Steel-concrete Composite Slabs Research Articles

Experimental investigation of steel-concrete composite slabs subjected to underwater near-field explosion

Experimental investigation of steel-concrete composite slabs subjected to underwater near-field explosion

Numerical simulation of steel-concrete composite beams and slabs at elevated temperatures

Steel-concrete composite beams with shear studs providing composite action between the concrete slabs and steel beams are widely used in modern steel-framed building construction. Three-dimensional finite element modelling has been a viable option for investigating the fire behaviour of composite beams. Although many finite element models are available in the open literature, most of them are simplified models verified by limited test data. Meanwhile, early test data often did not have all the required information for finite element simulation, and some assumptions need to be made. But more detailed test data are now available in the open literature for steel-concrete composite beams, which can be used to develop a generalised finite element model. In addition, National Institute of Standards and Technology has proposed new stress-strain models for steels at elevated temperatures, which can be compared with the more widely adopted Eurocode 4 steel material models in simulating composite beams. Accordingly, this paper selected 22 specimens, including two reinforced concrete slabs, 12 composite beams with reinforced concrete slabs, two composite slabs with profiled steel sheeting, two steel-concrete composite push test specimens with profiled steel sheeting, and four composite beams with profiled steel sheeting, from nine references to verify the developed finite element model. The proposed finite element model can capture different failure modes of composite beams, such as steel yielding/local buckling, concrete cracking/crushing, debonding of profiled steel sheeting, and stud fracture, which is crucial to comprehend the composite beam behaviour at elevated temperatures.

Vertical shear capacity of steel–normal concrete-UHPC composite slabs with steel ribs in the cantilever

UHPC is utilized to enhance flexural performance of tensile zone of composite slabs, which will enable reducing slab height. The vertical shear resistance of composite slabs in the cantilever might become insufficient with the reduction of slab height. In the paper, the vertical shear performance of steel-normal concrete-UHPC composite slabs in the cantilever is investigated based on five composite slabs tests, numerical simulation, and theoretical analysis. The results indicate that UHPC layer changes the failure mode of steel concrete composite slabs. The bearing capacity and ductility of composite slabs are effectively enhanced with the application of UHPC. The addition of a 10 cm UHPC layer makes the bearing capacity of composite slabs increase by 69.97%. And the reinforcement ratio of UHPC layer and the type of steel ribs exert a significant influence on the shear resistance. Additionally, an analytical model derived from modified compression field theory can well predict vertical shear bearing capacities of composite slabs in the cantilever.

Flexural Performance of Steel–Normal Concrete–Ultra-High-Performance Concrete Composite Slabs with Steel Ribs

For steel–concrete composite bridges, the cracking of concrete in the tensile zone influences the serviceability of bridges and decreases their durability. UHPC, as a high-tensile and -durability material, is used to replace a part of the concrete to enhance the tensile performance. Thus, the steel–normal concrete–UHPC composite slab, as a new composite structure, is formed. This paper investigates the flexural behaviours of steel–normal concrete–UHPC composite slabs through a full-scale experiment, numerical simulation, and theoretical analysis. The research results indicate that (1) UHPC enhances the flexural performance of the tensile zone and delays the development of cracks. The initial cracking force of concrete increases from 44 kN to 91 kN. (2) UHPC effectively enhances the carrying capacity of composite slabs. A 50 mm UHPC layer makes the flexural bearing capacity of steel–concrete composite slabs increase by 13.51%. (3) The construction methods influence the initial cracking force of composite slabs. For full-span scaffolding construction, the initial cracking force decreases from 91 kN to 69 kN compared with construction without brackets. (4) The theoretical model considering the tensile contribution of cracking UHPC can accurately predict the bearing capacity of the composite slabs. And the theoretical values of the bearing capacity are lower than the experimental values, which makes the composite slabs safer in service.

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.

