Headed Stud Shear Research Articles

Different load bearing mechanisms in headed stud shear connectors for composite beams with profiled steel sheeting

AbstractNominated for the Bernt Johansson Outstanding Paper Awards at Nordic Steel 2019The current design rules of EN 1994‐1‐1 covering headed stud shear connectors for composite beams with profiled sheeting lead, in some cases, to an overestimation of the load bearing capacity. Owing to their empirical nature, these equations are not able to capture the real behaviour of the connector. Therefore, 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 proposed, the concrete rib is modelled as a system of diagonal struts in combination with the stud in bending. It was observed that at 1–4 mm slip, a ”strut and beam“ mechanism prevails, where the resistance of the connector depends on the activation of the plastic hinges in the stud and on the capacity of the diagonal strut in front of it. By increasing the slip (approx. 4–10 mm), the surrounding concrete gradually crushes, while the tensile stresses at the edge of the rib reach the tensile strength of the material. Because of this loss of rotational stiffness, the bending moment in the stud decreases and the upper plastic hinge gradually moves towards the slab. At higher displacements (approx. 20–40 mm), high tensile forces develop in the stud due to non‐linear geometric effects and the load is carried through a ”strut and tie“ resistance mechanism, provided that the embedment of the stud is sufficient to prevent the rotation of the rib. As the slip increases further, failure occurs either in the form of concrete pull‐out or stud rupture.

Erratum for “Headed Shear Stud Fatigue Demands in Composite Bridge Girders Having Varied Stud Pitch, Girder Depth, and Span Length” by Brianna Ovuoba and Gary S. Prinz

Erratum for “Headed Shear Stud Fatigue Demands in Composite Bridge Girders Having Varied Stud Pitch, Girder Depth, and Span Length” by Brianna Ovuoba and Gary S. Prinz

Strengthening of Composite Steel-Concrete Beams Openings by Adopting Different Reinforcement Methods

This paper presents an experimental and numerical study carried out to investigate the flexural and shear behavior of concrete-steel composite beams with circular web openings strengthened using two different techniques around openings. The experimental program conducted on nine simply supported beams which were constructed with different variables. One steel beam and eight concrete-steel composite beams were experimentally tested. The tested beams are of 1500 mm length and BFI cross section of steel beam but composite beams were BFI steel section connected with concrete slab had 300 mm width and 70 mm depth, while this connection is done by headed stud shear connector. The tested specimens subjected to positive bending were loaded by one or two line load across the width of the concrete slab. The main parameters were the type of beams, web openings effect, location of web openings, strengthening techniques around openings externally CFRP strips and vertical steel links using steel plates placed on the top and bottom surface of beams anchored with fine threads, and number of CFRP strips layers. The effect of these parameters on the failure of modes, ultimate load, first cracking load and deflection were investigated. Moreover, a finite element models were developed by ANSYS (version 14) to simulate all the tested specimens, experimental test results were compared with FE results obtained. The experimental results showed that both strengthening systems applied in this research were remarkably increased the beam strength, and the capacity retrieve of beams without openings. This study approved that steel links technique gave more prominent simplicity of use and low cost. FEM models were in good agreement with the corresponding experimental ones. However, the calculated ultimate loads were slightly higher than the experimental ultimate loads up to 10%.

Behavior and strength of headed stud shear connectors in ultra-high performance concrete of composite bridges

This study presents an experimental and numerical investigation on the static behavior of headed stud shear connectors in ultra-high performance concrete (UHPC) of composite bridges. Four push-out specimens were tested. It was found that no cracking, crushing or splitting was observed on the concrete slab, indicating that UHPC slab exhibited good performance and could resist the high force transferred from the headed studs. The numerical and experimental results indicated that the shear capacity is supposed to be composed of two parts stud shank shear contribution and concrete wedge block shear contribution. The stiffness increment of a stud in UHPC was at least 60% higher than that in normal strength concrete. Even if the stud height was reduced from 6d to 2d, there was no reduction in the shear strength of a stud. Short stud shear connectors with an aspect ratio as small as 2 could develop full strength in UHPC slabs. An empirical load-slip equation taking into account stud diameter was proposed to predict the load-slip response of a stud. The reliability and accuracy of the proposed load-slip equation was verified by the experimental and numerical load-slip curves.

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.

