Steel-concrete Composite Systems Research Articles

Optimised rotational-spring component-based modelling strategy for seismic resistant steel-concrete composite joints and frames with continuous or isolated slab

Joints and frames in steel-concrete composite systems represent complex mechanical assemblies that require specific calculation procedures to optimise their detailing and structural capacity, particularly under seismic loads. To this aim, component-based modelling approaches should be able to account for the most relevant mechanisms and resistance/stiffness behaviours of individual members, and their mutual interaction. In this paper, two different simplified non-linear approaches are considered for steel-concrete composite beam-to-column joints, and are specifically applied to a seismic resistant case-study frame with X-concentric bracings. Both beam-to-column joints with or continuous (“JA” joint) or fully isolated (“JB” joint) slab are examined. First, non-linear axial springs are assembled and calibrated on the base of a previous study (“Type 1″ model (“T1″)), according to force-displacement relationships proposed in the DPC-ReLUIS Italian guidelines. Successively, a novel modelling approach based on non-linear rotational springs is presented (“Type 2″ model (“T2″)), to further simplify the computational cost of T1 strategy, and allow to efficiently account for the moment-rotation behaviour of the examined joints. The preliminary numerical validation is carried out based on past literature experiments. Moreover, the optimized T2 approach is used to explore the in-plane lateral, seismic performance of a 2D steel-concrete composite frame, which is specifically designed with X-concentric bracings. The seismic capacity of the frame (and the associated interaction of components, especially the joint zone with the bracing system) is addressed on the base of pushover analyses.

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.

Investigation of the Influence of Design Parameters on the Strength of Steel–Concrete Composite Shear Walls by Finite Element Simulations

In this paper, the influence of design parameters on the strength of steel–concrete composite shear walls is investigated by means of finite element (FE) simulations. The shear wall typology studied in this paper consists of multiple composite plate shear wall-concrete encased on one or both sides of the plates. The FE models include contact technology to capture debonding between concrete and steel, tensile cracking in concrete, and large deflection theory involving local instabilities. Some design parameters considered in this work are the height-to-width ratio of the steel plates and their thickness, number of steel plates, the cross-section of the columns, and the height-to-width ratio of the shear wall. Furthermore, a sensitivity analysis of the normalised shear strength per unit cost of structure for these design parameters is also studied. Our numerical predictions are validated successfully with experimental data reported in the literature, revealing the predictive capabilities of the model. The present results provide further insight into the structural behavior of steel–concrete composite shear walls and pave the way for the future development of more efficient and innovative steel–concrete composite systems.

Utilizations of Steel-Reinforced Concrete-Filled Steel Tubular (SRCFST) Constructions

In recent times, there has been a significant amount of research dedicated to traditional concrete-filled steel tubular (CFST) structures. This research has been broad and includes both practical testing and theoretical analysis. As of late, scholars have redirected their attention toward introducing innovations in the domain of steel-concrete composite systems. This piece delves into investigations involving experiments and simulations, as well as the underlying mechanisms and interplays of constraints. The focus is on rectangular columns made of Steel-Reinforced Concrete Filled Square Tubular (SRCFST), subjected to combined compression and torsion forces. By building upon previous investigations, the article not only provides a summary but also evaluates the pathways that research on SRCFST columns has taken. Additionally, it offers a glimpse into the potential directions for future studies. This comprehensive strategy not only serves as a point of reference for upcoming research endeavors but also furnishes practical insights for their real-world implementation.

Damage Detection in Steel-Concrete Composite Structures by Impact Hammer Modal Testing and Experimental Validation.

Steel–concrete composite systems are an efficient alternative to mid- and high-rise building structures because of their high strength-to-weight ratio when compared to traditional concrete or steel constructive systems. Nevertheless, composite structural systems are susceptible to damage due to, for example, deficient construction processes, errors in design and detailing, steel corrosion, and the drying shrinkage of concrete. As a consequence, the overall strength of the structure may be significantly decreased. In view of the relevance of this subject, the present paper addresses the damage detection problem in a steel–concrete composite structure with an impact-hammer-based modal testing procedure. The mathematical formulation adopted in this work allows for the identification of regions where stiffness varies with respect to an initial virgin state without the need for theoretical models of the undamaged structure (such as finite element models). Since mode shape curvatures change due to the loss of stiffness at the presence of cracks, a change in curvature was adopted as a criterion to quantify stiffness reduction. A stiffness variability index based on two-dimensional mode shape curvatures is generated for several points on the structure, resulting in a damage distribution pattern. Our numerical predictions were compared with experimentally measured data in a full-scale steel–concrete composite beam subjected to bending and were successfully validated. The present damage detection strategy provides further insight into the failure mechanisms of steel–concrete composite structures, and promotes the future development of safer and more reliable infrastructures.

