Composite Floor Slabs Research Articles

Experimental Study of the Bending Properties and Deformation Analysis of Web-Reinforced Composite Sandwich Floor Slabs with Four Simply Supported Edges.

Web-reinforced composite sandwich panels exhibit good mechanical properties in one-way bending, but few studies have investigated their flexural behavior and deformation calculation methods under conditions of four simply supported edges. This paper studies the bending performance of and deformation calculation methods for two-way web-reinforced composite sandwich panels with different web spacing and heights. Polyurethane foam, two-way orthogonal glass-fiber woven cloth and unsaturated resin were used as raw materials in this study. Vacuum infusion molding was used to prepare an ordinary composite sandwich panel and 5 web-reinforced composite sandwich panels with different spacing and web heights. The panels were subjected to two-way panel bending tests with simple support for all four edges. The mechanical properties of these sandwich panels during the elastic stage were determined by applying uniformly distributed loads. The non-linear mechanical characteristics and failure modes were obtained under centrally concentrated loading. Finally, simulations of the sandwich panels, which used the mechanical model established herein, were used to deduce the formulae for the deflection deformation for this type of sandwich panel. The experimental results show that webs can significantly improve the limit bearing capacity and flexural rigidity of sandwich panels, with smaller web spacing producing a stronger effect. When the web spacing is 75 mm, the limit bearing capacity is 4.63 times that of an ordinary sandwich panel. The deduced deflection calculation formulae provide values that agree well with the measurements (maximum error <15%). The results that are obtained herein can provide a foundation for the structural design of this type of panel.

EXPERIMENTAL STUDY ON FLEXURAL BEHAVIOR OF STEEL-CONCRETE COMPOSITE BEAM COMPRISING PRECAST COMPOSITE SLABS

Four-point bending tests including twelve specimens were carried out to investigate the flexural rigidity, failure mode and ultimate capacity of the steel-concrete composite beam with a composite floor slab comprising 30 mm thick precast prestressed concrete panels and T-shaped concrete ribs (PPCRP). The test parameters included support length of PPCRP, thickness of the composite floor slab, longitudinal compressive reinforcement ratio, degree of the shear connection and the direction of T-shaped concrete rib. Strain distribution along the depth of mid-span section was obtained by strain gauges. Based on the moment-deflection curves of specimens, it was showed that flexural behavior of precast composite floor slab was similar to that of concrete floor slab cast in-situ during the elastic stage. Two failure phenomena were observed: i) Interface bond slip between the precast panel and the cast in-situ layer; ii) Diagonal shear crushing in one shear span. Compared with the floor slab cast in-situ, a slight decline in the ultimate flexural capacity was observed for the composite beam with composite floor slab. Analyses about the effects of all parameters on composite beams’ rigidity and ductility were presented.

Slim‐floor construction – design for ultimate limit state

AbstractThis paper presents the design method for slim‐floor construction that comprises a steel beam and a concrete or composite floor slab in which the beam is integrated within the depth of the slab. The slabs are either supported on a plate attached to the bottom flange or the bottom flange of the beam itself. The main design parameters and load transfer mechanisms are discussed. Plastic analysis has been adopted for the design of the bending capacity at the ultimate load condition and the design procedures described are in accordance with the principles given in Eurocode 4. Attention is paid to the type of shear connection between steel and concrete.

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.

Cyclic Load Tests of SFRM-Insulated Steel Gravity Frame Beam-Column Connection Assemblies

AbstractEarthquake-induced damage to structural components and spray-applied fire-resistive material (SFRM) in steel gravity frame beam-column connection regions can impact connection performance during an ensuing fire. Bolted connections are particularly susceptible to failure at elevated temperatures due to a rapid loss in bolt capacity with increasing temperature, which occurs at an accelerated rate compared to the thermal degradation of structural steel. In order to characterize structural and SFRM damage over a range of seismic drift demands, two large-scale SFRM insulated beam-column connection assemblies utilizing single-plate and unstiffened seated connection designs, with composite floor slabs, were tested under combined gravity and lateral loading. SFRM cracking, debonding, and spalling were observed during both tests, exposing critical connection elements. In addition, the single-plate connection assembly, which was developed in accordance with U.S. national guidelines but contained design feat...

Experimental Investigation on Flexure Performance of New Steeldeck-Concrete Thermal Insulation Composite Floor Slabs

A new Steel deck-concrete composite floor slabs was proposed that with the effect of het preservation and insulation, and the flexure performance of the slabs has been studied. Calculation method of flexural bearing capacity was put forward. Based on comparative and analysis experimental results, it has been verified that the applicability of new formula of flexural bearing capacity of the new slabs.

