Shear Connectors Research Articles

EXPERIMENTAL STUDY ON THE WOODEN MEMBER CONNECTION METHOD IN SEISMIC PANEL DAMPERS FOR STEEL STRUCTURES

Recently, government of Japan has encouraged using forest resources to expand the use of timber. Although moderate-or large-scale buildings are generally steel constructed structures, the authors proposed using cross-laminated timber (CLT) as support members for seismic panel damper systems. The benefits of employing mass timber as support members include the effective utilization of forest resources and a reduction in the building weight. To investigate the shear transfer performance between the shear panel damper and the mass timber, 16 specimens were meticulously prepared. Based on the test results, steel types such as H-shaped steel, circular tube, cruciform steel and steel plate were shown to be effective as the shear connector. In cases where H-shaped steel, circular tubes, and cruciform steel are utilized as shear connectors, significant labor is required for welding to the H-shaped steel and cutting into the mass timber, demanding time and effort from workers. Ensuring the shear connector section has high stiffness is crucial to maintain the energy dissipation capacity of the shear panel. Steel plates offer an advantage in their flexibility to control both strength and stiffness through the size of the plate used.

Experimental and numerical studies on the behavior of corrugated steel-sprayed ECC composite arches with full-shear-connection

This paper proposes a novel corrugated steel-sprayed ECC (CSSECC) composite arch, which possesses high load-bearing capacity and fast construction speed. To investigate the ultimate load-bearing capacity, composite effect, and key mechanical indices, five 6 m-span arch specimens were tested. A finite element model was developed, and parametric analysis was conducted. The results indicate that the ultimate load-bearing capacity and damping ratio of the CSSECC composite arch specimens can reach 3.4 and 6.5 times that of the corrugated steel (CS) arch, respectively, and increasing the ECC thickness significantly enhances the damping ratio. Both studs and epoxy resin contribute to the composite effect, but studs are more reliable than epoxy resin even though their design shear connection degree is the same at 1.2. Finally, a design method for the stability bearing capacity under axial compressive was proposed.

Advancements in precast concrete sandwich panels for load bearing structures

Concrete sandwich panels consist of two concrete layers separated by an insulating foam core, offering thermal insulation, structural strength, and fire resistance. This study investigates sustainable precast concrete sandwich panels made with industrial waste materials like limestone slurry, quarry waste, and basalt fiber as shear connectors. The research evaluates the flexural and axial strength behavior of these panels and explores strategies to improve their structural performance. The panels were fabricated with outer concrete layers, an expanded polystyrene (EPS) insulation core, and basalt fiber connectors. Flexural tests using four-point bending and axial compression tests were conducted on panels with varying concrete layer thicknesses and basalt fiber widths. Findings revealed panels with thicker outer concrete layers (35mm) and wider basalt fiber connectors (11.5mm) exhibited higher cracking loads, load-hardening behavior, and increased ductility compared to thinner layers and narrower connectors. The axial test showed premature failure at the top and bottom quarters. Thicker concrete layers and wider basalt fiber connectors enhanced crack control, load distribution, and ductile behavior under flexural loading. Strengthening measures like additional reinforcement, proper anchorage detailing, and increased shear reinforcement at the end regions are recommended to improve axial load-bearing capacity and prevent premature end failures. The PCSP demonstrated up to 40% cost savings over commercial products while providing better thermal insulation than conventional brick masonry due to the EPS core. Overall, the study promotes developing sustainable, energy-efficient, and cost-effective load-bearing sandwich panel systems.

