Composite Floor System Research Articles

Structural Behaviour and Mechanical Characteristics of BlueDeck Profiled Steel Sheeting for Use in Composite Flooring Systems

The BlueDeck profiled steel sheeting system offers an innovative composite flooring solution, integrating high-strength steel sheets with reinforced concrete to form a unified structure. This study aimed to evaluate the development of full composite action, the ultimate bearing capacity, and the flexural stiffness of the system. A comprehensive experimental programme involving 18 four-point bending tests and 6 shear tests was conducted to quantify the mechanical interaction between the steel deck and concrete slab. This study specifically examined bending capacity and vertical deflection, comparing the results with predictions from AS/NZS 2327. It was found that the system consistently achieved full composite action, with composite specimens demonstrating higher flexural stiffness and load-bearing capacity as the concrete depth increased. For example, specimens with 200 mm slab depths exhibited a 60% improvement in ultimate capacity compared to those with 150 mm slabs, while those with 175 mm depths saw a 27% increase. Additionally, the BlueDeck system showed an 81% improvement in de-bonding resistance in thicker slabs. The experimental results exceeded the bending moment and deflection limits prescribed by AS/NZS 2327, confirming that the system is structurally sound for use in buildings. This study provides quantitative evidence supporting the system’s compliance with Australian standards, highlighting its potential for improving construction efficiency through reduced material use, while maintaining structural integrity under imposed loads.

Experimental study of composite cold-formed steel and timber flooring systems with innovative shear connectors

An experimental investigation into the structural response of cold-formed steel-timber composite flooring systems with innovative and irregularly spaced shear connectors is presented in this paper. Five composite beam tests and a series of supporting material and push-out tests were carried out. The obtained results showed that the innovative shear connectors enabled the generation of considerable composite action, resulting in up to about 45% increases in load-carrying capacity and 15% and 20% increases in the initial and mid-range stiffnesses respectively over the non-composite system. Methods for predicting the effective flexural stiffness and moment capacity of the examined cold-formed steel-timber composite beams are presented and validated against the derived physical test data. It is shown that accurate predictions for both the flexural stiffness and moment capacity can be obtained, with mean prediction-to-test ratios of 0.93 and 0.91 respectively.

Comparative life cycle assessment (LCA) of the composite prefabricated ultra-shallow slabs (PUSS) and hollow core slabs in the UK

Life cycle assessment studies of precast construction methods highlight their superiority over traditional cast-in-situ construction in reducing buildings’ environmental impacts. Among the extensively used precast structural elements, hollow core precast slabs have proven benefits with their practical implementation in flooring systems across various flooring spans and live loads. This paper presents a case study comparing the global warming potential and embodied energy impacts of a recently developed lightweight prefabricated composite flooring system (PUSS) with zinghollow core precast slabs in the UK. The analysis is based on 16 live load/flooring span scenarios, between 6 and 12m. The study examines the benefits and drawbacks of utilising different concrete types in PUSS flooring, namely normal weight concrete, lightweight aggregates concrete and geopolymer concrete. PUSS with GPC demonstrates potential savings of up to 50 % in GWP compared with hollow core slabs, while PUSS with LWC exhibits potential savings of up to 35 % in total EE compared with hollow core slabs.

Cyclic moment-rotation model for bolted double-angle connections with composite floor systems

This paper presents a simplified moment-rotation model for cyclic response of bolted double-angle beam-to-column connections in composite steel frames with concrete on metal decking floors. The proposed model employs mechanics-based equations to determine model parameters, along with empirical observations from previous studies and data from recent large-scale multi-bay frame experiments. Several design variables and construction details, such as orientation of the metal decking, concrete reinforcement layout, and deck splicing details around the connection, were considered in the proposed model. Comparisons between the connection model and experimental results showed reasonable agreement in moment-resisting capacity up to 8% interstory drift. Notably, the proposed model adequately simulated varying responses based on connection details not captured by existing moment-rotation models. Analyses of 2- and 4-story frames using the proposed model showed up to 1.3 times higher ductility and 47% lower initial rotational stiffness compared to those using the existing ASCE 41 connection models with strengths of 20% and 35% of the plastic moment capacity of the girder. These results indicate the potential overestimation of stiffness and moment-resisting capacity, and the underestimation of ductility when using existing moment-rotation models due to insufficient modeling parameters to represent actual behavior. Therefore, the proposed model demonstrates its applicability in incorporating various design variables and construction details of bolted double-angle connections with composite concrete on metal deck floors. This model can be used to account for the non-negligible strength and stiffness of bolted double-angle connections in steel gravity framing under seismic loads.

