Analytical and Numerical Investigation of Adhesive-Bonded T-Shaped Steel–Concrete Composite Beams for Enhanced Interfacial Performance in Civil Engineering Structures

This work deals with the behavior of structural continuous composite steel-concrete beams. In the present study, an experimental work has been done by casting and testing two simply supported composite beams, (with and without steel fibers) and two continuous composite beams (with and without steel fibers) up to failure to examine its behavior under static loads. The steel fiber volumetric percentage was 0.5 %. Also, cubic and cylindrical specimens have been cast and tested to determine the concrete compressive and tensile strengths. A high range water reducing admixture (HRWRA) and silica fume (SF) have been used as additives to enhance the fiber concrete properties. So, several trial mixes have been cast and tested to determine the better ratio of these mixtures with respect to the concrete mechanical properties. In the present research, available experimental tests on composite steel-concrete beams are theoretically analyzed using the finite element technique based on one dimensional model. The adopted one dimensional model is able to simulate the overall flexural behavior of composite beams, this covers; load-deflection behavior, longitudinal slip at the steel-concrete interface, and distribution of shear studs. Comparison between the experimental results (for deflection and loads of failure) with those obtained from the proposed finite element model indicates acceptable agreement. It is found that the difference in deflection value between experimental results and theoretical results for no-fiber simply supported composite beam reach 11%, and at 0.5 % steel fibers percentage reach 13 %. While in the continuous composite beam for plain concrete the difference in results may be 9 %, and at 0.5 % steel fibers percentage may be 12 %.

Steel-concrete composite beams with shear studs providing composite action between the concrete slabs and steel beams are widely used in modern steel-framed building construction. Three-dimensional finite element modelling has been a viable option for investigating the fire behaviour of composite beams. Although many finite element models are available in the open literature, most of them are simplified models verified by limited test data. Meanwhile, early test data often did not have all the required information for finite element simulation, and some assumptions need to be made. But more detailed test data are now available in the open literature for steel-concrete composite beams, which can be used to develop a generalised finite element model. In addition, National Institute of Standards and Technology has proposed new stress-strain models for steels at elevated temperatures, which can be compared with the more widely adopted Eurocode 4 steel material models in simulating composite beams. Accordingly, this paper selected 22 specimens, including two reinforced concrete slabs, 12 composite beams with reinforced concrete slabs, two composite slabs with profiled steel sheeting, two steel-concrete composite push test specimens with profiled steel sheeting, and four composite beams with profiled steel sheeting, from nine references to verify the developed finite element model. The proposed finite element model can capture different failure modes of composite beams, such as steel yielding/local buckling, concrete cracking/crushing, debonding of profiled steel sheeting, and stud fracture, which is crucial to comprehend the composite beam behaviour at elevated temperatures.

Lateral Distortional Buckling (LDB) is a mode of instability in Steel-Concrete Composite (SCC) beams that is yet to be fully understood by the structural engineering research and design community. This work investigated numerical methods to understand the LDB behavior of SCC beams under negative moments that exhibit nonlinear behavior. Focus of the study was to develop and validate 3-Dimensional finite element (FE) models which capture the LDB behavior of SCC beams precisely. Detailed 3-Dimensional FE models of the SCC beams were developed using ABAQUS. For modeling concrete, a nonlinear damage plasticity model was considered. A quad-linear curve was used to describe the stress-stain relationship for the steel beam. The stress-stain relationship for the rebar was described using a bi-linear curve while an elastic perfectly plastic model was assigned to the headed stud shear connectors. Steel hardening behavior was simulated using an isotropic hardening model. The interaction between the concrete slab, steel beam, and studs was described using appropriate interface elements combined under suitable constraints. The FE model’s accuracy was validated by results obtained from previous experiments found in literature together with a brief description of the experiments done by previous researchers to ensure completeness. Validation of the model was done by comparing Moment-Rotation curves obtained from the experimental tests, lateral displacements of the bottom flange along the axial direction and comparison of the failure modes between the numerical model and experimental test specimens. It was observed that the maximum relative error for the ultimate moment capacity of the composite beams from FE analysis and the experimental tests was less than 2% which shows that the FE model was in strong agreement with the experimental results. Accordingly, the numerical model developed herein proves to be capable of accurately representing the LDB phenomenon.

