Behavior Of Shear Connectors Research Articles

Experimental Analysis of the Mechanical Behavior of Shear Connectors for Precast Sandwich Wall Panels When Subjected to the Push-Out Tests

Precast concrete sandwich panels consist of two outer layers connected by a central connector and an inner insulating layer that enhances thermal and acoustic performance. A key challenge with these panels is eliminating thermal bridges caused by metallic connectors, which reduce energy efficiency. PERFOFRP connectors, made from perforated glass fiber-reinforced polymer (GFRP) sheets, have been proposed to address this issue. These connectors feature holes that allow concrete to pass through, creating anchoring pins that enhance shear resistance and prevent the separation of the concrete layers. This research aimed to evaluate the effect of the diameter and number of holes on the mechanical strength of PERFOFRP connectors. Three diameters not previously reported in the literature were selected: 12.70 mm, 15.88 mm, and 19.05 mm. A total of 18 specimens, encompassing 6 different configurations with varying numbers of holes, underwent push-out tests. The most significant resistance increase was a 15% gain over non-perforated connectors, observed in the configuration featuring three holes of 19.05 mm. The connections exhibited rigid and nearly linear behavior until failure.

Efficiency of shear connectors under combined shear and torsion

The connection of steel elements to concrete is typically achieved through embedded shear connectors (anchors) placed at the interface of concrete and steel. These shear connectors come in various types, such as headed studs, welded or coupled rebars, shear lugs, or a combination of these, designed to handle large shear forces. Shear connectors primarily resist shear forces and bending loads. However, when the load is not applied along the centroid of the shear connector, it generates a torsional moment in addition to shear- and flexure-induced moments, impacting the performance of shear connectors. To address this phenomenon, this experimental study assesses the behavior of shear connectors, including studs, shear lugs, and rebars, both individually and in combination, under three different load eccentricities relative to anchors spacing connectors (0, 0.25, 0.50, and 0.75). The results are then compared with the control specimen (without eccentricity). The findings revealed that vertical shear lugs can significantly enhance the shear capacity, and ACI 318-19 is conservative in this regard by 41.5% for a relative load eccentricity of 0.75. Nonetheless, it gives good estimations of the shear capacity of connectors without vertical shear lugs. HIGHLIGHTS Contributing to the very limited data on the performance of anchors under the combined action of shear and torsion. ACI 318-19 [1] provides reliable estimations of shear strength for studs/rebars, both with and without eccentricity. However, it tends to be conservative by 41.5% (for a relative eccentricity of 0.75) when horizontal and vertical shear lugs are utilized.

Lateral load behavior of shear connections between steel storage racks and the spine bracing with posts

High-rise steel storage racks are cold-formed thin-walled steel frames, which achieve their lateral strength and stiffness by the use of a spine bracing system in the down-aisle direction commonly located at a short horizontal distance away from the main rack frames. The shear connections between the main rack frame and the spine bracing system play a dominant role in the effectiveness of the spine bracing system. This paper experimentally investigates the behavior of the shear connections used in industrial practice between a steel storage rack and the spine bracing system with posts using four groups of three nominally identical connection specimens. By employing a digital image correlation (DIC) system, the tests generate comprehensive data and establish the real-time deformation fields of individual components of such shear connections. Based on the component-based approach, a linear-elastic analytical model is developed for the type of shear connections under consideration. The proposed analytical model explicitly captures the behavior of the individual connection components, including the three-dimensional flexural bending of endplates, as well as the distortions of the open sections of the upright and the bracing post. Based on the proposed model, this paper quantifies the contribution of each component towards the total deformation of the shear connections. The investigation establishes that the cross-sectional distortion of the bracing post and the out-of-plane bending of the upright web are the most flexible components of such shear connections. Recommendations associated with the shear connections under consideration are proposed for the rack designers and manufacturers.

