Shear Connection System Research Articles

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.

Demountable Steel‐Concrete Composite Floors for Circular Economy: State of the Art and Design Principles

AbstractThe construction sector activities contribute to irreversible effects on the environmental systems. New forms of construction are needed to increase the circular economy and sustainability within the built environment. Steel‐concrete composite floors are not demountable, because the typical shear connection with welded studs is permanent. To avoid demolition and promote the reuse of the structural components, demountable shear connection systems need to be adopted. This article presents a literature review of different forms of demountable shear connection solutions and an overview of suitable design rules for such solutions.

Shear connection of prefabricated ultra-lightweight concrete slab systems (PUSSTM)

This paper reports a detailed computational study of a recently developed novel steel–concrete composite flooring system (PUSS) with two different types of shear connectors: (i) web-welded shear stud connectors (WWSS), and (ii) web-welded shear stud with dowels (WWSS with dowels). In addition, different types of concrete, (normal and lightweight,) are used. A nonlinear FE model is developed and validated against two sets of full-scale push-out tests of the novel steel–concrete composite flooring system reported in a companion paper. The FE model replicated the experimentally determined failure loads, ultimate slips, and observed failure modes. Parametric studies are conducted to obtain the failure loads and ultimate slips of these PUSS untis with different types of concrete: normal weight concrete, light weight concrete and ultra light weight concrete (NWC, LWC and ULWC), and various diameters and heights of shear connectors (WWSS, WWSS with dowels). The concrete strength varied between 20 N/mm2 to 35 N/mm2, the shear connectors’ diameter varied between 16 mm, 19 mm, 20 mm and 22 mm, and the height of the shear studs between 75 mm and 100 mm. In conclusion, load-slip curves obtained from the FE parametric studies demonstrated that FE models with same diameter of shear connectors can result to different slip stiffnesses, while the failure loads and slips varied with the concrete strengths. The slip results were also compared with different shear connection systems’ dimensions at concrete strengths of 20, 30 and 35 N/mm2.

Testing a Prefabricated Ultra‐Shallow Composite Flooring System with Lightweight Concrete and Shear Studs

AbstractThis paper presents an experimental investigation on a recently developed prefabricated shallow steel‐concrete composite flooring system composed with lightweight concretes. The novel flooring system is consisted of two main structural components: two C‐channel steel beams and a partially encased concrete floor. The concrete floor, which is in the form of T‐ribbed slab sections, was constructed using three types of concrete (reinforced normal concrete, reinforced lightweight aggregate concrete, and reinforced ultra‐lightweight aggregate concrete), and the steel edge beams which partially encase the floor slab and provide clear and straight finish edges. Three full‐scale push‐out tests were conducted to investigate the effect of the lightweight concrete on the longitudinal shear behaviour of the new shear connection system, made of web‐welded shear stud connectors. It was observed that specimens with lightweight concretes demonstrated additional ductility when compared with specimen using normal concrete, and the failure mode of the shear studs alters. It is confirmed that the specimen with normal concrete has reached a higher failure shear load.

Flexural Behaviour of Prefabricated Ultra‐Shallow Steel‐Concrete Composite Slabs

AbstractThis paper presents the results of a parametric finite element (FE) study that investigates the flexural behaviour and bending capacity of a recently developed steel‐concrete composite flooring system subjected to static bending tests. The flooring system is composed from prefabricated ultra‐shallow slab units (aka PUSS) that consist of T‐ribbed concrete floors encased within and connected to two C‐channel steel edge beams with horizontally oriented shear connections. The study considers three unique types of shear connection systems, that compose of only horizontally oriented web‐welded shear studs (WWSS), only horizontal steel dowels or a combination of horizontal steel dowels with WWSS. The failure mechanism, the shear resisting capacity of the shear connection systems and their behaviour under flexural loads are examined. The present work explores the influence of variable parameters on the performance of the PUSS flooring system. In particular, the parameters under critical investigation are the type, arrangement, and size of the shear connectors (WWSS and steel dowels) as well as the location of the main pressure caused by the applied load. Based on the results, the location of the applied loads contributed greatly to the behaviour of the shear connectors, moment resistance capacity and failure mechanism of the slabs. In addition, horizontal dowels provided greater bond between concrete and steel in comparison to WWSS.

