Behavior Of Composite Slabs Research Articles

An insight into eurocode 4 design rules for thermal behaviour of composite slabs

Closed-form calculation rules for thermal responses of composite slabs with profiled steel decking are provided in EC4, which are only applicable to a specified range of slab geometries available in the 1990s and are unchanged for two decades. This paper aims to gain an insight into the thermal behavior of composite slabs, and to investigate the applicability of EC4 calculation rules to a wider practical range nowadays (usually beyond the specified range). Parametric studies are conducted to study the influence of moisture content and slab geometry on the temperature distribution in composite slabs. The results show that the calculation methods in EC4 are not applicable to composite slabs with geometries beyond the specified range. It is found that the insulation-based fire resistance of composite slabs is governed by the maximum temperature rather than the average temperature. The EC4 calculations overestimate the fire resistance and a reduction factor of 15% is recommended. The moisture content has a significant effect on the temperature distribution in composite slabs, and improvement to EC4 is proposed by considering its the effect in a rate of 5 min per 1% increase of moisture content. Tabulated results are given to determine the temperature of reinforcement in the thin portion and temperature distribution in the composite slabs.

Long-term behavior of continuous composite slabs made with 100% fine and coarse recycled aggregate

A composite slab is an efficient modern structural member. Recycled fine and coarse aggregates are alternative green materials for the depleting natural sand and natural gravels in the composite slabs. In recent years, the nonuniform shrinkage occurring in single-side-exposed concrete has been discovered to significantly affect the long-term behaviors of composite slabs, which have been included in newly published codes. Applying recycled aggregate concrete (RAC) would further increase the effect of nonuniform shrinkage on the long-term behaviors of composite slabs. However, most studies, with RAC or not, have only focused on simply- supported composite slabs. For continuous composite slabs (CCSs), in addition to increasing deflections, a nonuniform shrinkage would induce a larger negative bending moment, which would further increase the crack width at the interior support region. Hitherto, no experiment has been conducted regarding the time-dependent crack width of CCSs and CCSs with RAC. Therefore, the aim of this study is to investigate the effects of nonuniform shrinkage and RAC on the deflections, strains, and cracks of CCSs. Hence, a 500-d experiment was conducted on three full-scale specimens. Finally, a finite element (FE) model was established and benchmarked against the test results of this study and those reported in the literature. The results indicated that (1) nonuniform shrinkage significantly increased the crack width at the negative bending moment region; (2) the use of RAC resulted in a more significant effect of the nonuniform, e.g. mid-span deflections, soffit strains, and crack widths increased by 40%, 64%, and 38%, respectively; and (3) the FE model can predict the long-term behaviors of CCSs well.

Longitudinal shear behaviour of composite slabs with profiled steel sheeting and ECC

This paper studies the longitudinal shear behaviour of composite slabs composed of profiled steel sheeting and engineered cementitious composite (ECC), i.e., referred to as “ECC composite slab” in the following. A total of eleven full-scale ECC composite slab specimens were designed and tested under four-point flexural loading. The main testing parameters included the shear span ratio, the thickness of the steel sheeting, the depth of the composite slab, and the arrangement of the shear studs. The influence of these parameters on the failure modes and the longitudinal shear resistance of the specimens were evaluated based on the test results. The behaviour of the ECC composite slab was compared with that of the composite slab with traditional concrete topping. The formulae for calculating the longitudinal shear resistance and the ultimate shear bond stress of ECC composite slabs were proposed according to the m-k method and the partial shear connection (PSC) method, and the predictions agreed well with the test results. Finally, an advanced finite element model (FEM) was established and validated against the test results, which further proved that adopting shear studs as end anchorage could significantly improve the longitudinal shear resistance of an ECC composite slab.

