Slim Floor Beams Research Articles

Composite Delta Beam for Slim Floor Construction

Abstract: The structural behaviour of the composite Flush Beam for slim floor as a whole has been investigated. The deformation behaviour of the structural members Steel beams with trapezoidal cross-sections and specially punched webs were developed as composite beams in slim floors. The estimation of the flexural stiffness and bending capacity of composite slim beams is rather complicated, because the influence of many factors should be taken into account. These factors include variable section dimensions, Profile of the beam, stiffness of the beam and interaction between steel and concrete. In this paper, analytical investigations have been conducted to investigate the deflection behaviour of Flush beam specimens under monotonic loading. A design procedure is developed for composite slim floor Flush beams based on cross-sectional analysis and the flexural properties of the slim floor beams are evaluated. From the analytical investigation it was found that the deflection of delta beam is 48% less than the conventional I-beam More over the stiffness of the Delta beam is 49.8% higher than the I-beam

Structural capacity of a composite slim-floor beam with hollow steel tube shear connectors

A slim-floor composite beam’s structural performance relies on the composite action provided by shear connectors. However, the information on the performance of composite slim-floor beam with HSTs connectors in flexural in term of moment capacity, shear interaction and ductility still needs to be clarified. Thus, six specimens of the composite beams with square and rectangular HSTs with two different beam sections, I and inverted T, were tested. The main failure was found to be concrete crushing in the area of the connectors. HST connectors prevented the concrete slab from uplifting, particularly in the specimens without a top flange. Subsequently, this increased moment capacity to 230% and 152% for inverted T and I-beam sections, respectively. Furthermore, ductility behavior was also improved and met EC4 requirements. The degree of shear interaction was increased from 0.4 up to 0.9 compared to the beam without HST. The predicted results from the suggested procedure to estimate moment capacity agreed well with the experimental results, with a maximum difference of 7% in the I-section specimen. In contrast, the predicted value for the inverted T specimen overestimates about 26%. Overall, the beam with the HST shear connector significantly improved the flexural performance of the composite slim floor beam.

Innovation of Shear Connectors in Slim Floor Beam Construction

Composite slim floor systems are increasingly applied in the construction industry. Therefore, several experimental and numerical studies have been conducted to investigate the composite flooring systems and examine the various details that may affect the production of composite floors. This review paper summarises some important developments of composite slim floor beams, such as the type of steel beam cross section and shear connectors used, presenting essential results and important notes from various studies. The fundamental structural elements and the contribution of conducted studies towards improving the shear capacity of composite beams in enhancing the general structural behaviour were also described. Finally, the paper concludes with the potential of a deeper investigation of some issues that accompany the application of certain types of shear connects or steel shapes used to improve the composite slim floor system so that the improvement construction industry may make the most out of using composite construction techniques.

Numerical analysis of composite slim-floor beams

Abstract In this research work existing laboratory tests of slim floor beams with solid monolithic concrete slab were modeled and analyzed using GID and Atena software. After validating the advanced finite element model with the test results of the international literature, structural parameters were analyzed with the aim to study their influence on the load bearing and deformation capacity of the beams. The parameters were related to the geometric of the beam: size of web openings and top concrete cover. With these results conclusion can be noticed that focusing on the optimal arrangement of the geometrical parameters of the composite beam could lead to better structural behavior with more economical solutions.

Numerical model validation of non-composite slim floor beam subjected to fire

Abstract Compared to traditional composite steel-concrete beams, where the concrete slab is supported by the top flange of a steel profile, in slim floor systems, the beam is integrated into the height of the concrete slab. These configurations are popular due to their cost-effectiveness and fire performance. However, fire design requires advanced calculation models, as Eurocodes do not provide a simplified method for the analysis of these types of beams when exposed to fire. The validation of the numerical models is an important issue for researchers, designers, software developers, and authorities. The European Standard for the fire design of composite steel and concrete structures, EN 1994-1-2, states that advanced calculation models must be validated against experimental test results. The paper presents the validation of a numerical model, for the thermal and mechanical analysis of slim floor beams, using SAFIR software. SAFIR is a special purpose computer program, based on the Finite Element Method, developed for the analysis of structures under elevated temperature conditions. The model is validated against an existing experimental fire test, available in the literature. The temperatures on the cross-section and the vertical beam displacements obtained numerically are reproducing very well the experimental results.

