Shear Studs Research Articles

Experimental and numerical investigation of strengthening effect of shear studs in RC flat slabs with multiple openings

The punching failure, which is an abruptly developing brittle failure mechanism, is one of the most dangerous collapse mechanisms that can occur in beamless (flat) slabs. Therefore, it is important to consider both the ductility and strength in the design of slab-column connections. The effects of a strengthening technique using shear studs around the column perimeters of flat slabs are investigated experimentally and numerically in this study. The study is planned in two stages and involved fabrication and testing of twenty full-scale reinforced concrete flat slabs. In the first stage, ten reference test specimens and in the second stage, ten specimens that were strengthened with a shear stud were produced. In each series, one specimen without opening and nine specimens with double openings were designed. The presence of the opening, the size of the opening, the location of the opening, and the presence/absence of strengthening with shear studs were considered as the test variables. Based on the load-displacement graphs obtained from the testing of specimens, the maximum bearing capacity, initial stiffness, and energy consumption capacities of the specimens are calculated. Significant increases are obtained in the maximum bearing capacity, initial stiffness, and energy consumption capacities of the test specimens strengthened with shear studs. For numerical analysis, the test specimens were modeled in the ABAQUS finite element program, and a good agreement was observed between the experimental results and finite element predictions.

Experimental study on the effect of partial shear studs layout on flexural behavior of steel-concrete composite beams

In steel-concrete composite beams, partial shear connection offers advantages including greater ductility and lower cost. However, partial shear connection constraints on composite beam structural performance, such as reduced beam stiffness, increased steel-concrete interface slip, etc., should not be neglected. Several researches have revealed that shear connector layout is one of the main approaches to limit partially composite beam vulnerability. Shear connector layout optimization has not been completely investigated experimentally, and its effect on composite beam structural performance is still unknown. This paper focusses on the experimental study of the effect of shear connectors layout on the flexural performance of composite beams. It reports the optimization of the layout of shear connectors based on blocked distribution of shear connectors laid in a single row, while concentrating the highest number of shear studs towards the supports of a simply supported composite beam. A fully composite beam with normal layout of shear studs was tested as control specimen, while the rest of the beams used partial shear connection (η = 0.5). Beams with partial shear connection had 3 different layouts of shear studs. The first had uniformly distributed shear studs, and the rest had shear studs laid out in 2 and 3 blocks each of uniform spacing respectively. The results showed that the beam with 3 blocks layout each of equal spacing of shear studs had the closest best structural performance to the fully composite beam and had better ductility than the latter.

Bending and Vibration Behaviour of CLT-Steel Composite Beams

A strengthening of cross-laminated timber (CLT) by a composite effect with steel girders can widen the application of CLT ceilings to spans over 8 m. Most possible shear connectors are not stiff enough to ensure a completely rigid composite. At present, it has not been sufficiently clarified how the elastic bending behaviour is affected by the influences of the flexibility of continuously and discontinuously shear connectors, the number of transverse layers of the CLT and the span width. Thus, 4-point bending tests and vibration tests were performed with different cross-section configurations and two different shear connectors in continuous and discontinuous spacing in spans of 8.10 and 10.80 m. To date, no comparable bending tests have been carried out in these spans, with more than five CLT-layers and discontinuously arranged shear connectors. The composite beams deformed linear-elastically until the yield strength of the steel was reached. The composite effect increased the elastic bending stiffness up to twofold compared to no composite. Increasing the span resulted in a higher bending stiffnesses. The elastic bending stiffness of the composite beams with shear studs was significantly lower than with fully threaded screws. For a worthwhile composite effect, both materials should contribute a balanced share of the stiffness. A larger share of the CLT in the bending stiffness compared to the steel girder created a higher elastic limit load capacity but an equivalent bending stiffness. It is necessary to discuss which cross-sectional configurations are appropriate in terms of load bearing capacity, economic efficiency and sustainability. To assess the practical application potential in spans between 8 and 12 m, the tests were additionally evaluated for the equivalent load level for the serviceability limit state of office or industrial buildings. For spans of 8.10 m, the limits according to EC5 for the initial deflection of L/300 and fundamental frequency of 8 Hz can be met. For spans of 10.80 m, only less strict deflection limits are achieved. However, by increasing the degree of composite through more shear connectors, compliance with the limit values mentioned could already be possible with the cross-sections tested. In case of fire, it may be sufficient to consider only the CLT with the reduced cross-section method (EN 1995-1-2) for load transfer, even for longer fire durations.