Investigations on Blast Performance of Steel-Concrete Composite Structures

Blast performance of concrete and ultra-high performance fiber concrete (UHPFRC) has been subject to numerous publications in the past decades. The enhanced force-deflection diagram of fiber concrete and ultra-high performance fiber concrete provide massive increase on the protective function of these materials compared to regular concrete. Nevertheless, concrete spalling cannot be fully avoided even when using UHPFRC. The next step for harmful debris ejection prevention can be supplementing the concrete specimens with steel slabs. The steel slab will not just hold the debris, but can, if properly bonded with concrete, contribute to the load bearing capacity as steel-concrete composite structure. This paper presents an overview of recent experiments on blast resistance of steel-concrete composite slabs. In total 6 pairs of specimens (dimension 1.000/1.000/150mm) were prepared, 6 specimens using regular concrete and 6 specimens using UHPFRC. One pair of specimens was reinforced by a steel mesh at 30mm cover from the soffit, one pair was supplemented by a steel plate bonded with 4 studs in the corners, at the complementary specimen pair, the concrete was also covered with a steel plate at the side subjected to blast loading, in the case of the further pair of specimens, the steel plates were connected by steel bars arranged in a mesh 150/150mm. The final 2 pairs represented steel-concrete composite slabs, in the first case, the shear studs were supplemented with a steel mesh (according to provisions of the European standard for steel-concrete composite structures), in the last case, the shear studs were replaced by a shear plate. All specimens were subjected to the same contact blast loading. The paper presents the experimental arrangement, the achieved results and a brief discussion on the structural behavior.

Prediction of non-uniform shrinkage of steel-concrete composite slabs based on explainable ensemble machine learning model

The non-uniform shrinkage (NUS) of steel-concrete composite slabs has been proved to significantly affect the long-term performance of composite slabs. But the reliable analysis method has not yet been proposed due to the multi-factor coupling mechanism of material composition and boundary conditions. A database containing 782 samples was established in this paper, and the index set containing 5 feature parameters was selected by analyzing the physical mechanism of NUS of steel-concrete composite slabs. The predictive capabilities of 8 machine learning (ML) models with different working mechanisms were compared, and the reliability of ML models was verified by Taylor and box scatter from the perspective of global and single sample, respectively. Furthermore, sensitivity analysis was conducted using the SHapley Additive exPlanations (SHAP) method to evaluate the impact of each parameter on the NUS of steel-concrete composite slabs. Finally, a user-friendly graphical user interface (GUI) was developed to guide engineering design. The limitations and potential improvements of the ML models established in this paper were discussed. The results indicate that the variance inflation factor (VIF) method and correlation analysis can effectively mitigate the influence of data multicollinearity and variable collinearity, and the pearson coefficient and VIF value of the input variables are less than 0.35 and 5. Gradient boosting decision tree (GBDT) has the best prediction performance, with R2 of 0.933 and 0.927 on the training set and testing set, respectively. Relative distance (x) and age (t) are the key parameters affecting the NUS of steel-concrete composite slabs. The procedure and GUI developed in this paper can effectively guide the intelligent prediction of the composite slab NUS.

Experimental Study of Novel Demountable Shear Connectors for Steel-concrete Composite Buildings

Sustainable composite structures in building construction are assembled using demountable structural elements that can be reused in the circular economy. The current research and development project, in cooperation with Budapest University of Technology and Economics and KÉSZ Group, bim.GROUP Ltd., Hungary, aims to design a novel demountable steel-concrete composite slab and frame system for buildings. The key component of this construction is the demountable shear connector. In the current research, novel bolted shear connectors with embedded bolts and threaded rods are developed and studied that can fit the applied technology of the industrial partner. One of the leading aspects of this connection is the consideration of bolt hole clearance, since it occurs initial slip and stiffness reduction of the composite beam. In the first phase of the research program, demountable and economical structural details were developed, which can reduce the stiffness reduction with the proper resistance and ductility features. To study the behavior of these shear connections, a push-out experimental program was designed and completed in March and April 2023. It is observed that novel shear connectors have a proper behavior with sufficient resistance and ductility, which is applicable according to the Eurocode 4 standard and fits the objectives of the research and development project. In the paper, the developed structural details and the push-out experimental program are presented with general results and statements besides a detailed evaluation of a specified specimen type.