The dynamic behavior of three-layer composite beams, consisting of concrete slabs and steel beams, is influenced by the structural configuration of each layer as well as the shear connectors. The interlayer shear stiffness in three-layer composite beams governs their global dynamic behavior, while interlayer slippage-induced localized vibration effects represent a key limiting factor in practical applications. Based on the dynamic test results of steel–concrete double-layer composite beams, the feasibility of a finite element solid model for composite beams, which accounts for interlayer shear connectors and beam body characteristics, has been validated. Utilizing identical modeling parameters, an analytical model for the inherent vibration characteristics of three-layer steel–concrete composite beams has been developed. This study encompasses two types of composite beams: concrete–steel–concrete (CSC) and concrete–concrete–steel (CCS). Numerical simulations and theoretical analysis systematically investigated the effects of interface shear connector arrangements and structural geometric parameters on dynamic performance. Research indicates that the natural frequency of steel–concrete three-layer composite beams exhibits a distinct two-stage increasing trend with the enhancement in interlayer shear stiffness. For CSC-type simply supported composite beams, the fundamental vertical vibration frequency increases by 37.82% when achieving full shear connection at both interfaces compared to the unconnected state, while two-equal-span continuous beams show a 38.06% improvement. However, significant differences remain between the fully shear-connected state and theoretical rigid-bonding condition, with frequency discrepancies of 24.69% for simply supported beams and 24.07% for continuous beams. Notably, CCS-type simply supported beams display a 12.07% frequency increase with full concrete-to-concrete connection, exceeding even the theoretical rigid-bonding frequency value. Longitudinal connector arrangement non-uniformity significantly impacts dynamic characteristics, while the transverse arrangement has minimal influence. Among structural parameters, steel flange plate thickness has the most significant effect, followed by concrete slab width and thickness, with steel web thickness having the least impact. Based on the observation that the first-order vertical vibration frequency of three-layer composite beams exhibits a two-stage decreasing trend with an increase in the span-to-depth ratio, it is recommended that the span-to-depth ratio of three-layer steel–concrete composite beams should not be less than 10.

This paper presents an investigation on behaviour and design of composite beams with stiffened and unstiffened web openings. The composite beams were simply supported and had profiled steel sheeting oriented transversely to the steel beams. Nonlinear 3-D finite element models were developed to analyse the inelastic behaviour of composite beam components comprising the steel beam, concrete slab, profiled steel sheeting, headed stud shear connectors, reinforcement bars as well as interfaces among these components. In addition, the load-slip characteristic of the headed stud shear connectors in composite slabs with profiled steel sheeting were carefully incorporated into the finite element models. The finite element models of the composite beams have been validated against published experimental results. The composite beams had different moment-to-shear (M/V) ratios at the openings, stiffened and unstiffened web opening sizes, web opening locations, profiled steel sheeting, shear connections, beam lengths, concrete slab strengths and steel beam strengths. The ultimate loads of the composite beams, load-deflection relationships and modes of failure of the beams were predicted from the finite element analysis and compared well against the test results. Furthermore, the variables that influence the composite beam behaviour and ultimate load comprising different stiffened and unstiffened web opening sizes, M/V ratios at openings, web opening locations, beam lengths, concrete strengths and steel beam strengths, were also investigated in an extensive parametric study. It is shown that the ultimate loads of composite beams with stiffened web openings with horizontal stiffeners located above and below the openings, having an opening height equal to 0.6 the steel beam depth, can be considerably increased compared with that of unstiffened openings. It is also shown that the increase in structural steel strength has a remarkable effect on the composite beam ultimate loads. In addition, the ultimate loads of the composite beams with stiffened and unstiffened web openings predicted from the finite element analysis were compared with the design ultimate loads calculated using the Eurocode 4 and technical report SCI P355 published by the Steel Construction Institute for composite beams with profiled steel sheeting and rectangular stiffened and unstiffened web openings. Generally, it is shown that the design ultimate loads accurately predicted the ultimate loads of the composite beams within an average of 6% difference from the ultimate loads predicted using the finite element analysis.

Introduction. Steel-concrete structures are composite systems composed of steel beams and a reinforced concrete slab. The reliable transfer of shear forces between the beam and the slab is required for the structure to behave efficiently. Towards this end, anchoring devices are used to ensure a connection between the beam and the slab. The design of a steel-concrete beam, composed of a reinforced concrete slab and steel beams, having bent sections, is considered. The steel-concrete beam is a system of galvanized bent steel beams placed in parallel and partially embedded in the 90 mm thick concrete slab made of B25 concrete. Shear forces are transmitted due to adhesion between galvanized steel and concrete without anchoring devices or the additional treatment of the beam surface. Materials and methods. The samples, whose flat galvanized plate had been embedded in concrete, were tested to identify actual adhesion forces. Finite element models (FEM), developed using various software packages, were assessed. FEM parameters that ensured the accuracy, acceptable for practical use, were identified. Results. The strength of adhesion between the steel plate and concrete was experimentally identified for different options of its attachment to concrete. The mesh pattern was identified for the plate for the case when 3D finite elements were used. Conclusions. A steel-concrete beam with a span of 6–8 m, bent galvanized sections partially embedded in the reinforced concrete slab with a thickness of 90 mm was developed. The author experimentally identified the shear resistance of a galvanized steel plate embedded in concrete, which reached 0.248 to 0.415 MPa depending on how the surface of the steel plate embedded in concrete was prepared. Numerical models were tested using different computational packages designa­ted for the calculation of steel-reinforced concrete beams. The author suggests FEM improvements on the basis of numerical calculation methods applied with due regard for the experimental data obtained during the testing of the full-scale structure.

