Steel-concrete Beams Research Articles

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.

Structural performance of steel-concrete sandwich beams with carbon nanofiber reinforcement

Cementitious materials such as concrete are typically characterised as quasi-brittle with low tensile strength and low strain capacity, which hence affect the long-term durability of the structure. One of the most important issues in designing and maintaining massive concrete structures like offshore and nuclear power plants is concrete cracking, which is due to the low tensile strength of concrete. This can destroy the structural aesthetic and lead to deterioration of the structure.The addition of fibers to concrete has been proven to be a good mean to control its crack behaviour and maintain its ductility in tension. Further, since the discovery of carbon nanotubes/fibers (CNT/CNF), they have been also considered as efficient fibers for construction materials such as concrete.This study presents the structural performance of steel-concrete (SC) elements with a fiber reinforced concrete (FRC) core using both single and hybrid fibers (i.e. consisting of two types of fibers). For this study carbon nanofibers, and steel fibers which are conventionally used in practice, are used for the FRC. Static tests were conducted on eight SC beams with different concrete types. The paper reports on the experimental results obtained from four-point flexural loading of the SC beams. The study shows considerable improvement for both the strength and ductility of the tested specimens. The research laid the groundwork for additional in-depth studies on using carbon nanofiber reinforced concrete within structural members.

Flexural performance of the wood core composite T section beams

A new type of T section beam is proposed in this paper, which is mainly composed of Fiber reinforced polymers (FRP) shell and light wood core. The wood core composite T section beams has the following advantages:the integration of the vacuum infusion technology, can avoid the problem of interface slip of steel-concrete beams in the actual process, and between with the traditional composite beam interface with shear stud connections, few construction procedures, relatively simple, but also further improving the interface properties of T section beams. Through four point bending test, the mechanical properties, failure mode, flexural capacity, stiffness and ductility of T section beam with wood core composite were obtained. The test results show that the T-400-60 specimens compared to the specimens of T-400-40 and T-400-20 specimens, the bearing capacity is increased by 34% and 46%, while the stiffness is increased by 40% and 49% respectively, indicating the flange height type of The wood core composite T section beams on the bearing capacity and stiffness of the great influence.

Nonlinear Longitudinal Shear Distribution in Steel-Concrete Composite Beams

AbstractThis paper describes a fiber-based model proposed for computing the nonlinear longitudinal shear distribution in composite steel-concrete beams. The presented method incorporates the accurate stress-strain relationship with strain softening for concrete and bi-linear constitutive relation for structural steel, both in agreement with Eurocodes, however any one-dimensional constitutive relation can be used. The numerical solution for a simply supported beams loaded with the uniform load, concentrated force and both was presented. The results indicate that the highest value of the shear flow for a beam under an uniform load is at the ends and in the one third of the span length and for the point load, the maximum shear is in the proximity of the concentrated force.

Construction of an algorithm for the selection of rigid stops in steel concrete beams

Calculation of steel-concrete beams is performed with a rigid connection between concrete and a steel strip. This is possible if one installs hard stops that prevent the displacement of the strip with respect to concrete. The force acting on the stop, the number of hard stops and their pitch, are determined through the rotation angles between two adjacent stops. To determine the efforts that act on hard stops, as well as a step, one must first find a rotation angle between two cross-sections within the beams. The rotation angles of cross-sections are derived using a graph-analytical method. Calculation for the deformations of reinforced-concrete and steel-concrete beams is performed based on the reduced rigidities of cross-sections. When one chooses a step for hard stops and their number, it is necessary to strive for the optimization of a structure of steel-concrete beams. Optimization implies that the maximum stresses in a steel strip are equal to its limiting value while the effort acting in stops, and the step of stops, are the same. In order for the efforts in each stop to be the same, one must fabricate a zero section less than the others. In the course of our study we have developed an algorithm for selecting the number, a step of hard stops, and the efforts in them. The choice is based on the assigned characteristics of materials used, the acting external load, the length of a beam, known size of the cross-section of concrete and a steel strip. In this case, efforts in all stops are identical, the step of stops is constant except for the zero section, maximum effort in the steel strip, occurring in the middle of the span, does not exceed the boundary value obtained in the calculation. The reported algorithm makes it possible to calculate hard stops at the assigned value for efforts that act on them under existing load

