Profiled Steel Decking Research Articles

Long-term deformations in continuous composite concrete slabs

Relatively little research has been reported on the time-dependent in-service behaviour of continuous composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on continuous composite slabs subjected to both drying shrinkage and different levels of sustained load. The paper provides experimental evidence of the dominant role played by drying shrinkage in the long-term deflection and redistribution of internal actions in continuous composite concrete slabs. An analytical procedure for the determination of the time-dependent deflections in continuous composite slabs is described and the results of analyses are presented and compared with the experimental data.

High performance composite slabs with profiled steel deck and Engineered Cementitious Composite – Strength and shear bond characteristics

Composite slab/flooring system known as fast track construction with profiled steel deck and regular concrete topping is very popular. This paper presents the development and performance evaluation of a new high performance composite flooring system incorporating emerging green cost-effective Engineered Cementitious Composites (ECCs). The high strain capacity while maintaining low crack widths makes fiber reinforced an ideal durable material for the composite floor construction. The proposed ECC based composite floors can resolve the problems associated with regular concrete based composite floors. Experimental investigations as per current Standard Specifications accompanied by Code based theoretical investigations were conducted to evaluate the structural performance of such flooring system in the construction and service stages. Thirty full-scale composite slabs were fabricated and tested under simply supported four-point loading conditions. The variables in the tests included: two types of concrete (a green cost-effective ECC and a commercial self-consolidating concrete ‘SCC’), two types of profiled steel sheet/deck, five different shear span and presence/absence of stud shear connectors. The structural performance of ECC based composite slabs was compared with their SCC counterparts based on load-displacement response, shear load resistance, failure modes, strain development in concrete/steel, load-slip behaviour, ductility, energy absorbing capacity and steel-concrete shear bond resistance. ECC composite slabs have shown superior performance compared with their SCC counterparts in terms of strength, ductility, energy absorbing capacity and shear bond resistance.

Modified creep and shrinkage prediction model B3 for serviceability limit state analysis of composite slabs

Relatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. This paper presents the results of long-term laboratory tests on composite slabs subjected to both drying shrinkage and sustained loads. Based on laboratory measurements, a design model for the shrinkage strain profile through the thickness of a slab is proposed. The design model is based on some modifications to an existing creep and shrinkage prediction model B3. In addition, an analytical model is developed to calculate the time-dependent deflection of composite slabs taking into account the time-dependent effects of creep and shrinkage. The calculated deflections are shown to be in good agreement with the experimental measurements.

Available rotation capacity of composite beams with high-strength materials under sagging moment

Using high-strength (HS) materials in steel–concrete composite beams is an efficient approach to reduce the self-weight and to improve the sustainability benefits of such members. Due to a lack of precise knowledge of the ductility of composite beams beyond their first yield as a result of the non-linear response of their constituent materials, a comprehensive investigation is reported herein to quantify the available rotation capacity of composite beams using HS materials when subjected to sagging bending. An advanced three-dimensional finite element model is utilised to calculate the end rotation of single-point-loaded simply-supported composite beams. The model has demonstrated to be adequate and reliable in terms of predicting the flexural strength and load–deflection response by comparisons with numerous experimental results reported elsewhere. As many as 1380 beams with various strengths of steel and concrete as well as a wide range of the degree of shear connection and geometries are modelled, and both solid slabs and composite slabs using profiled steel decking are incorporated. Analyses of this body of data indicate that the depth of the neutral axis is the most essential parameter for determining the available sagging rotation capacity, of which an increased value leads to a lower rotation capacity. The yield strength of the steel also has noticeable effects with higher values resulting in poorer rotation performance. The available rotation capacity is also sensitive to the span-to-depth ratio of the beams. In addition, the effects of varying cross-sectional geometries, different patterns of shear connector distributions as well as of geometric imperfections and residual stresses are clarified, which are shown to be slight and can therefore be ignored. Finally, a non-linear empirical equation is developed to predict the available rotation capacity of composite beams using HS materials, which covers the range of numerical data with satisfactory consistency. The outcomes provide an important basis for evaluating the ductility of composite beams by comparing with the required rotation capacity.

