Steel-concrete Composite Slabs Research Articles

Influence of shear bolt connections on modular precast steel-concrete composites for track support structures

Through extensive research, there exist a new type of connection between railway bridge girders and steel-concrete composite panels. In addition to conventional shear connectors, newly developed blind bolts have been recently adopted for retrofitting. However, the body of knowledge on their influence and application to railway structures has not been thoroughly investigated. This study has thus placed a particular emphasis on the application of blind bolts on the Sydney Harbour Bridge as a feasible alternative constituent of railway track upgrading. Finite element modeling has been used to simulate the behaviours of the precast steel-concrete panels with common types of bolt connection using commercially available package, ABAQUS. The steel-concrete composite track slabs have been designed in accordance with Australian Standards AS5100. These precast steel-concrete panels are then numerically retrofitted by three types of most practical bold connections: head studded shear connector, Ajax blind bolt and Lindapter hollow bolt. The influences of bolt connections on load and stress transfers and structural behaviour of the composite track slabs are highlighted in this paper. The numerical results exhibit that all three bolts can distribute stresses effectively and can be installed on the bridge girder. However, it is also found that Lindapter hollow bolts are superior in minimising structural responses of the composite track slabs to train loading.

The parameters of the acoustic insulation capacity of a reinforced wooden ceiling

The article presents the parameters of the acoustic insulation capacity of a traditional wooden ceiling before and after renovation in a historical building from the beginning of the 20th century. Due to a change in the use of the building, the existing wooden ceilings were reinforced with two symmetrical C-bars with the use of Cofrastra 40 composite steel-concrete slab. The composite slab, being the ceiling support, made it easy to mount a suspended ceiling with thermal and acoustic insulation layers specifically selected for the building’s needs.

Identification of the hygro-thermo-chemical-mechanical model parameters of concrete through inverse analysis

A wide range of parameters is required in input when applying hygro-thermo-chemical-mechanical models to concrete components with the aim of determining the variations over time of temperature, relative humidity and shrinkage induced deformations. While a sub-set of these material parameters can be evaluated on the basis of the concrete mix specifications or from literature data, this paper presents a robust inverse analysis procedure for the identification of the remaining sub-set of parameters that are characterised by a large variability and, in some cases, do not have a precise physical meaning and are not amenable to a direct measurement. The particularity of this paper is to propose different strategies for the characterisation of these material parameters that account for the presence of different exposure conditions, as these affect the outcomes and requirements of the parameter identification procedure. After introducing the adopted hygro-thermo-chemical-mechanical model, representative results of an extensive sensitivity analysis are presented in the first part of the paper to give insight into most effective number, location and duration of measurements to be used in input of the inverse analysis. The inverse analysis procedure is then presented and applied to a number of selected scenarios to highlight its robustness considering different boundary conditions in terms of external temperature and relative humidity surrounding the concrete. The ability to characterise these parameters will support a wider use of these hygro-thermo-chemical-mechanical models, especially for those applications in which humidity and temperature profiles significantly influence the structural response, for example when predicting curling in industrial pavements and non-uniform shrinkage profiles in composite steel-concrete slabs.

Three-dimensional Finite Element Modelling of Composite Slabs for High Speed Rails

Currently precast steel-concrete composite slabs are being considered on railway bridges as a viable alternative replacement for timber sleepers. However, due to their nature and the loading conditions, their behaviour is often complex. Present knowledge of the behaviour of precast steel-concrete composite slabs subjected to rail loading is limited. FEA is an important tool used to simulate real life behaviour and is widely accepted in many disciples of engineering as an alternative to experimental test methods, which are often costly and time consuming. This paper seeks to detail FEM of precast steel-concrete slabs subjected to standard in-service loading in high-speed rail with focus on the importance of accurately defining material properties, element type, mesh size, contacts, interactions and boundary conditions that will give results representative of real life behaviour. Initial finite element model show very good results, confirming the accuracy of the modelling procedure

Free vibrations of precast modular steel-concrete composite railway track slabs

This paper highlights a study undertaken on the free vibration of a precast steel-concrete composite slab panel for track support. The steel-concrete composite slab track is an evolvement from the slab track, a form of ballastless track which is becoming increasingly attractive to asset owners as they seek to reduce lifecycle costs and deal with increasing rail traffic speeds. The slender nature of the slab panel due to its reduced depth of construction makes it susceptible to vibration problems. The aim of the study is driven by the need to address the limited research available to date on the dynamic behaviour of steel-concrete composite slab panels for track support. Free vibration analysis of the track slab has been carried out using ABAQUS. Both eigenfrequencies and eigenmodes have been extracted using the Lanczos method. The fundamental natural frequencies of the slab panel have been identified together with corresponding mode shapes. To investigate the sensitivity of the natural frequencies and mode shapes, parametric studies have been established, considering concrete strength and mass and steel

