Shear Connection In Composite Beams Research Articles

Structural performance of friction-grip bolted shear connectors in cold-formed steel composite beams

Nowadays, composite beams consisting of steel beams and concrete slabs are widely used in the construction industry. In this research, an experimental study was carried out to investigate the performance of friction-grip bolted shear connectors in composite beams with cold-formed steel sections. For this purpose, 17 full-scale push-out tests were examined according to EC4 in order to investigate the performance of this connection. Of particular interests were load-slip curves, the maximum shear capacity, ultimate slip (ductility) and failure modes. Experimental results show that the behavior of this connection is different from that of headed-stud shear connector. The diameter and strength of bolt and thickness of cold-formed steel section have the most critical effects on the shear capacity and ductility of these connections. Furthermore, 3D finite element modeling was performed and validated against experimental results. The results reveals that numerical models can estimate the capacity of friction-grip bolted shear connectors with acceptable accuracy. The results also highlight that the predominant failure mode in all specimens is bearing. Thus, the use of AISI equations to determine the bearing capacity of the screw holes as the shear capacity of friction-grip bolted shear connectors is recommended. It is also concluded that this connection possesses the necessary ductility according to the EC4 (= 6 mm) and is suitable for use in composite beams with cold-formed steel sections.

Statistical modeling and safety analysis for developing design resistance of deconstructable HSFGB shear connectors in composite beam

In recent years, the high-strength friction-grip bolt (HSFGB) shear connectors in steel-concrete composite beams as deconstructable connectors are of great research interest since they are aligned with sustainable construction. However, the design strength equation for this type of connector has not yet been provided by the design codes such as AISC and Eurocode 4. In this paper, with regard to the reliability aspect, the design strength equation of HSFGB shear connectors is investigated which is projected into a partial safety factor according to Eurocode 4. Accordingly, the three-dimension finite element (FE) push-out model of the composite connection is developed and verified via experimental results to predict the load-slip behavior and failure modes in this type of bolted shear connector. Then One-Factor-at-a-Time (OFAT) method as a sensitivity analysis and Plackett-Burman (PB) design method as a screening analysis are utilized to identify the effective factors of the ultimate strength of HSFGB connectors. Finally, based on a complete database of all existing experimental findings, the results obtained from 55 three-dimension finite element models conducted in this paper, and appropriate statistical analysis, a high-precision equation for predicting ultimate strength is provided. Then the value of the partial safety factor is determined through a reliability study in accordance with EN1990, which provides an acceptable level of safety for the proposed design equation based on Eurocodes. Reliability analysis found that a partial factor of 1.52 was justified for the design strength of HSFGB connectors, which differed from the partial factor of 1.25 stated in the EC for welded stud shear connectors.

DEFORMATION CAPACITY AND DUCTILITY OF SHEAR CONNECTORS

AbstractDeformation capacity and slip range (eventually called “ductility”) of shear connectors are key parameters for the design of shear connectors in composite beams, especially in partial shear connection. Existing design rules require a deformation capacity of at least 6 mm for the use of shear connectors with plastic design methods. This rule is combined with the assumption of rigid‐ideal plastic behaviour of the shear connectors. Still, the real characteristics of most of today's usual shear connectors differ considerably from these assumptions, even more for shear connectors used in combination with metal decking. The paper describes the results of a literature research conducted in order to obtain reliable values for the deformation capacity and the slip range of headed stud shear connectors. Based on these results, advanced design methods can be used to realise composite beams with more realistic lower limits for the degree of partial shear connection and thus better economic performance.