Experimental study on structural performance of 7A04-T6 high-strength aluminium alloy shear connections in and after fire

The present study addresses the structural behaviour and design of 7A04-T6 high-strength aluminium alloy double shear connections under elevated temperatures and post-fire conditions with air cooling. A total of thirty-three connection specimens, featuring different fastener types and geometric characteristics, including end distances and edge distances, were tested under varying temperature histories, ranging from 20 to 400 ℃. An electric furnace was employed to heat the connection specimens, while digital image correlation (DIC) technology was employed to record displacements of the specimens during testing. Three distinct failure modes were observed in the tested specimens, namely the bearing, shear-out, and net section tension failures. The experimental results obtained from this study were compared to the predictions generated by the current design methods outlined in the American specification (AA), European standard EN 1999–1-1 (EC9) and Chinese code GB 50429 (GB). The comparisons revealed that the design rules often exhibit conservatism in predicting the ultimate resistances of 7A04-T6 high-strength aluminium alloy shear connections under elevated temperatures and post-fire conditions. Notably, EC9 emerged as providing the most accurate predictions for both resistances and failure modes of the investigated shear connections.

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.

Analysis of wave propagation in multi‐physical environments for double‐layer auxetic FGP sandwich plates resting on Kerr elastic foundation

This is the first time the characteristics of wave propagation of infinite double‐layer auxetic functionally graded porous (FGP) sandwich plates connecting with shear connectors in a hygro‐thermal environment are explored. Each layer component consists of an auxetic FG sandwich material, which contains a core layer made of auxetic honeycomb, while the upper and bottom ones are made of FGP materials. The whole structure is placed on a three‐parameter Kerr elastic medium. Hamilton's principle is used to develop fundamental equations of motion. Then, a Navier closed‐form solution is employed to tackle propagating wave equations. By comparing the current findings with those found in the literature, the precision and validity of the suggested approach are proven. In addition, comprehensive parametric research is conducted to demonstrate the impact of the material‐graded value and shear connection on the propagation in the structure. In a hygro‐thermal condition, the outcomes of this study give early insights into wave propagation in double‐layer auxetic sandwich plates with shear connectors.

The Influence of Shear Connector Numbers on The Flexural Characteristics of Composite Geopolymer Reinforced Concrete Beams With Small Transverse Web Openings

Geopolymer concrete is a sustainable alternative to conventional Portland cement-based concrete, utilizes industrial by-products like fly ash and slag. Renowned for its reduced carbon footprint and exceptional durability, geopolymer concrete is gaining global recognition in eco-friendly construction practices. Steel composite reinforced geopolymer concrete beams combine the strength of steel with the sustainability of geopolymer concrete, offering a sturdy structural solution. This collaborative approach results in a composite material with excellent crack resistance and durability, harnessing the advantageous properties of both steel and geopolymer concrete. These beams present a promising option in construction by striking a balance between structural performance and environmental considerations through the incorporation of geopolymer technology. The focus of the current study is to investigate the impact of steel connectors on the flexural behavior of composite reinforced geopolymer concrete beams that have transverse web opening through experimental methods. The experimental program involves casting four geopolymer beams, with one being a traditional geopolymer-reinforced concrete beam (Control). The remaining three specimens are composite reinforced geopolymer concrete beams, each featuring a bottom 5 mm steel plate with six, twelve, and eighteen connectors near each support. The beams share common dimensions, with a total length of 1600mm, a height of 250mm, and a width of 180mm. The results showed that increasing the number of connectors near supports increased the resulted flexural behavior of beams. Such connectors increased the first crack load from 6.67% to 42.22% while the service load increased from 16.22% to 36.20%. the load carrying capacity was also increased from 12.00% to 24.80%. Finally, the mode of failure was moved from traditional tension failure to concrete crushing.

