Composite Slabs Research Articles

Deflection prediction of assembly integral steel-concrete floor voided with steel mesh boxes

Steel-concrete assembled hollow core slabs have witnessed widespread adoption in recent years owing to their inherent advantages of reduced self-weight, enhanced rigidity, and superior integrity. Nonetheless, to achieve extended spans and expedite on-site construction, further optimization of the connections and fillers in these assembled slabs is imperative, along with fortifying the overall structural performance. Therefore, this study introduces a novel variant of assembly integral steel-concrete composite floor, incorporating voids filled with steel mesh boxes, which utilizes four prefabricated slabs featuring hidden transverse and longitudinal girders and a steel frame system. Concurrently, a large-scale experiment was conducted to explore its mechanical and deformation recovery performance. The detections indicate that this innovative structure exhibits excellent integrity, as the four prefabricated components transform from individual one-way slabs into a continuous floor, facilitating the efficient transmission of forces in multiple directions. A finite element model was established to provide ideas for the research of scholars in allied domains and a fundamental framework for the subsequent parametric analysis of the structure. Building upon the analog cross-beam method, the deflection of the novel structure is calculated. The resulting discrepancy between the calculated and experimental results is merely 1.87%, attesting to the practical applicability of this method. These findings provide a solid foundation, both experimentally and theoretically, for the future design and engineering application of composite slabs, fostering the advancement of sustainable construction practices.

Pseudo-static tests on full-scale hybrid precast utility tunnel composed of double-skin sidewalls and cast-in-place bottom slab

This study investigated the seismic behavior of hybrid precast utility tunnel composed of double-skin sidewalls, cast-in-place (CIP) bottom slab and composite top slab base on pseudo-static tests. Two full-scale utility tunnels, including one precast specimen and one corresponding CIP specimen, were constructed and critical parameters related to failure mode, hysteretic response, load-carrying capacity, deformation performance, and stiffness degradation were investigated. Results demonstrated that both specimens exhibited flexural failure as their failure patterns. Plastic hinges initially appeared at the haunch sections of the sidewalls for both specimens, followed by their formation at the end of the top slab. Both specimens exhibited a stable and plump hysteretic response. The energy dissipation capacity of precast specimen was comparable to that of CIP specimen at each displacement level, as was the stiffness degradation. Additionally, the precast specimen and CIP specimen showed comparable load-carrying capacity, which was 305.90 kN and 315.10 kN respectively. The displacement ductility of precast specimen was approximately equivalent to the CIP specimen, which was 2.70 and 2.63 with a difference of less than 3%. These findings provide validation for designing and analyzing the hybrid precast utility tunnel using identical principles and models as applied in CIP structures. Furthermore, an evaluation based on the criteria presented in NEHRP-2003 indicated that the precast specimen exhibited satisfactory seismic performance.

Flexural properties of reinforced concrete slabs using highly ductile concrete (HDC) permanent formwork system

To optimize the construction process, this study proposes a highly ductile concrete (HDC) permanent formwork system, which consists of a steel truss and an HDC shee. It fully utilizes the advantages of the mechanical properties of HDC and factory prefabrication. The study first investigates the mechanical properties of a prefabricated HDC permanent formwork system under construction loads. The results show that the specimens maintain an elastic response with on-site support at a distance of 3.2 m, satisfying the requirements of the construction stage more comprehensively. Subsequently, a reference reinforced concrete (RC) slab and two identical composite slabs using the HDC permanent formwork system are tested as simply supported slabs under four-point bending. The results indicate that the bridging effect of polyethylene (PE) fibers allows the crack widths of the composite slabs to be controlled. Multi-crack behavior is observed in the HDC sheet. In addition, the HDC sheet improves the flexural behavior of the RC slabs in terms of flexural capacity, stiffness, and energy absorption owning to the strain-hardening behavior of the HDC composites. Finally, a calculation method based on the plane-section assumption is used to predict the flexural capacity, stiffness, and corresponding deflection of the composite RC slabs.