Seismic Damage Assessment of Reinforced Concrete Slab-Column Connections—Review of Test Data, Code Provisions and Analytical Models

Reinforced concrete slab-column connections are vulnerable to punching shear failure when subjected to combined gravity and lateral loadings during earthquakes. Over the years, many experimental campaigns have been conducted and assessed the seismic performance of flat slabs. The experimental findings were used to derive empirical equations for the design provisions. The paper aims to provide a detailed description of the code development for seismic punching shear. Two current code provisions (ACI 318-19, EC 2 & EC 8-2004) for seismic punching shear are presented and discussed. Relevant and updated experimental data of interior slab-column connections without and with shear reinforcement are selected and assessed against the current design provisions with a focus on key response parameters such as the drift ratio and the gravity shear ratio. The ACI 318-19 limit drift line is considered to assess the lateral deformation demand for the connections with respect to the updated database. The gravity shear ratio is shown to have a considerable impact on the limit drift ratio of slab-column connections without shear reinforcement. The majority of the test specimens with no shear reinforcement experienced punching shear failure, followed by the specimens which showed a combined flexure–punching failure. Punching shear failures occurred for a range of gravity shear ratios of 0.2 to 0.9, while all combined flexure–punching shear failures occurred for gravity shear ratio values below 0.5. The shear-reinforced concrete slab-column connections can achieve much higher drift ratios. Most of the slabs were reinforced with shear studs, particularly in the range of gravity shear ratios of 0.4 to 0.6. Most test specimens failed by flexure for gravity shear ratio values of 0.1 to 0.7, followed by the specimens which failed in combined flexure–punching for gravity shear ratio values that ranged from 0.3 to 0.9. Finally, the available numerical and analytical models for seismic punching shear are presented with the objective of observing their potential strengths and limitations.

Fatigue Characteristics of Steel–Concrete Composite Beams

Fatigue in steel–concrete composite beams can result from cyclic loading, causing stress fluctuations that may lead to cumulative damage and eventual failure over an extended period. In this paper, the experimental findings from fatigue loading tests on composite beams with various arrangements are presented. Fatigue tests were performed up to 1,000,000 cycles using four-point loading, encompassing various ranges of shear stress at a consistent amplitude. Additionally, the effects of external post-tensioning and the strength of the shear connection were investigated. Static tests were run until failure to assess the enduring strength of the specimens subjected to fatigue. The cyclic mid-span deflections, slippages, and strains were measured during the testing. Based on the experimental findings, it was found that the damage region that the shear studs caused in the concrete slab, which resulted in a reduction in stiffness within the shear connection, grew as the loading cycles increased, leading to an increase in residual deflections and plastic slippages. Controlling the longitudinal fatigue cracks in the concrete slab was largely dependent on the strength of the shear connection between the steel beams and concrete slabs. Moreover, the applied fatigue loading range affected the propagation and distribution of fatigue cracks in the concrete slab. The strains in different parts of the composite specimens were significantly reduced by applying the external post-tensioning. With no signs of distress at the anchors, the tendons displayed excellent fatigue performance.

Demountable composite beams for a circular economy: Large‐scale beam tests

AbstractThe circular economy approach has been introduced to the construction sector to design out waste, reduce carbon emissions and energy use in production of primary materials and achieve resource efficiency. ‘Design for deconstruction’ is increasingly important for a sustainable economy, especially for composite structure that is deemed as resource‐efficient in the first cycle of use. With this background, research has been conducted to facilitate the use of demountable composite beams in steel‐framed structures. This article presents the results of two 6 m full‐scale composite beam tests with prefabricated composite slabs. Demountable shear connectors were used, which have been newly developed within the frame of an EU project. The nominal degree of shear connection of the composite beam specimens was 0.37, which was slightly below the required 0.4 specified in EN1994‐1‐1 for welded shear studs. Based on the experimental observations, it can be demonstrated that (1) the tested demountable composite beam produced higher resistance but lower stiffness values than a comparable reference composite beam with welded shear studs; (2) the beam specimens showed a good plastic behaviour with high ductility despite the non‐ductile nature of the applied demountable shear connectors. Remarks on the demountability of the developed demountable composite beams are provided.