Numerical and experimental investigations of steel-concrete beams with thin-walled section

Introduction. Conducted is to the evaluation of the stress-strain state of the steel-concrete beams with thin-walled section. In recent times, steel-reinforced concrete structures have become widely used in civilian buildings (beams, slabs, columns). Thin-walled section have not found wide application in steel concrete structures, unlike steel structures. Presents the results of numerical studies of beams consisting of concrete, anchors and steel beams. Two investigating of the location of anchors are given. Numerical investigations are presented of steel-concrete beams with thin-walled section based on numerical studies. Testing procedure and test result are given. Results of calculations, comparison of numerical and experimental studies are presented. Materials and methods. For full-scale experiments, steel I-beams with filling of side cavities with concrete were adopted, screws are used as anchor ties, with varied both the lengths and their location (vertically and obliquely). As steel curved C-shaped steel profiles were used steel profiles from the range of the company “Steel Faces”. ANSYS software package was used for computer modeling. A total of 16 steel concrete beams were considered, for which the results of strength and stiffness evaluation were obtained in ANSYS. Results. The data of the stress-strain state of beams on the basis of computer simulation are obtained. The results are used for the production of field samples. Data of computer simulation are compared with the indicators of field experiments. Conclusions. The stress-strain state of steel-concrete structures was studied on the basis of numerical and experimental data. The proposed calculation method gives good convergence with the experimental data. Anchor connections made from self-tapping screws can be used in studies for modeling in steel-concrete beams structures and other anchor devices, ensuring the joint operation of concrete and steel profiles in structures.

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.

V-shaped shear connector for composite steel-concrete beam

Shear connectors are fundamental components for composite steel-concrete beams. Their function is to bring about a good degree of interaction between the concrete slab and the steel profile. The stud bolt connector is currently the most adopted solution, mainly because of its high productivity and practicability on construction sites. However, there are situations where stud bolts or the appropriate equipment for their application may not be available. Alternative shear connectors can substitute stud bolts. In this article, a new V-shaped shear connector is proposed. It was conceived to confine concrete in a larger frontal contact area and be easy to install and construct. With more contact area, the proposed connector distributes the shear force more uniformly, avoiding high stress concentration compared to the stud bolt option. The V-shaped connector has a higher moment of inertia. It is less flexible than stud bolts and U-connectors under bending. In this research, different V-shaped connectors, with varying thicknesses, are studied experimentally and numerically with push-out tests and FE modeling. The results are compared to standard stud bolts and show that the proposed V-shaped connector may be utilized as an alternative shear connector in composite steel-concrete beams. An equation for the shear resistance prediction of V-connectors is also developed.

Experimental studies on seismic behavior of precast hybrid steel–concrete beam

This study aims to investigate the seismic behavior of precast hybrid steel–concrete beams. Five full-scale beam specimens, including four precast hybrid steel–concrete beams and a conventional precast concrete beam, were tested under cyclic loading. Furthermore, a new connection form was proposed to facilitate the constructability of the steel-to-concrete connection. The main experimental parameters were the steel beam length and the longitudinal reinforcement ratio. In addition, the influence of the reduced beam section of the steel beam on seismic behavior of precast hybrid steel–concrete beams was observed and investigated. Detailed analysis was performed on the basis of the observed failure modes and the relationships obtained from the experimental data, such as hysteretic curves, deformation curves, stiffness degradation curves, energy dissipation capacity, load curvature curves, and strain development curves. Experimental results showed that the failure mode of precast hybrid steel–concrete beams was different from that of precast concrete beams. The precast hybrid steel–concrete beam retained ductility comparable to that of precast concrete beams. Generally, the initial stiffness of precast hybrid steel–concrete beams was smaller than that of precast concrete beams, but the stiffness degradation was more stable. On the basis of measured crack propagation and failure mode, deformation curves, and the development of strain in steel beams and longitudinal reinforcements, the stress between the steel beam and concrete beam can be effectively transmitted to one another by the proposed connection form.