Numerical study of the behavior of friction-grip bolted shear connectors in composite beams with cold-formed steel sections

The concurrent use of concrete slab, and cold-formed steel section as a composite beam improves strength and stiffness, thus preventing local and lateral buckling of the beam. The composite action could be fulfilled by suitable shear connectors, though the codes do not prescribe any equation to determine the shear capacity, and design rule of these connectors. The friction-grip bolted shear connectors were introduced and their mechanical performance was studied via the experimental tests and finite element modeling. At first, ANSYS software was used for the 3D finite element modeling of these connections. The obtained results were verified by experimental results. It can be shown that the proposed model can estimate the behavior of friction-grip bolted shear connectors in composite beams with cold-formed steel section. Then, extensive parametric studies with 72 specimens were carried out and the effect of diameter and strength of the bolts, thickness and strength of cold-formed steel sections, clearance between the bolt and concrete hole and pretension force on the behavior of these connectors were evaluated. The effect of each parameter on the shear capacity of the connection was evaluated. Some equations were proposed for figuring out the shear capacity and load–slip curve of these connections based on the experimental and 3D finite element results.

Capacity analysis of advanced bolt shear connectors in composite beams with finite element method using MIDAS FEA software

Prefabricated construction is now familiar and widely used in various parts of the world. The important thing in the composite structure is the shear connection. Advanced bolt shear connectors are one of the innovations for prefabricated construction because their use is more efficient. The shear capacity of the advanced bolt shear connectors was carried out with the nonlinear finite element method using MIDAS FEA software and then compared with the results of laboratory testing and theoretical equations. There were 8 models to be tested with 2 variations of bolt diameters (12 mm and 16 mm) and 3 variations of bolt pretension (without pretension, 0.2Pc pretension, 0.5Pc pretension, and 0.8Pc pretension). The results of the analysis show that the diameter of the bolts has a large effect on the shear capacity of the shear connectors where with the same bolt pretension, the shear capacity increases 71.4286% - 73.0769% on the test models with 16 mm bolts. Bolt pretension also affects the shear capacity of the shear connectors although the impact is small, 1.9231% - 7.6923% (12 mm diameter bolts) and 1.1111% - 6.6667% (16 mm diameter bolts) from the value of the shear capacity of the model without pretension. The most optimal pretension is 0.5Pc for 2 bolt diameter variations. In the results of the analysis of the finite element method and laboratory tests, the deflection is directly proportional to the shear capacity of the models.

Effects of Uniform Load on Externally Post-tensioning Composite Beams under Multiple Degrees of Shear Connection

Composite beams (steel and concrete) are used widely as the main structural elements in flexure in bridges and buildings. Such structures' design life would be decreased if the loads increased or if environmental deterioration could occur. Such modifications can reduce the strength of these members and therefore need to be considered for replacement or retrofitting.The current study presents an evaluation of the effect of shear connection with its different degrees from partial to full for the composite beams strengthened with post-tensioning tendons. It is known by design that the use of partial shear connection in composite beams requires that the sliding capacitance of the shear connectors shouldn’t be less than the maximum slip so that the composite section can reach the ultimate design load. The degree of shear connection over which the composite section is designed, as well as the span length of the beam, are the most important factors governing the maximum slip limit. This study was performed using numerical modelling by the finite element analysis method to simulate the bending behaviour of composite steel beams under uniform loading cases which were strengthened with three shapes of tendons profiles. The results of two finite element models have been compared with experimental results obtained from previous literature related to the same topic. This comparison was made to ensure the efficiency, effectiveness, and accuracy of the model used, using ANSYS Workbench Software.

Behavior investigation of powder actuated shear connectors in composite beams with profiled sheeting