Shear forces transfer in steel-concrete slim floor with circular web opening and PCHCS

An experimental study was developed to investigate the mechanisms responsible for the transfer of shear forces at the steel-concrete interface in slim floor beams with circular web openings and precast hollow core slab (PCHCS). For this purpose, four specimens were made and subjected to push-out test. The presence of the steel bar through the opening, the concrete compressive strength and the diameter of the steel bar were studied. It was observed that the presence of the steel bar contributed significantly to both the resistance of the connection and for the reduction of the relative slip values of steel-concrete. While the specimen without steel bar presented a post-peak behavior with a drop of resistant capacity, in the specimens with steel bar the load-slip relationship was quite ductile. The variation in steel bar diameter and concrete strength influenced both load-slip relationship and resistant capacity. It was observed that regardless of the presence of steel bar, until the concrete dowel rupture, the load-slip behavior of the specimens with and without steel bar was almost identical. The experimental results were compared to analytical models proposed by other researchers. However, none of the analytical models found in the literature were able to satisfactorily represent the resistant capacity of the specimens with and without steel bar. A good estimate of the theoretical results was obtained using the friction-shear theory for concrete corbels.

Analytical Method for the Bending Resistance of Slim Floor Beams with Asymmetric Double-T Steel Section under ISO Fire

The slim floor beams, characterized by the steel profile embedded in the concrete slab, may be found in different configurations, based on the shape of the steel profile cross-section, which can vary from a rectangular to double-T section. While the most common shape used nowadays is the double-T cross-section, the Eurocodes do not provide a simplified method for the fire resistance assessment. The literature offers a simplified method for computation of bending resistance under elevated temperature, based on existing research on thermal models, and was validated for a particular type of slim floor beams (SFB). The current study extends the scope of application of this method, for different types of slim floor beam, which include an asymmetric double-T steel cross-section. The objective was reached through a numerical procedure, by analyzing 162 configurations subjected to four different fire requirements (R30, R60, R90, R120), resulting in a total of 648 analyses, performed with a validated numerical model in SAFIR software. The results in terms of bending resistance showed that the simplified method represents a strong tool for the fire design of slim floor beams.

Finite Element Modelling for Structural Performance of Slim Floors in Fire and Influence of Protection Materials

Slim floor systems are very common nowadays and various types are currently being used for the construction of high-rise buildings and car parks. Concrete in slim floor beams encases the steel beam section which helps to improve their fire resistance. Despite their higher fire resistance, several fire protection materials like intumescent coatings are often used to achieve a higher fire resistance where desired. The thermal properties and behaviour of various intumescent coating materials were previously studied through experimental investigations. This paper presents finite element analyses to simulate the response of unprotected and protected slim floor beams in fire using different simulation tools. For this purpose, fire tests conducted on unprotected slim floor beams and intumescent coating materials are modelled using research and commercial software. Results from the analyses are compared and verified with the available test data. These validated models are later combined to study the behaviour of protected slim floor beams in fire. Results from the study show that the research and the commercial software replicate the behaviour of slim floor beams and protection materials with good accuracy. Due to the presence of the intumescent coating, the protected slim floor beams displayed a better fire resistance as the temperature of the steel part remained below 400 °C even after 60-min of standard heating. The protected slim floor beams continued to support the external loads even after 120 min of heating.

Shallow composite floor beams – Proposal of a simplified analytical method for standard fire rating

AbstractShallow composite floor beams are a widely accepted solution for office, residential and other types of buildings. In most of their applications a standard fire resistance between R30 to R120 is required. Several fire tests were carried out in different laboratories over the last decades with various structural configurations, showing that this structural solution exhibits an integrated fire resistance without additional fire protection. In the frame of various programs, extensive research has been done on the fire behavior, completed by numerical simulations. Several scientists have proposed analytical methods to assess the resistance. Nevertheless, the Eurocode does not contain a method for assessing the standard fire resistance of composite shallow floor beams. This paper presents a simplified analytical method to determine the sagging moment resistance of Slim Floor Beams (SFB – being composed by a rolled section (or equivalent) with a wider plate welded below the bottom flange) under standard fire exposure. First, an FE model has been developed and validated on experimental tests. Afterwards, a parametric study covering various geometrical configurations and material choices has been performed. An analytical model for determining the sagging moment resistance is proposed and validated by comparison with results obtained by numerical simulation.