On-Site Experimental Testing to Study the Vibration of Composite Floors

As a general trend, in order to reduce material consumption or to reduce the mass of the structures, composite floor slabs solutions are used to achieve large spans floor slabs. This solutions led to floors sensitive to vibrations induced generally by human activities. As a verification of the design concepts of the composite floors, usually, it is recommended a further examination of the floor after completion by experimental tests. Although the experimental values of the dynamic response of the floor are uniquely determined, the processing can take two directions of evaluation. The first direction consist in determining the dynamic characteristics of the floor and their comparison with the design values. Another way that can be followed in the processing of the experimental results is to consider the human perception and comfort to the vibration on floors. The paper aims to present a case study on a composite floor, with steel beams and concrete slab, tested on-site. Both aspects of data processing are analyzed, in terms of the structural element, and in terms of the effect on human perception and comfort. Experimentally obtained values for the dynamic characteristics of the floor are compared with numerical values from finite element analysis, while the second type of characteristic values are compared with various human comfort threshold values found in international standards.

철골모멘트골조의 연쇄붕괴저항력에 합성바닥슬래브가 미치는 영향

In this paper, a kinematic modeling of the composite floor slabs under the column missing scenario is proposed that can be used for more accurate evaluation of progressive collapse resistance of steel moment frames. To this end, the behavior of double-span composite floor slabs is first investigated using the advanced nonlinear finite element analysis. The functional form of the deformed shape of the double-span floor slab is derived from the numerical analysis and used for analytically modeling the energy absorption contribution of composite floor slabs under the column missing scenario. It is shown that the analytical model proposed in this study can be used in conducting more accurate energy-based progressive collapse analysis of steel moment frames.

Composite Floor Systems under Column Loss: Collapse Resistance and Tie Force Requirements

This paper presents a computational assessment of the performance of steel gravity framing systems with single-plate shear connections and composite floor slabs under column loss scenarios. The computational assessment uses a reduced modeling approach, while comparisons with detailed model results are presented to establish confidence in the reduced models. The reduced modeling approach enables large multibay systems to be analyzed much more efficiently than the detailed modeling approaches used in previous studies. Both quasi-static and sudden column loss scenarios are considered, and an energy-based approximate procedure for analysis of sudden column loss is adopted after verification through comparisons with direct dynamic analyses, further enhancing the efficiency of the reduced modeling approach. Reduced models are used to investigate the influence of factors such as span length, slab continuity, and the mode of connection failure on the collapse resistance of gravity frame systems. The adequacy of current structural integrity requirements is also assessed, and based on the computational results a new relationship is proposed between the uniform load intensity and the tie forces required for collapse prevention.

Effects of Composite Floor Slab on Seismic Performance of Welded Steel Moment Connections

Traditionally, domestic steel design and construction practice has provided extra shear studs to moment frame beams even when they are designed as non-composite beams. In the 1994 Northridge earthquake, connection damage initiated from the beam bottom flange side was prevalent. The upward moving of the neutral axis due to the composite action between steel beam and floor deck was speculated to be one of the critical causes. In this study, full-scale seismic testing was conducted to investigate the side effects of the composite action in steel seismic moment frames. The specimen PN700-C, designed following the domestic connection and floor deck details, exhibited significant upward shift of the neutral axis under sagging (or positive) moment, thus producing high strain demand on the bottom flange, and showed a poor seismic performance because of brittle fracture of the beam bottom flange at 3% story drift. The specimen DB700-C, designed by using RBS connection and with the details of minimized floor composite action, exhibited superior seismic performance, without experiencing any fracture or concrete crushing, almost identical to the bare steel counterpart (specimen DB700-NC). The results of this study clearly indicate that the beams and connections in seismic steel moment frames should be constructed to minimize the composite action of a floor deck if possible.