Eurocode 4 and Russian SP266.1325800.2016 composite structure design codes require touse shear connectors for providing a combined action of steel beam and concrete slab. Both codes also allow use steel profiled sheeting as a stay-in-place formwork. In this case, the designer has to use a reduction factor to define the real shear resistance. However, the existing method is mostly based on round-shape welded studs and does not take into account the peculiarity of powder actuated shear connectors.This paper presents the result of an investigation of the behaviour of powder actuated shear connectors Hilti X-HVB in composite beams. One of the goals was to explore the influence of the steel profiled sheeting`s geometry on shear resistance of the connectors. Fifteen test series were conducted with different numbers of connectors, slab thicknesses, installation parameters of the connectors and types of profiled sheeting. All types of sheeting that were used as the test samplesare manufactured according to the Russian national standard and are widely used for composite slab design. Some test cases had smaller edge distances for shear connectors installation in profiled sheeting than allowed by the technical data of the producer, because they took place in real practice in CIS countries.The test results have been evaluated according to Appendix B of Eurocode 4. The results for samples with solid slabs are in fully agreement with external experience. Most of series with profiled sheeting also match predicted design values; however, there were some series with insufficient results. Therefore, a deeper analysis and additional testing are necessary. The current investigation results could be used to specify the existing reduction factor that is included in the Russian composite structure design code SP266.1325800.2016

A study on structural performance of deconstructable bolted shear connectors in composite beams

An experimental study according to EC4 on deconstructable steel-concrete composite bolted shear connectors is carried out to investigate the effect of various bolt size, concrete strength, bolt strength and clearance size between the precast concrete slab and bolt on the static behaviour of this type of composite connection. Shear load capacity for the first bearing, average major slip at the first bearing, maximum shear load capacity per bolt, slip corresponding to the maximum shear load capacity, maximum average slip between the precast concrete slab and steel beam and failure modes are assessed. A total of 12 composite specimens were tested according to EC4 with different parameters using deconstrcutable bolted shear connectors. In addition, two steel-concrete composite connection specimens using welded headed stud shear connectors were tested as control specimens to determine the influence of prefabricated concrete panels and deconstructable friction-grip bolted shear connectors on the performance of the steel-concrete composite connection. The experimental results show that deconstrcutable steel-concrete composite bolted shear connectors have completely different behaviour compared to welded headed stud shear connectors. Furthermore, a 3D finite element model of the steel-concrete composite connection having precast concrete slabs and deconstructable bolted shear connectors was performed. Numerical model was verified against experimental results, and was shown to accurately simulate their observed structural behaviour.

Strength Evaluation of Angle Type Shear Connectors in Composite Beams

Composite structures are used in structural systems to take advantage of concrete and steel, and the role of shear connectors between the two is extremely important. Currently, anchor- and angle-type connectors are mainly used as shear connectors, and the angle type offers several advantages over the anchor type. The angle type can be manufactured as a shape that fits the composite structure with a greater basic strength than that of the anchor type, so it can be installed in wider spaces. Much research has been conducted on the anchor type, but that on the angle type has been insufficient so far. In this study, push-out and yield-strength tests were conducted on various angle-type shear connectors used for filling-type composite beams. The variables included the height, width, and thickness of the angle-type shear connector. The tests were terminated when a strength reduction of 80% of the maximum strength occurred. The slip capacity of the specimen was evaluated by referring to Eurocode. Based on the experimental results, the design equations have been reviewed to determine whether or not they can be used for the shear connection of concrete-filled composite beams. In addition, the strength was assessed by existing design equations. Meanwhile, a new design equation was proposed, including the height of the shear connector, which is not considered in the current design equations. The other strength was calculated by the new design equation.

Experimental and numerical study of shear connection in composite beams of steel and steel-fibre reinforced concrete

To explore the shear behaviour of high strength bolted connectors in steel-SFRC composite beams, push-out tests were carried out on 18 steel-fibre reinforced concrete (SFRC) specimens and 4 normal concrete (NC) specimens. The failure modes, ultimate shear strength, load-slip response as well as the shear stiffness of the tested specimens were determined accordingly. During the experiment, two failure modes that involved bolt shear failure and concrete splitting failure were observed in both NC and SFRC specimens. As the bolt-to-hole clearances of specimens were infilled, the slip plateau at the early loading stage therefor were avoided and the corresponding shear stiffness of bolted connectors increased as well. Compared to NC specimens, the extension of cracks on SFRC slabs were limited and the width of cracks efficiently decreased because of the addition of steel fibre in concrete. The ultimate shear strength of the bolted connectors in steel-SFRC composite beams was about 21.2% higher than that of the bolted connectors in steel-NC composite beams, with the volume percentage of steel fibre in concrete being approximate 1.0%. The applied pretension on bolted connectors had a significant effect on the shear stiffness of bolted connectors, but almost had no effect on the ultimate shear strength. The ultimate shear strength of bolted connectors increased with the increase of concrete compressive strength, bolt shank area and bolt tensile strength. Finite element models, which confirmed by the tested results, were also employed to perform the parametrical analysis involved in concrete compressive strength, as well as bolt pretension, and diameter and tensile strength. Upon the experimental and independent FE results, practical calculation formulas were further proposed, which can properly estimate the ultimate shear strength as well as the load-slip curves of high strength bolted connectors in steel-SFRC composite beams.