Experimental analysis of the flexural behaviour of precast concrete composite beams with discontinuous connections

Full-depth precast deck panels hold the potential to enhance constructability and productivity, and reduce the costs associated with highway bridges. This paper investigates the influence of discontinuous shear connections between girders and panels on the flexural behaviour of composite beams. Experimental findings from precast composite beams and direct shear tests are presented, including L-shape push-off tests and double shear tests to determine resistance at rough concrete-to-concrete plain interfaces and shear pocket connections. Composite beams with a full-depth precast slab connected through a shear pocket with shear keys into the upper face of a precast beam exhibit equivalent flexural resistance to monolithic beams when shear pocket spacing remains below the effective depth of the composite beam. However, composite beams with shear pockets featuring plain interfaces show a reduction in flexural resistance of up to 30% compared to monolithic beams. Moreover, composite beams with shear keys demonstrate interface shear stiffness up to four times greater than those with plain interfaces, indicating full interaction. The paper proposes simplified equations to estimate flexural resistance for composite beams with full-depth precast slabs joined by shear pockets, showing a coefficient of variation of only 12% compared to experimental results, offering a reliable method for predicting flexural resistance in composite beams with discontinuous connections.

A Constitutive Model for Stud Connection in Composite Structures

The complexity of finite element analysis for composite structures can be significantly reduced by representing the connector and adjacent concrete as a macroscopic element. Nevertheless, the prevailing macroscopic models for shear connections predominantly employ nonlinear elastic theory. This approach introduces inaccuracies in estimating structural stiffness and load-bearing capabilities, primarily due to its inability to precisely capture the cumulative effects of plastic damage. In response, this study introduces a novel macroscopic elastoplastic model grounded in plasticity theory, aimed at accurately characterizing the nonlinear behavior of stud connections subjected to concurrent shear and tensile forces. This paper meticulously delineates the implementation of the elastoplastic constitutive model using the backward Euler method for numerical integration. It further articulates the derivation of the consistent tangent stiffness, which aligns with the convergence efficiency of the Newton–Raphson iterative approach. The computation of the element stiffness matrix for a two-node element is executed via the governing equation inherent to the finite element method. An exemplar macroelement test conducted in ABAQUS affirms the implicit backward Euler scheme’s stability and consistency across varying tolerances. Validation of the elastoplastic model against empirical test outcomes corroborates its efficacy, demonstrating the model’s precision in predicting the load–displacement behavior of stud connections under the influence of shear and tensile forces.

Summary of the Calculation of the Shear Capacity of Perfobond Rib Shear Connectors

The analysis of longitudinal shear resistance based on shear capacity is the basis for assessing the reliability of steel-concrete joint structures. It is of great significance for the longitudinal shear of bridge structures and even for the establishment of a shear-resistant design code for steel-concrete bridge structures based on reliability theory. In this article, a more comprehensive overview of the test methods, the current state of research, and the remaining problems in the field of connectors for perfobond rib shear connectors (PBL) are presented. Firstly, the test methods for PBL connectors are categorized. The applicable characteristics of each test method and their advantages and disadvantages are summarized, and the research progress on the calculation of shear load-capacity in this structure is discussed in detail. Finally, it is concluded that the international research on the shear capacity of PBL connectors is still at a stage where the scope of their adaptation is small. Reasonable and accurate quantification of the sensitivity parameters of the PBL connectors was studied. The normality of the test form and other relevant factors should be taken into account to establish a set of more effective shear capacity calculation methods. This can be used to guide the shear capacity design of the structure more directly.

Experimental study and acoustic emission monitoring on damage mechanism of stud shear connectors

Stud shear connectors are popular connectors used in steel-concrete composite structures. Assessing the condition and damage process of studs embedded in concrete is difficult. This paper proposes to assess the condition and damage process of stud shear connectors using an acoustic emission (AE) technique. Nine steel-concrete push-out specimens with stud shear connectors were tested, and AE sensors were used to monitor the damage process and explore the damage mechanism. The test results showed that the specimens failed due to stud fracture, accompanied by concrete cracks. The damage process included three primary stages featuring different characteristics of AE energy. An unsupervised machine learning algorithm called fuzzy C-means clustering was used to analyze the AE signals, and AE events were classified into three clusters, and various damage modes (i.e., concrete cracks and steel-concrete interface debonding, stud fracture, and concrete crushing) were identified based on the parameter characteristics and positions of AE events.