Composite Concrete Slabs with Profiled Steel Decking: Comparison Between Experimental and Simulation Study

The research work is to study the behavior of the composite concrete slabs with CRIL DECKSPAN type profiled steel decking by experimental and simulation study. The slab is created by composite interaction between concrete and steel deck with rolled embossments to improve their shear-bond characteristics. However, it fails under longitudinal shear-bond due to the complex phenomenon of shear behavior. Therefore, an experimental full-size tests has been carried out to investigate the shear-bond strength under flexural test in accordance with Eurocode 4: Part 1.1. Eighteen specimens are split into six sets of three specimens each in which all sets are tested for different shear span lengths under static and cyclic loading on simply supported slabs. The full-size finite element (FE) modeling and analysis of the composite slabs is presented, in which the shear-bond interaction between the concreteand steel deck is simulated by the use of interface contact elements. The FE analysis is verified and validated by comparing the experimental results. Comparisons of the experimental and simulation results indicate that the FE analysis agrees well with the test results, and is capable of predicting the behavior and the load carrying capacity of composite slabs.

Sustainable and Deconstructable Semi-Rigid Flush End Plate Composite Joints

Composite construction is a popular and effective method of construction, exploiting the strengths of both reinforced concrete and structural steel in building construction in a complementary fashion. Within paradigms related to minimisation of emissions and maximisation of product recycling, these composite systems are problematic on a number of fronts. Firstly, common and traditional composite systems utilise ordinary Portland cement, which is known to be a very large contributor to atmospheric CO2 emissions. Secondly, for typical construction practices for steel-concrete composite systems, casting of the concrete onto profiled steel decking and conventional reinforcement placing are undertaken on-site, which is time consuming and labour intensive, and which can increase the cost of construction. Thirdly, composite action between the steel beam and the concrete slab is usually achieved by using headed shear studs. The headed shear studs connect these two elements permanently, which leads to much waste at the end of the service life of the building when it is demolished. This paper models a sustainable semi-rigid beam-to-column composite blind bolted connection with deconstructable bolted shear connectors using ABAQUS finite element (FE) software. In this “green” system, precast geopolymer concrete (GPC) slabs are attached compositely to the steel beam via pretensioned bolted shear connectors and the composite beam is connected to GPC-filled square columns using blind bolts. Non-linear material properties and non-linear geometric effects are considered in the simulation of a connection in hogging bending. Based on the FE modelling, using pretensioned bolts as shear connectors with GPC can improve the behaviour of semi-rigid flush end plate composite joints in terms of ductility and load capacity. Moreover, the behaviour of the bolted shear connectors should be considered in composite joint design as being very different to headed stud connectors.

Longitudinal shear stress and bond–slip relationships in composite concrete slabs

Composite one-way concrete slabs with profiled steel decking as permanent formwork are commonly used in the construction industry. The steel decking supports the wet concrete of a cast-in-situ reinforced or post-tensioned concrete slab and, after the concrete sets, acts as external reinforcement. In this type of slab, longitudinal shear failure between the concrete and the steel decking is the most common type of failure at the ultimate load stage. Design codes require the experimental evaluation of the longitudinal shear capacity of each type of steel decking using full scale tests.This paper presents the results of the short term testing up to failure of four types of profiled decking that are widely used in Australia. Full-scale, simply-supported slab specimens were tested in four-point bending with shear spans of either span/4 or span/6. The bond–slip relationship of each slab was determined during the testing and the values of maximum longitudinal shear stress calculated using different methods are described and compared. A finite element model is proposed and verified by experimental data using interface element to model the bond properties between steel decking and concrete slab and investigate the ultimate strength of composite slabs.