The behavior of Shear Connectors in Steel-Normal Concrete Composite Structure under Repeated Loads

In today's construction industry, the use of composite beams is becoming more and more important, particularly for long-span bridges that must withstand repeated loads from moving automobiles. This work investigates the behavior of composite beams through experimentation. Six push-out steel-concrete specimens are made and tested with various levels of static and repetitive loading applied. The specimens are made of rolled steel sections that are joined to concrete decks on both sides by stud shear connectors. Two approaches—one static and the other repeating—applied a push-out load to two sets of samples. One has a stud shear connector measuring 16 mm, and the other measures 25 mm. Three specimens were made for each group. To determine the final load, one specimen from each group underwent a static push-out test in the first stage. In the subsequent phase, repeated loads of 0-80% and 25-80% of the maximum static load were applied to the remaining ones. The analysis process measured the variation in slip between the concrete decks and the steel section over several load cycles. It was found that the recorded slip values at the ultimate load increased about four times just before the failure. The recorded values of the residual slip at the end of each load cycle decreased with the increase in load cycle numbers. Also, it was found that the values of the residual slip depend on the values of the lower and upper limits of the load level. Doi: 10.28991/CEJ-2024-010-01-013 Full Text: PDF

On the load‐carrying behaviour of CSTC slim‐floor beams

AbstractComposite steel truss and concrete (CSTC) beams are steel‐concrete composite structures mostly used as slim‐floor systems in industrial buildings. The proposed paper focuses on the load‐bearing behaviour of the so called NPS beam system as a specific type of CSTC beam. This system is made of a sinusoidal smooth steel truss welded to a steel plate, and embedded in cast‐in‐situ concrete. Unlike standard composite beams, NPS beams do not have dedicated shear connectors for transferring the longitudinal shear force from the steel part to the concrete. The shear connection between steel and concrete is enabled by the sinusoidal bar as an integrated part of the steel profile. The load‐slip behaviour of the shear connections in NPS beams was recently investigated through push‐out tests and appropriate design rules were proposed to predict their resistance. However, the longitudinal shear connection behaviour within the overall beam system is still not fully understood and requires further investigations. Furthermore, the ductility of composite slim floor systems depends strongly on their geometrical and mechanical properties. Strain‐limited analyses provide more reliable design predictions, but typically still simplify the shear connection behaviour strongly. It is therefore reasonable to conduct full‐scale experimental tests to investigate the structural behaviour at a cross‐sectional and a global level. The presented work addresses those issues through preliminary strain‐limited analyses and the description of an advanced measurement concept using fibre optical sensors for full‐scale beam tests.

Experimental studying structural behavior of shear connector in cold-formed steel - concrete composite beam

An experimental push-out test was carried out on 12 specimens in 6 groups to investigate the mechanical behavior of shear connectors in cold-formed steel-concrete composite beams. Specimen groups have differences in rivet spacing, shear connector spacing, tab aspect, and rebar through shear connectors. The mechanical behavior was evaluated through quantities such as shear resistance, relative slip between the steel beam and concrete slab, and failure modes. The results show that screw significantly affects the mechanical behavior of shear connectors in cold-formed steel-concrete composite beams.

Studying the effect of embedded length strength of concrete and diameter of anchor on shear performance between old and new concrete

Abstract This article illustrates the specifications required to accurately design, specify, and install embedded anchor bolts between old and new concrete composite specimens for concrete repair or reinforcing of collapse concrete a research hotspot. The concrete slabs are facing a major challenge with deterioration, especially for reinforcement corrosion caused mainly by severe cycles of various chemical attacks. In this research, the impact of using contact plates between composite specimens was investigated by testing grouped specimens, thereby the models were divided into two groups, which tested under static load. The findings of a series of tests conducted to evaluate the structural behavior of shear connections (by pushout test) by including many parameters; the diameter (8, 12 and 16 mm), bounding between different compressive strength should be changed [normal concert (NC) mixes , ultra-high performance fiber concrete (UHPFC), and self-compacting mortar (SCM)]. Also, the embedded length of bolts was varied from 70, 130, to 190 mm. These parameters were studied individually in two groups. The first group was without contact plate and the second group was with contact plate. Experimental findings were obtained and reported, including the failure modes, maximum resistance, slippage capacity, and load–slip characteristic responses of the connections. Based on the obtained data, a relationship between the studied parameters was investigated. Experimental findings showed that the ultimate strength of rough surface specimens (without contact plate) was about 31% greater than that of smooth surface specimens (with contact plate), and obviously, all pushout specimens failed due to stud shank failure.