Serviceability performance of steel–concrete composite beams

The use of steel–concrete composite beams in which wide-flanged steel beams act compositely with a concrete or steel–concrete composite slab above is well established in building construction. However, for composite beams with low degrees of shear connection between the beam and slab, significant additional deflections can occur due to slip in the shear connectors. A design formula is presented for the effective stiffness of composite beams taking account of the stiffness of the shear connectors, which is compared to measured deflections of six symmetric composite beams and an 11 m span composite beam of asymmetric profile. It is shown that the comparison is good when using a shear connector stiffness of 70 kN/mm for single shear connectors and 100 kN/mm for pairs of shear connectors per slab rib. The results of push tests on a range of slab profiles confirmed these initial elastic stiffnesses. To ensure that the slip at the serviceability limit state does not lead to permanent deformations of the composite beam, it is proposed that the minimum degree of shear connection should not fall below 30% for unpropped beams and 40% for propped beams of symmetric cross-section.

Damped frequencies of precast modular steel-concrete composite railway track slabs

This paper presents unprecedented damped oscillation behaviours of a precast steel-concrete composite slab panel for track support. The steel-concrete composite slab track is an innovative slab track, a form of ballastless track which is becoming increasingly attractive to asset owners as they seek to reduce lifecycle costs and deal with increasing rail traffic speeds. The slender nature of the slab panel due to its reduced depth of construction makes it susceptible to vibration problems. The aim of the study is driven by the need to address the limited research available to date on the dynamic behaviour of steel-concrete composite slab panels for track support. Free vibration analysis of the track slab has been carried out using ABAQUS. Both undamped and damped eigenfrequencies and eigenmodes have been extracted using the Lancsoz method. The fundamental natural frequencies of the slab panel have been identified together with corresponding mode shapes. To investigate the sensitivity of the natural frequencies and mode shapes, parametric studies have been established, considering concrete strength and mass and steel\'s modulus of elasticity. This study is the world first to observe crossover phenomena that result in the inversion of the natural orders without interaction. It also reveals that replacement of the steel with aluminium or carbon fibre sheeting can only marginally reduce the natural frequencies of the slab panel.

Numerical modelling of the shear-bond behaviour of composite slabs in four and six-point bending tests

An effective finite element model which reproduces the longitudinal shear behaviour of composite steel-concrete slabs with profiled sheeting has been developed. The steel-concrete interface was simulated with a non-linear shear behaviour law (τ-s) which properly defines the shear-bond behaviour of composite slabs. A simple methodology is proposed to calculate the above mentioned law from experimental load-deflection curves and the geometry of the slabs. The numerical model was assessed by comparison with the available experimental results of two different types of composite slabs previously tested to the m-k requirements of Eurocode 4. Since these requirements are for four-point bending tests and to extend the validity of the numerical model for the usual design case of uniform loads, with a non-constant longitudinal shear force acting on the slabs, a new set of composite slab specimens were subjected to six-point bending tests. The results confirm the validity of the model and its simplicity respect to other available models since only two values of the interface τ-s law are necessary to describe the whole behaviour of the slab. Additionally, an interpolation method was applied to obtain the τ-s values in the steel-concrete interface for composite slabs with the same steel deck but different geometry and unknown shear-bond behaviour.

Design and modelling of pre-cast steel-concrete composites for resilient railway track slabs

Australian railway networks possess a large amount of aging timber components and need to replace them in excess of 280 thousands m3 per year. The relatively high turnover of timber sleepers (crossties in a plain track), bearers (skeleton ties in a turnout), and transoms (bridge cross beams) is responsible for producing greenhouse gas emissions 6 times greater than an equivalent reinforced concrete counterparts. This paper presents an innovative solution for the replacement of aging timber transoms installed on existing railway bridges along with the incorporation of a continuous walkway platform, which is proven to provide environmental, safety and financial benefits. Recent developments for alternative composite materials to replace timber components in railway infrastructure construction and maintenance demonstrate some compatibility issues with track stiffness as well as structural and geometrical track systems. Structural concrete are generally used for new railway bridges where the comparatively thicker and heavier fixed slab track systems can be accommodated. This study firstly demonstrates a novel and resilient alterative by incorporating steel-concrete composite slab theory and combines the capabilities of being precast and modulated, in order to reduce the depth, weight and required installation time relative to conventional concrete direct-fixation track slab systems. Clear benefits of the new steel-concrete composites are the maintainability and constructability, especially for existing railway bridges (or brown fields). Critical considerations in the design and finite element modelling for performance benchmarking of composite structures and their failure modes are highlighted in this paper, altogether with risks, compatibilities and compliances.