A Novel Slip Sensory System for Interfacial Condition Monitoring of Steel-Concrete Composite Bridges

Steel-concrete composite (SCC) beams are widely employed in bridge decks. The interfacial shear transfer between the top concrete slab and the supporting steel beams significantly affects the overall load carrying capacity and performance of a bridge deck. The inaccessibility of the connection system makes the visual inspection difficult, and the traditional vibration-based methods are insensitive to this type of local damage. In this study, a novel interlayer slip monitoring system has been developed for interfacial condition assessment of SCC beams. The monitoring system is mainly based on the Ultra-flat Industrial Potentiometer Membrane (UIPM). The sensor film that is glued on a steel base is mounted on the concrete slab, and the wiper is installed on the steel beam. The interlayer slip between the concrete slab and steel beam is monitored by the relative displacement between the sensor film and the wiper. An experimental study has been carried out on a 6-m long composite bridge model in the laboratory. In the model, the concrete slab and the steel beams are bolt-connected, and the bolts could be loosened to simulate the defects in the shear connection system. Seven slip sensors are evenly installed along the bridge model. The sensors are calibrated using the testing machine before they are installed on the bridge model. Three damage scenarios are simulated by loosening bolts at different locations. Different loadings are also applied on the bridge to simulate the operational conditions. Undamaged and damaged scenarios have been considered within load increments, and data are collected and interpreted to find out how the slip changes. The results show that this system is reliable and efficient to monitor the interlayer slip for assessing the interface condition of composite structures.

Fundamental Behavior of Timber Concrete-Composite Floors in Fire

Timber-concrete composite (TCC) floors are becoming more commonly used in mass timber construction due to their increased stiffness and strength relative to nonconcrete composite timber floors. Current building codes do not recognize the contribution of the composite action of TCC floors to their combined strength and fire performance. Extensive structural testing is required for structural engineers to design fire protection in timber buildings that use TCC floors using either alternate means and methods or structural fire engineering. This paper presents two experimental studies conducted to examine (1) properties of shear connection systems used in TCC floors through ambient temperature direct shear tests, and (2) the behavior of TCC floors through large-scale fire tests performed at the National Research Council (NRC) in Canada. The main objective of this research is to collect data on the fundamental behavior of TCC floors in a fire. The results indicate that TCC floors have improved fire performance when compared with mass timber floors. In addition, the research quantifies the force-slip behavior of the shear connectors used and benchmarks the flexural behavior of TCC floors at ambient and elevated temperatures to existing analytical models.

Modelling and design method for static resistance of a new connection between steel tubular column and flat concrete slab

This paper presents the results of a numerical and analytical investigation into the punching shear behaviour of an innovative simple and effective shear connection between steel tubular column and flat concrete slab using welded shear studs, steel plates and bent-up rebars. The finite element numerical simulation model was validated against two full-scale physical tests carried out by the authors. The validated numerical simulation model was used to perform extensive numerical parametric studies to investigate the effects of changing different design parameters including flat slab depth, concrete grade, bent-up rebar design, shear stud dimensions (length and diameter) and steel tube size, so as to develop thorough understanding of their punching shear behaviour and to provide comprehensive data for development of an analytical method for design. The developed analytical design method can be used to check capacities of shear studs, bent-up rebars and slab punching shear resistance. For this shear connection system, it is easy to prevent shear stud yield failure and bent-up rebar failure so that the system behaves as an enlarged column for calculating punching shear resistance of the slab. For the enlarged column, punching shear resistance calculation method in Eurocode 2 [2] can be used.

Experimental Study on a Novel Shear Connection System for FRP-Concrete Hybrid Bridge Girder.