The composite slim beam has become popular throughout Europe in recent years and has also been used on some projects in China. With its steel section encased in a concrete slab, the steel-concrete composite slim beam can provide the floor construction with minimum depth and high fire resistance. However, the design method of the T-shape steel-concrete composite beam is no longer applicable to the composite slim beam with deep deck for its special construction, of which the present design models are not available but mainly depend on experiences. The elevation of the flexural stiffness and bending capacity of composite slim beams with deep deck is rather complicated, because the influences of many factors should be taken into account, such as the variable section dimensions, development of cracks and non-linear characteristics of concrete, etc. In this paper, experimental investigations have been conducted into the flexural behavior of two specimens of simply supported composite slim beam with deep deck. The emphases were laid on the bonding force on the interface between steel beam and concrete, the stress distribution of beam section, the flexural stiffness and bending capacity of the composite beams. Based on the experimental results, the reduction factor of equivalent stress distribution in concrete flange is suggested, and the calculation method of flexural stiffness and bending capacity of simply supported slim beams are proposed.

Flexural behavior of prefabricated composite beam with cast-in-situ UHPC: Experimental and numerical studies

Flexural performance of innovative sustainable composite steel-concrete beams

Composite beams formed by connecting the concrete slabs to the supporting steel beams have been in use for many years. Much of the research into this form of construction has concentrated on the more traditional reinforced concrete and metal deck construction. In composite beam design, the strength of the shear connector is of great importance since longitudinal shear forces must be transferred across the steel-concrete interface by the mechanical action of shear connectors. The shear strength and stiffness of the connection is not only dependent on the strength of the connector itself, but also on the resistance of the concrete slab to longitudinal cracking caused by the high concentration of shear force at each connector. Present knowledge of this behaviour is limited to shear connectors in solid reinforced concrete slabs and concrete slabs with profiled sheeting, little information is given for the shear connector capacity on composite steel beam with precast hollow core slabs. A new horizontal push off test is proposed to determine the shear capacity of the connector on the composite beams with precast concrete hollow cored floor slabs. The results showed the new test is compatible with all type of floor and shear connectors, and can replace the existing vertical push off tests.

Experimental and numerical investigation of steel–concrete composite beam subjected to contact explosion

Nonlinear behaviour of unprotected composite slim floor steel beams exposed to different fire conditions

Composite structures are commonly used in bridge and building construction. A typical example is a bridge deck comprising of concrete slab and steel beam girders, with shear connectors linking the concrete slab and the steel beams to form the composite effect. The behaviour of a composite structure is dependent not only on the condition of the main constituent components, namely concrete slab and the steel beams, but also on the effectiveness of the shear connectors. In fact, the influences of damage to the main components (herein called flexural damage) and damage to the shear connectors on the overall structural performance are distinctively different. Therefore it is important that damages in a composite structure be distinguished between these two types of parameters. However, not much attention has been paid in differentiating the flexural and shear connector damages in the existing damage identification literature. In this paper we will provide an overall discussion on the distinctive effects of flexural and shear-connector damages to the rigidity and its distribution in a composite beam. A vibration based approach is then presented for the identification of the mixed presence of flexural and shear-link damage parameters by means of supervised machine learning. The wavelet packet node energy (WPNE), which has been shown to be sensitive to structural changes in previous studies, is chosen as input features. Appropriate selection of the wavelet packet transformation levels in the case using a single measurement sensor, as well as using multiple sensors, are discussed. Results demonstrate that with WPNE features combined with supervised machine learning, it is possible to differentiate and identify flexural and shear-connector damages, and hence the actual structural condition, of a composite beam.KeywordsDamage assessmentComposite beamsFlexural damageShear-link damageWavelet packet transformMachine learning

This study presents an experimental investigation on composite beams (CB) to explore the effectiveness of adding external post-tensioning (EPT) force, as a strengthening technique, on the monotonic flexural performance of composite samples. Two experiments on CB were conducted under three-point loading. High-strength steel strands post-tensioned to 46% of the ultimate strength were used to apply the EPT. Moreover, a finite element (FE) model is developed to present numerical investigations on the monotonic and fatigue behaviors of the CB with and without EPT by considering the slip between the concrete slabs and steel beams as well as the fatigue deterioration in the concrete slabs. A FE parametric study is conducted using the proposed FE model to investigate the effect of steel beam grade, tendon eccentricity, span-to-depth ratio, and fatigue loading. The optimum span-to-depth ratio to obtain the maximum contribution of the EPT force in improving the CB capacities is 9.0.

Experimental and numerical study of an innovative OMEGA-shaped connector for composite beams