Bolted Shear Connectors Research Articles

Optimum use of composite structures for demountable construction

This paper explores the concept of the optimum span to depth ratio of reusable composite beams with demountable bolted shear connectors so that the beams may be designed most efficiently in terms of their weight and the shear connector distribution along the span. Three patterns of shear connectors were evaluated by a simple pseudo-plastic model and calibrated by finite element modules in terms of their effect on the overall composite beam stiffness in the range of 9 to 15 m span. The optimum span to depth ratio of symmetrical and asymmetrical beams was determined and compared to equivalent beams with welded shear connectors. It was found that the optimum span to depth ratio of uniformly loaded unpropped composite beams with demountable bolted shear connectors may be taken as 22 which allows for a utilisation factor of 0.7 at the ultimate limit state to ensure that plasticity does not occur in the first use cycle. It was found that the effect of asymmetry on the optimum span to depth ratio is small. For propped beams with demountable shear connectors, the optimum span to depth ratio may be increased to 24.

Elastic behaviour of a tapered steel-concrete composite beam optimized for reuse

Steel-concrete composite beams are widely used in practice because of their simple construction sequence and economic cross-section design. Reuse of traditional composite beams is not possible due to the permanent connection between the steel beam and concrete deck established by welded headed studs. To allow for fast construction, demountability and reuse of composite beams, various demountable shear connectors can be used. In this paper the results of experiments carried out on demountable and reusable tapered composite beams, consisting of a tapered steel beam and large-scale prefabricated concrete decks, are presented. The performance of various arrangements of resin-injected bolt-coupler shear connectors was considered to optimize the beneficial effect of composite action whilst minimizing the number of shear connectors. An advantage of resin-injected bolted shear connectors is that composite action is obtained instantaneously and simultaneously for all connectors. Demountability and reusability of the composite beam were successfully demonstrated experimentally. Experimental and numerical results indicated that the number of shear connectors necessary to fulfil deflection and end-slip limits can be reduced by concentrating them near the supports of a simply-supported beam. Results obtained using finite element models closely matched the experimental results in terms of deflection, stresses and curvature.

Cyclic Performance of Steel–Concrete–Steel Sandwich Beams with Rubcrete and LECA Concrete Core

Due to the structural and economic features of steel–concrete–steel (SCS) structural systems compared with conventional reinforced concrete ones, they are now used for a range of structural applications. Rubcrete, in which crumbed rubber from scrap tires partially replaces mineral aggregates in concrete, can be used instead of conventional concrete. Utilizing rubber waste in concrete potentially results in a more ductile lightweight concrete that can introduce additional features to the SCS structural members. This study aimed to explore different concrete core materials in SCS beams and the appropriate shear connectors required. In this study, four SCS sandwich beams were tested experimentally under incrementally increasing flexure cyclic loading. Each beam had a length of 1000 mm, and upper and lower steel plates with 3 mm thickness sandwiched the concrete core, which had a cross-section of 150 mm × 150 mm. Two of the beams were constructed out of Rubcrete core with welded and bolted shear connectors, while the other two beams were constructed with welded shear connectors and either conventional concrete or lightweight expanded clay aggregate (LECA) concrete cores. The performance of the SCS sandwich beams including damage pattern, failure mode, load-displacement response, and energy dissipation behavior was compared. The results showed that, while Rubcrete was able to provide similar concrete cracking behavior and strength to that of conventional concrete, LECA concrete degraded the strength properties of SCS. Using bolted shear connectors instead of welded ones caused a high number of cracks that resulted in a reduced ductility and deflection capacity of the beam before failure. The rubberized concrete specimen presented an improved ductility and deflection capacity compared with its conventional concrete counterpart.

Design of composite flooring systems for reuse

Composite floor systems are frequently used for high-rise buildings and multi-storey car park buildings, mainly because of the competitive combination of the steel beam and the concrete deck. Traditionally, composite beams are cast in-situ and shear interaction between the concrete and steel beam is provided by welded headed studs. The application of welded headed studs prevents the non-destructive separation of the composite beam, which leads to a very low scoring in the sustainable assessment in terms of the reuse of structural components. An alternative to welded headed studs are bolted shear connectors, which allow for demountability and reusability of a (prefabricated) composite floor system. A key challenge for demountable and reusable composite beams consisting of prefabricated elements is to provide sufficient tolerances to allow for easy execution and demounting, but also to achieve a stiff and strong shear connection under live loads. The required tolerances can, for instance, be obtained by using large bolt-to-hole clearances. The, at first glance, contradictory requirement of a large hole clearance in the execution phase and high stiffness under live loading conditions was solved by using injection bolts. The goal of this paper is to demonstrate how the demountable and composite structures fit in the circular economy framework, and to show that such a demountable and reusable structure was successfully erected and demounted under laboratory conditions. In addition, a cost assessment will be addressed using a simple methodology based on estimated service life (ESL) factors to estimate the annual environmental costs of a composite floor system.