Finite element study of headed shear studs embedded in ultra-high performance concrete

A novel bridge repair method has been developed to strengthen steel bridge girders with section loss due to end corrosion. The repair comprises of welding headed shear studs to the non-corroded portion of the web plate and encasing them in ultra-high performance concrete (UHPC) to create an alternate bearing load path. The interaction between the headed studs and the UHPC panels is crucial in the force transfer. Therefore, a careful study is needed through high-fidelity finite element analysis to complement the experimental results. This paper presents the development of a model in Abaqus finite element software that enables capturing the behavior of studs embedded in UHPC. The model was validated using a series of experimental results from push-out tests with headed shear studs welded onto a thin web plate. Experimental results from push-out tests performed on stud diameters of 12, 16 and 19 mm and two levels of eccentric loadings were used to calibrate the modeling methodology. The model explicitly considers effects of material damage, contact between the studs and UHPC, and the precise geometry of the weld collar of studs. After validation, design parameters such as interaction of in-plane torsion and direct shear, and limits for web thickness-to-stud diameter ratio were studied to compliment the experimental data. The results are expected to inform engineers about the design of this novel repair method. In addition, this paper may enable future finite element studies on the performance of studs in UHPC.

Durability Evaluation of Headed Shear Studs Embedded in Ultrahigh-Performance Concrete via Electrochemical Corrosion

Durability Evaluation of Headed Shear Studs Embedded in Ultrahigh-Performance Concrete via Electrochemical Corrosion

Characterisation of a new flat mechanical shear connection mean for steel-concrete composite columns

For buildings in steel-concrete composite structure, the current practice of the shear connection in fully embedded columns is the implementation of headed shear studs. This type of connector has been mainly developed for composite beams and some disadvantages have been identified for column application. For example, due to the shear stud geometry, the difficulty of the reinforcement application and more complicated handling of the column are recognised. Taking into account the additional high resistance, stiffness, ductility and production efficiency criteria, an innovative type of flat shear connection, with the potential for a fully automatic fabrication process has been developed. The proposed new type of shear connectors is made out of regular reinforcement bars welded to the flanges of steel profiles under a specific arrangement. The conducted investigation consisted of three different variants: transversal, longitudinal and angled (V-shaped) of connectors applied to the HEB120 steel profiles. In addition, tests without any mechanical connectors were conducted as reference tests. The specific load-bearing behaviour in terms of load-slip curves for each connector variant has been obtained and analysed. After the tests, the specimens were opened and the failure patterns were investigated. 3D non-linear numerical simulations in the FE code Abaqus® have supported the performed investigations. In the results, the load flux, the decisive force-transfer mechanisms and resistance limits have been identified.

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.

Analytical prediction of the deformation behavior of headed studs in monotonic push-out tests

The deformation behavior of headed studs is an important issue in the design of steel and concrete composite structures. In recent years, there is a rapid increase in the application of headed stud shear connectors in new types of concrete such as crumb rubber concrete and ultrahigh-performance concrete. In this article, totally 154 monotonic push-out tests from the literature on experiments of headed stud in various types of concrete were gathered and evaluated with the aim to study the deformation behavior of headed studs. As a result of a careful analysis on the effects of stud diameter and concrete properties on the shear stiffness of studs through the historic database, a new equation for shear stiffness was proposed. The new formula is a reasonably good predictor and is suitable for studs with a diameter ranging from 10 to 30 mm in the concrete with cylinder compressive strength ranging from 22.0 to 200.0 MPa. New formula for the load-slip curve of headed stud which includes a parameter related to the shear stiffness was also proposed. It can give good prediction for the slip not only at low load level but also large load level.

A finite element based approach for fatigue life prediction of headed shear studs

Steel shear studs in bridges are subjected to rapidly fluctuating stresses causing fatigue failure. Research on fatigue of shear studs mainly focused on tests. Both AASHTO and Canadian design curve for fatigue resistance of shear studs are based on the tests conducted in the mid1960s by Slutter and Fisher. This paper presents a finite element based approach using push-out specimen for fatigue life estimation of headed shear stud connectors. Both crack initiation and crack propagation life are estimated and an excellent correlation is found when compared against test results. In addition, since a significant amount of push-out tests data on headed shear studs are now available, this paper evaluates the fatigue design curves of different standards, with special focus given to evaluation of the value of constant amplitude fatigue limit (CAFL) given in the current AASHTO and Canadian code (CSA S6-14). The regression analysis also shows that the current fatigue curves in different codes can be used for shear studs as large as 31.8 mm. Thus, restriction of use of studs larger than 25 mm (1 in.) in different bridge codes (CSA S6, Eurocode 4, and AASHTO) can be waived.