Experimental and numerical investigations on slim floor beams exposed to fire

Slim floor systems possess favourable thermal and thermo-mechanical behaviour in comparison with the traditional steel-concrete composite beams. Despite a recent surge in their usage in the construction sector, there is limited research on their performance at elevated temperatures. Due to limited investigations, there is a lack of fire design guidance for slim floor beams in major structural design codes. This study addresses the response of slim floor systems at elevated temperatures through experimental and analytical investigations. The experimental work consists of fire tests to study the thermo-mechanical response of SFBs in standard fire conditions. In addition to their thermo-mechanical response in fire, the efficiency of the rebars as an aid to enhance their fire resistance being an alternative to fire protection materials is also investigated. The test results show that the fire resistance of slim floor beams is significantly higher than the traditional steel-concrete composite beams due to the thermal gradient resulting from the concrete encasement. Further, the presence of longitudinal steel rebars enhances the fire resistance of SFBs significantly as they add to the flexural resistance of SFBs. During the tests, additional fire resistance of 79 min was achieved by the aid of steel rebars, a useful alternative to the fire protection materials which have been found to be toxic to the environment. Keeping in view the useful contribution of the steel rebars, a sensitive study was conducted using the finite element modelling to analyse the influence of their size and positioning on the fire resistance of the slim floor beams. Finite element modelling was later used to conduct a parametric study to analyse the influence of the degree of utilization on the response of slim floor beams exposed to standard fire. Degree of utilization represents the ratio between the applied load during a fire limit state and the capacity of the structural member at the ambient temperatures. The results from the parametric study were used to develop a simple design methodology by relating the degree of utilization and the average critical temperatures. Due to lack of fire design guidance in Eurocode 4, engineers usually use the design guidance proposed in Eurocode 3 which produces conservative results if applied to perform the fire design of slim floor beams as they have been developed for steel and traditional composite beams. The proposed methodology during this study is similar to that available in the Eurocodes for steel and composite beams but is developed specifically for the fire design of slim floor beams.

Ultimate flexural strength analysis of composite slim floor beam

This paper presents a new type of composite slim floor beam, determined by combining the results of an experimental study and theoretical analysis of the ultimate flexural strength of slim floor beams. The shear connectors play a significant role in the mechanical properties of this type of composite slim floor beam, because the precast concrete slab is laid on the bottom flange of the steel section and because the upper portion of the steel beam is encased in the cast-in-place concrete slab. To investigate the ultimate flexural strength, three specimens, which included headed studs, transverse steel bar shear connectors and no shear connectors, were tested. Additionally, a detailed numerical analysis was performed to verify the experimental results, which indicated that a higher-strength steel beam and thicker concrete slab can effectively enhance the stiffness and flexural capacity of the composite slim floor beam. Based on plastic mechanics and limit analysis theory, a calculation method was derived to estimate the ultimate flexural strength of a composite slim floor beam, and a comparison between the calculation and experimental results shows that the theoretical results exhibit good agreement with the experimental results, and the proposed analysis method can be used in future studies to gain a better understanding of the ultimate flexural strength of composite slim floor beams.

Experimental and numerical investigation of the flexural behavior of shallow floor composite beams

This article summarizes a research campaign on the flexural behavior of a certain type of slim floor beam, generally known as Deltabeam. Seven (7) full-scale composite specimens with various cross-sections were tested under three-point sagging bending up to large displacements to test the robustness of the system. Experimental load–displacement curves, slip values and damage patterns are reported and compared with those obtained from non-linear FE analyses using the finite element analysis code ABAQUS. The tests showed that the ductility and robustness of beams, which are important properties for the design of flexural members, depend not only on the classification of the steel plated parts under compression, but also on the ability of the concrete section outside the steel beam to sustain large strains without stress reduction. The importance of appropriate detailing, and especially confinement of the concrete, and its influence on the performance of Shallow Floor-beams under large displacements is revealed by the results.

A review on fire resistance of steel-concrete composite slim-floor beams

The use of steel-concrete composites (SCCs) is growing rapidly in the construction industry because of their improved constructability, decreased labor cost, improved bond to reinforcing steel, improved structural integrity and accelerated project schedules compared to conventional composites. Fire is a constant danger to these structural composites. Therefore, the effect of fire on the behavior of SCCs must be evaluated and included in design provisions. Slim-floor beams (SFBs) are cost-effective systems which permit a major decrease in the thickness of industrial and commercial buildings floors. The present study reviews the recent advancements and history of SCCs together with recent studies investigating the fire performance of SFBs. First, the evolution of SCC systems is briefly discussed. Then, the fire resistance and specific thermal definitions of the main structural members are presented. Finally, analytical and numerical methods for predicting fire resistance, as well as the relevant experimental results are presented. The main focus of this study is on analyzing the performance of SFBs as a flooring system under fire. It is found that further investigation is required to improve Eurocode 4 provisions for enabling the rapidly growing construction industry to benefit from the advantages provided by composite construction methods with safety considerations. Numerous studies have so far been conducted in terms of enhancing the design quality of these systems, among which some will be discussed in this study.