A Review of the Fatigue Strength of Shear Bolted Connections

Steel bolted connections are the typical joints used in civil engineering but also in the field of mechanical engineering. In particular, slip-resistant bolted connections are those most used in bridge construction. In these applications, bolted joints are subjected to a cyclic load that arises from traffic flow. It is well known that joints are the critical components of constructions subjected to cyclic loads, due to stress concentration that causes fatigue crack initiation. The purpose of this paper is to provide a summary of considerations, from principal scientific studies of fatigue strength and the behaviour of bolted joints, as well as an up-to-date comprehensive assessment for future development. In particular, a discussion is proposed regarding the parameters that influence the fatigue of bolted joints. The paper concludes with a summary of the major results reported in terms of S–N curves.

Finite element modelling of demountable precast reinforced concrete deck slabs with external confining system

This paper investigates the enhanced loading capacity and structural behaviour of a transversely confined precast reinforced concrete (RC) deck slab with deconstructable post-installedfriction-grip bolted (PFGB) shear connectors. A detailed 3D non-linearcontinuum-based finite element (FE) model of the deconstructable composite deck with external confining systems (i.e. cross-bracings or ties) and PFGB shear connectors is developed and analysed using the commercial software ABAQUS. The non-linearity of the contacts/interfaces, geometrical and material non-linearities are considered in the FE models. The developed FE models are validated against experimental results and it is shown that the proposed FE model can adequately predict the enhancing effect of arching action in a transversely confined deconstructable precast RC deck slab. Lastly, a parametric study is carried out and effect of different parameters such as compressive strength of concrete, yield strength and proportion of reinforcing bars, clearance between concrete slab and PFGB shear connectors and pretension stress in the PFGB shear connectors on the stiffness and strength enhancement provided by the arching action are evaluated and discussed.

Comparative Study between Linear-Interpolation and Stress-Block Methods of Composite Design Using Cold-Formed Steel Section

For decades, Hot Rolled Steel (HRS) section was in use in construction of buildings and bridges. The simple reason is that the use of HRS section in composite systems is well established by standard rules and their design necessities as provided in the codes. In this paper, the use of doubly oriented back-to-back Cold-Formed Steel (CFS) section coupled with bolted shear connectors in composite floor system was demonstrated. The bolted system of shear connector provides an alternative to headed stud shear connector with CFS section as welding of the stud connector is practically not feasible on CFS section because of its thinness nature. The loading system used was four-point bending test to determine the flexural strength capabilities of the composite floor system. The resulting composite floor system has proven to provide adequate strength and stiffness properties under the applied loads. The results have shown that the theoretical value of flexural capacities calculated agrees reasonably well with the experimental values. In conclusion, the composite floor system can be used in small and medium size buildings, as well as in light weight construction industries.

Bolt shear connectors in grout pockets: Finite element modelling and parametric study

Recent laboratory experiments have demonstrated the superior performance (high stiffness, load-carrying capacity and ductility) of bolt shear connectors embedded in the pockets of cementitious grout compared to conventional fasteners (e.g. screws) for developing composite action between steel beams and timber slabs. Accordingly, this paper investigates the structural behaviour of steel-timber composite (STC) joints with bolt connectors embedded in grout pockets (BCGP) using 3-D continuum-based finite element (FE) models. Following validation of the FE models against available push-out test data, they are used to conduct a parametric study that elucidates the influences of the compressive strength of the grout, the yield strength and size of the bolt shear connectors, the size of the grout pockets and the thickness of the steel profile flange on the load-slip behaviour, service stiffness, peak load-carrying capacity and failure modes of STC joints with BCGP. Simple formulae for the stiffness and load-carrying capacity of the STC joints with BCGP are derived from linear regression of the results of the parametric study.

2개의 볼트를 갖는 고강도 알루미늄 합금 일면전단 볼트접합부의 내력

2개의 볼트를 갖는 고강도 알루미늄 합금 일면전단 볼트접합부의 내력

Structural Behavior of Steel-Concrete Composite Beam using Bolted Shear Connectors: A Review

Conventional steel-concrete composite beams have been recognized to exhibit stronger structural characteristics, in terms of strength and stiffness, when compared to pure steel or reinforced concrete beams. However, currently most steel beam is fully attached to the concrete slab; this means that the shear connectors are welded through the steel decking on to the steel beam and cast into concrete slab to fulfill the necessary shear connection. Recently, the deconstruction and reuse of the components almost impossible. In order to achieve a sustainable structural system, precast concrete slabs are attached to a steel beam using bolted shear connectors in prefabricated holes have been introduced as an alternative to the conventional connectors in steel – concrete composite beam system. This paper reviews the structural behavior of composite beam system such as the strength, stiffness, slip behavior, failure mode and sustainability obtained by experiment and numerical studies in order to address the applicability and efficiency of the composite beams having precast concrete slabs and bolted shear connectors.