Thermal capacity of composite floor slabs

ObjectiveThermal building simulation tools take account of the thermal capacity of the walls and floors by a one-dimensional characterization. The objective was to obtain thermal equivalent parameters for ribbed or composite slab elements that can be input into one-dimensional models. MethodTransient finite element calculations (FEM) were used to establish the heat transfer to and from composite floors using four deck profiles and for daily heating cycles in compartments with defined heat gains and operating conditions. ResultsThe performance of composite slabs was compared to a concrete flat slab for a typical office in the UK and Germany. It was shown that a deep ribbed slab generates a maximum heat flux of 30.5W/m2 for a 5°C temperature variation about the mean, and that the daily heat absorbed by a typical composite slab was 220Wh/m2 floor area. ConclusionsUsing the thermal capacity of the ribbed floor slabs, the comfort conditions defined in terms of the number of hours over 25°C are acceptable for many classes of offices. Practical implicationsThermally equivalent properties of ribbed slabs can be used in conventional software to predict the thermal performance.

Experiments on membrane action of composite floors with steel fibre reinforced concrete slab exposed to fire

The resistance of composite floor structures traditionally composes of the elemental resistance of the concrete slab and that of the composite beams. The fire resistance of a properly designed floor structure increases due to its membrane behaviour. Its evaluation is based on advanced as well as simple design procedures approved by tests, for partially protected floors reaching 60min and more. Composite structures are increasingly reinforced by steel fibres instead of steel bars. Due to an equal distribution of reinforcement steel fibre reinforced concrete (SFRC) achieves better deformation capacity compared to the traditional reinforced concrete even at elevated temperatures. Therefore, questions have been raised about its fire resistance and utilisation of membrane action of the floor.In the last two years, composite SFRC floor slabs at ambient and at elevated temperature have been tested at the Czech Technical University in Prague. At elevated temperatures, the floor was only partially fire protected. Intermediate beams and SFRC slab in steel sheeting remained unprotected. Concrete slabs were reinforced by steel fibres only without added steel bars. The main aim of the tests was to demonstrate the sufficient properties of the SFRC slab in fire. For the fire resistance of the floor slabs, it is important for the material to have sufficient ductility and adequate tensile and shear strength. These material properties of the SFRC allow for the slab to create a different load bearing mechanism, which increases its fire resistance. Hence, the SFRC slabs have been tested at ambient and at elevated temperature with a focus on ductility and tensile strength of the material.

The Influence of Tensile Membrane Action on Fire-exposed Composite Concrete Floor-steel Beams with Web-openings

On the basis of a series of the full-scale fire tests carried out on the composite frame at Cardington, a design method is now well established to calculate the performance of composite flooring systems subject to fire. The method models in a simplified fashion the influence of tensile membrane action in composite floor slabs which are formed as an array of composite beams using solid-web steel downstand beams which are largely unprotected. The development of membrane action depends on the conditions of vertical support maintained around the boundaries of the fire-affected slab panels by protected beams. Cellular beams can achieve the same strength as unperforated I-beams of the same depth, with significantly reduced steel mass, and the ability to accommodate service ducts within the beam depth, and therefore the use of composite cellular beams as floor members is becoming increasingly popular in construction. Due to the general lack of research on perforated sections, the guidance about their design for fire conditions remains rather primitive. Moreover, tensile membrane action in composite floor slabs with cellular steel downstand beams could exhibit very different behaviour in fire from that when solid-web sections are used. A parametric study has been carried out as an initial investigation into the fire performance of cellular beams within composite slab systems, including the effects of tensile membrane action in enhancing the load-carrying capacity. The effects of changes to the edge support conditions are also investigated. The results show the protected perimeter beams maintained their load-carrying capacity and were subject only to small vertical displacements, although web-post buckling was observed to occur on the protected secondary beam near to a support. This suggests that maintenance of vertical support is not sufficient for a slab panel with cellular beams. Web-post buckling or the Vierendeel mechanism may govern the mode of structural failure, indicating that the sizes of openings and their positioning necessitate careful design.

Study on Short-Term Rigidity of Precast Composite Slab with Steel Truss and Concrete

Composite slab by steel bar truss and concrete was a new style of floor slab. Because there were the small steel bar trusses in precast member, its short-term rigidity was higher than the normal composite floor slab. The structure was divide into four kinds, according to the relative location of the neutron-axis and the combined interface of slab; the relative value of the moment in first phase and the cracking moment of the precast slab. The different formulas to calculate short-term rigidity of precast member for four kinds were obtained. Through the models of composite slab by steel bar truss and concrete with different dimensions were established using finite element structural program, the formula feasibility was confirmed

Development of Thermal Resistance Elements for Thermal Analysis of Composite Structural Members in Fires

Building fires, which may cause failure of buildings, occur frequently in cities all over the world. Composite structural members, such as concrete filled steel tube columns and steel-decked composite floor slabs, are being increasingly used in buildings for their dual advantage of excellent load bearing capacity and fire resistance. Because the heat transfer across a steel-concrete interface is difficult to model using ordinary elements, most existing finite element analysis models ignore the effect of thermal contact resistance. In this paper, several two- and three-dimensional new thermal resistance elements (referred as TRE for brevity), which have been embed in the special purpose finite element software TFIELD coded by authors, are proposed. Two numerical examples are given. Numerical simulating results demonstrate that the proposed thermal resistance elements are extremely effective.