Numerical investigation on slim floors: comparative analysis of ASB and CoSFB typologies

abstract: Innovative composite structures have been intensively studied towards meeting the demands of civil construction. An example of such structures is slim floor, comprised of concrete or composite slabs positioned at the height of steel beams, reducing the total height of the floor. In Brazil, studies on this system are still in early stages, and due to the lack of both experience and national normative codes, it is hardly used in civil construction. Given the possible combinations between concrete slabs and steel beams, the system exhibits different typologies. This article reports a numerical investigation on two typologies of slim floor, namely Asymmetric Slimflor Beam (ASB), composed of an asymmetric I beam, and Composite Slim-Floor Beam (CoSFB), comprised of an asymmetric beam with small openings at the top of its web. Nonlinear numerical models of ASB and CoSFB typologies were developed by Finite Element-based software ABAQUS®. The models were calibrated with the use of experimental studies from the literature, and showed high accuracy and good results. After calibration, the materials properties and geometric dimensions of the models, such as height and thickness, were standardized for a comparison of the typologies. The comparative analysis showed the particular characteristics of CoSFB promoted higher stiffness and flexural capacity compared to ASB, and a parametric analysis evaluated the influence of steel and concrete parameters on the flexural behavior of the typologies. The parametric study revealed the steel parameters exerted a more substantial influence on the slim floors behavior than the concrete ones.

Internally fire protected composite steel-concrete slim-floor beam

The slim-floor beam is a composite concrete-steel beam fully integrated into the floor depth that was developed at the beginning of the 1990s. This composite beam presents a very good behaviour during the fire event because most of the steel parts of the section remain protected by the concrete encasement. Indeed, in a fire event, only the bottom surface of the lower steel plate results exposed to the heat source. The use of intumescent coating or other fireproof materials is the most common way to insulate the steel beam from fire but requires an accurate application and also appropriate maintenance during its whole life cycle to ensure proper fire protection. Thus, related to this last idea, the objective of this work is to present a new slim-floor configuration which increases the insulation of the beam from fire by using a design strategy that avoids the needed for maintenance. This new beam configuration has been called “Internally Fire Protected Slim-Floor Beam” (IFP-SFB) and implies a thermal break included within the beam cross-section. This paper presents the results of a series of thermal tests applied to this innovative slim-floor type proposed by the authors and its comparison against the most commonly used slim-floor configurations. Finally, the benefits of the proposed IFP-SFB configuration are presented, resulting in up to 30–60 min of additional fire resistance time. The IFP-SFB configuration is at present right-protected and under evaluation by the Spanish Office of Patents and Trademarks with reference number P201930438.

Study on the structural behavior of flush beam for slim concrete floor

The structural behavior of the composite flush beam for slim floor as a whole has been investigated. The deformation behavior of the structural members steel beams with trapezoidal cross sections and specially punched webs were developed as composite beams in slim floors. The estimation of the flexural stiffness and bending capacity of composite slim beams is rather complicated, because the influence of many factors should be taken into account. These factors include variable section dimensions, profile of the beam, stiffness of the beam and interaction between steel and concrete. In this paper, analytical investigations have been conducted to investigate the deflection behavior of flush beam specimens under monotonic loading. A design procedure is developed for composite slim floor flush beams based on cross-sectional analysis, and the flexural properties of the slim floor beams are evaluated. From elastic linear analytical investigation, it was found that the deflection of delta beam is 48% less than the conventional I-beam; moreover, the stiffness of the delta beam is 49.8% higher than the I-beam.

Research on the Efficiency of Composite Beam Application in Multi-Storey Buildings

Over the past decade, several types of composite slim floor constructions have been used in multi-storey buildings in Lithuania. In order to study the efficiency of composite beam application in steel-framed multi-storey buildings, Thorbeam (A1), Deltabeam (A2), slim floor beam (A3) and asymmetric slim floor beam (A4) were chosen and evaluated according to nine assessment criteria (beam cost (K1), initial preparation on site (K2), installation time (K3), complexity of installation technology (K4), labour costs (K5), fire resistance (K6), load bearing capacity (K7), beam versatility (K8), and availability of beams (K9)). First, the significance of the rating criteria was selected and the order of the ranking criteria was obtained (K1˃K7˃K3˃K6˃K4˃K5˃K2˃K8˃K9) by means of a survey questionnaire. Second, the beams were ranked according to the points given by the questionnaire respondents as follows: 160 points were given to A2, 144 points to A1, 129 points to A4, and 111 points to A3. Deltabeam is considered to be the most rational alternative of the four beams compared. Calculations done using the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) analysis method revealed that composite beam A2 was the best slim floor structure alternative for an eight-storey high-rise commercial residential building frame, A1 ranked second, A4 ranked third, and A3 ranked fourth. In addition, the four composite beams were compared to a reinforced concrete beam (A5) according to three assessment criteria (beam cost including installation (C1), beam self-weight (C2) and fire resistance (C3)). Deltabeam was found to be efficient for use as a slim floor structure in a multi-story building due to having the lowest cost, including installation, and self-weight, and the highest fire resistance compared to other composite beams studied. Although Deltabeams are 1.4 times more expensive than reinforced concrete beams, including installation costs, they save about 2.5% of the building’s height compared to reinforced concrete beams.

