Rib Shear Connectors Research Articles

News: Steel Construction 2/2019

AbstractECCS NewsECCS R&D ActivitiesECCS Training CoursesECCS Member EventsECCS PublicationsIn MemoriamBauhaus, Modernism and the Contribution of EngineersBauhaus, Modernism and the Contribution of EngineersNewsCooperation between German and Chinese bridge engineersPHD‐ThesisComposite Bridges: Innovative ways of achieving composite actionStructural behavior of steel columns in fireStructural performance of steel and concrete hybrid beams with rib shear connectors and large web opening)Investigation of the Load‐Bearing Behaviour of CoSFB‐Dowels

Experimental study on the shear resistance of a comb-type perfobond rib shear connector

A comb-type perfobond rib shear connector that can be applied to a prefabricated steel and concrete composite bridge is proposed in this paper by arranging perfobond rib shear connectors (hereinafter referred to as PBL shear connectors) at intervals. The mechanical property of shear resistance is investigated through experimental and numerical methods. Push-out tests covering various design variables and a comparison between comb-type and conventional PBL shear connectors are conducted. FEM models are established to simulate the test and for further studying the mechanism during entire loading process. The proposal mechanism of connectors under shear load was developed according to the analysis based on numerical simulation. It was concluded that comb-type connectors exactly performed better in stiffness and shear capacity than conventional ones, and a conceivable reason was given according to the analysis on mechanism.

Experimental Study of the Mechanical Behavior of the Steel–Concrete Joints in a Composite Truss Bridge

The mechanical behavior of the steel–concrete joints in a composite bridge was investigated. Pull-out tests on eight specimens were carried out to evaluate the connection performance of Perfobond rib shear connectors (PBL shear connectors). In addition, static load tests were conducted on three composite joint specimens with a scale of 1/2 in a composite truss bridge. The crack load, load–displacement curves, strain distribution, and the joint stiffness were obtained from the composite joint to analyze the mechanical behavior of steel–concrete joints. The experimental results show that the embedded depth plays an important role in the ultimate bearing capacity and the deformation of PBL shear connectors and could even change the failure mode. Based on the test results of composite joints, the displacement increased almost linearly with the horizontal load on the concrete chord. There was no evident failure, and large deformation occurred in composite joints. In addition, the ultimate loads obtained from three composite joint specimens were greater than 2.93 times the design load (2050 kN). These investigated composite joints had excellent bearing capacity (above 6000 kN). This study will provide an experimental reference for the design of steel–concrete joints for composite truss bridges.

Numerical simulation of Y-type perfobond rib shear connectors using finite element analysis

This study presents finite element analysis (FEA) on a Y-type perfobond rib shear connection using Abaqus software. The performance of a shear connection is evaluated by conducting a push-out test. However, in practice, it is inefficient to verify the performance by conducting a push-out test with regard to all design variables pertaining to a shear connector. To overcome this problem, FEA is conducted on various shear connectors to accurately estimate the shear strength of the Y-type perfobond rib shear connection. Previous push-out test results for 14 typical push-out test specimens and those obtained through FEA are compared to analyze the shear behavior including consideration of the design variables. The results show that the developed finite element model successfully reflects the effects of changes in the design variables. In addition, using the developed FEA model, the shear resistance of a stubby Y-type perfobond rib shear connector is evaluated based on the concrete strength and transverse rebar size variables. Then, the existing shear resistance formula is upgraded based on the FEA results.

