Calculation of Shear Studs in the Load Introduction Area of Concrete-Encased Steel Composite Columns: A Review of Current Design Approaches

Innovative structural solutions have been achieved in the fields of structural and mechanical engineering by combining different materials to produce more economical and efficient elements. The interaction between different materials has been achieved in various manners and this paper is concerned with those situations in which layers of different materials are interconnected by means of flexible mechanical devices. Of particular interest to this paper are composite members with partial shear interaction which have been studied for several decades. One of the first papers dealing with the partial interaction analysis of two-layered composites was the one by Newmark et al. [1] who focussed their attention on steel-concrete composite beams. Due to the wide acceptance of this work, its formulation is simply referred to in the literature as Newmark model. This paper extends the applicability of this model to study the time-dependent behaviour of multi-layered composite beams with partial shear interaction formed by n layers. A generic displacement-based finite element formulation is presented for the derivation of n-layered beams and is then applied to the case of a three-layered element representing the particular case of a composite steel-concrete beam stiffened by a longitudinal steel plate in which the partial interaction occurs between the slab and the steel joist as well as between the joist and the stiffening plate. The accuracy of the proposed procedure is validated against closed form solutions for the two limiting cases in which both shear connection stiffnesses tend to infinity, representing the full interaction condition; and also where only one connection stiffness is infinitely high, thus degenerating to the conventional two-layered composite partial interaction behaviour. Applications are then presented to investigate the effects of the two interface connection stiffnesses on the structural response of the stiffened composite beam. For this purpose, different lengths are considered for the longitudinal plate and the time-dependent behaviour of the concrete is modelled by means of the step-by-step method.

A study on the behavior and design of composite transmission towers was carried out using the finite element software ABAQUS. The finite element models were validated against experimental results done by other researchers for various configurations of composite columns and tapered transmission poles. The specimens considered for verification purposes include simple composite columns consisting of steel case and core concrete, composite columns with embedded shear studs, composite columns with embedded steel section and shear studs, double skin filled steel columns and twelve-sided tapered transmission poles. The validation was achieved by comparing the axial load vs. axial strain, axial load vs. mid-span deflection, bond stresses vs. slip for composite columns and applied force vs. tip displacement curves for tapered transmission poles. An investigation and calibration of the Concrete Damage Plasticity (CDP) material model’s parameters was performed to achieve the most accurate results using such model for this application. An analysis was performed on twelve-sided composite columns (dodecagonal) under four- point bending test based on ASTM standards in order to investigate their behavior. The parameters considered for this stage were: number of studs (2, four, six, and twelve) and interaction type (fully restrained, and composite). The effect of these parameters was studied in terms of: load vs. deflection, moment vs. curvature, moment vs. slip, shear stresses in studs, and bond stresses vs. slip curves. Furthermore, a parametric study was performed on the behavior of tapered composite transmission towers in a bending test. The variables considered for this study were: cross-section shapes, composition percentages, number of studs in cross-section, arrangement of studs in cross-section, and studs dimensions. The effect of these parameters was studied in terms of: load vs. deflection, moment vs. curvature, moment vs. slip, shear stresses in studs, and bond stresses vs. slip curves. P-M interaction diagrams were developed for composite columns with various polygonal shapes and different diameter to steel thickness (D/t) ratios which intends to highlight and extend beyond the limitations of AISC code provisions (higher than 120 which is the AISC code limit). To achieve this, the concrete reduction factor for the studied geometrical shapes was investigated using multiple methods to confirm the resulted factor values. Non-dimensional version of the P-M interaction diagram was developed, and the studs’ effect on these equations was studied to provide a better understanding and prediction of these structures’ behavior. Finally, a design procedure was developed for composite transmission towers exposed to real case loading including wind load based on AISC code, Finite Element Analysis (FEA) and previously constructed P-M diagrams and load-deflection curves. A comparison was carried out between the proposed composite and steel truss transmission towers in order to emphasize the economic benefits of the proposed structures.