Recent developments and fire design provisions for CFST columns and slim-floor beams

This paper summarizes the latest technical and scientific progresses on steel-concrete composite structures exposed to fire, presenting the recent research carried out on this subject and the progress of the design codes. In particular, this review focuses on concrete-filled steel tubular columns and slim-floor beams, topics where the authors have carried out extensive research during the last years. The more recent experimental and numerical studies performed by the authors as well as those available in the literature are presented, along with applications where these composite elements have been used in practice. The use of advanced materials, such as high strength steel and concrete, stainless steel, lightweight concrete or geopolymer concrete is considered for the enhancement of the fire behaviour of concrete-filled steel tubular columns and slim-floor beams. Finally, the currently available design methods for the calculation of isolated members at elevated temperatures are reviewed and the recent progress of the code provisions for the fire design of these composite elements is presented.

Innovative solutions for enhancing the fire resistance of slim-floor beams: Thermal experiments

Slim-floor beams have attracted the attention of designers in the last decades, owing to their ability for supporting intermediate loads without increasing the floor thickness. However, the behaviour of this type of beams at elevated temperatures has not been well understood yet. This paper presents the results of an experimental campaign carried out at the testing facilities of the Universitat Politècnica de València, Spain, where a series of slim-floor configurations were exposed to elevated temperatures into an electrical furnace. These tests had the novelty of considering different slim-floor beam typologies, as well as alternative ways for thermal protection, such as using intumescent coating, stainless steel or lightweight concrete into different cross-section parts. The test results were used to validate a finite element thermal model which allows for a detailed analysis of the cross-section thermal behaviour and the assessment of different ways to improve the slim-floor beam fire performance. The temperature results were subsequently imported into a computer code developed by the authors where a non-linear procedure was applied to obtain the plastic bending capacity of the cross-section at elevated temperatures. These final results reveal the different thermal performance of the analysed configurations and are used as a basis for providing design recommendations for future slim-floor developments.

A detailed investigation on thermal behaviour of slim floor beams with web openings at elevated temperatures

Purpose In recent times, the use of steel sections with web openings has become common as slim floor beams because they offer a reduction in weight of the steelwork, accommodate services within the floor depth and provide the composite action. The composite action in these beams is achieved either through the concrete dowels or through concrete plugs. Though these web openings offer several benefits in slim floor beams, they induce the material discontinuity in the steel web, which may affect their shear capacity and/or thermal behaviour. The purpose of this study is to investigate the thermal behaviour of slim floor beams with web openings in fire. Design/methodology/approach This research presents findings from experimental and analytical investigations conducted to study the thermal behaviour of slim floor beams with web openings in fire. For this purpose, an experimental investigation was conducted, which shows that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. The behaviour of the tested slim floor beam is validated using finite element modelling. The validated finite element model is then used to conduct a sensitivity study to analyse the influence of different opening spacings, sizes and shapes on the thermal performance of slim floor beams in fire. Findings Test results show that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. Temperatures on the web below the openings are found to be higher as compared to those recorded on the adjacent solid steel web. It is also observed that temperatures on the steel web above the openings are lesser than those on the adjacent solid steel web. Parametric studies conducted using the verified analytical modelling methods show that different opening spacings, sizes and shapes have a variable impact on the thermal behaviour of slim floor beams in fire. Closely spaced and larger opening sizes were found to have a more severe influence on their thermal behaviour in fire as compared to widely spaced and smaller openings. It was also found that the behaviour of these beams is influenced by the shape of the openings with rectangular openings resulting in more severe thermal distributions as compared to circular openings. Originality/value The findings from this research study are highly valuable as they contribute to the existing knowledge database. There is a lack of experimental and analytical investigation on performance of slim floor beams with web openings at elevated temperatures. The results and conclusions from this study will help in developing innovative designs for slim floor beams and will help in reducing the fire related risk associated with structures comprising of slim floor beams with web openings.