Failure Modes and Resistance of Perforated Steel Rib Shear Connectors under Uplift Forces

In recent years, there is a rapid increase in the application of perforated steel rib shear connectors in steel and concrete composite structures. The connectors must not only ensure shear transfer but also sufficient uplift resistance. The shear behavior of connectors has been extensively investigated. However, studies on uplift resistance are lacking so far. Therefore, three push‐out test specimens were tested to investigate the shear and tension behavior of perforated L‐shaped and plain steel rib shear connectors. The failure modes of connectors were analyzed, and analytical models for the determination of uplift resistance were derived based on test results. The results showed that the ductility of perforated steel rib shear connectors under uplift force was smaller than that under shear force, and more severe concrete damage surrounding the rib and larger bending deformation of transverse steel bar was observed. The rib flange of L‐shaped perforated rib has a significant contribution to the uplift resistance. It was suggested to increase the rib height of L‐shaped rib to avoid the horizontal crack at the height of the rib flange. The validity of the proposed analytical models was confirmed by comparing the failure modes and capacities of specimens.

Hysteretic performance of stubby Y-type perfobond rib shear connectors depending on transverse rebar

The shear behavior of stubby Y-type perfobond rib shear connectors differs according to the diameter of the transverse rebar used for composite action. Pull-push test specimens with transverse rebar of different diameters (D10, D13, D16) were manufactured for monotonic and cyclic loading tests to investigate the effects on not only the shear resistance but also the hysteretic performance. The energy dissipation capacity, shear strength, and ductility increased with the diameter of the transverse rebar, while the stiffness degradation appeared comparable. The specimens with D16 transverse rebar had high ductility, while those with D10 and D13 transverse rebar had moderate ductility.

Experimental behavior of double-row Y-type perfobond rib shear connectors

Although existing studies have only analyzed Y-type perfobond rib shear connectors arranged in a single row, practical applications can apply numerous such connectors to beams with narrow spaces between them. The present study aimed to evaluate the structural behavior of double-row Y-type perfobond rib shear connectors, and thus describe grouped Y-type perfobond rib shear connectors. Push-out tests were conducted in accordance with Eurocode-4, and the relative slip, shear resistance, and ductility were measured. There were two primary variables (spacing and number of Y-type perfobond rib shear connectors) and three types of test specimens: single row, double rows (120 mm spacing), and double rows (300 mm spacing). The representative single-row specimen was used to validate the push-out test results by providing a comparison with previous tests, and provided a shear resistance reference value. The other two specimen types consisted of multiple Y-type perfobond rib shear connectors attached in parallel to an H-beam. Test results revealed that shear resistance increased as the number of shear connectors increased; however, the structural behavior depended on the shear connector spacing. The specimen with wider spacing demonstrated a better ultimate load and ductility relative to the specimen with narrower spacing. Wider shear connector spacing thus leads to better structural behavior retention.

Load Sharing and Slip Distribution in Multiple Holes of a Perfobond Rib Shear Connector

AbstractPerfobond rib shear connectors (PBL shear connectors) are widely used in composite structures for their excellent mechanical performance. However, the mechanism responsible for the mechanic...

Internal force transfer effect-based fatigue damage evaluation for PBL shear connector groups

This study presents an analytical method to analyze fatigue damage in Perfobond rib (PBL) shear connector group under cyclic loading. A step-by-step calculation procedure is proposed and implemented to quantify the fatigue damage in PBL shear connector groups, considering the uneven shear force distribution at different layers of shear connectors. The fatigue life of the PBL shear connector group is evaluated, and the effect of uneven shear force distribution on fatigue life is studied. The investigation results indicate the coupling effect between fatigue damage and internal force distribution, and reveal that the fatigue damage indices are different at different layers of a PBL shear connector group. The uneven force distribution reduces the fatigue life of PBL shear connector group, and the unevenness decreases with the development of fatigue damage. The degree of fatigue damage in each layer of the PBL shear connectors is sensitive to the upper load level. The proposed approach offers an analytical tool for evaluating the fatigue behavior of PBL shear connector groups.

Influence of transverse rebar on shear behavior of Y-type perfobond rib shear connection

This study experimentally investigated the effects of transverse rebar on the shear behavior of Y-type perfobond rib shear connectors. Push-out tests were performed on 12 specimens for which the strength and diameter of transverse rebar were utilized as variables. Test results from a previous study were used to confirm the shear strength and ductility of the Y-type perfobond rib shear connectors, along with the initial cracking and failure modes of the concrete. The results showed that shear strength increased as the diameter of the transverse rebar increased, and this effect was amplified in concrete with lower compressive strength.