Experimental and numerical analyses on the shear behavior of grouped single-embedded-nut high-strength bolts in steel–ultra-high-performance concrete composite slabs

Incorporating utilization of ultra-high-performance concrete (UHPC) slabs and single-embedded-nut high-strength bolts (SENHSBs) can optimize the structural performance and construction efficiency of steel–concrete composite slabs. Typically, SENHSBs are required to be densely arranged in groups to transfer sufficient interfacial shear forces in complex stress regions. However, the investigations focused on the performance of grouped SENHSBs embedded in UHPC slabs is limited. Against this background, 15 push-out tests were conducted, accompanied by comprehensive numerical analyses, to study the shear behaviors of grouped SENHSBs in steel–UHPC composite slabs. The test results demonstrated that the failure model was governed by SENHSB fracture. Specimens with the longitudinal spacing of twice the bolt diameter exhibited overlapping crushing areas in the UHPC slabs. The longitudinal spacing significantly influenced both the ultimate shear and ultimate slip capacities of the grouped SENHSBs, whereas the transverse spacing significantly affected both the shear stiffness and maximum slip of grouped SENHSBs. Additionally, the per bolt ultimate shear capacities of the specimens with multi-layer SENHSBs were significantly lower than those with single-layer SENHSBs. The SENHSBs located at various positions experienced different shear stresses, and the deviations became more significant as the longitudinal spacing decreased. Consequently, a formula was proposed to evaluate the strength reduction factor of the grouped SENHSBs. Furthermore, accurate models were developed for determining the ultimate shear capacity and load–slip relationship of grouped SENHSBs in steel–UHPC composite slabs.

Strength calculation of composite slabs by the partial shear connection method considering the friction

This paper aims to evaluate the behavior and longitudinal shear strength of the steel-concrete composite slab using the Steel Deck P75 through the partial shear connection method considering the contribution of the friction acting in the interface of the steel deck with the concrete at the region of supports. The method proposed by EN 1994-1-1:2004 for the design of composite slab systems is based in the analytical model similar to that of composite beams which allows to determine the degree shear connection between the steel sheeting and the concrete. This method allows to analyse the influence of friction at the support, in addition to the contribution of stud bolts on the mechanical resistance of composite slab. The composite slab was tested in the Federal University of Minas Gerais structure laboratory which used the semi-empirical "m-k" method to obtain its resistance. The behavior of the composite slab system was analysed through of the graphics deflections, end slips and strains, allowing the determination of its failure mode. Finally, the results obtained from the longitudinal shear resistance considering the friction at the support were applied in one practical example.

Experimental investigation on the dynamic response of half steel-concrete composite slabs under low-velocity impact

The current research on the dynamic response of half steel–concrete (HSC) composite slabs is not only limited but also primarily concentrated on high-velocity impacts. This study investigates the dynamic response of such structures by examining failure modes, impact resistance mechanisms, and energy dissipation under low-velocity impacts through drop hammer impact tests conducted on five HSC specimens. In addition, the variation of the out-of-plane residual bearing capacity with the damage degree of specimens and impact energy is analyzed using static loading tests. Finally, the dynamic response differences between half steel–concrete slabs and steel–concrete (SC) slabs are analyzed by comparing multiple indicators. The results indicate that HSC slabs exhibit five distinct failure modes when subjected to low-velocity impact within a range of 3.13–7.00 m/s. Additionally, five stages of the dynamic response process of the HSC slabs are proposed. Moreover, the bottom steel plate plays a crucial role in retaining structural out-of-plane residual bearing capacity. Furthermore, compared with the SC structure, the HSC slab is capable of absorbing input impact energy within a much smaller displacement.