Experimental study on fatigue behavior of prefabricated high-strength steel-concrete composite bridge beams

To investigate the fatigue performance of prefabricated high-strength steel-concrete composite beams (P-HS-CCB), six specimens were designed with different fatigue load amplitudes, different fatigue load upper limits, and varying degrees of shear connection. Among them, specimen S560 underwent static failure testing, while the remaining five specimens underwent fatigue testing. The analysis was conducted from the perspectives of fatigue failure modes, fatigue life, and stiffness after specific cycles, with a comparison of the fatigue life calculation formula from different international codes. The results demonstrate that the fatigue failure mode of the P-HS-CCB is cracking in the vicinity of the steel beam at the mid-span, followed by crack propagation along both the web and flange widths. The P-HS-CBB exhibits excellent combination effects and anti-fatigue performance, maintaining nearly constant stiffness during fatigue loading with minimal composite section slip. The fatigue life of the P-HS-CBB is mainly influenced by the fatigue load amplitude during the testing. The S-N curve provided by AASHTO shows a good fit with the curve fitting based on experimental data and can be used to guide the anti-fatigue design of this type of beam.

Experimental investigation on flexural behaviour of prefabricated ultra-shallow steel concrete composite slabs

This paper presents the test results of four static full-size four-point bending tests to investigate the flexural behaviour of a recently developed prefabricated steel-concrete composite ultra-shallow flooring system (PUSS®). The flooring system comprises of T-ribbed concrete floors partially-embedded within and connected to side C-channel beams and horizontally-oriented shear connectors. This study investigates the effects of three parameters on the flexural behaviour of PUSS® and the performance of the shear connectors under bending. The parameters under study are the type of concrete, degree of shear connection and depth of the slab. Four 4 m span test specimens are constructed using two types of concrete, two with reinforced normal weight concrete (NWC) and the remaining two with reinforced lightweight aggregates concrete (LWC). Three of the test specimens employ the unique shear connection system composed of horizontally-oriented steel dowels with horizontally-oriented web-welded shear studs (dowels with WWSS) while the last one employs horizontal steel dowels only. The contribution of the above parameters on flexural behaviour and failure mechanisms are examined. The study concludes that replacing NWC with LWC of similar strength does not affect the flexural behaviour of PUSS® in terms of slab capacity, ductility and failure mechanism. However, LWC demonstrates lower initial stiffness and leads to the development of larger cracks as loads increases. Also, reducing the degree of shear connection lowers the moment capacity of the slabs and results in failure of some shear connectors during testing. PUSS® units exhibit ductile behaviour under bending conditions regardless of the degree of shear connection.

Study on shear behavior and acoustic emission characteristics of precast concrete segmental cover beams with large key teeth

AbstractThe mechanical characteristics of segmental joints are pivotal in defining the comprehensive stress behavior of prefabricated assembled cover beams. In this research, direct shear tests were conducted on dry key‐tooth joints, and acoustic emission technology was employed for monitoring purposes. The shear failure mechanism was explored under a range of influential parameters. Building upon these observations, the study delved into the mechanical response of joints within segmental cover girders subjected to concurrent bending and shear forces. Specimen K‐3‐3 exhibited a higher shear carrying capacity compared to other specimens, indicating that the shear resistance of dry joints proportionally increases with the height of the specimen and the strength of the concrete. The carrying capacity of Specimen K‐4 was marginally lower than that of Specimens K‐3‐1 and K‐3‐2, suggesting that increasing the number of keys does not significantly impact the shear resistance of dry joints. Notably, Specimen K‐3 demonstrated exceptional shear carrying capacity, exhibiting minimal relative slip during failure, and streamlined the casting process. Consequently, these dry joints featuring large key teeth are deemed more appropriate for use as shear connectors in precast concrete segmental cover beams. Crack patterns in large key tooth precast concrete segmental cover beams propagate along the joints. A damage evolution model for the specimens, based on spatial b‐values and T‐values, visually depicts the damage extent in large key tooth precast concrete segmental cover beams. This model demonstrates excellent agreement with experimental results and provides a solid foundation for theoretical research and practical applications of large key tooth precast concrete segmental cover beams.