Mechanical Response of Steel Sheets with Perforations for Composite Floor Systems with Reinforced Concrete and the Application of Emitted Magnetic Signals as an Approximate Tool for Structural Monitoring.

Mechanical Response of Steel Sheets with Perforations for Composite Floor Systems with Reinforced Concrete and the Application of Emitted Magnetic Signals as an Approximate Tool for Structural Monitoring.

Essential Load-Bearing Characteristics of Steel–Concrete Composite Floor System in Fire Revealed by Structural Stressing State Theory

Essential Load-Bearing Characteristics of Steel–Concrete Composite Floor System in Fire Revealed by Structural Stressing State Theory

Numerical analysis of full-scale structural fire tests on composite floor systems

Recent experiments conducted at the NIST examined steel-concrete composite floor systems designed per U.S. practice under standard fire. The first experiment designed per prescriptive provisions for a 2-h fire rating with 60 mm2/m of reinforcement, developed a central breach integrity failure after approximately 1 h of exposure. The second and third experiments, designed with 230 mm2/m of reinforcement, with the third one omitting the fire protection on the central steel beam, showed no failure within 2 h. This paper describes a numerical investigation to gain further insights into the fire behavior of the composite systems tested in these experiments. Nonlinear finite element models were validated against the tests. Simulation of the first test shows concrete damage and rebar fracture in the hogging moment area corresponding with the cracks observed experimentally. Simulation of the third test captures the development of tensile membrane action, confirming the redistribution from the unprotected secondary steel member to the floor reinforcing steel. A sensitivity analysis allows identifying the minimum reinforcement steel for protected and unprotected central beams configurations. The results can support improvements of the fire requirements in the U.S. codes as well as application of performance-based structural fire design for composite structures.

Experimental investigation on flexural behaviour of prefabricated ultra-shallow steel concrete composite slabs

This paper presents the test results of four static full-size four-point bending tests to investigate the flexural behaviour of a recently developed prefabricated steel-concrete composite ultra-shallow flooring system (PUSS®). The flooring system comprises of T-ribbed concrete floors partially-embedded within and connected to side C-channel beams and horizontally-oriented shear connectors. This study investigates the effects of three parameters on the flexural behaviour of PUSS® and the performance of the shear connectors under bending. The parameters under study are the type of concrete, degree of shear connection and depth of the slab. Four 4 m span test specimens are constructed using two types of concrete, two with reinforced normal weight concrete (NWC) and the remaining two with reinforced lightweight aggregates concrete (LWC). Three of the test specimens employ the unique shear connection system composed of horizontally-oriented steel dowels with horizontally-oriented web-welded shear studs (dowels with WWSS) while the last one employs horizontal steel dowels only. The contribution of the above parameters on flexural behaviour and failure mechanisms are examined. The study concludes that replacing NWC with LWC of similar strength does not affect the flexural behaviour of PUSS® in terms of slab capacity, ductility and failure mechanism. However, LWC demonstrates lower initial stiffness and leads to the development of larger cracks as loads increases. Also, reducing the degree of shear connection lowers the moment capacity of the slabs and results in failure of some shear connectors during testing. PUSS® units exhibit ductile behaviour under bending conditions regardless of the degree of shear connection.

Flexural Performances of Novel Wet Joints with Sleeve Connections in Precast Composite Floor System

A new type of assembled integral multi-ribbed composite floor system with novel wet joint and steel sleeve connections, which exhibits satisfactory strength and stiffness, was proposed in the previous study. To further study the flexural performances of the joints, six groups of specimens, including two cast in situ concrete slabs and four composite slabs sized 4700 mm × 1200 mm × 300 mm and 2450 mm × 1200 mm × 300 mm, were investigated under four-point flexural tests. Four main influence factors were experimentally studied, i.e., casting methods, joint amounts, shear span lengths, and steel sleeve layout directions, on the failure modes, crack distributions, and deflection–load carrying capacity relationship. Test results indicated that the proposed composite slab system could provide the ultimate bearing capacity lower by 7% than that of the cast in situ concrete slabs, largely exceeding the code-predicted strength. No strain difference between the steel sleeve connections and steel rebars indicated good wet joint connection behavior. More hollow-core sections and long shear spans increased the potential of interfacial splitting cracks, leading to a shorter elastic stage and lower elastic stiffness. A finite element model was further parametrically conducted to explore the structural performances. Finite element results also indicate that the precast concrete slab had a more significant influence on the failure loads than the influences of concrete compressive strength and lap-splice steel rebar strength. These findings indicate that the proposed composite slab systems possess a satisfactory performance in the ultimate bearing capacity and deformability. Thus, such an assembled integral multi-ribbed composite floor system can be widely applied in construction.