Deep residual learning for acoustic emission source localization in A steel-concrete composite slab

Large errors can be introduced in traditional acoustic emission (AE) source localization methods using extracted signal features such as arrival time difference. This issue is obvious in the case of irregular structural geometries, complex composite structure types or presence of cracks in wave travel paths. In this study, based on a novel deep learning algorithm called deep residual network (DRN), a structural health monitoring (SHM) strategy is proposed for AE source localization through classifying and recognizing the AE signals generated in different sub-regions of critical areas in structures. Hammer hits and pencil-leak break (PLB) tests were carried out on a steel-concrete composite slab specimen to register time-domain AE signals under multiple structural damage conditions. The obtained time-domain AE signals were then converted into time-frequency images as inputs for the proposed DRN architecture using the continuous wavelet transform (CWT). The DRNs were trained, validated and tested by AE signals generated from different source types at various damage states of the slab specimen. The proposed DRN architecture shows an effective potential for AE source localization. The results show that the DRN models pre-trained by the AE signals obtained in the undamaged specimen are able to accurately classify and identify the locations of different types of AE sources with 3–4.5 cm intervals even when multiple cracks with widths up to 4–6 mm are present in the wave travel paths. Moreover, the influence factors on the model performance are investigated, including structural damage conditions, sensor-to-source distances and AE sensor mounting positions; in accordance with the parametric analyses, recommendations are proposed for the engineering application of the proposed SHM strategy.

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.

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.

Damage modes and mechanism of steel-concrete composite bridge slabs under contact explosion

The steel-concrete (SC) composite bridge slab is widely used in long-span bridges. With the increasing threat of explosive attacks on bridges, understanding the blast-resistant performance of composite bridge slabs is important. In this paper, SC composite slabs with different types of interfaces between concrete slab and steel plate, and different steel plate thickness, were tested under contact explosion. The damage modes and dynamic responses were carefully observed and measured. Refined FE models were developed to investigate the damage mechanism by analyzing and comparing the detailed damage process of slabs and characteristics of stress wave propagation. The results revealed that the damage modes of SC composite slabs varied significantly depending on the type of interface. For slabs with stud connectors, the compressive stress wave propagated within the composite slab in a spherical pattern and finally induced a circular concrete crater and steel plate deformation. Increasing the thickness of steel plate significantly reduced steel plate deformation. For slab with PBL connectors, the stress wave in the concrete was attenuated when it propagated across the PBL ribs, while the stress of concrete between the ribs nearest to the explosion was much large than that outside the ribs. Stress reflection on the top of PBL ribs increased the damage degree of concrete, potentially leading to induced cracks along the ribs. The overall response of composite slabs could be divided into the combined phase and separated phase. The PBL ribs could better restrain the interface detachment compared to studs.

Experimental study and numerical modelling of a novel two-way steel-concrete composite slab

This study proposes a new innovative two-way steel-concrete composite slab system. The experimental work investigates the structural capacity, shear behaviour and two-way load distribution of the proposed composite slabs consisting of a new profiled steel deck and concrete. The innovative deck is developed by providing 90° bends in corrugated steel sheets to form hat sections, which then are placed on a corrugated base sheet in the perpendicular direction. Five composite slabs were tested under uniform loading, in which three slabs contained shear studs, and the remaining two were tested without shear studs. The slabs failed by flexural failure and shear bond failure, and the composite slabs with and without studs showed comparable load-carrying capacity and two-way action. The unique geometry of the deck profile provides good longitudinal shear capacity in the main direction. The slip is absent in the main longitudinal direction of the slab due to the corrugated top-hats. The provided shear studs further complement the role of the top-hats by resisting interface shear failure in the perpendicular direction. Therefore, the new deck type can be used effectively in two-way composite slabs for shear and load capacity by reducing the quantity of additional shear connectors, which is a significant advantage of the proposed deck compared to conventional deck types. A finite element (FE) model of the composite slabs with and without shear connectors is developed and validated against the experimental results and then used to investigate the slab's performance in two-way load distribution.

Longitudinal shear tests and design methods for corrugated steel–concrete composite slabs with recycled coarse aggregate