Effect of Stud Connector Diameter on the Behavior of Steel–Lightweight Self-Compacting Concrete Composite Beams with Partial shear Connection

This study investigates the efficacy of using lightweight self-compacting concrete (LWSCC) in steel-concrete composite beams, focusing on the role of headed stud connectors in shear connection. The research aimed to evaluate the behavior and shear strength of M16 and M20 headed stud connectors within LWSCC. To this end, six push-out test samples and six simply supported steel-LWSCC composite beams were fabricated and tested, with variables including the degree of shear connection (DSC) and stud diameter. The results demonstrated that an increase in DSC significantly enhanced the ultimate load capacity, service load, and stiffness of the composite beams, with marked improvements observed in the beams with M16 connectors (94%, 95%, and 122%, respectively) and those with M20 connectors (43%, 43%, and 20%, respectively). Furthermore, increasing the stud diameter from 16mm to 20mm resulted in a 38% increase in shear strength of the connectors and notably improved the mechanical characteristics of the beams. The study also found that while an increased DSC reduces deflection at ultimate and service loads due to heightened stiffness, a larger stud diameter has only a marginal effect on deflection. This research highlights the potential of LWSCC in enhancing the structural performance of steel-concrete composite beams, particularly with optimized shear connections, offering valuable insights for advancements in construction materials and methods. Highlights : Enhanced Load Capacity: Increase in the degree of shear connection significantly boosts ultimate load capacity and stiffness in composite beams. Stud Diameter Impact: A 38% rise in shear strength is achieved by increasing stud diameter from 16mm to 20mm. Deflection Reduction: Higher degree of shear connection effectively minimizes deflection, though stud diameter has minimal impact. Keywords : Lightweight Self-Compacting Concrete, Steel-Concrete Composite Beams, Shear Connection, Headed Stud Connectors, Structural Performance.

Characterization of the elevated temperature behaviour of demountable shear connectors in steel-concrete composite beams through push-out tests

Demountable shear connectors are a key component of reusable structural systems. The intention behind the development of these systems is substituting, or at least providing a valid alternative to the widely utilized beam-to-slab connection via shear studs, which are welded to the flange of the steel profile and embedded in the concrete slab, therefore eliminating the possibility for the slabs to be reused in a new structure. To ensure that these demountable connectors are a valid option in practice, it is necessary to analyse them under different actions, including the fire situation. This is the primary purpose of the experimental campaign presented in this investigation, where a series of push-out tests at elevated temperatures are performed to extend the previously available results at ambient temperature, as a response for the need of characterization of the behaviour of the proposed demountable shear connectors in the fire situation, thus facilitating their applicability in the construction sector. This study shows how temperature affects the shear resistance of the connectors, their ductility, and the slip resistance. The available design provisions in EN 1993–1-8 and the reduction factors in Annex D of EN 1993–1-2 for bolts loaded in shear are tentatively applied to high temperatures, as a way to assess their validity for fire design.

Improvement of Composite Beam with Web Opening Using Posttensioning Tendons under Static and Cyclic Loadings

In practice, the passage of service utilities through web opening causes a significant load‐carrying capacity loss and introduces a change of failure mode of the composite beam. This study aims to improve the load‐carrying capacity and stiffness of open‐web composite beams subjected to static and cyclic loading using posttensioning tendons. To achieve the desired objective, 18 mechanical models have been developed using ABAQUS by considering the shape and location of the web opening, span/depth ratio, and degree of connection as study parameters. The finite element analysis result was validated with experimental results from relevant literature. Results indicate that the external posttensioning tendons increase load‐carrying capacity to 25.05% for rectangular and 20.61% for circular web opening under static loadings. Under cyclic loading, the improvement is 9.24% for rectangular while 2.50% reduction in deflection has been observed for circular web opening. As a span‐to‐depth ratio increased as 11.54, 15.38, and 23.08, the load‐carrying capacity improved by 26.35%, 20.67%, and 8.65%, respectively, for static loadings. Likewise, 2.03%, 1.24%, and 4.95% improvement were observed under cyclic loadings, respectively. Furthermore, compared to one row of 16 mm shear stud provision, the load‐carrying capacity increased by 30.67% for connection in two rows under cyclic loading.