Different load‐bearing mechanisms in headed stud shear connections in composite beams with profiled steel sheeting

ABSTRACTThe current regulations of EN1994‐1‐1 for headed stud shear connections in composite beams with profiled sheeting lead, for some configurations, to an over‐estimation of the load‐bearing capacity. Since these design equations are based on empirical considerations, they are not able to capture the real mechanical behaviour of the connector and they do not consider appropriately the influence of the geometry of sheeting on the shear capacity. For this reason, the load‐bearing mechanisms of the shear connection are identified in this work with the support of experimental and numerical results. According to the static system presented, the concrete rib is modelled as a system of diagonal struts acting simultaneously in combination with the stud in bending.It is observed that at 2÷4 mm slip, a “Strut and beam” mechanism prevails where the resistance of the connector depends mostly on the plastic hinges activated in the stud and on the capacity of the diagonal strut in front of it. By increasing the slip (ca. 4÷10 mm), the surrounding concrete progressively crushes while the tensile stresses at the edge of the rib reach the tensile strength of the material. As a consequence of this loss of rotational stiffness, the bending capacity developed in the stud reduces and the upper hinges gradually moves towards the slab. At higher displacements (ca. 20÷40 mm), due to nonlinear geometric effects, high tensile forces develop in the stud and the load is carried through a “Strut and Tie” resistance mechanism, if the embedment of the stud is sufficient. By further increasing the slip, the whole rib rotates or the failure occurs either for concrete pull‐out or stud rupture.This contribution describes the sequence of the activated load‐bearing mechanisms in headed stud shear connections with profiled steel sheeting at different displacements.

Parametric study on non‐ductile demountable shear connectors

ABSTRACTThe basic principle of the circular economy is to reduce or totally eliminate waste and carbon dioxide production with the help of a multiple, efficient usage of resources. The application of reusable structural elements plays an important role and can contribute essentially to a low‐carbon future. Within the European research project REDUCE (Grant Agreement number: 710040), composite beams and steel‐based flooring systems, which are demountable and reusable, have been developed and investigated. The experimental investigations showed that the structural behaviour of the newly developed shear connectors differs from the behaviour of the traditionally applied welded studs. Some behave in a non‐ductile way.In order to assess, how far the regulations of EN1994‐1‐1 for shear connections can still be applied, parametric studies have been conducted. The respective numerical models were developed with the use of the commercially available finite element software ABAQUS® and were validated against the experimental observations. The effects of the lack of ductility of the shear connectors on the structural behaviour of the entire composite beam was examined with different types of shear connectors, shear connector layouts and material grades.This contribution presents the underlying laboratory tests as well as the results of the supplementing numerical parameter studies. The outcome provides valuable information for future design guidance concerning the use of demountable shear connectors in composite beams.