Puzzle-shaped rib shear connectors subjected to combined shear and tension

Open rib shear connectors are increasingly used as shear connectors and anchors between concrete and steel members of composite structures. In many cases, the rib connectors are subjected to combined shear and tension forces. However, until now, the structural response and interaction behavior of rib shear connectors exposed to tension and shear has not been analyzed. The current design guidelines do not provide a recommendation for computing the strength of rib shear connectors (traditionally used as shear connectors) under combined tension and shear. Therefore, the present paper presents systematic studies on the interaction behaviour of puzzle-shaped rib shear connectors, also called composite dowels. Based on tests results gained in a novel test setup and FE-simulations, the interaction properties of composite dowel rib connectors are analyzed and a model approach for the tension and shear interaction is proposed.

Experimental investigation on the bearing mechanism of Perfobond rib shear connectors

The bearing capacity of Perfobond rib shear connectors (PBL shear connectors) mainly comes from adhesion, interfacial frictional force, dowel actions, and end bearing force. However, the contribution of each component to the total bearing capacity has not been deeply addressed. An experimental study on 18 PBL shear connectors deeply embedded in massive reinforced concrete was performed to determine the bearing mechanism. The strain distributions were sophisticatedly measured by the optical fibers on the perforate steel plate and passing rebar. Results showed that key design parameters such as diameter of the holes in the perforated steel plate, diameter of passing rebar and the transverse reinforcement ratio influenced the bearing capacity. A formula was proposed for estimating the bearing capacity of PBL shear connectors, which quantifies the portions of shear-friction force and the dowel action of the passing rebar. Comparisons between the analytical solution and test results validated the proposed formula. With this validated formula, further dissection of the bearing mechanism of PBL shear connectors was carried out.

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.

Direct and Flexural Shear Strength of Composite Beam with Perforbond Rib

When Perfobond Rib shear connectors are used as flexural materials in structures such as bridges, they show flexural shear behavior due to external force, rather than direct shear behavior. The aim of this study is thus to analyze the difference between both behaviors. First, we prepared a specimen to analyze direct shear behavior using Perfobond Rib shear connectors, analyzed the characteristics of behavior with a push-out test and proposed a formula of shear resistance assessment. Proposed formula shows a relatively good fit with less than 10% error. A flexural shear test was then conducted based on the result of the direct shear test. Based on the static flexural test it analyzed the flexural behavior and the flexural shear stress it calculated. Direct shear stress and EN 1994-1-1 to lead and be calculated, it compared the flexural shear stress and it analyzed in about the shear resistance stress which it follows in load direction. Finally, we compared both test results, and the comparison showed that the flexural shear stress is approximately 6% stronger than the direct shear stress.

A new approach to determine strength of Perfobond rib shear connector in steel-concrete composite structures by employing neural network

The main objective of this study is to introduce a novel numerical approach, based on Artificial Neural Network (ANN), to predict the shear strength of Perfobond rib shear connector (PRSC). For this purpose, 90 records were extracted from the literature and were used to develop a number of Bayesian neural network models for predicting the shear strength of PRSC. An accurate ANN model was attained with a high value of correlation coefficient for the train and test subsets. Having a reliable ANN, a parametric study on the shear strength of PRSC was carried out to establish the trend of main contributing factors. The majority of assumptions, considered by empirical equations, were predicted by the developed ANN. Moreover, a sensitivity analysis of input variables was conducted; the outcomes revealed that the area of concrete dowels had the strongest influence on the shear strength of PRSC. Eventually, using the validated ANN, an abundant number of curves (Master Curves) were generated to introduce a user-friendly equation. According to the results, both the ANN model and the proposed equation reflect a higher accuracy than other existing empirical equations.