Degree of composite action of steel beams with precast concrete hollow core slabs

Different construction challenges followed by harsh environmental conditions triggered the human intention to precast composite structures. The precast concrete hollow core (PCHC) slabs have been popular, especially for multi-story long-span composite structures. In comparison to conventional solid concrete slabs, they have the advantages of being more lightweight, fire-resistant, soundproof, and cost-effective. However, the composite action between the steel beams and PCHC slabs is neglected in the design codes. This paper aims to investigate the composite action between the PCHC slabs and steel beams through an experimental study. Two full-scale flexural tests were performed on specimens of 203 cm and 254 cm PCHC slabs connected to the steel beam via 19 mm diameter shear studs. Instrumentations and data acquisition systems recorded the failure modes and crack formations. Also, the digital image correlation (DIC) technique was applied to capture the neutral axis position during the loading process. Finally, the degree of composite action (DCA), an important parameter to describe the structural behavior of the composite beam, was calculated based on the analytical and experimental bending moments of the specimens.

Studying the effects of shear studs on the punching shear resistance of thin flat slabs with edge column connections and openings

Studying the effects of shear studs on the punching shear resistance of thin flat slabs with edge column connections and openings

Seismic behaviour of FRP-concrete-steel double-tube columns with shear studs: Experimental study and numerical modelling

FRP-concrete-steel double-tube columns (i.e., double-tube concrete columns or DTCCs) are a novel type of structural members composed of two concentrically-placed tubes (i.e., an outer FRP tube and an inner steel tube) with all the space inside the two tubes filled with concrete. Shear studs on the inner steel tube are recommended to increase the composite action when DTCCs are subjected to large bending moments. The optimized section configuration of DTCCs allow the three constituent materials in the columns to deliver their respective advantages and to avoid their respective shortcomings. The limited existing studies on DTCCs have been focused on their compressive behavior. These studies have demonstrated the excellent ductility of DTCCs, an important advantage for their potential applications in regions with seismic risk. However, the seismic behaviour of DTCCs has not been systematically investigated. Against this background, this paper presents a combined experimental and numerical study on the seismic behaivour of DTCCs, where the experimental part included a series of large-scale DTCCs tested under combined cyclic lateral loading and constant vertical compression, while the numerical part included the development of a finite element model incorporating beam-column elements and specific stress-strain models to consider the unique behaivour of the two parts of concrete in DTCCs (i.e., the concrete core inside the inner steel tube and the concrete ring between the two tubes). The experimental results revealed that: (1) the increase of FRP thickness had a positive effect on their hysteretic behavior; (2) when the steel ratio was constant, the peak lateral load of DTCCs increased with the steel tube diameter; (3) the concrete core not only enhanced the lateral load capacity and the ductility of DTCCs, but also provided efficient suppression on the buckling of the steel tube. The numerical model, established using the OpenSees platform, is able to provide reasonably accurate predictions of the hysteretic behaviour of all specimens.

Experimental hysteretic behavior of CFST column-foundation connections with novel detailing in embedded region

This paper presents a novel CFST column-foundation connection detail to improve stress transfer and damage control. To achieve this aim, seven specimens were created in the lab in three different configurations: exposed connection (base plate), embedded connection without reinforcement, and embedded connection with reinforcement. These specimens were subjected to cyclic lateral load and constant axial load tests. The effect of using internal reinforcement (including reinforcing anchor bar and internal tube) and external reinforcement (including shear studs, external diaphragm, and through diaphragm) in the embedded region on the reduction of the embedded depth was assessed. Performance indices of the tested connections, including the stiffness, lateral loading capacity, energy-dissipation capacity, ductility, and strain distribution of steel tubes, were analyzed based on hysteresis and pushover graphs. The test data demonstrated that all the specimens experienced flexural failure, and consequently, the local buckling of the steel tube was observed in all experiments with the exception of the specimen that had an exposed connection. The specimens with reinforcement in the embedded region had acceptable behavior with ductility coefficients higher than 4.8. The seismic response of the connection with the novel detail showed that the performance indices of the connection with reinforcing anchor rebars and reinforcing internal steel tube in the embedded region were considerably higher than those of the connection without reinforcement in the embedded region and the one in the exposed form. Moreover, the depth at which the connection is embedded was reduced by up to 0.7 times the diameter of the column due to the utilization of reinforcement in the embedded region.