Numerical evaluation of the plastic hinges developed in headed stud shear connectors in composite beams with profiled steel sheeting

For composite beams using novel steel sheeting, the current Eurocode 4 rules sometimes overestimate the load-bearing capacity of headed stud shear connectors. This is due to the larger rib heights and the smaller rib widths in comparison with the old studies, which have been carried out to calibrate the current design equations. The RFCS Project “DISCCO” investigated this phenomena and the working group under mandate M515, CEN/TC250/SC4/SC4.T3 is enhancing this equation and working on a proposal to be taken over in the new version of Eurocode 4.The proposed new equation covers the failure behaviour of the shear connection more in detail. The test results show, that the failure consists in a combined concrete cone and stud in bending. Due to the geometry of novel steel sheeting, the load bearing capacity of the headed stud shear connector is no more limited by its shear capacity, but by its bending capacity.A 3D non-linear finite element model is developed and validated through the support of the DISCCO push-out tests. A good agreement between numerical and experimental results in terms of force-slip behaviour is achieved. Special attention of this work lies on the numerical evaluation of the number of plastic hinges ny: a stress-based procedure is presented and the results are compared to the equations presented for new Eurocode 4.The numerical simulations show that the upper plastic hinge moves up as the slip increases due to the progressive crushing of the concrete in the rib. From the parametric study, it turns out that ny is linearly proportional to the embedment depth. Compared to pre-punched hole decking, through-deck welding specimen activates less plastic hinges in the studs because of the higher stiffness provided at the base of the stud.

Resistance of stud shear connectors in composite beams using profiled steel sheeting

In composite beam design, headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface. This paper describes the structural performance of shear connection in composite beams with profiled steel sheeting. An accurate and efficient nonlinear Finite Element (FE) model was developed to study the behavior of headed stud shear connectors welded through the deck. The concrete slab considered in this article uses profiled steel sheeting with ribs perpendicular to the longitudinal axis of the steel beam. The material nonlinearities were included in the FE model. The concrete was modeled considering a damaged plasticity model available in ABAQUS software. The results obtained from FE analysis were verified against experimental results. A parametric study was conducted to observe the effects of changing of both the stud position inside the rib of profiled steel sheeting and the concrete strength on the resistance of the stud shear connector. The shear resistance of stud connectors obtained from the FE analysis and many experimental push-out tests whose results are available in the literature were used as a database to compare with design shear resistance calculated using AISC-LRFD and Eurocode 4. It is found that the shear resistance of stud connectors, obtained from the design rules specified in these codes, in some cases is greatly underestimated, and in other cases significantly overestimated.

Effect of Shear Connector Layout on the Behavior of Steel-Concrete Composite Beams with Interface Slip

In a steel-concrete composite beam (hereafter referred to as a composite beam), partial interaction between the concrete slab and the steel beam results in an appreciable increase in the beam deflections relative to full interaction behavior. Moreover, the distribution type of the shear connectors has a great impact on the degree of the composite action between the two components of the beam. To reveal the effect of shear connector layout in the performance of composite beams, on the basis of a developed one-dimensional composite beam element validated by the closed-form precision solutions and experimental results, this paper optimizes the layout of shear connectors in composite beams with partial interaction by adopting a stepwise uniform distribution of shear connectors to approximate the triangular distribution of the shear connector density without increasing the total number of shear connectors. Based on a comparison of all the different types of stepped rectangles distribution, this paper finally suggests the 3-stepped rectangles distribution of shear connectors as a reasonable and applicable optimal method.

Finite element analysis of shear connection in composite beams exposed to fire

Finite element analysis of shear connection in composite beams exposed to fire

Experimental study on impact behaviour of stud shear connectors in composite beams with profiled steel sheeting

This paper deals with the shear behaviour of steel stud connectors in composite beams with profiled steel sheeting under static and impact loads. An experimental program including five static and ten impact push-out tests is firstly carried out, and the failure modes, the time history of impact load and slippage displacement, as well as the shear capacity of stud connectors are presented and discussed. Based on the dynamic responses, the influence of the arrangement form of profiled steel sheeting on the shear mechanism of steel stud connectors under impact loading is examined. Moreover, a design proposal developed previously by the authors is verified to reasonably predict the shear capacity of stud connectors with profiled steel sheeting parallel to the steel beam under impact loading. However, it is unsafe to predict the dynamic shear capacity of stud connectors with profiled steel sheeting transverse to the steel beam when the strain rate effect is considered. Additionally, the failure mode of shear connectors with solid slab in this paper is different from that of the previous work, which lead to the lower dynamic shear capacity of the connectors with the solid slab, and some further discussion is also carried out. The testing results can provide an essential data for future analytical and design-oriented study of composite beam with shear stud connectors with profiled steel sheeting under extreme loading conditions.