Study on post-fire resistance of ceramsite foamed concrete sandwich composite slabs

The ceramsite foamed concrete sandwich composite slab has the characteristics of light weight and good heat insulation performance. At present, there are few research on the fire resistance of ceramsite foamed concrete sandwich composite slab at home and abroad, and the damage mechanism of ceramsite foamed concrete sandwich composite slab under fire is not clear. To fill this gap, constant load-temperature rise fire test and static loading test on five slab specimens are conducted by varying the parameters such as sandwich layer thickness, reinforcement pattern, shear span ratio and construction method. Based on the test, the results are studied, including the temperature distribution and deformation characteristics under fire, load–displacement curves, crack pattern and damage mode, residual bearing capacity of the slab after fire. The results show that ceramsite foamed concrete sandwich composite slab has good thermal insulation performance, the overall working performance, flexural bearing capacity and deformation ability of the slab is mainly affected by the slip at the composite surface. The integrity of the slab and the residual bearing capacity and ductility after fire could be significantly improved by the configuration of truss rebar. It is suggested to decrease the time difference of concrete placement at the composite surface or set shear keys and truss rebar to improve the cooperative working ability between the surface layer and the sandwich layer. Moreover, Finite Element analysis is carried out by ABAQUS software and the results show good agreement with experiment results. A new compositeness degree analysis (CDA) method for calculating the residual bearing capacity of ceramsite foamed concrete sandwich composite slab after fire considering different compositeness degree is proposed, which could be used for the practical engineering design.

Experimental and theoretical research on flexural performance of truss reinforced concrete two-way composite slab with prefabricated baseplate

This paper presents experimental and theoretical research on a novel truss reinforced composite concrete two-way slab using full-scale testing. In contrast to conventional composite slabs, the precast concrete layer with a thickness greater than 60 mm is replaced by a high toughness prefabricated inorganic baseplate with a thickness of 12 mm. The baseplate options include glass fiber and magnesium cement board, as well as fiber cement board. Four full-scale two-way slabs were subjected to eight points simulated uniform vertical loads, comprising one conventional truss reinforced concrete two-way slab (RCS) and three truss reinforced concrete composite two-way slabs with prefabricated baseplates (RCSB). The test results indicate that the failure mode of the truss reinforced concrete composite two-way slab with baseplate is similar to that of a common truss reinforced concrete two-way slab. However, a rectangular yielding region appears at the central part, instead of a single yielding line. The cracking load and ultimate load are increased due to the effect of prefabricated baseplate. Moreover, the beneficial effect of glass fiber and magnesium cement board is superior to that of fiber cement board. Finally, the calculation methods for determining the cracking load and ultimate bearing capacity of truss reinforced concrete composite two-way slabs with baseplates were improved, and the calculated results are in good agreement with experimental data.

Research on Ultra-High Performance Concrete (UHPC) overlay composite steel deck to repair Thang Long bridge deck

Thang Long bridge, after many years of operation with increasing traffic volume, leads to the steel face plate of the bridge not ensuring the conditions of stiffness and deflection within the allowable limit. After scientific conferences and experimental studies, it was shown that the solution "using Ultra High Performance Concrete (UHPC) technology associated with orthogonal steel decks to form composite lightweight deck slabs" design selection to repair Thang Long bridge deck. In order to successfully apply UHPC coating in this project, it is necessary to determine the technological parameters such as: flow, setting time, rheology and shrinkage according to actual construction conditions at site ( temperature and humidity). In addition, other physical and mechanical properties of UHPC must be determined such as compressive strength, tensile strength, elastic modulus and dry shrinkage. This study has determined the technological parameters for the construction of UHPC coating during the period from August 25, 2020 to December 31, 2020 to meet the technical requirements of the Thang Long bridge deck repair project.

Flexural Response of GFRP–UHPC Composite Slabs under a Hogging Moment

Flexural Response of GFRP–UHPC Composite Slabs under a Hogging Moment

Tensile membrane action of RC slabs and steel-concrete composite slabs at elevated temperatures

Slabs can take full advantage of tensile membrane action (TMA) in fire conditions to improve the ultimate bearing capacity. This paper proposed a novel analytical method to determine the ultimate bearing capacity of both reinforced concrete slabs and composite slabs at elevated temperatures, considering the influence of TMA. In this analytical model, a well-defined equation for the elliptical boundary of the TMA region is reasonably determined, and the enhancement of TMA is derived from a series of force and moment equilibria. The analytical method shows a good agreement with the test results. The analytical analysis reveals that while increasing temperature has little effect on the geometry of the membrane action region, it significantly influences the enhancement of ultimate load due to the temperature-induced stress redistribution in the slab. In addition, the membrane action predicted by the analytical method aligns well with that predicted by the numerical method. The development of TMA progresses from the boundary of ellipse to centre, according to the stress distribution predicted by numerical analysis. Finally, with the aid of test results and numerical results, span/10 and span/8 are suggested as the failure criteria for reinforced concrete slabs and steel-concrete composite slabs in fire conditions, respectively.

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.