Tensile resistance and shear-tension interaction relationship of T-type perfobond rid shear connectors

This study aims to investigate the mechanical performance of T-type perfobond rib (T-type PBL) shear connectors under complex load cases. Initially, the experimental tests were conducted and finite element analyses (FEA) were performed. Subsequently, a parametric study was carried out to assess the impact of geometric parameters on tensile resistance and the effect of tension ratio on the shear-tension interaction resistance of T-type PBL connectors. Finally, based on the test and FEA results, prediction methods were developed for evaluating the tensile resistance and shear-tension interaction relationship of T-type PBL connectors. The test results showed that the pull-out of the concrete below the flange led to the failure of T-type PBL shear connectors under tension. The concrete failure angles were approximately 33°. The failure under shear was manifested as concrete collapse and connector yielding. The ultimate capacity decreased with the increase in tension ratio. The specimens with tension ratios of 25%, 45%, and 65% decreased 7.9%, 16.3%, and 24.2%, respectively, compared to the specimen under pure shear. The parametric study suggested that the rib height and perforated rebars were the main factors impacting the tensile resistance of T-type PBL shear connectors. When the tension ratio reached 55% of the ultimate, the failure mode of the shear connectors was dominated by the pull-out of the concrete. The tensile resistance evaluation formula was verified by the test and FEA results, demonstrating an average calculated-to-FE-results ratio of 0.99 with a standard deviation of 0.04. The suggested shear and tension interaction relationship for T-type PBL connectors had reliable predictive outcomes, with a coefficient of variation of 0.02. This study could provide guidance for the design of T-type PBL shear connectors and promote the application in long-span composite structures.

3D non-linear finite element modeling of one-way RC slab strengthened with concrete overlay

Reinforced concrete (RC) slabs often require strengthening due to deterioration, increased loads, or design changes. Concrete overlay is a commonly used technique for strengthening, but predicting the behavior of overlays can be challenging. To address this challenge, this study presents a three-dimensional non-linear finite element model using Abaqus/CAE to analyze the structural performance of one-way reinforced concrete (RC) slabs strengthened with concrete overlays. The model considers three different bonding conditions at the interface: friction, epoxy, and shear connectors. The predictions of the model were compared to experimental results, and it was found that the model accurately captures the load–deflection response, cracking behavior, and interfacial slip in the strengthened slabs. Additionally, the model accurately predicts the new structural capacity of the strengthened slabs, showing good agreement with experimental data. These findings offer valuable insights into the effectiveness of concrete overlays as a traditional strengthening technique for RC slabs. Moreover, the developed finite element model provides a useful tool for optimizing the design of these overlays.

Developments and bending behaviors of GFRP-concrete composite girders at low temperatures

This paper reported the experimental and theoretical studies on the low-temperature performance of GFRP box-concrete composite girders (GCCGs) under four-point bending. GFRP box section with three vertical webs was adopted to improve the shear resistance of web. The horizontal shear force at GFRP box-concrete interface (concrete on top of the GFRP box) was resisted by the combined shear connectors with T-bolts and sand coating (TBSC). The effects of low temperatures (T = 20, −30, −60, and −80 ℃) on the mechanical behaviours of composite girders under four-point bending were studied. Test results indicated that the composite girders failed in shear fracture of the GFRP web and compressive fracture of the GFRP box under sagging and hogging moments, respectively. The plane section assumption was not applicable for composite girders under sagging moment because of the shear failure of sand coating. Meanwhile, the low temperatures improved the ultimate resistance (FuT) of GCCGs under four-point bending. Finally, theoretical models with consideration of GFRP box-concrete partial composite action were developed to determine the low-temperature behaviours of GCCGs under four-point bending.