Generalised Beam Theory (GBT) for composite beams with partial shear interaction

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

The results of an analysis of wood joist floors, including the effects of the nonlinear force‐slip relationship for nails, are presented. The finite‐element analysis procedure includes an iterative scheme for solving the resulting nonlinear equations, thereby satisfying equilibrium and compatibility. To assess the ability of the model to predict deflections above the service load level, the computed deflections were compared with those measured in tests of full‐scale point‐loaded and uniformly loaded floors. These comparisons were made at the known failure loads of the test floors. Also, a comparison was made between the results of a linear analysis of each test floor in which the connector stiffness was assumed constant throughout the load range and the experimental deflections. The nonlinear analysis proved superior, particularly for the uniformly loaded floors.

Theoretical analysis on long-term deflection of GFRP-concrete hybrid structures with partial interaction

Hinge-locked structures of the folding wing for high-speed vehicle contain gaps, contact and friction effects, and these factors increase the complexity of solving the local connection stiffness. In this paper, a finite element model and displacement vector equations of the folding structure are established, which provides a direct simulation method of connection stiffness. The influence of flexible deformation of the airfoil and the deflection of wing root are considered in the displacement vector equation. The effect of the clearance on the connection stiffness is discussed by adjusting the clearance between the shaft and sleeve. The load effect on stiffness is studied by varying the load distribution on the out-wing surface. The stiffness analysis method is finally established and meets the requirements of engineering design. The results show that the deformation of the hinge-locked structure is several times than that of the monolithic structure under the same load, which means that the stiffness is significantly reduced; the tension and compression asymmetric stiffness characteristics are also investigated; in addition, the increase of clearance between the hinge-locked structure shaft and wing holes decrease the connection stiffness; the load distribution on out-wing surface has no significant effect on the connection stiffness.

The strengthening technique which attaches steel plates to the side faces of existing reinforced concrete (RC) beams using anchor bolts has received worldwide acceptance in the past several decades. The performance of this type of beam, i.e. the bolted side-plated (BSP) beam, is mainly controlled by the degree of partial interaction at the steel-concrete interface. This partial interaction is a result of the longitudinal and transverse slips. This paper introduces an experimental study on the behavior of slips and shear force transfer in the BSP beams. A total of seven moderately reinforced BSP beams with different steel plate depths and bolt spacing were tested under four-point bending. Their behaviors were compared to the available test results for lightly reinforced BSP beams obtained by other researchers. Then a nonlinear finite element model was also developed to predict the behavior of BSP beams. The numerical simulation was also verified by the results of the experimental study successfully. The results show that moderately reinforced RC beams can be effectively enhanced in flexural strength and ductility by using deep steel plates. It was also found that the longitudinal and transverse slips were controlled by both the stiffness ratios of the steel plates to the RC beam and the force-slip response of the anchor bolts. This study enhances the basic understanding of behavior of BSP beams and the internal shear-transfer mechanism between the steel plates and the RC beam.

An analytical study using non-linear finite-element modelling was conducted to evaluate the capacity improvement of adding studs between the concrete and steel plates in a steel-plate–concrete wall subjected to bending and shear. Non-linearity of the contact, connection details and material properties were considered when modelling the wall. The size of the model was determined through a literature review and by referring to code requirements. The model outputs compared well with the results of a laboratory experiment conducted in an earlier study. Different types and arrangements of studs were modelled to check they met Kepic-SNG criteria, the relevant design standard. After reviewing bending moment and buckling strength requirements, the optimum type and arrangement of studs were determined.