Ductility of composite floor slabs under idealised fire conditions

This paper is concerned with the ductility of composite floor slabs under extreme loading conditions. Although the consideration given to the assessment of ductility is of general relevance to various applications, it is of particular significance to conditions resembling those occurring during severe building fires. The main purpose of the study is to examine the failure of composite floor slabs which become lightly reinforced in a simulated fire situation owing to the early loss of the steel deck. An account of the main results from 15 large-scale tests on simply supported slab specimens is presented. A simplified expression for predicting the ductility of this type of member is proposed, after calibration and validation against the experimental results and more detailed analytical relationships. The experimental results and observations enable a direct assessment of the influence of a number of important parameters, such as the reinforcement type, properties and ratio on the ultimate response. The tests and proposed failure prediction relationships also provide a fundamental insight into the key factors that govern the ductility and failure behaviour of lightly reinforced slabs. With due consideration of the findings and verifications from other complementary experimental and analytical studies under various geometric and temperature conditions, this work suggests a fundamental basis for developing quantified and realistic failure criteria.

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.

Membrane Action of Composite Fibre Concrete Slab in Fire

The fire resistance of a properly designed floor structure increases by its membrane behaviour. The membrane fire resistance is evaluated by advanced as well as simple design procedures, approved by tests, and for partially protected floors reaching 60 mins and more. Composite constructions are more and more reinforced by steel fibres without added steel bars. Due to distributed mesh, steel fibre concrete can achieve good deformation capacity compared to traditional reinforced concrete even at elevated temperatures and questions have been raised about its fire resistance. The composite floor slabs with fibre concrete at ambient and at elevated temperature were tested at the Czech Technical University in Prague in the last two years. At elevated temperature, the floor was only partially fire protected. Intermediate beams and fibre-concrete slab in steel sheeting were without protection. Concrete slabs were reinforced by steel fibre only without added steel bars. The main aim of the tests was to demonstrate the suitable properties of the steel fibre concrete slab in fire. For the fire resistance of the floor slabs it is important that the material has sufficient ductility and adequate tensile and shear strength. These material properties of the fibre-concrete allow the slab to create a different load bearing mechanism, which increases the fire resistance of the floor slabs. The fibre-concrete was tested at ambient and at elevated temperature with a focus on ductility and tensile strength of the fibre-concrete.

Structural response of interlocking composite masonry slab

This study introduces a semi-fabricated composite floor slab system that consists of a precast inverted ribbed ferrocement panel interlocked in situ with a brick–rib layer to form a composite slab. The effectiveness of the interlocking mechanism of the composite slab was investigated under separate shear and flexural loadings. Ten composite slab specimens having different shear connectivity between the two layers were cast and tested under pure shear loading (push-off test). Six further slab specimens were cast and tested under two line loadings to explore the structural response of the composite slab system under flexural loading. The flexural tests focused on the effect of different brick layouts and orientation and thus different numbers of interlocking ribs in longitudinal and transverse directions on the overall structural response of the composite slab. The results of push-off tests indicate that the proposed interlocking system is as effective as using steel truss shear connectors in composite slabs. The flexural test results in terms of load–deflection, crack pattern, ductility and failure loads indicate that the response of the composite slab to flexural loading is satisfactory for use as a structural floor slab.

Experimental Research and Numerical Analysis on Fiber Reinforced Plasterboard-Reinforced Concrete Composite Floor Slabs

Fiber-reinforced plasterboard is patent product which was developed by Rapid Build Structure Ltd. of Australia. Fiber reinforced plasterboard can be used as baseboard , and after casting, it integrate with reinforced concrete to make up fiber reinforced plasterboard-reinforced concrete composite floor slabs. In this paper, numerical analysis method is accepted to analyze the process of bearing the loads of fiber reinforced plasterboard-reinforced concrete composite floor slabs. The calculated results, such as load- section strain curve and bearing capacity are compared with experimental data. Based on the results analysis, a mechanical analysis model is built, which provides some reference basis for computer simulation experiment of this type of structure.