Longitudinal shear resistance of composite slabs containing crumb rubber in concrete toppings

This paper investigates the behaviour and longitudinal shear capacity of metal deck composite slabs with the inclusion of crumb rubber in the concrete toppings.The ability of the slabs to act compositely is governed by the shear interaction between the concrete topping and the profiled steel deck. Results here show that crumb rubber concrete (CRC) improve the overall shear bond capacity between the steel deck and topping following an experimental study on full scale loading tests in accordance with Eurocode 4.The results confirm that composite slabs incorporating crumb rubber had no effect on the longitudinal shear resistance with similar failure loads and behaviours to plain concrete. It also demonstrates a practical use for recycled tyres in the form of crumb rubber which are an environmental problem.

Calculation of Time-Dependent Deflection of Composite Concrete Slabs: Simplified Design Approach

AbstractRelatively little research has been reported on the time-dependent in-service behavior of composite concrete slabs with profiled steel decking as permanent formwork, and little guidance is available for calculating long-term deflections. The drying-shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. Based on an existing analytical model developed by the authors to calculate the time-dependent deflection of composite slabs, a simplified procedure, suitable for use in structural design, is proposed for calculating the time-dependent deflection of composite concrete slabs with steel decking as permanent formwork that takes into account the time-dependent effects of creep and shrinkage. The method is illustrated by three examples and the results are compared with the experimental data.

Time-dependent deflection of composite concrete slabs: A simplified design approach

Relatively little research has been reported on the time-dependent in-service behaviour of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. Based on an existing analytical model developed by the authors to calculate the time-dependent deflection of composite slabs, a simplified procedure, suitable for use in structural design, is proposed for calculating the time-dependent deflection of composite concrete slabs that takes into account the time-dependent effects of creep and shrinkage. The method is illustrated by three examples and the results are compared with experimental data.

Time-Dependent Deflection of Composite Concrete Slabs: A Simplified Design Approach

Relatively little research has been reported on the time-dependent in-service behaviour of composite concrete slabs with profiled steel decking as permanent formwork and little guidance is available for calculating long-term deflections. The drying shrinkage profile through the thickness of a composite slab is greatly affected by the impermeable steel deck at the slab soffit, and this has only recently been quantified. Based on an existing analytical model developed by the authors to calculate the time-dependent deflection of composite slabs, a simplified procedure, suitable for use in structural design, is proposed for calculating the time-dependent deflection of composite concrete slabs that takes into account the time-dependent effects of creep and shrinkage. The method is illustrated by three examples and the results are compared with experimental data.

Effects of shrinkage on the long-term stresses and deformations of composite concrete slabs

Composite one-way concrete floor slabs with profiled steel decking used as permanent formwork are commonly used in the construction of floors in buildings. The steel decking supports the wet concrete of a cast in situ slab and, after the concrete sets, acts as external reinforcement. Relatively little research has been undertaken on the time-dependent in-service behaviour of such slabs and little guidance is available to structural engineers for predicting the long-term deflection. The drying shrinkage profile through the thickness of a slab is known to be greatly affected by the impermeable steel deck at the slab soffit, but this has not been quantified to date. This paper presents the results of laboratory measurements of the non-uniform distribution of shrinkage through the thickness of composite slabs, and the resulting effects on the long-term deflection of such slabs are considered. An analytical procedure for the determination of time-dependent stresses and deformations in composite floor slabs is described, and the results of analyses are presented for several common decking profiles using the measured shrinkage profiles.

Design of composite slabs with profiled steel decking: a comparison between experimental and analytical studies

This paper presents the structural behavior of composite concrete slabs with CRIL DECKSPANTM (Colour Roof India Limited (CRIL), Mumbai, INDIA) type profiled steel decking by experimental and analytical studies. The slab is created by composite interaction between the concrete and steel deck with embossments to improve their shear bond characteristics. However, it fails under longitudinal shear bond due to the complicated phenomenon of shear behavior. Therefore, an experimental full-size tests has been carried out to investigate the shear bond strength under bending test in accordance to Eurocode 4 - Part 1.1. Eighteen specimens are split into six sets of three specimens each in which all sets are tested for different shear span lengths under static and cyclic loadings on simply supported slabs. The longitudinal shear bond strength between the concrete and steel deck is evaluated analytically using m-k and partial shear connection (PSC) methods and compared the values. The experimental results is verified and compared with the results of both m-k and PSC methods. Comparison of experimental and analytical results of the load-carrying capacity of composite slabs revealed that agreements between these values are sufficiently good. As a result, m-k method proved to be more conservative than PSC method.