Vibration Behavior of Composite Slab with Precast Ribbed Panels due to Transient Impact

Excessive floor vibrations due to human activities such as heel-drop and jumping can induce annoyance to occupants and cause a serious serviceability problem. Both field tests and finite element analysis were conducted to study the vibration behavior of the composite slab with precast ribbed panels (CSPRP), a relatively new floor system compared with the cast-in-place reinforced concrete (RC) slab. In addition, both heel-drop and jumping impacts were employed to generate the acceleration response of the floor, from which two important vibration characteristics of natural frequencies and damping ratios are obtained. A comparison of the vibration behavior of CSPRPs with RC slabs indicates that the former exhibits more satisfactory perceptibility in terms of vibration. Appropriate coefficients (i.e. [Formula: see text] and [Formula: see text]) with the root-mean-square and peak accelerations subjected to heel-drop and jumping excitations are proposed for both CSPRPs and RC slabs. Lastly, an extensive parametric study considering different boundary conditions, floor types, and floor spans was carried out using the finite element method. It is recommended to use CSPRP under 3.3[Formula: see text]m span in order to keep the fundamental frequency above 3.0[Formula: see text]Hz.

Experimental study of the influence of friction at the supports on longitudinal shear resistance of composite slabs

Abstract The aim of this work is to evaluate the behavior and strength of composite slabs considering the influence of the friction at the sheeting-concrete interface in the region of the support. Results from tests conducted in the Structural Engineering Department of Federal University of Minas Gerais (UFMG) were used. A Steel Deck 60 system was considered, which consists of a trapezoidal profile with “V” shaped embossments. Deflections, end slips and strains of the steel decks were measured, allowing for the analysis of the behavior of the composite slab system and for the determination of its failure mode. The influence of friction of the region of support in the longitudinal shear resistance was evaluated through the partial shear connection method, which also allowed for establishing criteria and determination of analytical expressions for calculating the ultimate load. Comparative analyses reveal that the influence of the friction of the region of support in the shear-bond resistance is more significant in composite slabs with short shear spans. Design expressions which incorporate friction will also be presented. Their application have demonstrated the efficiency of the method for evaluating the longitudinal shear resistance.

Experimental investigation of longitudinal shear behavior for composite floor slab

This paper presents an experimental study on the behavior of composite floor slab comprised by a new steel sheet and concrete slab. The strength of composite slabs depends mainly on the strength of the connection between the steel sheet and concrete, which is denoted by longitudinal shear strength. The composite slabs have three main failures modes, failure by bending, vertical shear failure and longitudinal shear failure. These modes are based on the load versus deflection curves that are obtained in bending tests. The longitudinal shear failure is brittle due to the mechanical connection was not capable of transferring the shear force until the failure by bending occurs. The vertical shear failure is observed in slabs with short span, large heights and high concentrated loads subjected near the supports. In order to analyze the behavior of the composite slab with a new steel sheet, six bending tests were undertaken aiming to provide information on their longitudinal shear strength, and to assess the failure mechanisms of the proposed connections. Two groups of slabs were tested, one with 3000 mm in length and other with 1500 mm in length. The tested composite slabs showed satisfactory composite behavior and longitudinal shear resistance, as good as well, the analysis confirmed that the developed sheet is suitable for use in composite structures without damage to the global behavior.

Experimental studies on behaviour of composite slab with profiled steel sheeting

Investigation of the midspan deflection and end slip of the composite slabs is presented in this paper. The deflection of composite slabs depends on the shear stiffness of the connection between profiled sheet and concrete. Results of the experimental investigations of a composite slab with profiled sheeting (Trapezoidal type) and concrete are presented in this paper. Total four specimens were cast and tested to interpret the actual behaviour of the composite slab. Experiments were performed on composite slabs with a trapezoidal type of profiled sheeting of 0.8 mm and 1.2 mm thickness. Two specimens were cast with 0.8 mm profile steel sheet and two specimens with 1.2 mm sheet thickness. In the results of these investigations, load versus displacement and load versus slip behavior was observed. A comparison of experimental values of deflections and end slip revealed that agreement between these values was sufficiently good at all stages of the slab's behaviour.