Static behaviour of bolted shear connectors with mechanical coupler embedded in concrete

The research of shear connectors composed from mechanical couplers with rebar anchors, embedded in concrete, and steel bolts, as a mean of shear transfer in composite connections is presented in the paper. Specific issues related to this type of connections are local concrete pressure in the connector vicinity as well as the shear flow along the connector axis. The experimental research included 18 specimens, arranged in 5 series. Nonlinear numerical analyses using Abaqus software was conducted on corresponding FE models. Different failure modes were analysed, with emphasis on concrete edge failure and bolt shear failure. The influence of key parameters on the behaviour of shear connector was examined: (1) concrete compression strength, (2) bolt tensile strength and diameter and (3) concrete edge distance. It is concluded that bolted shear connectors with mechanical couplers have sufficient capacity to be used as shear connectors in composite structures and that their behaviour is similar to the behaviour of post installed anchors as well as other types of connectors anchored without the head.

Composite connections between CLT slab and steel beam: Experiments and empirical models

A composite floor comprising of steel beams connected to cross laminated timber (CLT) panels is a sustainable alternative to composite floors with reinforced concrete slab. The structural performance of the steel-CLT floor depends strongly on the load-slip behaviour (particularly the stiffness and strength) of the shear connection between the steel beams and the CLT slabs. In this paper, the short-term behaviour of steel-CLT joints is studied by laboratory push-out experiments conducted on CLT-steel-CLT specimens, being analogous to familiar push tests on steel-concrete specimens. In addition to coach screws and bolts, a high-performance steel-CLT composite connection comprising of high-strength bolted shear connectors embedded in pockets of grout is proposed and tested. The push-out experiments are used to determine the load-slip, failure mode, stiffness and ultimate strength/capacity of the steel-CLT composite joints and to calibrate an empirical formula for the load-slip response of the CLT-to-steel connections. Furthermore, simple empirical formulae for the stiffness and ultimate capacity of the CLT-to-steel composite connections are proposed.

고강도 오스테나이트계 스테인리스강(STS201) 일면전단 볼트접합부의 최대내력평가

고강도 오스테나이트계 스테인리스강(STS201) 일면전단 볼트접합부의 최대내력평가

Fatigue behaviour of transversely restrained precast steel fibre reinforced concrete slabs in a deconstructable composite deck

This study investigates fatigue behaviour and failure of transversely restrained precast reinforced concrete (RC) deck slabs with and without steel fibres (SF) in a novel deconstructable steel-concrete composite deck that takes advantage of bolted shear connectors. In total, seven precast (SF)RC slabs were tested under a static load to establish the peak load capacity of the specimens and the another eight slabs were tested under cyclic loads. The types of lateral restraint (i.e. cross-bracings or ties) provided for the slabs, reinforcing configuration and steel fibre dosage (i.e. 0.25% and 0.5%) were the main variables in this study. The results of experiments showed that increasing the level of service load on accounting of strength enhancement provided by arch action has no negative impact on the fatigue behaviour of transversely restrained (SF)RC deck slabs. Furthermore, it was concluded that adding 0.25% and 0.5% fibres have similar effect on the static load capacity, but significant enhancement in the fatigue life was only observed in the transversely restrained slabs with a fibre dosage of 0.5%.

Computational modelling of the moment-rotation relationship for deconstructable flush end plate beam-to-column composite joints

This paper presents a three-dimensional finite element modelling of an innovative flush end plate semi-rigid beam-to-column composite joint comprising deconstructable post-installed friction-grip bolted shear connectors. The moment versus rotation relationship for these prototype joints subjected to a hogging bending moment with the influence of partial shear connection is investigated using ABAQUS software. This relationship is an indicator of the ductility of a composite joint and is a necessity for a semi-rigid frame analysis. A detailed finite element model of the connection region including the precast concrete slab, steel beam, flush end-plate, bolted shear connectors and the steel column is developed in the paper. Material and geometrical non-linearities as well as the non-linearity of the interfaces are incorporated in the model. The accuracy and reliability of the numerical formulation are verified against experimental data reported elsewhere. In addition, a composite joint with partial shear connection is constructed and tested in this study, and the numerical predictions are compared with the test results. An extensive parametric study is then conducted, using several parameters that include the degree of shear connection, reinforcement ratio, thickness of the precast concrete slab, spacing of bolted shear connectors, size of the bolts in the connection zone, thickness of the flush end plate, steel grade for the beam, column and end plate and the column flange thickness. Finally, moment versus rotation models for deconstructable flush end plate beam-to-column composite joint are proposed, and it is demonstrated that the design models developed can also be used for composite joints with high strength steel components.