Parametric Push‐Out Analysis on Perfobond Rib with Headed Stud Mixed Shear Connector

In steel and concrete composite structures, it is unfavourable to install many headed studs or perfobond ribs with narrow spacings at the joints. To solve this problem, a new type of a mixed shear connector was developed by combining a headed stud and perfobond rib at the same steel beam flange. In this paper, totally nine push‐out tests were conducted. The main purpose was to compare the failure mode and the load‐slip behavior of the headed stud, perfobond rib, and mixed shear connector. Furthermore, 19 nonlinear finite element simulations were performed. The effects of connector dimension and material properties on the structural behaviors of mixed shear connectors were studied. Based on the experimental and parametric study, an analytical equation was finally proposed to evaluate the shear capacity of perfobond rib with a headed stud mixed shear connector.

Static and fatigue push-out tests of short headed shear studs embedded in Engineered Cementitious Composites (ECC)

Engineered Cementitious Composites (ECC) is a family of high-performance fiber-reinforced cementitious composites with high tensile ductility and emerging in steel-concrete composite structures. In the composite structures, shear force transfer through shear connectors plays a critical role to integrate the steel and concrete. This study experimentally investigates the static and fatigue behaviors of short studs embedded in ECC through push-out tests of nine specimens. The test results of the shear strength, slip capacity, and fatigue resistance are compared with current design codes. The shear strength agrees well with that obtained from AASHTO LRFD, while the Eurocode 4 and Chinese code underestimate the shear strength. The slip capacity satisfies the ductility requirement in Eurocode 4. Based on the fatigue tests results, an S-N curve related to a survival probability of 95% is proposed. Empirical formulas are derived as a tool to help predict the load-slip behavior of the specimen under fatigue loading.

Influence of Elevated Temperatures on the Composite Joint of a Composite Beam in Fire

The use of partial connection theory for composite beams at ambient temperatures is state of the art according to Eurocode 4 (EN 1994-1-1 2009), hereby the number of shear connectors can be reduced up to a minimum degree of shear connection. When designing for fire resistance, the partial shear connection theory is, however, not directly applicable in accordance to Eurocode 4—Part 1-2 (EN 1994-1-2 2008). Due to the different behaviour of steel and concrete components at elevated temperatures, high residual stresses are to be expected in the composite beam. In certain situations, the effect of these stresses on the composite joint may lead to a slip of the composite joint higher than the minimum ductility of the headed stud shear connectors given in the Eurocode 4 (EN 1994-1-1 2009). This paper shows how the usage of partial connection theory affects the load carrying capacity of a composite beam in the event of fire. A series of four large-scale fire tests was conducted to investigate various effects of a reduced degree of shear connection on the deflection behaviour and the composite joint. The experimental setup will be described, as well as the 9.0 m composite beams and test sequence. Furthermore, the deflection and temperature measurements as well as the given boundary conditions will be explained. The presented results of one fire test provide an initial conclusion about the deflection behaviour of the composite girder with a reduced degree of shear connectors as well as the behaviour of the composite joint at elevated temperatures. Due to the transient thermal conditions in the composite section and the following variation of the reduction of the yield stresses in the components of a composite section, a rising degree of shear connection has to be expected with rising temperature. Furthermore, three major effects on the slip caused by rising temperature on the composite joint will be presented.

Effect of Angle Shear Connectors on the Behavior of Composite Concrete Steel Flexural Members Under Negative Moment

This research presents an experimental program to study the effect of using angle shear connectors instead of the headed stud on the flexural behavior of composite beams under negative bending moment (NBM). Both the angle and headed stud shear connectors used in this study have the same cross-sectional area. Five composite beams were casted and tested using three-point load configuration to ensure the NBM effect. Different parameters were included in this study such as the type of shear connector, bond interaction (partial and complete bond interaction) and arrangement of angle shear connectors. Two proposals method were suggested for angle setting in this study to investigate the structural behavior of the composite section. It has been found that, in the case of single angle shear connectors, the ultimate strength decreased by 4.12% compared with samples with the headed stud shear connectors. The direction of the angle setting has been shown to affect the flexural behavior of the composite section.