Analytical model for the load-slip relationship of bearing-shear connectors

The shear behavior of shear connectors in steel-concrete composite structures mainly depends on its load-slip relationship. The load-slip relationship not only reflects the shear capacity and slip capacity of the shear connectors, but also the degradation of shear stiffness during loading. In this study, fifteen push-out tests were carried out to investigate the load-slip relationship of the novel bearing-shear (B-S) connectors, which consist of pressuring-bearing plates and shear plates. Based on push-out tests, the influence of the shape and height of the pressure-bearing plate, and the shear plate shape on the load-slip relationship of the B-S connectors was analyzed. Then, an effective finite element model, validated by push-out tests, was used to study the influence of the concrete strength, and the thickness and tensile strength of the shear plate on the load-slip relationship of B-S connectors. Finally, based on the push-out tests, numerical analysis and theoretical analysis, an analytical model expressing the load-slip relationship of the B-S connectors was proposed.

A Lego‐like steel‐framed system for standardization and serial production

AbstractA Lego‐like steel‐framed structural system has been developed within the frame of an RFCS project, REDUCE, to facilitate 1) deconstruction of composite structures, 2) circularity at structure and element levels, and 3) serial production in construction by promoting a greater standardization of structural elements. The system utilizes innovative demountable shear connections for composite flooring solutions with precast concrete elements, and adjustable steel connections for use in both beam‐to‐beam and beam‐to‐column connections. The first use case of the structural system has been realized in the Petite Maison project which is a demonstration project for circularity and contributes to the event ESCH2022. Each construction element is linked to a digital database and remains available for future reuse, as a result of the plug‐and‐play, demountable and robust features of the developed system. This paper presents the proposed demountable system, the results from experiments and finite element analyses on the behaviour of shear connections, composite beams, and steel connections, and indicates the analysing methods for structural engineers to open a pathway for full implementation of the structures built into digital tools, fabrication, and construction.

Experimental studying structural behavior of shear connector in cold-formed steel - concrete composite beam

An experimental push-out test was carried out on 12 specimens in 6 groups to investigate the mechanical behavior of shear connectors in cold-formed steel-concrete composite beams. Specimen groups have differences in rivet spacing, shear connector spacing, tab aspect, and rebar through shear connectors. The mechanical behavior was evaluated through quantities such as shear resistance, relative slip between the steel beam and concrete slab, and failure modes. The results show that screw significantly affects the mechanical behavior of shear connectors in cold-formed steel-concrete composite beams.

Application of Fibre Optical Sensors in Push‐out Tests on Composite Steel Truss and Concrete Beams

AbstractExperimental push‐out tests have been playing an essential role for the evaluation of the structural behaviour of shear connectors in steel‐concrete composite beams along with the development of analytical design guidelines for predicting the respective longitudinal shear capacity. Although standard push‐out tests allow to quantify the global response of the specimen in terms of load‐slip behaviour, numerical simulations are usually needed to broaden the mechanical insight with a special focus to the areas involved in the mechanical failure. This holds in particular for composite steel truss and concrete beams, where a dedicated shear connection does not exist. The shear connection relies instead on a mechanical interlock between the steel parts and the concrete.Modern measurement devices allow expanding the experimental insight to internal mechanisms of combined concrete‐steel failure. This paper reports on the instrumentation of push‐out tests on composite steel truss and concrete (CSTC) beams with the support of a distributed fibre optical sensing (DFOS) system and evaluates the experimental results. The content presents different concepts of fibre installation and discusses the respective rate of success and the measurement ranges along the global load‐slip curves of the push‐out specimens. The results from the DFOS system provide the strain field histories along essential structural elements embedded in concrete within a crucial range of the load‐slip curves. Hereby it was possible to gain more insight into the load‐bearing mechanisms and identify the material component most likely involved in the stiffness degradation of the push‐out specimens.

Perforated board shear connector for timber-concrete composites

ABSTRACT Timber-concrete composites systems offer major structural advantages, as well as additional benefits in terms of sustainability in comparison with only-timber or only-concrete solutions in building work. This paper describes the behaviour of shear connections for a new and simple construction system. It is based on the transmission of shear forces between the two layers of the system through perforations in the wooden boards, without the necessary collaboration for additional connecting elements (fasteners, adhesive or notches). Tests were performed to analyse how the behaviour of the shear connectors was affected by the arrangement of the boards (single or separated), the type and distribution of the perforations and the use of slab reinforcement. The experimental results indicate that this solution has high strength values, with very high service stiffness and ductile failure when at ultimate state, which enables a high level of composite action for connection design. The stiffness coefficient varies from 283.5–887.7 kN/mm per metre. The test pieces with separated boards and reinforcement bars showed the best results, regardless of the size and arrangement of the holes in the boards.