Deconstructable variable stiffness shear connectors in FRP deck resting on multigirder bridge system: Analytical model

Deconstructable structures offer great flexibility and reduce material waste. Fiber Reinforced-Polymer (FRP) decks resting on steel girders combine high durability, lightweight, fast construction, and deconstructablility. Composite action between the decks and girders is achieved using shear connectors. Until now, most shear connectors use adhesives or grouts, limiting their maintenance, reuse, or recycling. This paper presents a closed-form solution to analyze the behavior of an FRP deck connected to multi-girders using variable sequential stiffness shear connectors considering partial Degree of Composite Action (DCA). The analytical model, which is verified using Finite Element model and prior experimental studies, is further used to study stress and deflection for various multigirder configurations. Finally, the DCA considering variable stiffness shear connectors is presented and linked to effective width ratios, paving the way for adopting variable stiffness in bridge standards.

The investigation on flexural performance of prestressed concrete-encased high strength steel beams

This paper reports an experimental on the flexural performance of prestressed concrete-encased high-strength steel beams (PCEHSSBs). To study the applicability of high-strength steel (HSS) in prestressed concrete-encased steel beams (PCESBs), one simply supported prestressed concrete-encased ordinarystrength steel beam (PCEOSSB) and eight simply supported PCEHSSBs were tested under a four-point bending load. The influence of steel strength grade, I-steel ratio, reinforcement ratio and stirrup ratio on the flexural performance of such members was investigated. The test results show that increasing the I-steel grade and I-steel ratio can significantly improve the bearing capacity of PCESB. Increasing the compressive reinforcement ratio of PCEHSSB can effectively improve its bearing capacity and ductility properties, making full use of the performance of HSS in composite beams. Increasing the hoop ratio has a small improvement on the load capacity of the test beams; setting up shear connectors can improve the ductile properties of the specimens although it does not lead to a significant increase in the load capacity of the combined beams. Then, combined with the test data, the comprehensive reinforcement index considering the location of reinforcement was proposed to evaluate the crack resistance of specimens. The relationship between the comprehensive reinforcement index and the crack resistance of specimens was given.

Structural Design and Mechanical Behavior Investigation of Steel–Concrete Composite Decks of Narrow-Width Steel Box Composite Bridge

Steel–concrete composite decks are commonly employed in narrow-width steel box composite girder bridges to augment their lateral spanning capabilities, while the concurrent omission of longitudinal stiffeners leads to a substantial reduction in the number of components, thereby yielding a structurally optimized bridge configuration. This paper delineates the structural design parameters of a narrow-profile steel box composite girder bridge and assess the mechanical behavior of its incorporated steel–concrete composite deck under static and fatigue loading conditions. To this end, two full-scale segment specimens from the composite bridge decks were subjected to equal amplitude cyclic fatigue tests. The investigation specifically concentrated on the impacts of two types of shear connectors—namely, perforated steel plates combined with shear studs and perfobond rib shear connectors (PBL connectors)—on the static and fatigue performance, including fatigue stiffness, of the steel–concrete composite bridge decks. The results indicate that, under the static bending condition, the composite deck specimen equipped with stud connectors demonstrates superior overall flexural stiffness in comparison to the specimen featuring PBL connectors. Furthermore, the flexural stiffness of the steel–concrete composite specimens experiences a negligible alteration across two million fatigue loading cycles. Upon the completion of two million fatigue loading cycles, the composite deck specimens incorporating the shear connectors composed of perforated steel plates and shear studs exhibit relatively wider crack widths under the static peak load. Both configurations of the steel–concrete composite bridge deck specimens manifest evident interfacial detachment, signifying insufficient tensile pull-out stiffness of the shear connectors. It is recommended to increase the quantity of the shear connectors or select the pertinent types in order to enhance the interface shear resistance.