The study presents experimental results of an investigation on a novel shear connection system for hybrid bridge girders composed of laminated composite beams and concrete slabs. The special connector comprised of a steel plate and welded bolts is attached to beam’s top flange by adhesive bonding and with a preset torque of nuts. The study’s purpose is to check ductility, safety, reliability and robustness of the shear connection before its implementation in the first Polish composite bridge. Three static push-out tests and fatigue test were performed to evaluate the shear connection behavior under static and cyclic loading. The load–slip curves, shear capacity, fatigue strength and failure mechanisms of the novel shear connectors are discussed. The high-slip modulus indicates that the connectors can very efficiently promote the composite action. The ultimate resistance and the fatigue strength obtained from the test was about 12% and 66% higher than the characteristic resistance and the fatigue strength of common headed studs, according to Eurocode 4, respectively. An estimated global safety factor of 3.67 showed the high safety, reliability and robustness of the novel connection system. The study discusses the structural performance of the proposed connection system, demonstrating its technical suitability.

Shear connection of prefabricated slabs with LWC - Part1: Experimental and analytical studies

This paper studies the shear strength and load-slip behaviours of a recently developed novel steel-concrete composite flooring system (PUSS) with two different types of shear connectors while also using lightweight concrete. PUSS consists of a T-ribbed lightweight concrete floor and C-channel steel edge beams. The proposed shear connection system is using either web-welded shear studs only, or combined with horizontally lying steel dowels. This unique system further minimises its structural depth and results in ultra-shallow floors.Eight full-scale push-out tests were conducted to investigate the connection under the direct shear force with three different concrete types (normal concrete, lightweight and ultra-lightweight concretes) and two different shear connection systems (web-welded shear studs only and horizontally lying steel dowels together with web-welded shear studs). Three types of failure were recorded from the push-out tests; shear failure with bending near the roots of the connectors, shear failure of the weld toe of shear studs, and concrete cracking. Among the conclusions, it was validated that the compressive strength of the concrete significantly influences the ultimate shear strength capacity loads while it is influencing the failure mode of the connection. The failure mechanisms of the shear connectors were extensively studied, which led to the development of a calculation method for the shear strength and load–slip behaviours of the new connectors embedded in lightweight concrete. The analytical results are compared with those predicted by modern codes of practices and available methods from the literature. It is concluded that the proposed formulae offer a reliable prediction.

Prefabricated Composite Flooring Systems with Normal and Lightweight Concretes

ABSTRACTThe use of lightweight concrete in structural applications for the sustainable design of composite slabs require the revision of today's flooring systems and the development of more efficient shear connectors. This paper studies a novel prefabricated and shallow steel‐concrete composite flooring system which is consisted of two main structural components: two C‐channel steel beams and a partially encased concrete floor. The concrete floor, which is in the form of T‐ribbed slab sections, was constructed using three types of concrete (reinforced normal concrete, reinforced lightweight aggregate concrete, and reinforced ultra‐lightweight aggregate concrete), and the steel edge beams which partially encase the floor slab and provide clear and straight finish edges. This paper includes the work of 2 full‐scale push‐out tests aimed at investigating the longitudinal shear behaviour of the new shear connection system (made of shear studs and steel dowels) when the normal concrete is replaced by lightweight and ultra‐lightweight concrete.

03.27: Punching shear behaviour of an innovative connection between steel tubular column to flat concrete slab

ABSTRACTThis paper presents the results of an experimental investigation into the punching shear behaviour and resistance of a simple and effective method of connection between steel tubular column and concrete flat slab using welded shear studs. The shear stud used is the same type as used in conventional steel/concrete composite beams. A major difference between the shear stud behaviour in the proposed system and in composite beam is that in the proposed system, the amount of concrete available to resist punching shear is limited due to small depth of the flat concrete slab. The experimental studies have investigated the effects on punching shear behaviour and resistance of the proposed shear connection system under different design variables including concrete depth above the shear stud, concrete grade, and shear stud dimensions (length and diameter). The results indicate that it is possible to use the proposed simple connection system to provide sufficient punching shear resistance in realistic flat slab construction. Punching shear resistance is dependent on the concrete depth above shear stud. Concrete grade is also important, however, it is the concrete tensile strength that directly determines punching shear resistance. The dimensions of shear stud have relatively minor influences.