Analysis of the Shear Behavior of Stubby Y-Type Perfobond Rib Shear Connectors for a Composite Frame Structure.

Shear connectors are used in steel beam–concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13.

Experimental measurement of dynamic properties of composite slabs from frequency response

Nowadays, in order to increase the live load bearing capacity and provide large-scale cost savings associated withconstruction projects, using structures with a lower dead load and higher strength is extremely common throughout the world. This issue causes structures to be highly susceptible to vibration and, asa consequence, meeting vibration serviceability dominates design criteria. Hence, identifying dynamic characteristics is crucial to provide a desirable serviceability. Recently, unfilled steel-concrete composite decks with perfobond rib shear connectors are used in buildings and bridges asa novel structural system. A little amount of research has been reported till date on the dynamic characteristics of this structural system. Thus, this study focuses on the dynamic characteristics of unfilled steel-concrete decks, including normal-weight high-strength concrete (HC) and lightweight high-strength concrete (LHC). Some of the main dynamic characteristics such as damping ratio, natural frequencies, and frequency response functions (FRFs) assessed by means of non-destructive technique (NDT) with hammer excitation. Subsequently, the experimental results in terms of natural frequencies were compared with the finite element model (FEM) predictions. It is concluded that there is good agreement for natural frequencies with difference of less than 13% and consequently the developed FEM model can be used for structural performance prediction and damage detection of composite decks with reliable accuracy. The results show that the damping ratios and natural frequencies of the decks fabricated with LHC (DLHC) and HC (DHC) decreases in comparison to those of decks fabricate with plain concrete (DPC). The most effective mode was the first mode with a damping ratio of almost 0.5% for both DHC and DLHC. DPC and DLHC had approximately similar serviceability, whereas DLHC can be more applicable than DPC due to lower weight.

Push-out tests and evaluation of FRP perfobond rib shear connectors performance

The behavioural characteristics of FRP (fibre-reinforced polymer) perfobond rib shear connector was examined through push-out tests in order to verify the applicability for pedestrian bridge structure. The aim of this study is to determine interaction between high performance concrete slab and handmade FRP plate which represent web of the composite beam. Combination of these modern materials leads to structural system with both great load bearing capacity and also sufficient flexural stiffness of the composite element. Openings cut into the GFRP plate at a variable spacing allow GFRP reinforcement bars to be inserted to act as shear studs. Hand lay-up process can increase suitable properties of FRP for connection by perfobond rib shear connectors. In this study, three push-out tests on fiber-reinforced polymer were performed to investigate their shear behaviour. The results of the push-out tests on FRP perfobond rib shear connector indicates great promise for application in full scale structures.

Analytical Study on Internal Force Transfer of Perfobond Rib Shear Connector Group Using a Nonlinear Spring Model

Analytical Study on Internal Force Transfer of Perfobond Rib Shear Connector Group Using a Nonlinear Spring Model

Assessing the pry-out resistance of open rib shear connectors in cracked concrete – Engineering model with aggregate interlock

In steel and concrete composite structures, an efficient type of open rib shear connector, the so called composite dowel connector, can be used to transfer shear forces between the concrete slab and the steel section. In regions with negative bending moment, where concrete cracking occurs, the shear capacity of composite dowels with pry-out failure is significantly reduced. Concrete cracks appear as discrete discontinuities in the pry-out cone, which induce a pry-out cone detachment. In the cracks, the shear stress transfer is restricted to aggregate interlock. So far, the well-known design models do not account for concrete cracking. Therefore, they usually overestimate the composite dowels’ shear resistance in cracked concrete. To resolve that structural safety deficit, the present article proposes a mechanical model for the assessment of the pry-out resistance of composite dowels. The novel approach can be applied to cracked and uncracked concrete slabs and shows good agreement with experimental investigations. The model is validated by a test data base and afterwards converted to the design load level. In the future, the approach can be assigned to other types of shear connectors, for example to fasteners and headed studs in cracked concrete.