Experimental investigation on steel-concrete composite beams with expansion joints in concrete slab

This study examines experimentally the mechanical performance of composite steel and concrete beams with expansion joints in the concrete slab. Four composite beams with expansion joints in the concrete slab were tested, and various aspects of such beams including the effects of expansion joint locations ([Formula: see text], [Formula: see text], and [Formula: see text], where [Formula: see text]), expansion joint sizes (through and half-through of the concrete depth), and loading conditions (positive bending moment and negative bending) etc., were investigated. Load versus vertical deflection responses at key sections, and the strain development and distribution on the steel beam were measured. To explore the behavior of shear connectors on or near the expansion joint sections, the normal strain on shear connectors was measured. The bending strain and axial strain of shear connectors on joint sections were also discussed in detail. The theoretical methods for predicting the rigidities and ultimate load-carrying capacities of the composite beams were examined, and it was found that the current AASHTO-LRFD criterion without considering expansion joints in a concrete slab can still provide conservative estimations of ultimate loads of such beams under a negative moment. For composite beams under a positive bending moment, however, they are not applicable, due to the different failure modes. The test results from this research provide new information for improving the design, construction, management, maintenance, and structural health assessment of such beams that can be used in bridges and buildings, etc.

Push–out Test of Timber Concrete Composite Construction

In this study, push – out test specimen is proposed to explore the behavior of shear connectors in timber–concrete composite beams. Since there are no standard shapes and dimensions for determining the strength of connectors, push–out specimens such as those used for steel-concrete composite beams are suggested to study the behavior of connectors in timber concrete composite beams. Four specimens are tested. Two of these specimens are with one connector per side. The other two are with two connectors per side. The load and slip are recorded during testing. The results show that the ultimate load per connector ranges from 24.9 kN to 29.4 kN, with an average value of 26.9 kN. An equation is proposed to determine the ultimate load of the connector. Good agreement is achieved between the theoretical and experimental results. An average value of 0.98 is obtained for theoretical to experimental results.

The Behaviour of Shear Anchors with Different Grout Properties

AbstractDuring the assembling of a steel structure with anchors, grout should be used in connections between steel elements and a reinforced concrete support element. In horizontal and vertical joints, grout is used as a good construction practice for solving geometric tolerance problems. Grout can be used with cast‐in anchors or post‐installed anchors. However, the relation between anchor shear resistance and characteristic grout compressive strength is not described in detail in technical regulations. The behaviour of a connection considering achieved slip tolerances should match the boundary conditions set in the global analysis. In the support joint, grout properties could influence the value of the slip between a steel part and a concrete part of the joint. Slip value could be significant for the relevant design cases featuring the interaction of shear force and tension force. In this paper, results of the push‐out test conducted on anchors are presented. Based on the experimental test, the finite element analysis was performed to investigate the shear connection behaviour. According to the preliminary results, it can be concluded that a grout strength and a grout thickness influence the connection response when serviceability loads are applied, although they do not influence the ultimate load bearing capacity of anchors. In some cases, using the contemporary solutions of high strength grout materials, the slip between steel and concrete parts in the connection could be reduced.

Application of multi-hybrid metaheuristic algorithm on prediction of split-tensile strength of shear connectors

Shear connectors play a major role in the development of composite steel concrete systems. The behavior of shear connectors is usually calculated by push-out measurements. These experiments are expensive and take a lot of time. Soft Computation (SC) may be applied as an additional solution to remove the need for push-out testing. The objective of the research is to explore the implementation, as sub-branches of the SC approaches, of artificial intelligence (AI) techniques for the prediction of advanced C-shaped shear connectors. To this end, multiple push-out tests on these connectors will be carried out and the requisite data is obtained for the AI models. The Grey Wolf Optimizer algorithm (GWO) is built to define the parameters that influence the shear strength of angle connectors. Two regression metrics as determination coefficient (R2) and root mean square (RMSE) were used to measure the results of model. Furthermore, only four parameters in the predictive models are sufficient to provide an extremely precise prediction. It was found that GWO is a faster method and is able to achieve marginally higher output indices than in experiments.