Finite element study of effective width in steel-concrete composite beams under long-term service loads

Abstract In this work, a finite element-based approach is presented to study the effective width variation in non-pre-stressed steel-concrete beams under the serviceability stage, including time dependent effects such as concrete creep, shrinkage and cracking. For this purpose, the viscoelasticity theory in conjunction with a nonlinear cracking monitoring algorithm is used to trace the nonlinear viscoelastic response of the structure along time. The present numerical model is fully three-dimensional and permits the inclusion of partial interaction at the slab-beam interface. A comprehensive study is carried out on the long-term response of a composite girder bridge previously studied by other researches. Then, previous results are revised and extended herein. Potential shortcomings of some standard codes related to the effective width evaluation are also investigated. It is demonstrated that the slab effective width varies sharply along the beam axis in the short-term, while it approaches to the actual slab width in the long-term. For the studied example, the common assumption of using only the middle layer of the reinforced concrete (RC) slab for the effective width calculation is revised with a through-thickness integration procedure. The influence of some creep and shrinkage models as well as the ultimate tensile concrete strain on the effective width response is also assessed. Finally, a simple formula is proposed to evaluate the short-term slab effective width for the studied example.

Effectiveness of Surface Preparation on the Capacity of Plated Reinforced Concrete Beams

One of the most important methods for strengthening and repairing reinforced concrete beams is to use external bonded steel plates, however, the success of this technique depends on the effectiveness of the surface preparation of the steel and concrete beams. The International Concrete Repair Institute (ICRI) recognises ten standard concrete surface profiles (CSP), according to the level of roughness, which ranges from CSP 1 (nearly smooth) to CSP 10 (very rough). Each level of roughness is associated with particular bond strength. The purpose of this investigation is to study the effectiveness of four different levels surface preparation, namely; no surface preparation (NSP), wire brushing (WB), scabbling (SC) and hand chipping (HC), on the capacity of plated reinforced concrete beams.The quality of the surface preparation established was measured based on the flexural performance of the externally strengthened steel-concrete beams. A total of 9, 250 × 450 × 3600 mm reinforced concrete beams were prepared, strengthened with glued steel plates on their soffits, and tested under two-point static loading until failure. The results showed that beams with rougher surface preparation have a high bond strength as compared to smoother surface preparations. The increase in flexural capacity of the roughened beams in Group A ranges from 18% to 32% as compared to the control beam, whilst the increase in flexural capacity of the roughened beams in Group B ranges from 20% to 42%.

Truss-type shear connector for composite steel-concrete beams

Shear connectors are important in composite steel-concrete beams. This work presents a new connector, named truss-type shear connector. This connector is an alternative to replace stud bolt in special situation. The connector’s geometry was conceived aiming at low cost, easy execution, high resistance, and efficiency concerning slipping and uplift. Six specimens were constructed for push-out tests comparing this alternative connector with stud bolts. The behavior of the specimens was investigated for collapse, slipping and uplift. Experimental results were compared against numerical FE simulation showing good agreement and providing a global view of the truss-type shear connector behavior and its viability.

Analysis on natural vibration characteristics of steel-concrete composite truss beam

In order to study the natural vibration characteristics of steel-concrete composite truss beam (SCCTB), the influence of multiple factors such as interface slip, shear deformation and moment of inertia are considered. Afterwards, based on the Hamilton principle the vibration control differential equation and natural boundary conditions of SCCTB are deduced. By solving SCCTB differential equations of vibration control, an analytical calculation method is proposed for analyzing the natural vibration characteristics of SCCTB. The natural frequencies of SCCTBs with different degrees of shear connection and effective lengths are calculated by using the analytical method, and the results are compared against those obtained from ANSYS finite element numerical calculation method. The results show that the analytical method considering the influence factors such as interface slip, shear deformation and moment of inertia are in good agreement with those obtained from ANSYS finite element numerical calculation method. This evidences the correctness of the analytical method and show that the method proposed exhibits improvement over the previously developed theories for the natural vibration characteristics of SCCTB. Finally, based on the analytical method, the influence factors of SCCTB natural vibration characteristics are analyzed. The results indicate that the influence of interface slip stiffness on SCCTB\'s natural frequency is more than 10% and therefore cannot be neglected. Moreover, shear deformation has an effect of more than 35% on SCCTB\'s natural frequency and the effect cannot be ignored either in this case too.