Shear bond mechanism of composite slabs — A universal FE approach

The strength of concrete slabs composited with cold-formed profiled steel decks is normally governed by the longitudinal shear bond failure at the steel concrete interface. The design methods for the longitudinal shear bond strength adopted in the current construction practice such as the m-k method and partial interaction method all based on the full-size tests, which are expensive and time consuming, however are also semi-empirical. A universal FE approach of composite slabs is presented, in which the shear bond interaction between the steel deck and the concrete is treated as a contact problem considering adhesion and friction. Both geometrical and material nonlinearities are all considered in the FE model. The preliminary FE analysis is verified in simulation of the pull-out tests as far as the cohesion and the frictional bond of the contact interface are considered. The fine FE analysis using the contact model is further carried out in study of the composite slabs in flexural bending. The FE analysis based on the nonlinear contact concept is verified and validated by comparing the test results for both the pull out and bending tests of the composite slabs. Comparisons of the experimental and the FE analytical results indicate that the FE analysis based on the interface contact model, agree well with the test results, and is capable of predicting the performance and the load carrying capacity of composite slabs.

Nonlinear behaviour of unprotected composite slim floor steel beams exposed to different fire conditions

An efficient nonlinear 3D finite element model has been developed to investigate the structural performance of composite slim floor steel beams with deep profiled steel decking under fire conditions. The composite steel beams were unprotected simply supported with different cross-sectional dimensions, structural steel sections, load ratios during fire and were subjected to different fire scenarios. The nonlinear material properties of steel, composite slim concrete floor and reinforcement bars were incorporated in the model at ambient and elevated temperatures. The interface between the structural steel section and composite slim concrete floor was also considered, allowing the bond behaviour to be modelled and the different components to retain its profile during the deformation of the composite beam. Furthermore the thermal properties of the interface were included in the finite element analysis. The finite element model has been validated against published fire tests on unprotected composite slim floor steel beams. The time–temperature relationships, deformed shapes at failure, time–vertical displacement relationships, failure modes and fire resistances of the composite steel beams were evaluated by the finite element model. Comparisons between predicted behaviour and that recorded in fire tests have shown that the finite element model can accurately predict the behaviour of the composite steel beams under fire conditions. Furthermore, the variables that influence the fire resistance and behaviour of the unprotected composite slim floor steel beams, comprising different load ratios during fire, cross-section geometries, beam length and fire scenarios, were investigated in parametric studies. It is shown that the failure of the composite beams under fire conditions occurred for the standard fire curve, but did not occur for the natural fires. The use of high strength structural steel considerably limited the vertical displacements after fire exposure. It is also shown that presence of additional top reinforcement mesh is necessary for composite beams exposed to short hot natural fires. The fire resistances of the composite beams obtained from the finite element analyses were compared with the design values obtained from the Eurocode 4 for composite beams at elevated temperatures. It is shown that the EC4 predictions are generally conservative for the design of composite slim floor steel beams heated using different fire scenarios.