Suitability of Foamed Concrete for the Composite Floor System in Mid-to-High-Rise Modular Buildings: Design, Structural, and Sustainability Perspectives

This study investigates the application of lightweight foamed concrete (FC) in modular building floor systems to address challenges in lifting and transportation within modular construction. Initially, a literature review identifies FC’s characteristics and optimum mix design, considering its sustainability and strength. The comprehensive review highlights that FC can be a lightweight alternative to replace traditional concrete in floor structures. Further, this study conducted the life cycle assessment and indicates that FC with coarse fly ash substitution is the optimum mix, which releases less greenhouse gas emission (i.e., 740.89 kg CO2-eq/1 m3) than other mixes. Subsequently, the study conducted design verification and parametric study of composite floor systems (i.e., cold-formed steel-FC, timber-FC, and steel deck-FC). The results show similar flexural and shear performance compared to normal-weight concrete despite its lower density (1600 kg/m3) compared to normal-weight concrete (2400 kg/m3). Further, the reduction of modulus of elasticity (43% of normal-weight concrete’s value) in FC increases deflection by 22–46% and 11–15% for steel-FC and timber-FC floor systems, respectively. Overall, the outcome shows that FC can be an efficient alternative for mid-to-high-rise modular building floor construction. Its lightweight nature can reduce the module’s weight, making modular construction more cost-effective.

Hardwood and softwood timber - natural stone composite connections

This paper describes fabrication and testing to ultimate of timber-stone composite (TSC) connections using unreinforced limestone slabs fastened to hardwood or softwood stubs by screws at 45° or 90° to the interface, bonded-in meshes or interface bonding. The stone’s tensile strength prevented crack-formation during drilling or grooving of holes to accommodate the screws and meshes. Connections failed by splitting of the stone along the connectors (meshes, 90° screws in hardwood), pullout of 45° screws from softwood (S45), shear-flexure yield fracture of 90° screws in softwood (S90), longitudinal shear failure of softwood adjacent to interface adhesive, and tensile yield fracture of 45° screws in hardwood (H45). In descending order the glued, H45 and mesh connections were the strongest while the glued, meshed and 45° screw connections exhibited the highest slip stiffnesses, with the S90/S45 connections showing the most ductility. Likely influences of randomness in the stone’s tensile strength and in observed bond variabilities from fabrication of the mesh connections are discussed. The TSC connections performed well against timber-concrete composite connections. Stiffness predictions incorporating screw axial and lateral contributions are excellent for H45 and S90, but need improvement for S45 and H90. Strength predictions work well for all screw connections. These TSC connections can significantly reduce consumption of the natural materials stone and timber in low-carbon composite floor systems.

Corrugated Structural Metal Decking System under Tensile Strength Test

Corrugated metal decking has been widely used in the construction industry for many years due to its benefits towards the sustainability, improve time performance of the projects and environmental aspects. This article includes the investigation of tensile strength and identify the failure behaviour of different corrugated surface profile of the metal decking that innovated for structural slab. Novelty of this research is the discovery of the tensile performance of a cold rolled corrugated metal decking profiles at various points of interest for a composite flooring system. Tensile strength specimen preparation complies with the ASTM E8 Standard. A total of 60 specimens with different thicknesses and different parts of metal deck have been tested by the universal testing machine (UTM). The findings on how Base Metal Thickness (BMT) affects the tensile strength and the unique roll formed of the corrugated metal decking system, with 0.75BMT & 1.00BMT, are discussed and analysed in this article. Results showed that the average tensile strength value for 0.75BMT and 1.00BMT from part A was 592.47MPa and 554.41MPa, respectively, and the metal decking is up to the designed strength and the unique roll forming embossment provides better bonding quality between concrete and steel to be used in the industry.