Limitations on the use of partial shear connection in composite beams with steel T-sections and uniformly spaced rib shear connectors

Design codes like EC4 allow the bending resistance of composite beams with partial shear connection (PSC) to be assessed by plastic analysis procedures, based on equilibrium of forces across the composite section (equilibrium method). However, these plastic design models are limited to connectors, usually shear studs, with sufficient deformation capacity (at least 6mm) and composite beams, where the steel sections have either equal flanges or only slightly differing areas of top and bottom flange. Beyond that, EC 4 defines a minimum degree of shear connection to be provided, that was derived for composite members with double flange steel section and stud connectors through systematic FE analysis. For composite beams with steel T-section (without top flange) and uniformly spaced rib shear connectors, limitations on the use of partial shear connection have not yet been investigated. Due to significant discrepancies in terms of steel section geometry and ductility of the connectors a simple adoption of regulations from EC4 is not possible and presumably unsafe. To resolve that problem, the paper presents the results of numerical simulations, based on which limitations on the use of partial shear connection have been derived for beams with steel T-sections and uniformly spaced connectors.

08.03: Mechanical model to predict the resistance of the shear connection in composite beams with deep steel decking

ABSTRACTThe resistance of a typical shear connection with headed shear studs in a composite beam is analysed in the normal case in accordance with EN 1994‐1‐1. The reducing effect of a trapezoidal metal decking onto the ultimate load bearing capacity is considered with empirically derived reduction factors and equations, which have been developed in the last century between the late 70th and the early 80th. The RFCS research project “DISCCO” [1] investigated the shear stud resistance with novel types of steel decking. In many cases, the shear resistance, which was predicted by EN 1994‐1‐1 [2] was not reached in tests.In the respective experiments with composite beams and deep decking, a concrete cone failure mode was identified and not a pure shear failure of the stud. This failure mode acted in combination with the load bearing capacity of the shear stud, which formed one or two plastic hinges in the shaft – depending on the available geometry.Based on these observations, new equations have been developed to predict the shear connection's resistance with more accurcy. The yield hinge mechanism of the shear stud, which was developed by Lungershausen [3], was extended by the above mentioned load bearing component ‘concrete cone’. The formulae consider the geometry of the stud and the steel decking, the material strength of the stud and of the concrete material. The statistical evaluation of the developed equations shows a good accordance with test results.

Mechanical model to predict the resistance of the shear connection in composite beams with deep steel decking

The resistance of a typical shear connection with headed shear studs in a composite beam is analysed for the normal case in accordance with EN 1994-1-1. The reducing effect of a trapezoidal metal decking to the ultimate loadbearing capacity is considered with empirically derived reduction factors and equations that were developed between the late 1970s and early 1980s. The RFCS research project ”DISCCO“ [1] investigated the shear stud resistance with novel types of steel decking. In many cases, the shear resistance predicted by EN 1994-1-1 [2] was not reached in tests. In the respective experiments with composite beams and deep decking, a concrete cone failure mode was identified and not a pure shear failure of the stud. This failure mode acted in combination with the loadbearing capacity of the shear stud, which formed one or two plastic hinges in the shaft depending on the actual geometry. Based on these observations, new equations have been developed to predict the shear connection's resistance with more accuracy. The yield hinge mechanism of the shear stud, which was developed by Lungershausen [3], was extended by the aforementioned loadbearing component ”concrete cone“. The formulae consider the geometry of the stud and the steel decking and the material strength of the stud and the concrete. The statistical evaluation of the equations developed demonstrates good agreement with test results.