Mechanical behaviour of pre-stressed spruce timber–timber 2.5-mm-step grooved connections under shearing tests

A smart shear connection system was tested in order to be used in manufactured elements of a lattice of wooden slats and a cross offset. This type of floor element can present advantages both in terms of weight and suitable insulating filler (Adalberth et al. 2001; Kawasaki and Kawai 2006; Kermani and Hairstans 2006; Dodoo et al. 2014). This connection is made to provide a substitute for a glue connection. The shear connection proposed is made by double-sided grooving timber interfaces to form a cross section. A specifically designed test assembly was constructed to measure and guarantee homogeneous contact pressure in interface test specimens. Shear test results are presented and compared in terms of capacity and stiffness with glue connections. The principal conclusions are as follows: the allowable shearing resistance of the grooved timber–timber joints can approximately reach the resistance of glued connections. The stiffness of the joints is improved by increasing the pre-stress applied for holding contact in the assembly. The grooved timber-to-timber joints exhibit non-linear behaviour which dominates the behaviour of the whole system. Therefore, the behaviour of a unit connection must be determined to obtain the mean load-carrying capacity and stiffness of a system with grooved connections.

Dynamic behaviour of steel-concrete composite beams retrofitted with various bolted shear connectors

In structural engineering, composite construction has become increasingly widespread due to the improvement of mechanical properties it provides. Retrospective application of the composite construction principle to old structures may be beneficial. Many end of life structures are decommissioned and replaced. If the structural integrity of old structures could be improved their service life may be extended. Recently research on the development of post-installed or retrofitted shear connectors has been conducted. Most of the research in this area is concerned with modified versions of welded shear studs or various threaded rod and nut configurations, and refer to only one type of shear connector. Therefore, the suitability of the proposed models across differing shear connection types is unknown. An experimental study has been undertaken to ascertain the differences in dynamic behaviour of cast-in and retrofitted shear connectors using a series of identical steel-concrete composite beams with various shear connection systems. Two blind bolt connector types were used as shear connection systems in steel-concrete composite beams alongside a welded shear stud specimen in both cast-in and retrofitted configurations. A finite element model was then developed. The nature of changes in dynamic behaviour due to damage were investigated using the finite element model. It was found that at increased loading the behaviour of the cast-in and retrofitted connectors was fundamentally different due to the retrofitting procedure.

Effective shear connection for shallow cellular composite floor beams

Shallow cellular composite floor beam is a new type of composite floor beam that usually consists of a structural steel beam with regularly spaced web openings and concrete slab casted above the steel decking. In this study, the shear transferring mechanisms of shallow cellular composite beams design with innovative shear connection systems are investigated. A detailed finite element analysis program was performed to investigate the force transferring mechanism, load bearing capacity and failure behavior of the shear connections under direct longitudinal shear forces by simulating the push-out tests. Four different configurations of shear connections (web opening configurations) were designed and an intensive parametric study was conducted to determine the material and geometric parameters that likely influence the behavior of the shear connection. Finally, the findings from this investigation are incorporated with the bending and push-out test results to develop design methods for this form of shear connection. The failure mechanisms of the shear connection were confirmed, and it was also revealed that this type of shear connection is effectively capable to provide the desired shear resistance and ductile behavior if designed properly.

Concrete wedge and coarse sand coating shear connection system in GFRP concrete composite deck

In recent years, Glass Fiber-Reinforced Polymer (GFRP) has become a widely used material in Fiber-Reinforced Polymer (FRP) composite structures. Several studies have been performed on the bonding methods of FRP sheets and plates, but limited research has been undertaken on the critical shear connection systems for innovative GFRP concrete composite bridge decks structures. Coarse sand coating shear connection systems for GFRP structures show strong bondage in the shear direction but poor grip in the normal direction. An innovative concrete wedge system, supplementary to coarse sand coating overcomes the normal split between GFRP panel and concrete, in composite bridge deck structures. This study presents a finite element (FE) investigation on GFRP concrete composite deck using a concrete wedge shear connection system based on existing experimental evaluation. In this research, the thickness of the GFRP module was varied and the deflection behaviour of GFRP concrete composite deck was furthermore studied. FE results indicate that thickness increments of the GFRP module significantly reduce the mid-span deflection of the composite deck and subsequently increase the ultimate load. In order to investigate the interaction behaviour between GFRP and concrete in the numerical analysis, a structural interface element is proposed for finite element modelling (FEM) analysis. In order to undertake a rapid evaluation of deflection of the composite deck, an equation is proposed to estimate the deflection at the mid-span of the GFRP composite bridge deck based on the FEM results. In addition, the GFRP composite bridge deck was numerically analysed using light-weight concrete (LWC) and results were compared with GFRP composite deck with conventional concrete. The results indicate that using LWC increases the ultimate load proportionally till failure.