Parametric Finite Element Analyses of Demountable Shear Connection in Cold-Formed Steel–Concrete Composite Beams

It is known that steel–concrete composite systems are very efficient. However, such steel–concrete composite systems can be optimised using cold-formed steel elements and innovative shear connections. In other words, by considering demountability and reusability, the negative impact of the built environment on the whole ecosystem can ultimately be reduced. This paper, therefore, presents a numerical study of an innovative solution for a composite floor system consisting of built-up cold-formed sections and concrete slabs. Through parametric numerical analysis, parameters such as the diameter and quality of bolts, the concrete class, the type of concrete slab, and the steel quality of sections and bolts were varied. The numerical analysis results show that the system with a solid concrete slab had a higher shear resistance and ductility than the system with a concrete slab made with profiled sheeting and showed different failure modes. The presented results form the basis for push-out tests for the proposed shear connection types.

Optimal Design of a Novel Large-Span Cable-Supported Steel–Concrete Composite Floor System

This paper optimizes the design of a novel large-span cable-supported steel–concrete composite floor system in a simply supported single-span, single-strut configuration, aiming for cost-effective solutions and minimal steel consumption. The optimization considers various cross-sectional dimensions, adhering to building standards and engineering practices, and is based on a non-linear programming (NLP) algorithm. Parameters of live loads ranging from 2 to 10 kN/m2 and spans from 20 to 100 m are considered. The optimization results show that cable-supported composite floors with a single strut exhibit robust economic feasibility for spans of less than 80 m and live loads under 8 kN/m2. Compared to conventional composite floors with welded I-beams, the cable-supported system offers more cost-effective cross-sections and reduces steel consumption. The savings in economically equivalent steel consumption range from 20% to 60%. Discussion on the area ratio of cables to steel beam in the optimal cross-section reveals that the secondary load-bearing system (i.e., bending of the main beam with an effective span length of L/2) may require more steel in cases of ultra-large spans. Therefore, the economical efficiency of cable-supported composite beams with multiple struts and smaller effective span lengths warrants further exploration in future studies.

Vibration Properties and Serviceability Performance of a Modular Cross-Laminated Timber-Steel Composite Floor System

Vibration Properties and Serviceability Performance of a Modular Cross-Laminated Timber-Steel Composite Floor System

Flexural behavior of modular steel channel–concrete composite floor systems with bolted connections

This paper presents an innovative modular steel channel–concrete composite floor system designed for rapid assembly. This system, compared to traditional steel–concrete composite floors, connects adjacent modules solely through the use of high-strength bolts. This design eliminates the need for on-site wet construction, thereby yielding superior economic benefits. To investigate the proposed system’s mechanical behavior, bending tests were conducted on four composite floors with various support conditions, the numbers of bolts, and the degrees of shear connection. The load–displacement responses, torsional behavior of the channel beams, interfacial slip, and strain development of the composite floor systems were analyzed. The test results show that the simply supported composite floor, without bolted connections, undergoes flexural failure. In contrast, the semi-continuous composite floors, with bolted connections, display punching shear-flexural failure. The pre-tension forces applied to the bolts can effectively mitigate the torsional deformation of the channels and module separation, ensuring that the system maintains excellent structural integrity, sufficient load-bearing capacity, and adequate ductility. The semi-continuous composite floors, when fitted with high-strength bolts, demonstrate an increase in ultimate load-bearing capacity by 13–15%. However, there is a corresponding decrease in ductility by 18–23% when compared to the simply supported composite floor without bolts. The use of perforated steel plates as shear connectors offers efficient shear resistance between the steel channels and concrete slabs, facilitating full composite action of the system throughout the loading process. The paper concludes with the development of a model that calculates the flexural strength and punching shear strength of the composite floors based on the yield-line theory.

Flexural behavior of open-web composite slab with I-shaped steel bottom chord and vertical flat webs

Traditional composite floor truss systems with top and bottom chords and web trusses have encountered difficulties in system erection, installation, and the passage of utilities. In order to address these challenges, this study introduces a novel open-web composite floor system that only consists of a bottom chord and vertically placed flat web elements. These vertical web members are essentially short I-shaped steel elements and are connected to the I-shaped steel beam bottom chord and concrete slab through steel top plates and shear connectors, forming an innovative composite floor system. This paper presents the results of static loading tests conducted on two specimens with distinct web members, evaluating deformation, cracking characteristics, ultimate bearing capacity, failure mode, and stress and strain distributions. The findings indicate that the new composite floor system offers good flexural performance. Furthermore, finite element models of the composite floor system have been developed to analyze the influence of the web element’s geometry on the composite slab’s ultimate bearing capacity. This study also develops a theoretical calculation method for determining the internal force, elastic deflection, and ultimate bearing capacity of the composite floor system. The theoretical calculation results regarding the failure mode and ultimate load capacity align closely with the experimental values, and the deformation calculation formula can be used to estimate the deformation curve shape and elastic deflection of the floor system.

