connectors. A modified test rig was developed, instead of the standard push-off test rigs. Both monotonic and cyclic loadings were considered. The experiments allowed the exploration of several currently unknown effects of various loads on components of steel-concrete composites, such as transverse loading and low-level cyclic loading on shear stud capacity. The results allowed the splitting failure mode to be characterised in unprecedented detail. It was found that for the case of cyclic loading, when many cycles were applied, it did not lead to premature failure of the composite beam, but instead increased the capacity of the beam against longitudinal splitting. This is significant for composite members under variable loading, such as floor supporting beams in car parks. It was also shown that the transverse compression forces across the base of the studs would increase the capacity of the beam against longitudinal splitting. Also studied were the differences and limitations of EuroCode 4 and New Zealand (NZS) standards and their effects on composite beam failure characteristics. It was shown that the presence of anti-splitting reinforcement would result in a gradual loss of load carrying capacity, compared to a sudden loss when not present. Even with sufficient side cover from the stud to the edge of the concrete, following the NZS standard, longitudinal splitting in composite beams continues to be observed.

Structural behavior of reinforced concrete segments of tunnel linings strengthened by a steel-concrete composite

Structural defects of existing segmental tunnel linings call for strengthening techniques. This was the motivation for conducting real-scale bearing-capacity tests and computational analysis of strengthened segments by means of a steel-concrete composite (SCC). Two load cases were considered: (i) a sagging moment, resulting in intrados and extrados fibers in tension and compression, respectively, and, conversely, (ii) a hogging moment. The experimental observation has shown that, for both load cases, the strengthened segments failed in a ductile fashion. In case of sagging moments, the strengthening effect of the SCC is characterized by the fact that the yield moment and the post-cracking stiffness of the strengthened segments with a 40-mm-thick SCC are by 393% and 315%, respectively, larger than those of the unstrengthened segments. As for hogging moments, the strengthening effect of the SCC is considerable, albeit less significant than that for sagging moments. The derived formulae allow for description of the structural behavior of the strengthened segments and for quantification of the tractions at the interface between the steel shell and the concrete. Two main conclusions are drawn from the computational analyses: (i) Concerning the increase of the strengthening effect, in case of a sagging moment, an increase of the thickness of the steel shell is more efficient than that of the new concrete. The converse situation occurs in case of a hogging moment. (ii) For a sagging moment, the interface is in shear-tension, whereas for a hogging moment it is in shear-compression.

Theoretical and Numerical Analyses of an Aluminium-Concrete Composite Beam with Channel Shear Connectors

This paper presents a numerical simulation and a theoretical investigation of an aluminiumconcrete composite (ACC) beam subjected to bending. ACC structures are similar to steel-concrete composite (SCC) structures. However, their girders are made of aluminium instead of steel. The use of ACC structures is limited because of the lack of relevant design rules. Due to this fact the authors suggest applying the theory for SCC structures to ACC structures. In this paper, the methods for calculating the bending resistance and the stiffness of ACC beams were presented. What is more, the results from the theoretical investigation were compared with the results from the laboratory tests conducted by Stonehewer in 1962. The calculated plastic resistance moment of the ACC beam with partial shear connection was 1.2 times lower than the bending resistance from the laboratory test. The calculated stiffness was 1.1 higher than the stiffness from the laboratory test. What is more, the authors of this paper prepared two numerical models of the ACC beam. The analysed models had different types of connection between the aluminium beam and the concrete slab. In the first variant, the aluminium beam was permanently connected with the concrete slab to model full composite action. In the second variant, the aluminium beam and the concrete slab were connected using zero-length wires, the characteristics of which were taken from the laboratory test, to take slip into account. The numerical model with zero-length springs adequately captured the elastic response of the ACC beam from the laboratory test conducted by Stonehewer.

Displacement response analysis of steel-concrete composite panels subjected to impact loadings

Steel-concrete composite (SC) panels consist of two steel faceplates and a concrete core. The past studies have shown that the SC panels are effective against impact loadings. This paper presents a method for evaluating the displacement response of SC panels subjected to impact loadings using the equivalent single-degree-of-freedom (SDOF) model. The resistance and stiffness of the SC panels are theoretically derived and validated to develop an idealized trilinear resistance function model. The validations against the past experimental results show that the proposed model provides a basis for the dynamic response analysis of SC panels and lays a foundation for further design methods.