Flexural behavior of composite ribbed slabs employing cold-formed steel lipped channels

By means of a series of full-scale laboratory tests, this research studied the flexural behavior of a composite ribbed slab employing cold-formed steel profiles as formwork before and after concrete casting. An experimental program was devised and separated in two sets of tests. The first set consisted of the execution of four-point bending tests on eight specimens to represent the system during construction, featuring three specimen types; isolated profile, profile with plastic spacers along the channel and a full assembly including the profile, the plastic spacers and a rebar truss. Displacement and strain as a function of load were measured and the data was used to analyze the influence of the different components on the flexural strength and stiffness of the system. On the second set of tests, three ribbed composite slab specimens featuring steel profiles were subjected to four-point bending. Displacement was registered along with strain on the concrete layer. A formulation to determine the flexural strength of the slabs based on Eurocode is presented and compared to experimental observations. The first phase indicates significant increases of flexural strength and stiffness by coupling a truss to the profile and varying the height of the former, namely a maximum increase of 708% in stiffness and 357% in strength. Isolated profiles and profiles with plastic spacers all failed by distortional buckling, while the full assembly specimens failed by instability of the top chord on the trusses. Second phase results show that the analytical prediction is adequate to determine the flexural strength of the prototype slabs, with approximately 95% accuracy for this sample size. All slab specimens failed by plastic hinge formation within the pure moment span. Furthermore, strain measurements on the concrete indicate that the formulae chosen to determine the effective width of the concrete “tee” section is also adequate.

Geometry optimization of steel formwork for steel–concrete composite slabs

The use of steel formwork incorporated into composite steel–concrete slabs stands out for contributing to sustainable development in civil construction. However, this construction system still has limited usage in Brazil, which may be due to the restricted availability of formwork geometries in the national market. As such, this study aims to determine the optimal steel geometry that results in the lowest steel consumption during manufacture of the composite slabs, taking into consideration the initial construction phase, in which the formwork is under the highest load demand. The Direct Strength Method (DSM) and the traditional Effective Width Method (EWM) are applied for designing the steel formwork during the construction phase, where the cold-formed steel profile resists the applied forces independently. For DSM, the critical buckling moments are determined using the elastic stability analysis program CUFSM, via Finite Strip Methods. The solution of the optimization problem was implemented in MATLAB® using Particle Swarm Optimization and considering two design variables: the thickness and the bend angle of the formwork web. In addition, the reliability of the proposed formulation was evaluated in the implementation phase of DSM and EWM. Numerical analyses are carried out on four different steel geometries currently available in the Brazilian market. The main results showed that the developed computational program was successful in finding optimal solutions for said geometries, as the optimization reduced steel consumption by an average of 21.6%. Thickness had a greater effect on the steel savings, and this variable decreases in the optimal solution, while the height and bend angle increase.

Stiffness Warming Potential: An Innovative Parameter for Structural and Environmental Assessment of Timber–Concrete Composite Members

Timber hybridization with concrete is a rising widespread strategy to obtain members with a structural performance comparable to traditional ones—e.g., RC members—but characterized by a greater sustainability potential thanks to the presence of timber-based materials; this solution is of great interest due to its low embodied carbon content, which supports the decarbonization goals set, especially for the building sector. Such systems enhance the concrete and timber favorable properties and ameliorate their detrimental characteristics, both from the structural and environmental perspectives. In general, since these two aspects are generally considered separately, a new parameter is proposed to simultaneously combine a structural performance indicator with a warming potential one. Focusing on composite slabs in bending, the stiffness warming potential (λ) is introduced, which combines the evaluation of effective bending stiffness (according to Eurocode 5 γ-method) with the Global Warming Potential—GWP (on the basis of data from Athena Impact Estimator for Building software and data from an Environmental Product Declaration of a timber panel). The method provides a multi-criteria analysis concerning the slab design accounting for vibration, deflection, and acoustic criteria when optimizing the member span. On the other hand, GWP is assessed according to cradle-to-cradle Life Cycle Assessment analysis, where two scenarios with different sustainability levels are encompassed. Results firstly confirm the viability of the novel methodology, with a different outlook on timber–concrete hybrid members, stressing the importance of maintaining thinness of the concrete layer and clearly bringing out the importance of correct re-use and/or a timber recycling management to guarantee effective reductions in terms of CO2 emissions.