Monotonic behavior of C and L shaped angle shear connectors within steel-concrete composite beams: an experimental investigation

Shear connectors are essential elements in the design of steel-concrete composite systems. These connectors are utilized to prevent the occurrence of potential slips at the interface of steel and concrete. The two types of shear connectors which have been recently employed in construction projects are C- and L-shaped connectors. In the current study, the behavior of C and L-shaped angle shear connectors is investigated experimentally. For this purpose, eight push-out tests were composed and subjected to monotonic loading. The load-slip curves and failure modes have been determined. Also, the shear strength of the connectors has been compared with previously developed relationships. Two failure modes of shear connectors were observed: 1) concrete crushing–splitting and 2) shear connector fracture. It was found that the L-shaped connectors have less shear strength compared to C-shaped connectors, and decreasing the angle leg size increases the shear strength of the C-shaped connectors, but decreases the relative ductility and strength of L-shaped connectors.

A novel approach to predict shear strength of tilted angle connectors using artificial intelligence techniques

Shear connectors play a prominent role in the design of steel-concrete composite systems. The behavior of shear connectors is generally determined through conducting push-out tests. However, these tests are costly and require plenty of time. As an alternative approach, soft computing (SC) can be used to eliminate the need for conducting push-out tests. This study aims to investigate the application of artificial intelligence (AI) techniques, as sub-branches of SC methods, in the behavior prediction of an innovative type of C-shaped shear connectors, called Tilted Angle Connectors. For this purpose, several push-out tests are conducted on these connectors and the required data for the AI models are collected. Then, an adaptive neuro-fuzzy inference system (ANFIS) is developed to identify the most influencing parameters on the shear strength of the tilted angle connectors. Totally, six different models are created based on the ANFIS results. Finally, AI techniques such as an artificial neural network (ANN), an extreme learning machine (ELM), and another ANFIS are employed to predict the shear strength of the connectors in each of the six models. The results of the paper show that slip is the most influential factor in the shear strength of tilted connectors and after that, the inclination angle is the most effective one. Moreover, it is deducted that considering only four parameters in the predictive models is enough to have a very accurate prediction. It is also demonstrated that ELM needs less time and it can reach slightly better performance indices than those of ANN and ANFIS.

Laced steel–concrete composite sandwich system in flexure: Experiments, analysis and design

Steel–concrete sandwich composite system consists of steel skin and concrete core. The aim of this paper is to present methods for analysis and preliminary design of a recently developed new class of sandwich composite system laced steel–concrete composite for flexural loads. In laced steel–concrete composite system, continuous lacings are used in place of discrete shear connectors which are generally welded to the skin of the composite. Specimen laced steel–concrete composite systems were subjected to laboratory-controlled experimental investigations. Subsequently, three analytical methods are formulated for evaluating the moment–curvature relation of laced steel–concrete composite system. All the methods exploit the prismatic nature of the laced steel–concrete composite system to derive the moment–curvature relation and employ virtual work principle to evaluate the deflection of the laced steel–concrete composite system. In the first method, the stress–strain relationship of the steel and concrete in tension and compression is utilized to analyse the cross-section of laced steel–concrete composite system. In the second method, fibre-based analysis is used to obtain the response of laced steel–concrete composite system. The third method is based on equivalent transformed section in which the tensile stress–strain behaviour of concrete is represented by an equivalent area under tension. The methods are validated by comparing the predicted values with those of the two- and multi-point loading experiments carried out on laced steel–concrete composite beam and one-way laced steel–concrete composite slab, respectively. All the three methods are found to satisfactorily predict the response of laced steel–concrete composite system. A limited parametric study is carried out by using these analytical methods to identify the role played by the lip and web of the cover plates, tensile strength of concrete and confinement of concrete on the structural response of the laced steel–concrete composite system. In the end, guidelines and charts which can be used for preliminary design of laced steel–concrete composite system for flexure loads are presented.