Seismic performance of special-shaped hexagonal concrete filled steel tubes with inner diaphragm plates and shear studs

With the development of the high-rise buildings, the columns with special cross-sectional shapes are frequently adopted for architectural and aesthetic purposes. The concrete filled steel tube (CFST) is a reasonable choice for such requirement due to the characteristics of excellent seismic performances, construction efficiency and strong adaptability to special shapes. This paper focuses on the seismic performance of a special-shaped hexagonal CFST column with an inner diaphragm plate and shear studs adopted in a super high-rise building. Experiments were conducted on five column specimens under axial compressive force and lateral cyclic loading to investigate the influence of various parameters including loading angle, axial compression ratio, shear studs and the type of in-filled concrete. In one of the specimens, the ultra-high performance concrete (UHPC) was used as the in-filled concrete to substitute the conventional normal strength concrete, and the effects on the capacity and ductility of the column were revealed. Then the failure mode, the load-deflection curves, seismic performance indexes and the strain distribution were analyzed. The flexural capacities of the columns were evaluated by the fiber section model, where the failure criterion considering the buckling of steel tube was proposed and the effects of studs were included. Finally, the contribution to axial force and bending moment from outer steel tubes, inner diaphragm plate and in-filled concrete were calculated and compared based on the proposed model. It is found that the fiber section model considering the steel plate buckling and strengthening effects of studs precisely predicted the moment-curvature curves and the flexural capacity of the test specimens. The contribution of the inner diaphragm plate was considerable which could not be neglected.

Cyclic performance of prefabricated composite shear stud connectors for accelerated bridge construction

This study examines the cyclic shear-slip performance of a novel prefabricated composite shear stud (PCSS) connector designed for accelerated bridge construction (ABC) of composite structures. An in-depth experimental procedure is employed involving the design and fabrication of four push-out specimens with two different stud configurations. The specimens are then tested under both monotonic and cyclic-to-monotonic loading protocols. Upon completion of the testing phase, a meticulous inspection of the fractography is conducted to delineate and qualify the failure mode of the PCSS connectors. Simultaneously, a comprehensive shear-slip curve is derived from the measured data, enabling a detailed analysis over the mechanical performance. Furthermore, the study calculates a series of deformation-associated indicators from the shear-slip curve, effectively quantifying the ductility, recoverability, and capacity of the PCSS. The test results accentuate a well-deformed and ductile failure mode of the tested PCSS specimens, marked by the stud fracture and crushing of surrounding concrete. This could be attributed to the constraint of vertical plates of the PCSS on the concrete, which improves the capacity and recoverability of the PCSS. Whereas, the performance of the PCSS is also notably influenced by the group nail effect, for which the ductility and per-stud capacity degrade with the increase in the number of studs. Especially, the PCSS specimen exhibits full elastic-to-plastic hysteresis loops under cyclic loads, together with the satisfied ductility, implying an excellent potential of the PCSS to dissipate energy under impact loads. In addition, the PCSS displays a robust stiffness across different cyclic loading blocks. Hence, satisfactory post-damage ductility has still been observed in the PCSS under the monotonic loading after the cyclic loading. In conclusion, this work elucidates the superiority of the PCSS in terms of capacity, ductility, and recoverability, providing a promising basis for their application in the accelerated construction of composite bridges.

Experimental investigation using demountable steel-concrete composite reduced web section (RWS) connections under cyclic loads

This paper presents an experimental study of demountable steel-concrete composite reduced web section (RWS) connections for use in seismic areas. Four composite connection specimens were subjected to sagging and hogging moments to investigate the performance of RWS connections under reversible actions. For such purpose, a single web opening was created near the beam-column joint. Focus was made on the effects of perforation location and composite beam-slab action induced by bolted shear studs within the protected zone. Results indicate that employing RWS connections for seismic retrofit is a viable solution capable of achieving a performance similar to that observed for RBS connections in new buildings. Notably, a Vierendeel Mechanism is formed, allowing for plasticity development in the beam. All RWS connections were capable of achieving an interstory drift larger than 4%, thereby complying with the performance targets set by ANSI/AISC 358-16, ANSI/AISC 341-16 and EC8. Moreover, the deformation of beam-slab shear-transfer bolts was small enough to allow for disassembly after the tests, indicating that the proposed solution could enable reuse and post-earthquake retrofitting.