Carbon emission calculation of prefabricated concrete composite slabs during the production and construction stages

Prefabricated buildings provide favorable technical support to achieve the "carbon peak and carbon neutral" target in the building field. The accurate and reliable quantification of building carbon emissions is an important basis to achieve the dual carbon target. However, research on the carbon emissions of prefabricated buildings is limited, and few studies have been conducted on the calculation of carbon emissions from prefabricated components. Based on the process inventory analysis method, the carbon emission calculation model for prefabricated components in the production and construction stages was established. The prefabricated concrete composite slabs and cast-in-place floor slabs of two typical residential buildings were selected for the case study, and a comparative study was conducted on their carbon emissions during the production and construction stages. The results indicated that the carbon emissions per unit area (net floor area) of prefabricated concrete composite slabs (43.31 kgCO2e/m2 and 43.01 kgCO2e/m2, respectively) were lower than those of cast-in-place floor slabs (46.32 kgCO2e/m2 and 46.09 kgCO2e/m2, respectively) in the production and construction stages. The carbon emissions in the production and construction stages of prefabricated concrete composite slabs accounted for about 97.45 % and 2.55 %, while those of cast-in-place slabs accounted for about 91.21 % and 8.79 %, respectively. The carbon emissions at the building material production stage mainly originated from rebar and cement. When the change rate of building materials consumption and materials carbon emission factors was the same, the change rate of carbon emissions per unit area was ranked as rebar > cement. Furthermore, the cases showed that the prefabrication rate of case B was higher than that of case A, but the carbon emissions per unit area of case B were lower than those of case A. This study provides a scientific calculation method for the carbon emissions of prefabricated components, as well as enriches the data for studying building carbon emissions.

Pseudo-Static Tests on Top Joints of Hybrid Precast Utility Tunnel

This paper introduces a new type of hybrid precast MUT, consisting of precast composite top slab and double-skin sidewalls with reserved rebar. The seismic behavior of the top joints was examined through pseudo-static tests. Four full-scale specimens, including both exterior and interior precast joints, in addition to two corresponding cast-in-place (CIP) joints, were fabricated and subjected to reversed cyclic loading. The results showed that both the precast and CIP joints exhibited flexure failure, characterized by the formation of a plastic hinge at the end of the sidewall. The hysteresis curves of both precast and CIP joints exhibited comparable shapes and quantities of hysteresis loops. The load-carrying capacities for exterior precast joints and corresponding CIP joints were 141.25 kN and 143.5 kN, exhibiting a difference of less than 1.6%. The load-carrying capacities for interior precast and corresponding CIP joints were 60.5 kN and 62.75 kN, displaying a variance of less than 3.6%. The precast specimens demonstrated comparable levels of ductility, energy dissipation, and structural integrity as the CIP specimens. These findings provide validation for designing and analyzing the hybrid precast utility tunnel using identical principles and models as applied CIP structures.

The permeability, mechanical and snow melting performance of graphene composite conductive-pervious concrete

Snow on the roads poses a serious threat to the safety of vehicles, and the traffic system will be paralyzed under harsh conditions. In this study, composite conductive concrete with straight pervious channels were prepared by using carbon fiber, steel fiber and reduced graphene oxide (RGO) as conductive materials to remove snow from roads as soon as possible. The effects of RGO on the workability, mechanical properties and electrical conductivity of composite conductive concrete were studied, and the influence of pervious channels on snow melting efficiency and energy consumption of composite conductive concrete snow melting slabs were analyzed. Results showed that the permeability coefficient of composite conductive concrete with pervious channels reached 6.28 mm/s, meeting the requirements of pavement pervious concrete. For the RGO content of 0.09 % cement mass, the mechanical properties and conductivity of the composite conductive concrete were improved because of the filling effect of nano-RGO on the matrix, while it exerted adverse effects when RGO contents were over 0.09 %. The pervious channels weakened the mechanical and conductive properties of composite conductive concrete. However, compared with the composite conductive concrete without straight pervious channels, the snow melting time and energy consumption were reduced by more than 10 % and 15 %, respectively.

Optimizing ultra-high performance cementitious functionally graded composite slab towards bullet impact resistance

This study develops functionally graded composite slab (FGCS) by a one-time grouting approach based on the design concepts of ultra-high performance fibre reinforced concrete (UHPFRC) and two-stage concrete (TSC). The anti-penetration performance of the FGCS targets is investigated against 7.62 mm in-service bullets with shooting velocity of 843 m/s. The results show that while the TSC target presents superior bullet penetration resistance, it concurrently poses a significant threat of widespread cracking damage. Upon weighing the factors of bullet penetration and risk of cracking, the FGCS emerges as a more viable candidate for protective structures. The FGCS target is cast through a one-time grouting method, and there is no interface delamination under the projectile impact. The optimized FGCS exhibits enhanced in-service bullet impact resistance and a reduced safety thickness of 80 mm compared to the normal UHPFRC.