Steel concrete composite systems for modular construction of high-rise buildings

Modular prefabrication technology promotes off-site manufacturing of modules and on-site assembly by improving the construction efficiency, safety and productivity. However, the joining of individual modules needs special connectors that must be fast to install and robust enough to ensure structural integrity. The restrictions on the overall dimension and weight of the modules for lifting and transportation provide the impetus to develop a more efficient structural module system that is lightweight and fast to install. This paper discusses the design and construction challenges of existing modular construction of high-rise buildings and provides solutions to resolve these challenges. A novel lightweight steel-concrete composite system is introduced to reduce the weight of the module without compromising the strength and stiffness. To increase the available headroom, a slim floor system is proposed to reduce the floor-to-floor depth and ensure the integration of buildings service within the structural zone. High strength concrete is used as an infill material for tubular columns to maintain the same column size to avoid complex joining details involving modules with different column sizes. Long-span steel concrete composite modular system is proposed to reduce the number of joints and columns for fast track construction. A fast and easy joining technique is developed to ensure fast installation of modules. Inter-module joints are modelled as semi-rigid to capture the realistic joint behaviour in global analysis to ensure the structural integrity and overall stability of the building.

Failure Monitoring and Condition Assessment of Steel-Concrete Adhesive Connection Using Ultrasonic Waves

Adhesive bonding is increasingly being incorporated into civil engineering applications. Recently, the use of structural adhesives in steel-concrete composite systems is of particular interest. The aim of the study is an experimental investigation of the damage assessment of the connection between steel and concrete during mechanical degradation. Nine specimens consisted of a concrete cube and two adhesively bonded steel plates were examined. The inspection was based on the ultrasound monitoring during push-out tests. Ultrasonic waves were excited and registered by means of piezoelectric transducers every two seconds until the specimen failure. To determine the slip between the steel and concrete a photogrammetric method was applied. The procedure of damage evaluation is based on the monitoring of the changes in the amplitude and phase shift of signals measured during subsequent phases of degradation. To quantify discrepancies between the reference signal and other registered signals, the Sprague and Gears metric was applied. The results showed the possibilities and limitations of the proposed approach in diagnostics of adhesive connections between steel and concrete depending on the failure modes.

Composite Shear Walls an Efficient Seismic Resistant System for Multi-Story Buildings

Steel-concrete composite systems have seen widespread use in recent decades because of the benefits achieved by merging the two materials. Due to their high stiffness and lateral load resistance, reinforced-concrete shear walls (RCSW) and steel-plate shear walls (SPSW) are considered ideal for resisting earthquake lateral loads in moderate and high-rise buildings. Recently, various schemes of composite shear walls (CSW) have been the focus of recent research. The objective of this paper is to investigate analytically the behaviour of composite shear walls as a lateral-load resisting system in comparison to RCSW. The investigation is performed on buildings with variable heights provided with either (RCSW) or (CSW). Three dimensional models for the case-study buildings are assembled using ETABS, computer software based on the Finite Element Method. The buildings are analyzed for static lateral forces computed by the Equivalent Static Load Method. Response spectra dynamic analyses, and dynamic time-history linear analyses using IZMIT earthquake record. Results are compared and interpreted so as the major findings include: First, to highlight on the structural characteristics and behaviour of composite shear walls as a seismic resistant system. Second, to compare between the structural behaviour of RCSW and CSW concerning their drifts, base shear and strength.

Numerical analysis of tilted angle shear connectors in steel-concrete composite systems

This study investigates numerically the behavior of tilted angle shear connectors embedded in solid concrete slabs. Two different tilted angle connectors were used, titled angle with 112.5 and 135 degrees between the angle leg and steel beam flange. A nonlinear finite element model was developed to simulate and validate the experimental push-out tests. Parametric studies were performed to investigate the variations in concrete strength and connector's dimensions. The results indicate that the ultimate strength of a tilted angle shear connector is directly related to the square root of the concrete compressive strength. The effects of variations in the geometry of tilted angle connectors on the shear capacity are discussed in details. Based on the numerical analyses, two equations are proposed to estimate the ultimate capacity of tilted angle shear connectors of 112.5 and 135 degrees in the defined range of parameters.