This study aims to investigate the effects of natural coarse aggregate (NCA) replacement ratio and end anchorage conditions on the longitudinal shear performance of corrugated steel-recycled aggregate concrete (CSRAC) composite slabs. Six composite slab specimens were tested to determine their failure mode, bearing capacity, and deformation behavior. A finite element model of CSRAC composite slabs was established using ABAQUS, and its reliability was validated based on the experimental results. A parametric analysis was conducted to determine the effects of each key parameter on the longitudinal shear performance of CSRAC composite slabs. A design method for the longitudinal shear capacity of CSRAC composite slabs was proposed, taking into account the NCA replacement ratio. The experimental results revealed that the incorporation of end anchorages can significantly improve the longitudinal shear performance of CSRAC composite slabs, resulting in an increase of 45.06% and 62.34% in ultimate bearing capacity for specimens with NCA replacement ratios of 50% and 100%, respectively, when compared to those without end anchorages. As the NCA replacement ratio increases, the longitudinal shear capacity of CSRAC composite slabs decreases. The reduction in longitudinal shear capacity was found to be 2.75%-4.98% and 5.55%-10.02% for specimens with 50% and 100% NCA replacement ratios, respectively, when compared to natural aggregate concrete (NAC) specimens. The NCA replacement ratio is a significant parameter that affects the longitudinal shear performance of CSRAC composite slabs and the proposed design method based on the m-k method for the longitudinal shear capacity of composite slabs can accurately predict the longitudinal shear capacity of CSRAC composite slabs by considering the NCA replacement ratio.

Experimental and analytical investigation of notched steel plate as a novel shear connector

To ensure durability and save time in construction, steel–concrete composite slabs are widely used in aging bridge replacement. This paper proposes a novel type of shear connector named notched steel plate (NSP). The shear properties of four types of NSP shear connectors with heights of 50 mm and 75 mm and thickness values of 9 mm and 12 mm were evaluated by conducting push-out tests. Concrete cracks occurred firstly during the loading. After removing the concrete block, fracture of NSP shear connectors at the welding zone between NSP and steel plate was observed. A finite-element (FE) analysis was conducted considering the nonlinear properties of materials and interface between the NSP and concrete block. The shear stiffness, shear capacity and failure pattern obtained using the FE model matched with the test data. The verified FE model was used to investigate the failure mechanism of NSP and to clarify the effect of the constraint force, concrete compressive strength and steel strength on the NSP shear capacity. The experimental shear capacity values were compared with the values calculated by the specifications for channel and angle shear connectors. The results of the NSP shear capacity were similar to those obtained based on the American Institute of Steel Construction (AISC) specifications and Eurocode 4.

Design Procedures for Predicting Long-Term Responses of Continuous Steel–Concrete Composite Slabs

Although the effect of nonuniform shrinkage on the time-dependent behavior of simply supported composite slabs has been extensively investigated, continuous composite slabs have not garnered enough attention. This paper aims to propose the routine design procedures for continuous composite slabs, including the hogging moment over the interior support and the mid-span deflection. Thus, the long-term test data on two-span continuous composite slabs provided by the authors and the related literature were collected to benchmark the current design methods in international specifications. The routine design procedures for calculating the long-term moment distribution and the mid-span deflection of two-span composite slabs were proposed considering the time-dependent range of hogging moment zones. Moreover, the effects of different shrinkage distributions and hogging moment ranges on the long-term performance of these slabs were further quantified. The results showed that the mid-span deflection and the hogging moment over the interior support increased significantly over time; both could not be accurately predicted using the typical design methods described in international specifications. The hogging moment declined by 28.0% when a uniform shrinkage profile was adopted for the design of composite slabs, and the mid-span deflection decreased by 15.0% when a constant range of the hogging moment zones was used. The design procedures proposed herein well described the long-term behavior of continuous composite slabs by accounting for the combined effects of the nonuniform shrinkage and time-dependent hogging moment range. The calculated hogging moment and mid-span deflection differed from the measured ones on average by 2.0% and 9.0%.

Study on the Vertical Vibration Comfort of Prefabricated Skyscraper Steel-Concrete Composite Industrial Plant

Steel-concrete composite structure is widely used in the present skyscraper industrial plant. This type of structure has a lot of advantages, such as high structural strength, efficient construction etc. However, the stiffness of this composite structure is lower than that of steel structures or reinforced-concrete structure, especially in the skyscraper industrial plant. The skyscraper industrial plant has a large span and high floor height, which means that the vibration comfort issues must be considered. This paper takes the actual skyscraper industrial plant under construction as the background, adopts the two methods of field measurement and finite element simulation, to obtain the first order vertical self-vibration frequency value of the steel-concrete composite slabs. The results show that the value is within the allowable range of error.