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.

Numerical Study of Deconstructable Flush End Plate Composite Joints to Concrete-filled Steel Tubular Columns

This paper describes a three-dimensional finite element modelling of an innovative flush end plate semi-rigid composite joint, to a concrete-filled steel tubular column, using high strength blind bolts. This innovative composite joint is formed by connecting a precast concrete slab to the top flange of a steel beam using post-installed friction-grip bolted shear connectors to facilitate the deconstructability of the entire system. A finite element model is developed using ABAQUS software to study the structural behaviour and failure modes of these prototype joints. Both geometrical and material non-linearities, as well as the non-linearity of the contacts and interfaces, are incorporated in the model. Four full-scale laboratory test specimens having deconstructable flush end plate composite semi-rigid joint to CFST columns using bind bolts are tested, with the results then used for validation of the finite element model. The proposed numerical models developed are used for conducting an extensive parametric study, in which the effects of the reinforcement ratio, thickness of the precast concrete slab, degree of shear connection, number of bolted shear connectors, size of the blind bolts in the connection zone and thickness of the flush end plate on the structural behaviour of the composite joint to concrete-filled columns are investigated. A design recommendation in the form of an empirical equation is then formulated.

Finite element analysis of HSS semi-rigid composite joints with precast concrete slabs and demountable bolted shear connectors

High-strength steel has a higher yield strength, greater corrosion resistance and superior toughness compared to mild steel, and its use can contribute to the sustainability of a steel structure by increasing its structural life whilst reducing steel usage and maintenance. In addition, using deconstructable steel-concrete composite floors can facilitate component recycling and reuse and can improve the sustainability of the building industry significantly by reducing energy consumption and construction waste at demolition. This paper investigates the structural behaviour of an innovative beam-to-column composite semi-rigid joint with deconstructable post-installed friction-grip bolted shear connectors and grade S690 high strength steel flush end plates. Non-linear continuum-based finite element models are developed and validated against results of four full-scale laboratory tests of this innovative joint. The validated finite element models are used for conducting an extensive parametric study in which the effects of the reinforcement ratio, thickness of the precast concrete slab, degree of shear connection, number of bolted shear connectors, size of the bolts in the connection zone, size of the steel beam and thickness of the flush end plate on the structural behaviour of a composite joint with deconstructable post-installed friction-grip bolted shear connectors and grade S690 high strength steel flush end plates are investigated. A simple analytical model is proposed to predict the moment capacity and rotation capacity of this type of composite joint.

Behaviour of precast concrete deck slabs with transverse confining systems

The enhanced loading capacity of transversely confined concrete deck slabs has been demonstrated through different studies, but the available transverse confining systems used in conjunction with cast in situ concrete deck slabs are not conducive to deconstruction. This paper presents the results of an experimental study on precast slabs attached to girders using bolted shear connectors. Ten half-scale precast slabs are tested under a monotonically increasing force applied at the mid-span. The configuration and proportion of the reinforcing steel bars and types of transverse confining system (cross-bracings or ties) are the main test variables. The experimental results demonstrate the efficiency of the proposed system for mobilising arching action in the precast concrete deck slabs. Also, it is shown that the location of reinforcing bars in single-span concrete slabs with transverse confinement can significantly influence the load capacity and ductility, but the top reinforcing steel bars have negligible influence on the peak load and ductility. In addition, detailed finite-element models of the specimens are developed and verified against test results and it is shown that the adopted finite-element models can adequately capture the local and global response of the transversely confined deconstructable precast concrete deck slabs.

Experimental Investigation on Shear Connectors in Steel-concrete Composite Deck Slabs

Background/Objectives: The steel-concrete composite construction has become an effective construction practice in the recent years. The cold form profiled sheet acts a platform for during the construction phase and acts as an external reinforcement after the construction. In steel-concrete composite construction, the shear connectors transfer the longitudinal shear force across the steel flange/concrete interface. The ability to transfer longitudinal shear force by shear connectors mainly depends on the strength of concrete against longitudinal cracking and mechanical properties of the shear connectors. This research investigates shear connector's capacity; the experimental investigation is involved using push-out test for two sets with different shear connectors framing to the profile steel sheet. Methods/Statistical Analysis: Set-W consists of three composite slab specimens with welded stud shear connectors, while set-B consists of three composite slab specimens with bolted shear connectors. Trapezoidal profile steel sheet of thickness 1 mm with rectangular embossments is used. Several key parameters of the composite slab are examined and measured, including slippage capacity, load carrying capacity, composite slab ductility and failure mechanism. Findings: the welded shear connectors provided a better performance in resisting slippage and providing a welded set higher load carrying capacity, however, the bolted shear connector specimens set showed more ductile behavior as compared to of specimens.