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.

Fatigue performance of steel–concrete composite slabs with a cementitious adhesive subjected to water leakage

A steel–concrete composite slab using a cementitious adhesive has been developed to simplify the design of shear connectors between concrete and a steel bottom plate. Fatigue is one of the critical issues for constructed bridge decks, so a moving-wheel fatigue test was performed using the composite slab in a previous study. The test showed the superior fatigue behavior of the proposed composite slab system, while the needs for follow-up research emerged because existing bridge deck slabs frequently suffer from water leakage. The study deals with testing thirteen composite slabs having the cementitious adhesive subjected to water leakage in static and cyclic loadings. Test results show that the fatigue life of the composite slabs in water leakage is significantly lower than that of the slab tested in a dry condition. To further understand the effect of water on reducing the efficacy of the adhesive, supplementary tests are conducted with an emphasis on water-absorption and shear capacity in a wet environment.

Robustness analysis of 3D Composite buildings with semi-rigid joints and floor slab

Analysis of composite building structures has been performed mostly on skeleton frames or on plane frame (2D) without the presence of composite slabs and semi-rigid joints. This is because detailed modelling of non-linear behavior of steel–concrete composite joints and the floor slab is rather tedious and involves other structural components including interaction between floor beams with slab and beam-to-column joints. This paper proposes simplified composite slab and composite joint models, which can be easily incorporated within a commercial software for the analysis of three-dimensional composite building frames with less computational time. The steel concrete composite slab is modelled by representing the profile metal deck by rows of rebars with equivalent areas and the profile concrete slab is converted into an equivalent uniform concrete section. The semi-rigid composite joints in the building framework are modelled using the Eurocode's component model represented by axial and rotation spring connectors. The proposed simplified models have been verified against the established test and numerical data available in the literature and found to be accurate enough for analysing 3-D composite frames with less computational time. The robustness of moment frames and simple braced frames was then investigated under a column loss scenario. The incorporation of semi-rigid joints and composite slabs in 3D frame analysis tends to produce more realistic estimate of large scale steel–concrete composite frames subjected to accidental loads.

Improvement of the behaviour of composite slabs: A new type of end anchorage

The application of composite steel-concrete slabs with profiled steel sheeting has increased, due to the various advantages in relation to reinforced concrete slabs such as, the reduced thickness, the reduced amount of lost formwork needed, as well as the speed of execution. The loss of longitudinal shear resistance is, generally, the governing design mode for simply supported spans of common lengths. For common distributed loadings, the composite behaviour is influenced by the partial shear connection between the concrete and the steel sheeting. The present research work is intended to contribute to improving the ultimate limit state behaviour of composite slabs using end anchorage. Eurocode 4, Part 1.1 (EN 1994-1-1) provides an analytical methodology for predicting the increase of longitudinal resistance, achieved by using shear studs welded through the steel sheeting as the end anchorage mechanism. The code does not supply an analytical methodology for other kinds of end anchorage so, additional tests or studies are needed to prove the effectiveness of these types of anchorage. The influence of end anchorage mechanisms provided by transverse rebars at the ends of simply supported composite slabs is analysed in this paper. Two experimental programmes were carried out, the first to determine the resistance provided by the new end anchorage mechanism and the second to analyse its influence on the behaviour of simply supported composite slabs.

Experimental and numerical study of end anchorage in composite slabs

Composite steel-concrete slabs are widely used in floor construction in steel-framed buildings where the connection between the steel beam and the concrete slab through shear connectors exploits the best combination of each component. The end anchorages in combination with other shear transfer mechanisms play an important role into the strength, stiffness and ductility of composite slabs. In this paper, a series of tests were carried out on both solid and profiled composite slabs to investigate the effect of end anchorage on the ultimate load carrying capacities and failure modes. The test programme consisted of eight composite slab specimens under restrained and unrestrained conditions. The load-deflection relationships and failure modes of all slabs are presented. The test results showed that end anchorage has a positive effect on the ultimate strength of both solid and composite slabs irrespective of the long term loading conditions. A three-dimensional finite element model is developed to simulate the behaviour of composite slabs with end anchorages. The model was validated against experimental results for its accuracy and a parametric study was conducted to investigate the influence of concrete strength, shear stud strength and profiled steel sheeting thickness in profiled composite slabs. The results showed that the effect of concrete strength and sheeting thickness on the load-deflection behaviour is significant. However, the shear bond stress-slip rather than the strength of the shear studs governs the contribution of the end anchorage to the shear bond capacity of composite slabs.