Theoretical and experimental study on deflection of steel-concrete composite truss beams

This paper investigates the deflection of the steel-concrete composite truss beam (SCCTB) at the serviceability limit state. A precise solution for the distributed uplift force of the SCCTB, considering five different loading types, is first derived based on the differential and equilibrium equations. Furthermore, its approximate solution is proposed for practical applications. Subsequently, the shear slip effect corresponding to the shear stiffness of the stub connectors, uplift effect corresponding to the axial stiffness of the stub connectors and shear effect corresponding to the brace deformation of the steel truss are considered in the derivation of deflection. Formulae for estimating the SCCTB deflection are proposed. Moreover, based on the proposed formulae, a practical design method is developed to provide an effective and convenient tool for designers to estimate the SCCTB deflection. Flexure tests are carried out on three SCCTBs. It is observed that the SCCTB stiffness and ultimate load increase with an increase in the shear interaction factor. Finally, the reliability of the practical design method is accurately verified based on the available experimental results.

Bending Resistance of Composite Sections with Nonductile Shear Connectors and Partial Shear Connection

The paper presents the nonlinear section analysis for composite steel‐concrete beams with different degrees of shear connection. The analysis is fiber based, i.e., integration over the cross section is performed numerically, and any uniaxial nonlinear material model can be assigned to the steel and concrete parts of the cross section or to the reinforcement bars. The analysis assumed full interaction between steel and concrete and therefore, is suitable for analysis of composite steel‐concrete beam cross sections with nonductile shear connectors. Its accuracy is verified on few experimental results. The presented section analysis is used in the parameter study in order to evaluate different methods proposed by design codes for determining the bending moment resistance of composite cross sections with nonductile shear connectors and different degrees of shear connection. The following effects are considered: variation of concrete and steel material models, presence of slab reinforcement, and creep of concrete. Special attention is paid on two different constructional methods: propped and unpropped. The weaknesses of the simplified design method in determining bending moment resistance are identified and recommendations for practical design analysis are formulated.

Experimental characterisation of Perfobond shear connectors through a new one-sided push-out test

In steel-concrete composite beams, the perfobond shear connectors (PSCs) are commonly utilised as an alternative to the widely used headed studs, as the latter have limited shear capacity and susceptible to fatigue problems. The structural assessment of the PSCs is typically obtained experimentally, and mainly through a type of destructive test known as push-out test (POT). POT specimen typically consists of an I- steel section attached to two concrete slabs through the connectors under investigation, the slabs are then simultaneously tested by the application of a direct shear force to the steel section until the fracture of the specimen is reached. The shear strength of PSCs can be evaluated from the POT results. However, the weaker of the two concrete slabs tend to fail before the other side, which thus inevitably affects the results. In this paper, an efficient one-sided POT (OSPOT) is used to characterise the behaviour of the PSCs in composite steel-concrete beams. POT and OSPOT specimens are similar, but the shear force in the OSPOT is directly applied to one slab each test. As a part of this study, ten OSPOT have been carried out to investigate the behaviour and the shear resistance of the PSC. The results were compared against POT results from other researchers and the predictions offered by several shear resistance equations. It has been found that the OSPOT results are consistent with the analytical predictions offered by these expressions compared to the previous research using POT. Among the key advantages of the proposed OSPOT procedure: similar to the traditional POT, it is possible to quantify the relationship between applied loads and displacements in the shear connectors, which is the most important information for the structural design of composite steel-concrete beams; it is effectively doubled the number of results for the same research resources; the fabrication of the samples is simplified.