Mechanical behavior of composite slab using perfobond rib shear connectors

Mechanical behavior of composite slab using perfobond rib shear connectors

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.

Long-term behaviour of simply supported composite slabs with recycled coarse aggregate

This paper describes an experimental programme and theoretical analysis of the long-term behaviour of composite slabs prepared with recycled aggregate concrete (RAC). The test programme consisted of four full-scale slab samples of thickness 120 mm and 180 mm, with two specimens subjected to sustained loads and two unloaded companion samples. All the specimens were subjected to shrinkage effects and measured in a simply supported static configuration over a period of 268 d. A non-linear numerical model was developed to account for the time-dependent behaviour of the composite slabs by including the effects of non-uniform shrinkage, creep and concrete cracking. The model was validated against the test results. A parametric study was then carried out to evaluate the influence of time effects on the long-term deflections of RAC composite slabs. A design approach to be used for routine design of RAC composite slabs was developed and validated through a comparison of calculated values and experimental measurements. Based on the experimental data collected as part of this study, it was found that both the numerical model and the proposed design approach estimated well the time-dependent deflections of RAC composite slabs by considering the influence of the non-uniform shrinkage profile.

Bending and Shear Experimental Tests and Numerical Analysis of Composite Slabs Made Up of Lightweight Concrete

The aim of this paper is to understand the structural behaviour of composite slabs. These composite slabs are made of steel and different kinds of concrete. The methodology used in this paper combines experimental studies with advanced techniques of numerical simulations. In this paper, four types of concrete were used in order to study their different structural strengths in composite slabs. The materials used were three lightweight concretes, a normal concrete, and a cold conformed steel deck which has embossments to increase the adherence between concrete and steel. Furthermore, two lengths of slabs were studied to compare structural behaviours between short and long slabs. m-k experimental tests were carried out to obtain the flexural behaviour of the composite slabs. These tests provide dimensionless coefficients to compare different sizes of slabs. Nonlinear numerical simulations were performed by means of the finite element method (FEM). Four different multilinear isotropic hardening laws were used to simulate the four concretes. Coulomb friction contact was used to model the coefficient of friction between steel and concrete. Finally, a chemical bond was included to consider sliding resistance in the contact surface between steel and concrete. Experimental and numerical results are in good agreement; therefore, numerical models can be used to improve and optimize lightweight composite slabs.

Flexural Capacity of Composite Beams (Steel & Concrete) – A Review

Many researchers have been working on the flexure capacity of composite steel and concrete beams and found out various studies on the same. This work gives the review of work done by various researchers who investigated the flexural capacity of composite steel and concrete beams and the behavior of composite slabs subjected to shear and bending. The review revealed the advantages of composite construction & the most effective utilization of steel and concrete. It was seen that a more prudent and efficient steel section is adequate in composite construction as compared with the traditional non-composite construction and deflect less as compared to steel beams; keeping the span and loading unchanged. They also have improved fire and corrosion resistance.

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 Study of In-Plane Shear Behavior of Fiber-Reinforced Concrete Composite Slabs

AbstractThis study investigates the in-plane shear behavior of composite slabs reinforced with different types of secondary reinforcements. Experimental results of 20 large-scale composite slabs constructed with two different deck profiles (reentrant and trapezoidal) are presented. The slabs were instrumented and tested in a cantilever diaphragm configuration under monotonic in-plane shear to assess and compare the effect of secondary reinforcement on their in-plane shear capacity. Five types of secondary reinforcements were considered: Conventional WWM of sizes A142 and A98, synthetic macrofibers at dosage rates of 3.0 and 5.3 kg/m3, and hooked-end steel fibers at a dosage rate of 15.0 kg/m3. Tests were carried out for both strong and weak orientation of decking. The load-deflection and load-strain responses were measured, and the cracking pattern and sequence were observed. The results showed that fibers notably improved the in-plane shear behavior (strength and ductility) of the composite slabs. Stee...