Experimental and Numerical Study on Flexural Behavior of a Full-Scale Assembled Integral Two-Way Multi-Ribbed Composite Floor System

An assembled floor system is a main step in the industrialization of construction in civil engineering, where the stiffness and anti-crack properties under designed loads and its self-weight are the main concerns. This paper presents a new type of assembled integral composite floor system, which is composed of precast ribbed bottom slab, lightweight infills, cast-in-situ upper slab and joints. Through the couplers for squeezing and splicing of longitudinal bars, shear keys and cast-in-situ joints between the precast panels and cast-in-situ upper part, the whole hollow floor system could not only exhibit satisfactory mechanical performance, but also lower the self-weight and shorten the construction time. To study its flexural behaviors, a full-scale specimen sized 9.2 m × 9.2 m was designed and tested under static area load. With the load increased to the designed loads of Chinese design code GB50010-2010, mechanical performance (i.e., crack distribution, deformation and stress distribution) were analyzed. To further study its load-carrying capacity and working mechanism, an effective finite element model was established in ABAQUS and compared with experimental and simulation results. It was found that the deflection of the floor under the normal service load and the crack width met the needs of normal use, and the finite element model could serve as a reliable method for the load-carrying capacity calculation.

Experimental and Design Parametric Study of a Novel Grouted Square Steel Tube Upper Chord–Concrete Composite Floor

A novel composite floor consisting of an upper chord of a grouted square steel tube truss and a lower chord of a reinforced concrete slab is proposed to address existing problems with precast composite floors, such as a complex construction process, high cost, significant resource consumption, and severe environmental pollution. Sixteen-point loading tests were carried out on five simply supported one-way slabs to simulate the stress state of the floor under a uniform load and to investigate the stiffness, cracking moment, load-carrying capacity, and failure mode of the composite floor system. The results showed that the composite floor system exhibited ductile failure, with cracks uniformly distributed at the bottom of the slab; additionally, the grouted steel tube did not experience uplift or out-of-plane buckling, and the truss welds did not fracture, indicating that the composite floor system still had further deformation capacity and load-carrying capacity with satisfactory stress conditions. After unloading, the residual deformation of the composite floor accounted for 28% to 36% of the maximum deflection, demonstrating good deformation recovery ability. The bottom slab thickness and truss height are key parameters that influence the new composite floor, and increasing the two parameters enhances the cracking load, deformation resistance, and flexural capacity of the composite floor, with a significant improvement achieved by increasing the truss height. The floor slab should have a minimum thickness of 60 mm, as required by China’s Code for Design of Concrete Structures, and the truss height-to-span ratio should be 1:30, which meets the deformation and load-carrying requirements of the floor and conforms to the design concept of green buildings.

Dynamic Properties of Timber–Concrete Composite Beams with Crossed Inclined Coach Screw Connections: Experimental and Theoretical Investigations

Due to the low density and stiffness of wood, traditional timber floor systems are prone to producing large vibration responses. By combining timber beams with concrete floors, timber–concrete composite (TCC) floor systems show stronger bearing capacity, higher bending stiffness, and better thermal and sound insulation behaviors when compared with traditional timber floor systems. In this study, the vibration performance of TCC beams with crossed inclined coach screw connectors was investigated using dynamic tests. The influence of the screw diameters and slab dimensions on the dynamic performance of the composite beams was evaluated. The test results demonstrated that TCC beams show good dynamic performance when used as a floor component and meet the preliminary requirements of floor vibration comfort for fundamental frequency. The fundamental frequency and damping ratio of TCC beams decreases with the increase in slab dimensions. The bending stiffness and natural frequency of TCC beams decrease smoothly when reducing the screw diameter from 16 to 12 mm. Additionally, two theoretical models were used to predict the natural frequencies of the TCC beams, and the predicted values show good consistency with the measured ones.