Experimental and numerical study of the bond–slip relationship for post-tensioned composite slabs

Post-tensioned composite steel–concrete slabs provide an attractive combination of the structural advantages of post-tensioned concrete slabs and profiled composite slabs in building floor systems. The bond between the concrete and the profiled steel sheets is usually assumed to have a significant effect on the strength, stiffness and ductility of these types of slabs. Push tests provide a less expensive and convenient method to investigate the complex interaction between the profiled steel sheets and concrete, in spite of some obvious differences of behaviour between small scale tests and composite slab bending tests. In this context, this paper presents results from a push test study incorporating post-tensioning at the steel bar to apply precompression to the concrete in order to determine the potential influence of prestress on the bond between the profiled steel sheets and concrete. The parameters investigated in this study were (a) level of prestress and (b) bond length. The results of this study indicated that the prestress has a detrimental effect on the bond between the profiled steel sheets and concrete in post-tensioned composite slabs. This is an important finding which needs to be considered in the ultimate strength determination of post-tensioned profiled composite slabs. This paper also presents a three dimensional nonlinear finite element model of post-tensioned push specimens. The results indicated that incorporating the effects of prestress produces satisfactory results for the overall bond stress–slip behaviour of post-tensioned push test specimens.

Effects of non-uniform shrinkage on the long-term behaviour of composite steel-concrete slabs

This paper presents the results of a series of tests aimed at investigating the development of shrinkage gradient considering slab samples of different concrete thicknesses and exposed to different drying conditions. For this purpose, two types of solid concrete specimens and two types of composite specimens were considered. Stramit Condeck HP® and PrimForm® profiles were used for the profiled sheeting of the composite samples. A total of twelve specimens were prepared and monitored for a period of four months. The experimental data was then used to further validate a previously proposed theoretical model capable of incorporating the effects of non-uniform shrinkage inside a composite slab. A simplified approach was also proposed to account for the occurrence of non-uniform shrinkage in routine design.

Non-uniform shrinkage in simply-supported composite steel-concrete slabs

This paper presents the results of four long-term experiments carried out to investigate the time-dependent behaviour of composite floor slabs with particular attention devoted to the development of non-uniform shrinkage through the slab thickness. This is produced by the presence of the steel deck which prevents moisture egress to occur from the underside of the slab. To observe the influence of different drying conditions on the development of shrinkage, the four 3.3 m long specimens consisted of two composite slabs cast on Stramit Condeck HP® steel deck and two reinforced concrete slabs, with the latter ones having both faces exposed for drying. During the long-term tests, the samples were maintained in a simply-supported configuration subjected to their own self-weight, creep and shrinkage for four months. Separate concrete samples were prepared and used to measure the development of shrinkage through the slab thickness over time for different drying conditions. A theoretical model was used to predict the time-dependent behaviour of the composite and reinforced concrete slabs. This approach was able to account for the occurrence of non-uniform shrinkage and comparisons between numerical results and experimental measurements showed good agreement. This work highlights the importance of considering the shrinkage gradient in predicting shrinkage deformations of composite slabs. Further comparisons with experimental results are required to properly validate the adequacy of the proposed approach for its use in routine design.

Experimental and Numerical Investigation of Steel-Concrete Composite Waffle Slab Behavior

AbstractThis paper proposes a new kind of composite waffle slab that consists of orthogonal steel girders and flat RC slab. The steel beams help decrease the cracking that occurs with concrete, and using prefabricated RC slabs reduces the framework and speeds up the construction. An experimental investigation of steel-concrete composite waffle slabs is conducted, and the specimens are proved to have excellent ductility and load-bearing capacity. Then a mixed finite-element (FE) model combining the beam elements and shell elements is proposed to predict the behavior of composite waffle slab. Based on the numerical model, a series of parameter analyses are conducted, and the influences of different parameters on the mechanical behavior of the composite waffle slab are intensively investigated. Simplified formulas for the ultimate capacity of the composite waffle slab are derived based on the test observations and numerical analysis. Reasonable recommendations are proposed to help engineers design the composi...

Experimental study on fatigue durability and punching shear load-carrying capacity of steel-concrete composite hollow-core slab

Experimental study on fatigue durability and punching shear load-carrying capacity of steel-concrete composite hollow-core slab

Experimental Studies on Corrugated Steel-Concrete Composite Slab

Experimental Studies on Corrugated Steel-Concrete Composite Slab