This paper presents a novel analytical formulation for the analysis of composite beams with partial shear interaction stiffened by a bolted longitudinal plate accounting for time effects, such as creep and shrinkage. The model is derived by means of the principle of virtual work using a displacement-based formulation. The particularity of this approach is that the partial interaction behaviour is assumed to exist between the top slab and the joist as well as between the joist and the bolted longitudinal stiffening plate, therefore leading to a three-layered structural representation. For this purpose, a novel finite element is derived and presented. Its accuracy is validated based on short-and long-term analyses for the particular cases of full shear interaction and partial shear interaction of two layers for which solutions in closed form are available in the literature. A parametric study is carried out considering different stiffening arrangements to investigate the influence on the short-and long-term behaviour of the composite beam of the shear connection stiffness between the concrete slab and the steel joist, the stiffness of the plate-to-beam connection, the properties of the longitudinal plate and the concrete properties. The values of the deflection obtained from the finite element simulations are compared against those calculated using the effective flexural rigidity in accordance with EC5 guidelines for the behaviour of elastic multi-layered beams with flexible connection and it is shown how the latter well predicts the structural response. The proposed numerical examples highlight the ease of use of the proposed approach in determining the effectiveness of different retrofitting solutions at service conditions.

The partial interaction (PI) mechanics of tension stiffening governs crack widening and the consequential deflection of reinforced concrete (RC) beams and, therefore, is essential in the serviceability design of RC structures. Both behaviors are dependent on the PI global load slip behavior of the tensile reinforcement relative to the surrounding concrete at a crack face, which in turn is dependent on the local PI material bond‐stress/slip relationship between the reinforcement and adjacent concrete. Due to the complexity of PI theory, it has been difficult to directly incorporate PI mechanics into design procedures. Consequently, empirical approaches to quantify effective flexural rigidities and crack widths are commonplace. While empirical approaches can be derived relatively simply for short‐term loading, the influence of concrete shrinkage and creep is difficult to incorporate. In this paper, pure mechanics‐based PI solutions to describe the crack spacing and tension stiffening behavior of RC beams subjected to long‐term loads are derived. They only require material properties and clearly show the interaction among shrinkage, creep and bond properties. They are simple enough to use directly in design and will help in the experimental derivation of the material properties. The results of these PI analyses are used in a companion paper to develop design rules for the time‐dependent serviceability deflection of RC beams and compared with test results.

Composite beams with both longitudinal and transverse partial interaction subjected to elevated temperatures

Steel-concrete composite bridges are commonly designed with full composite action between the steel girders and the concrete deck to enhance structural efficiency and durability. This composite action is achieved through shear connectors, which transfer shear forces and ensure that both materials act as a single unit. While full composite action is preferred, partial composite action may be sufficient in certain cases, depending on interlocking effects between steel and concrete. One strategy to improve the performance of composite bridges is the implementation of horizontal trusses between the lower flanges of the steel girders, which enhance load distribution and lateral stability. Although previous research has investigated the effects of horizontal trusses on global load distribution, their influence on shear force distribution, particularly at shear connectors, remains largely unexplored. Studies on monorail track beams indicate that transverse shear forces significantly affect shear connectors, reducing their capacity and altering failure mechanisms. A similar effect may occur in composite bridges with twin girders and horizontal trusses. This paper presents a case study of a single-span steel-concrete bridge in Sweden, examining the impact of a torsional rigid structure with a semi-closed cross-section on local shear flow distribution. The study also investigates how shear connector rigidity affects force distribution along the steel-concrete interface.

This paper presents an alternate analysis method for calculating the deflection and internal forces for arbitrary boundary and loading conditions of composite beams with partial interaction. The internal axial force was approximated by the Fourier series to solve the governing equation of composite beam. Then, the coefficients of the Fourier series were determined using the Euler-Lagrange equation of minimizing a definite integral. An evaluation of the convergence and the accuracy for the proposed method in the determination of the deflection for four types of boundary conditions with four types of loading cases was made. The results were agreed with those obtained by other analytical methods. The displacement of the partial composite beam depends on the stiffness of shear connectors, boundary conditions and loading conditions.

On the Interaction of Partial Interaction and Shrinkage in Composite Steel-Concrete T-Beams