Fire tests on composite steel-concrete beams prestressed with external tendons

This paper presents an experimental study on fire resistance of composite steel-concrete beams prestressed with external tendons. A total of four beams were tested under combined fire load and positive moment. Parameters investigated include load level, prestress level and type of cable strands configuration. Results show that the tested beams without fire protection had fire resistance of 20min to 30min. The fire resistance of composite steel-concrete beams prestressed with external tendons was highly influenced by the stress in the cable strands. The tested beams with bent-up cable strands had more fire resistance than the tested beams with straight cable strands. Prestress level had little influence on failure temperature of the tested beams, but the slack of cable strands induced failure of the test beams at high temperature. Furthermore, a finite element (FE) model was developed and successfully used to predict the fire behavior of the prestressed composite steel-concrete beams.

Experimental research and finite element analysis on the dynamic characteristics of concrete steel bridges with multi-cracks

Complex bridges will inevitably have cracks in operation. Dynamic characteristics with crack structures have been researched central issues. In the past, few researches were conducted from the whole structure of bridges with multi-cracks. In the meanwhile, related experimental research and systematic numerical simulation were lacking. In addition, researches on cracks seldom considered the high-order vibration characteristics of structures with multi-cracks. Aimed at this problem, this paper selected the whole bridge structure which was widely applied in engineering to study dynamic characteristics. For the concrete steel bridge with two cracks, this paper established finite element models for concrete steel beam and bridge with cracks under three different conditions and obtained vibration frequency and three order modes through simulation. Then, this paper analyzed and verified the correctness of numerical simulation result through experiment. Based on the verified model, this paper conducted a systematic analysis and summary, and obtained the following findings: The vibration frequency of concrete steel beams with cracks was obviously affected by cracks. The higher the order was, the greater the impact of cracks on frequency would be and the smaller the impact of cracks on the amplitude of modes would be. With the increased crack depth, the impact on the vibration frequency of concrete steel beams was more obvious. Additionally, crack distance also had some impacts on the dynamic characteristics of concrete steel beams. Numerical simulation model and method in this paper provided foundation and reference for continuing to analyze concrete steel beams with other crack forms or other structural forms. In the meanwhile, the three-dimensional analytical contour in this paper could help engineers to more intuitively understand and valuably apply the change rule of impact of crack depth and position on concrete steel beams.

08.53: Integral analysis of steel concrete beams, Regarding creep of concrete according EC2, versus (AAEMM) of bažant

ABSTRACTThe paper presents analysis of the stress‐strain behaviour due to creep in statically determinate composite steel‐concrete beam according to AAEM method of Bažant in comparison with numerical method. The analysis is based on the results obtained by numerical solution with Volterra integral equations derived for determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time “t” and creep of concrete according EC2 provisions. On the basis of the theory of the viscoelastic body of Arutyunian–Trost‐Bažant it is analysed the migration of stresses from concrete plate to steel beam using two independent Volterra integral equations of the second kind and two independent algebraic equations, during the period of 70 years. The closeness of the results obtained by the two methods is shown with an example from the bridge practice.

EXPERIMENTAL STUDY OF RESTRAINED STEEL-CONCRETE COMPOSITE BEAMS UNDER CYCLIC LOADS

Composite structures are made from steel connected with slab concrete holding together with shear connectors. This facilitates in loading capacity according to AISC and AASHTO standard design. The test on restrained steel-concrete beams under monotonic loading and cyclic loading condition is with the fully composite and the partially composite. The result of this research is that the fully composite is more loading capacity than the partially composite. Moreover, the study also focuses on the deformation capacity ratio between the fully composite and the partially composite under both mentioned conditions. In this aspect, it is found that the deformation capacity of the fully composite is less than the partially composite. From the study, it is suggested that the steel-concrete composite be design for the fully composite because it can hold the highest strength, prevent slipping between steel and slab concrete, and increase the durability.