Strength Capacity and Failure Mode of Shear Connectors Suitable for Composite Cold Formed Steel Beams: Numerical Study.

In this paper, the findings of numerical modeling of the composite action between normal concrete and Cold-Formed Steel (CFS) beams are presented. To obtain comprehensive structural behavior, the numerical model was designed using 3-D brick components. The simulation results were correlated to the experimental results of eight push tests, using three types of innovative shear connectors in addition to standard headed stud shear connectors, with two different thicknesses of a CFS channel beam. The proposed numerical model was found to be capable of simulating the failure mode of the push test as well as the behavior of shear connectors in order to provide composite action between the cold-formed steel beam and concrete using the concrete damaged plasticity model.

Experimental Study on an Innovative Shear Connector in Steel-UHPC Composite Structure

In order to improve the stiffness and shear bearing capacity of steel-UHPC composite bridge, an innovative shear connector named arc-shaped reinforcement shear connector was proposed and compared with the stud and perforated bar steel plate shear connector using the static push-out test. Considering shear connector diameter, a total of ten push-out specimens for five groups were designed. The results indicated that the failure modes and failure mechanism of the arc-shaped reinforcement shear connectors were significantly different from stud shear connector and perforated bar steel plate. Obvious failure characteristics such as crack and reinforcement were not observed for the arc-shaped reinforcement specimens except for fine cracks on the top of one specimen, but these were observed for the others two types of shear connector. The relative slip value of arc-shaped reinforcement shear connector at the maximum load was the smallest and less than 1 mm in three types of shear connectors. The stiffness and shear bearing capacity of arc-shaped reinforcement were higher than those of stud and perforated bar steel plate under the same diameter. Increasing arc-shaped reinforcement diameter could improve significantly static behavior of shear connector. When the diameter of arc-shape reinforcement was increased from 8 mm to 12 mm, the ductility factor, stiffness, and shear bearing capacity of arc-shaped reinforcement shear connector were improved by 174.32%, 214.76%, and 54.2%, respectively. A calculation method of shear bearing capacity was proposed by the least square method and multiple regression analysis and agreed well with the test result.

Long-term coupled analysis of steel-timber composite (STC) beams

In this paper, the long-term behaviour of steel-timber composite (STC) beams under sustained load is numerically investigated. The long-term constitutive law of timber that accounts for the effect of elastic modulus change due to the moisture content (MC) variation, creep, mechano-sorption, inelastic shrinkage/swelling, and thermal strain is adopted from the literature to develop a 1D fibre element model for long-term analysis of the timber components. The time-dependent behaviour of shear connectors is considered in the formulation by a time-dependent shear-slip model calibrated against the results of long-term pushout tests. A 3D diffusion analysis based on finite difference (FD) scheme is coupled with the 1D fibre element model to simulate the variation of MC and temperature within the timber section due to variations in the ambient relative humidity and temperature. The coupled hygro-thermo-mechanical model is verified against experimental and numerical models available in the literature and incorporated into the 1D composite fibre element formulation to simulate long-term behaviour of the STC beams under variable environmental condition. The accuracy of the analytical tool is verified against available experimental data and the model is used to estimate the creep coefficient of the STC floors for a service life of 50-year. Furthermore, the evolution of nonlinear time-dependent stress–strain in timber and shear forces in shear connectors are comprehensively investigated and discussed, and the influence of service load level, panel width, and shear connectors’ spacing on the long-term performance of the STC floors are highlighted. The results of parametric studies suggest a creep coefficient of 0.35 for 50-years’ design life of STC beams (applicable to a wide range of shear connectors).

State of the art on composite cold‐formed steel flooring systems

AbstractThis article presents a comprehensive review of the state of the art in composite cold‐formed steel flooring research over the past couple of years. The most relevant and significant literature references were reviewed to provide some insights into trends and developments in composite cold‐formed steel floors. Advantages of this type of composite flooring system are also highlighted. A broad description of mainly two types of composite floor – mainly consisting of cold‐formed steel and concrete, and cold‐formed steel and timber‐based floorboards – are outlined in this study. The experimental and numerical investigations that have been carried out worldwide are likewise discussed in the paper. The most important aspects covered are shear connection behaviour and the flexural and dynamic behaviour of the floors. There is also a brief description of fire testing.