Experimental and numerical studies on concrete encased embossments of steel strips under shear action for composite slabs with profiled steel decking

The subject of the ongoing research work is to analyze the composite action of the structural elements of composite slabs with profiled steel decking by experimental and numerical studies. The mechanical and frictional interlocks result in a complex behaviour and failure under horizontal shear action. This is why the design characteristics can be determined only by standardized experiments. The aim of the current research is to develop a computational method which can predict the behaviour of embossed mechanical bond under shear actions, in order to derive the design characteristics of composite slabs with profiled steel decking. In the first phase of the research a novel experimental analysis is completed on an individual concrete encased embossment of steel strip under shear action. The experimental behaviour modes and failure mechanisms are determined. In parallel with the tests a finite element model is developed to follow the ultimate behaviour of this type of embossment, assuming that the phenomenon is governed by the failure of the steel part. The model is verified and applied to analyse the effect of embossment's parameters on the behaviour. In the extended investigation different friction coefficients, plate thicknesses, heights and the size effects are studied. On the basis of the results the tendencies of the ultimate behaviour and resistance by the studied embossment's characteristics are concluded.

STUDY ON ULTIMATE STRENGTH OF COMPOSITE BEAM WITH ENDS RESTRAINED AGAINST ROTATION IN FIRE

The paper is intended to summarize findings from fire resistance tests on composite beams with ends restrained against rotation. The specimens were comprised of H-shaped steel beam and overlying composite slab with profiled steel decks, with studs at the interface. A total of four models were tested. The test parameters included the level of load. Based on the test results, a new formulation is proposed to calculate with a good accuracy, the flexural strength under positive moment on the basis of the plastic theory taking account of the heat-induced degradation of steel / concrete materials and shear capacity of studs in the positive moment area, and the local buckling strength under negative moment on the basis of the models taking account of the post-peak strength behaviors which were obtained from stub-column tests.

Non-linear curling of wide single-flange steel panels

An original analytical model to study the non-linear flange curling in wide single-flange panels is presented in this paper. Flange curling phenomenon is the tendency of the wide thin flanges (in compression or tension) to move towards the neutral axis, when thin-walled members are subjected to bending. Despite the simplicity of the formula developed in earlier works of Winter to account for the flange curling effects, which is used in current steel codes, recent work has showed that this expression is rather restrictive and does not apply for all cases. The analytical expressions reported here are rather general since they (i) consider the restraining effect provided by the web, (ii) account for the shift of the neutral axis due to curling, (iii) incorporate the decrement of the second moment of area due to curling, and (iv) are fully analytical, thus avoiding iterative techniques. The analytical model is applied to study the curling behaviour of profiled steel decks and cassette-wall panels and is validated by means of comparisons with experimental results available in the literature. Since the EC3 rules state that the tensioned wide flange in liner trays should be reduced if the curling displacement is higher than 5% of the web height, approximate expressions to evaluate the reduced width of the wide thin flange under curling are proposed.

Push-out tests and a new approach for the design of secondary composite beam shear connections

Most of the design approaches currently used around the world take into account the weakening effect of trapezoidal types of steel decking in the vicinity of a shear connection by applying a reduction factor to the nominal strength that the same connection would have in a solid concrete slab. Numerous push-out test results on shear connections incorporating this type of decking are presented. These demonstrate that not every shear connection incorporating profiled steel decking which is within the limits of the associated standards, can be classified as sufficiently ductile. A new and more reliable design approach is proposed which also allows for the inclusion of special reinforcing devices to overcome these brittle behaviours. The key element of this design approach is to classify the anticipated connection behaviour, with respect to its deformation capacity, into either ductile or brittle, hence ensuring satisfactory shear connection behaviour where these types of trapezoidal steel decking are used.

EXPERIMENTAL STUDY ON ULTIMATE FLEXURAL STRENGTH OF COMPOSITE BEAM IN FIRE

The paper is intended to summarize findings from fire resistance tests on simply supported beams conducted as part of a study on the fire resistance of steel-concrete composite beams. The specimens were comprised of H-shaped steel beam and overlying composite slab with profiled steel decks, with studs at the interface. The composite beams were designed to be partial composite. A total of six models were tested. The test parameters included the level of load, cross section of steel beam and presence of fire protection. Based on the test results, a new formulation is proposed to calculate with a good accuracy the flexural strength of composite beam on the basis of the plastic theory taking account of the heat-induced degradation of steel / concrete materials and shear capacity of studs.