Behaviour and push-out test of concrete dowel connectors for longitudinal shear in shallow-hollow composite beams

The shear transferring mechanisms of shallow-hollow composite beams with concrete slab cast in place are different with conventional headed shear studs and have not been investigated previously. In this study, the behavior and push-out test of concrete dowel connectors for longitudinal shear in shallow-hollow composite beams are described. The theory prediction for concrete dowel connectors without tie-bars adopted in this study was based on EN 1992-1-1 and EN 1994-1-1. Push-out tests of three specimens were conducted and the results were compared with theory prediction and published formula to identify longitudinal shear resistance. The failure of specimens and the ultimate failure load values of push-out test were proved that the behavior of concrete dowel in shallow-hollow composite beams was not under pure shear stress.
 Keywords: steel-concrete composite beam; shallow-hollow composite beam; concrete dowel connectors; longitudinal shear resistance; shallow floor structure.

Design considerations for headed shear studs embedded in ultra-high performance concrete as part of a novel bridge repair method

This paper presents design parameters and considerations for headed studs embedded in UHPC as part of a novel bridge repair method. The method is developed for retrofitting of steel bridge girders with severe corrosion at the ends. In this repair method, headed shear studs are welded to the undamaged portion of the web plate at the girder end and encased with Ultra-High Performance Concrete (UHPC). The end bearing capacity is increased by transferring shear forces from the web to UHPC casts through the studs. Sixteen push-out tests were performed to evaluate design considerations prior to field implementation. The effects of a) eccentric loading, b) concrete material variations, c) clear and side cover, d) welding/surface preparation, and e) curing of UHPC on shear capacity of studs were studied. The results were used to establish design and installation recommendations for the proposed repair.

Push-out behavior of headed shear studs welded on thin plates and embedded in UHPC

A novel repair method has been developed for steel bridge girders with corrosion damage at the ends. The concept involves welding headed studs to the intact portion of the web plate and encasing them in Ultra-High Performance Concrete (UHPC). This creates a bearing force transfer mechanism to bypass the corroded web plate. Since the headed studs play a crucial role in transferring the shear forces to the UHPC, a careful study is needed to validate their shear capacity when welded to thin web plates typical of steel girders. This paper presents the experimental results from a series of push-out specimens with studs welded to a 9.5-mm thick plate extracted from an old steel bridge. The objective of the study is to understand the influence of design parameters including diameter, spacing and layout on the capacity and failure mechanism of headed studs in UHPC. The experimental results indicate that the capacity was consistently higher than that predicted by design codes such as AASHTO or Eurocode-4. The results show that studs with significantly smaller spacing than what is typically used in practice reach their full capacity. This enables placement of many studs in small regions of the web as may be required in this repair design. The consistent mode of failure was shear rupture at the stud shank. Based on these results, an existing capacity formulation was refined for headed studs embedded in UHPC.

Comparative Study between Linear-Interpolation and Stress-Block Methods of Composite Design Using Cold-Formed Steel Section

For decades, Hot Rolled Steel (HRS) section was in use in construction of buildings and bridges. The simple reason is that the use of HRS section in composite systems is well established by standard rules and their design necessities as provided in the codes. In this paper, the use of doubly oriented back-to-back Cold-Formed Steel (CFS) section coupled with bolted shear connectors in composite floor system was demonstrated. The bolted system of shear connector provides an alternative to headed stud shear connector with CFS section as welding of the stud connector is practically not feasible on CFS section because of its thinness nature. The loading system used was four-point bending test to determine the flexural strength capabilities of the composite floor system. The resulting composite floor system has proven to provide adequate strength and stiffness properties under the applied loads. The results have shown that the theoretical value of flexural capacities calculated agrees reasonably well with the experimental values. In conclusion, the composite floor system can be used in small and medium size buildings, as well as in light weight construction industries.

Finite element modelling of steel-concrete composite beams with profiled steel sheeting

Steel-concrete composite beams have been widely used in modern construction industry, where headed shear stud connectors are commonly welded through profiled steel sheeting to ensure full/partial composite action between the beam and the composite slab. For such composite beams, there are complex interactions between different components, leading to different failure modes. Finite element (FE) analysis could be used to understand the fundamental behaviour of such beams. But previous FE models have adopted various assumptions to simplify the modelling of some complex interactions such as the interaction between the shear studs and concrete. Accordingly, those FE models have limitations to capture certain types of failure modes. Meanwhile, the actual forces carried by the studs and profiled steel sheeting have not been quantitatively determined. In this context, this paper aims to develop a detailed FE model for composite beams with profiled steel sheeting by considering realistic interaction between different components, fracture of the shear studs and profiled steel sheeting, as well as tensile and compressive damage in concrete. The developed FE model can satisfactorily predict the full-range load–deformation curves of the composite beams and the shear force–slip relationship of the embedded shear studs. The predictions agree very well with a wide range of test data reported in the literature.