Influence of Shear Connector Size on Ultimate Strength in Composite Construction with Cold-Formed Steel Channel Lipped Section

In conventional composite construction for buildings and bridges, Hot-Rolled Steel (HRS) section is well known to be used. The composite action is usually achieved by using conventional headed stud shear connectors. However, for Cold-Formed Steel (CFS) section, the use of headed stud shear connectors is not feasible as the section is very thin and incapable to be weld. Therefore, a suitable shear connection system of bolt and nut is proposed in this study by varying the size of the bolted shear connectors. This paper presents the prospect of using a bolt and nut as shear connector that could be well-suited with CFS section when integrated in Self-Compacting Concrete (SCC). The experimental test comprised of push-out and was conducted to determine the strength and ductility of the proposed bolted shear connectors as used in composite construction. Eight push-out test specimens of bolted shear connector size consist of M12, M14 and M16 of grade 8.8 were fabricated and tested to failure. The experimental results show that the bolted shear connectors used to possess good shear resistance capacity. Influence of varying the size of the bolted shear connectors was investigated. The results show that the size of bolted shear connectors influenced the ultimate strength capacity of the shear connectors significantly.

Dynamic behaviour of steel–concrete composite beams with different types of shear connectors. Part II: Modelling and comparison

In the first paper of these two companion papers an experimental study was undertaken to ascertain the dynamic behaviour of identical steel–concrete composite beams with differing shear connection systems. Two blind bolt connector types were used as shear connection systems in steel–concrete composite beams. Alongside these, a welded shear stud specimen, and a non-composite specimen were tested for comparison. In this, the second paper a Timoshenko beam model for steel–concrete composite beams is developed and is compared with the experimental results. An uncertain boundary condition is investigated using the Timoshenko beam model and an empirical relation between the displacements at the beam supports and the rotation of the cross section face is proposed.

Dynamic behaviour of steel–concrete composite beams with different types of shear connectors. Part I: Experimental study

In civil engineering, composite construction has become increasingly widespread due to the improvement of mechanical properties it provides. Recently, research on the development of post installed or retrofitted shear connectors has been conducted. The benefits of this are the ease of installation and the ease of removal for decommissioning structures at the end of their life. Most of the research in this area is concerned with modified versions of welded shear studs or various threaded rod and nut configurations and refers to only one type of shear connector. Therefore, the suitability of the proposed models across differing shear connection types is unknown. In the first of two companion papers an experimental study has been undertaken to ascertain the dynamic behaviour of identical steel–concrete composite beams with differing shear connection systems. Two blind bolt connector types were used as shear connection systems in steel–concrete composite beams. Alongside these, a welded shear stud specimen, and a non-composite specimen were tested for comparison.

Evaluation of bending tests on composite glulam–CLT beams connected with double-sided punched metal plates and inclined screws

Composite beam elements made of glulam beams and cross laminated timber (CLT) panels, and connected with a new shear connection system were tested under four point bending. The beams tested represent a section of a cassette floor element to be used in a multi-storey CLT construction system. The shear connection is primarily made of double-sided punched metal plate fasteners, connecting the CLT and glulam members to form a T-cross-section. Due to the uncertainty about the capacity of the double-sided nail plates to resist possible separation forces between the timber members, the shear connection may be secured with screws. Bending tests were performed with three shear connection configurations: double-sided punched metal plate fasteners only, inclined screws only, and double-sided punched metal plate fasteners combined with inclined screws. An additional test with a screw-glued connection was made for comparison. The results show that a shear connection with double-sided nail plates can be designed to provide a sufficiently high level of composite action and load-carrying capacity and represents an alternative shear connection system for glulam–CLT composite floors.