A new method of interlayer shear performance evaluation for permeable composite pavement (PCP) in laboratory

Permeable composite pavement (PCP) has been increasingly applied for road design and construction. However, interlayer shear resistance is still a challenge for the road performance improvement of PCP. This paper presents a new method of interlayer shear performance evaluation for PCP with a self-made molding device and shear clamp. PCP test slabs are made in two ways, the porous asphalt mixture + impermeable and + permeable concrete layer, named PAIC and PAPC, respectively. The interlayer shear test of PCP slab specimens is conducted under different bonding material types, dosage, temperature, and interlayer contact interface morphology. The results indicate that: (1) The type and amount of bonding materials influence the interlayer shear performance of PCP slabs. The stronger the bonding property of the interlayer material, the greater the interlayer shear strength (ISS) of the PCP. There is the best amount of the same material as the interlayer bonding material. The optimum dosage of styrene-butadiene-styrene (SBS), matrix, and spraying cationic emulsified (PCR short in Chinese) asphalt on the PAIC board is 0.8, 0.6, and 0.4 L/m2, respectively. However, the optimal amount for each bonding of the PAPC slab is 0.6 L/m2. (2) The temperature has a great influence on the ISS of the permeable composite slab due to asphalt being a temperature-sensitive material. For the two slabs, the ISS decreases with the increase in temperature, and even the ISS at 5 °C is 10 times that at 50 °C. (3) The interface morphology of interlayer contact affects the performance of ISS. For PAPC, the contact interface between the two materials is rougher, and the high friction between layers leads to the larger ISS. PAPC's ISS is at least twice that of PAIC. (4) A new method of interlayer shear performance evaluation for the optimization design and application of PCP has been proposed in the final. The method includes material design, specimen making, testing, and quick evaluation. This method has the potential to contribute to the development of PCP tests in the laboratory.

Design, implementation and performance prediction of profiled steel sheet-mixed aggregate recycled concrete hollow composite slab

Profiled steel sheet-mixed aggregate recycled concrete composite slabs are widely studied and applied in engineering applications by virtue of their good durability and recyclability. As an alternative to concrete composite slabs, concrete hollow composite slabs that can reduce their self-weight are also attracting people’s attention. However, the internal holes will increase the risk of collapse and shear failure of the concrete composite slabs. In order to reduce the risk and ensure the flexural performance of the concrete hollow composite slabs, this paper designs the recycled concrete hollow composite slabs with PVC pipes. A full-scale experiment is carried out on five open-mouth profiled steel sheet-mixed aggregate recycled concrete hollow composite slab specimens, to explore the influence of whether the bottom of the plate is reinforced, the thickness of the concrete surface layer and the hollow size on the working performance of the composite slabs. In order to predict the mechanical performance of the proposed hollow composite slabs, a prediction model based on artificial neural network (ANN) consisting of several sub-ANN modules is established. Moreover, according to the priority of the factors affecting the mechanical performance of composite slabs, a decision tree is designed to select appropriate testing sub-ANN module and thus improve the testing accuracy. Predicted results and experimental results are given to validate the feasibility and effectiveness of the developed ANN-based prediction framework for the mechanical performance prediction of composite slabs.

Retracted: Impact Sound Insulation Performance Testing of Nano-Inorganic Composite Floor Slabs for Green Buildings.

[This retracts the article DOI: 10.1155/2022/5642361.].

Flexural Behavior of Ferrocement Composite Slab

Abstract: This project presents a Flexural behaviour of composite ferrocement slabs to investigate the effect of impact and ultimate flexural load on ferrocement slabs of size 600mmx400mmx15mm (thickness) reinforced with PVC coated steel weld mesh, and compare the results with slabs made of GI-coated steel weld mesh. PVC-coated weld mesh is used as non-corrosive reinforcement in ferrocement slab. The ferrocement slab was cast using Ordinary Portland Cement, locally available river sand and portable water with cement mortar ratio of 1:3 and water cement ratio of 0.5. The aim of this study is to observe the influence of PVC coated weld mesh ferrocement slab using ferrocement in enhancement of the mechanical properties of slabs subjected to impact and flexural load. The flexural load, maximum deflection, crack- pattern and crack-width of ferrocement slabs reinforced with PVC and GI coated weld mesh were analysed. Finally, the analytical results were compared with experimental results to predict the effectiveness of ferrocement techniques in structural applications.