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.

Strength of composite slabs with end-anchorage studs

A finite-element model is proposed to simulate the load behaviour of composite slabs with studs as end anchorages. The model is verified against physical tests on 36 composite slabs with varying thickness of steel deck, diameter and height of the studs, concrete strength and length of shear span. The longitudinal shear strength contributed by the end anchorage is evaluated and compared with the design shear strength of individual studs proposed in different design codes. The contribution of studs as end anchorages to the shear-bond strength of composite slabs is found to be substantial and should be considered in design assessments. A tentative design method to evaluate the strength of composite slabs with end-anchorage studs is proposed.

Flexural Behavior of Composite Slab

Flexural Behavior of Composite Slab

An experimental study on the ultimate behaviour of simply-supported post-tensioned composite slabs

Post-tensioned composite steel-concrete slabs consist of thin-walled profiled steel sheeting, post-tensioned strands and concrete. This paper presents the preparation and results of two ultimate test series aimed at evaluating the contribution of the profiled sheeting on the load carrying capacity of this form of construction, and whether this is affected by time effects. For this purpose, six samples were prepared and tested to failure in a simply-supported static configuration by means of two transverse line loads applied near the mid-span. These consisted of two post-tensioned solid slab and four post-tensioned composite ones cast using Stramit Condeck HP® and Stramit PrimeForm® profiled sheeting. The flexural strengths observed for the composite specimens prepared with Condeck HP and PrimeForm profiles were in average 77% and 20% greater, respectively, than the moment capacity of the post-tensioned solid slab counterpart. These values did not appear to be affected by time effects for the material and geometric properties considered in this study. All samples exhibited a ductile response and all tests were terminated due to concrete crushing. A theoretical model was proposed to account for the partial shear connection behaviour of the composite slabs. The model was then applied to evaluate the influence of different geometric and material parameters on the moment capacity calculated for different post-tensioned composite slabs. It is expected that further comparisons with experimental results need to be carried out to properly validate its adequacy for use in routine design.

Numerical analysis of partially fire protected composite slabs

The paper presents a numerical investigation, done with the computer program SAFIR, in order to obtain simpler finite element models for representing the behaviour of the partially protected composite steel concrete slabs in fire situations, considering the membrane action. Appropriate understanding and modelling of the particular behaviour of composite slabs allows a safe approach, but also substantial savings on the thermal insulation that has to be applied on the underlying steel structure. The influence of some critical parameters on the behaviour and fire resistance of composite slabs such as the amount of reinforcing steel, the thickness of the slab and the edge conditions is also highlighted. The results of the numerical analyses are compared with the results of three full scale fire tests on composite slabs that have been performed in recent years.

Experimental study on shear bond behavior of composite slabs according to Eurocode 4

An experimental study was conducted to investigate the shear-bond behavior of composite slabs and to analyze Eurocode requirements on the longitudinal shear strength of composite slabs. The m–k and partial shear connection methods were analyzed. Two different types of profiled steel sheeting with up to three different thicknesses were considered. The experimental determination of these parameters must satisfy some requirements established in the Eurocode. These requirements penalize experimental results, so they can be very conservative in some cases. The present study explored the influence of such requirements on the estimated longitudinal shear carrying capacity and provided results that lead to a better understanding of the shear-bond behavior of composite slabs. This involved testing 30 composite slabs with different experimental requirements. The study assessed the influence of the previous cyclic load and the placement of crack inducers on the longitudinal shear strength. Moreover, bending tests of composite slabs with different steel sheet thicknesses were performed. Therefore, the study also analyzed the influence of steel sheet thickness on longitudinal shear strength estimated according to Eurocode 4 methods. Based on these results, the paper discusses the suitability of the experimental requirements applied to the profiled composite slabs tested.