Structural behavior of steel-concrete-steel sandwich slender and deep beams considering different connectors

Steel-concrete-steel (SCS) sandwich deep beams, with a shear span ratio of less than 2.0, are commonly employed in high-rise buildings and bridges. However, their failure mechanism differs from that of SCS sandwich slender beams, which have a shear span ratio greater than 2.0. This study systematically investigates the failure mechanisms of SCS sandwich deep beams and compares them with those of SCS sandwich slender beams. To improve their structural performance, ultra-high performance concrete (UHPC) was utilized as the core material to form S-UHPC-S sandwich deep beams, with shear studs serving as the sole shear connectors. The influence of these shear connectors was explored in comparison to cross ties. Three S-UHPC-S sandwich deep beams were subjected to static loading, and their performance was compared with ten existing SCS sandwich deep and slender beams. The analysis focused on failure modes, mechanical behaviors, and contributions of each component, including the steel plate (SP), core concrete (CC), and shear connectors. The results revealed distinctions in force transferring models, load-displacement curves, and the contributions of cross ties in deep beams compared to slender beams. Additionally, finite element (FE) analyses were employed to examine the force transferring mechanism of shear connectors. Based on both experimental and FE simulation analyses, theoretical models for predicting the ultimate capacity of S-UHPC-S sandwich deep beams and slender beams were proposed, accounting for different shear connectors. These models offer valuable insights for practical structural design and application.

Numerical simulation analysis of Steel-concrete Vierendeel Sandwich Plate Composite Bridge under a close-in blast loading

This study utilizes the CEL finite element method to investigate the performance of the Steel-concrete Vierendeel Sandwich Plate Composite Bridge (SVSPB) under the close-range blasting load. The effectiveness of the method is validated by reproducing experiments from the literature through numerical simulation. A three-dimensional model of SVSPB is established using Abaqus to analyze various aspects such as vertical displacement, slip between the reinforced concrete slab and the steel structure frame, failure mode, and material stress. The research findings indicate that: (1) SVSPB exhibits good ductility under explosive loads, as the overall structural framework retains a certain bearing capacity despite severe damage to the reinforced concrete slab. The structure also demonstrates favorable explosion venting performance. (2) Horizontal sliding occurs between the reinforced concrete slab and the steel frame in the absence of shear studs, highlighting the necessity of incorporating them. (3) During anti-riot design, attention should not only be given to the known weak points of the structure at the Bottom Chord nodes but also to the top chord nodes and stiffened plates of the main side beams on both sides. These findings offer reference in comprehending the dynamic response of SVSPB when subjected to explosive loads.

Residual Post-fire Strength of Shear Studs in Composite Beams with Solid Slabs

Residual Post-fire Strength of Shear Studs in Composite Beams with Solid Slabs

Flexural behavior of externally prestressed continuous steel-concrete composite beams

To investigate the flexural behavior of continuous externally prestressed steel–concrete composite (EPSCC) beams, flexural tests were conducted on two two-span continuous beams with a total length of 9.8 m. The test parameter focused on the number of deviators in each span. With the aid of detailed measurement of deviator displacement, slip distribution on the steel-slab interface and strain along shear connectors, the shear mechanism of headed studs and the second-order effect in continuous EPSCC beams were evaluated. The test results indicated that both beams underwent concrete cracking over their interior supports, followed by the formation of a plastic hinge in the hogging moment zone, the subsequent formation of a plastic hinge in the sagging moment zone, and ultimately the crushing of concrete slabs in the sagging moment zone. Prior to failure, full plasticity was developed at both the mid-span section and interior support section of each beam. The local moment acting on the shear studs reached its maximum hogging values at the shank root, while its maximum sagging value was attained at approximately the mid-height of the shank. Due to the second-order effect, the removal of deviators at midspans resulted in a 7.1% decrease in the sagging moment of the beam. At the ultimate limit state, the measured degree of moment redistribution values for hogging moment ranged between 52% and 58%, which were higher than the specified limits in current design guidelines. The predictions of the ultimate hogging and sagging moment calculated from plastic theory were consistent with experimental results.