Seismic Behavior of Fiber Reinforced Steel-concrete Composite Systems

The addition of Steel Fibers (SF) to concrete has been widely studied in the past decades as a mean to control its crack behavior and maintain its ductility in tension. It has been verified that the use of these fibers at an appropriate dosage can change the behavior of structural members from brittle to ductile. Further, since the discovery of carbon nanotubes/fibers (CNT/CNF), they have been also considered as efficient fibers to be used in construction materials such as concrete. Previous experimental work has shown that incorporation of CNF in cementitious composites can enhance the mechanical behavior of material by reducing the size of macro- and micro-cracks resulting in higher strength and ductility. In addition, due to tunnel conductivity effect, CNF concrete exhibits properties necessary for self-sensing and self-health monitoring ability. This study aims to expand upon the use of SF and CNF concrete in structural members focusing on Steel-Concrete (SC) double skin Composite systems. SC systems are quickly gaining popularity in the nuclear power industry worldwide mainly because of their many advantages such as modular and accelerated construction, cost effectiveness, good strength properties for given size members, in addition to excellent seismic and blast resistance. The use of both SF and CNF fiber reinforced concrete in SC systems could potentially be advantageous under normal and hazard loading conditions. The study includes experimental tests and numerical studies to evaluate the performance of fiber-reinforced SC walls. The study confirmed the benefits gained using the enhanced SC panel systems.

Sustainable and Deconstructable Semi-Rigid Flush End Plate Composite Joints

Composite construction is a popular and effective method of construction, exploiting the strengths of both reinforced concrete and structural steel in building construction in a complementary fashion. Within paradigms related to minimisation of emissions and maximisation of product recycling, these composite systems are problematic on a number of fronts. Firstly, common and traditional composite systems utilise ordinary Portland cement, which is known to be a very large contributor to atmospheric CO2 emissions. Secondly, for typical construction practices for steel-concrete composite systems, casting of the concrete onto profiled steel decking and conventional reinforcement placing are undertaken on-site, which is time consuming and labour intensive, and which can increase the cost of construction. Thirdly, composite action between the steel beam and the concrete slab is usually achieved by using headed shear studs. The headed shear studs connect these two elements permanently, which leads to much waste at the end of the service life of the building when it is demolished. This paper models a sustainable semi-rigid beam-to-column composite blind bolted connection with deconstructable bolted shear connectors using ABAQUS finite element (FE) software. In this “green” system, precast geopolymer concrete (GPC) slabs are attached compositely to the steel beam via pretensioned bolted shear connectors and the composite beam is connected to GPC-filled square columns using blind bolts. Non-linear material properties and non-linear geometric effects are considered in the simulation of a connection in hogging bending. Based on the FE modelling, using pretensioned bolts as shear connectors with GPC can improve the behaviour of semi-rigid flush end plate composite joints in terms of ductility and load capacity. Moreover, the behaviour of the bolted shear connectors should be considered in composite joint design as being very different to headed stud connectors.

Flexural performance of an innovative Hybrid Composite Floor Plate System comprising Glass–fibre Reinforced Cement, Polyurethane and steel laminate

This study explored the flexural performance of an innovative Hybrid Composite Floor Plate System (HCFPS), comprised of Polyurethane (PU) core, outer layers of Glass–fibre Reinforced Cement (GRC) and steel laminates at tensile regions, using experimental testing and Finite Element (FE) modelling. Bending and cyclic loading tests for the HCFPS panels and a comprehensive material testing program for component materials were carried out. HCFPS test panel exhibited ductile behaviour and flexural failure with a deflection ductility index of 4. FE models of HCFPS were developed using the program ABAQUS and validated with experimental results. The governing criteria of stiffness and flexural performance of HCFPS can be improved by enhancing the properties of component materials. HCFPS is 50–70% lighter in weight when compared to conventional floor systems. This study shows that HCFPS can be used for floor structures in commercial and residential buildings as an alternative to conventional steel concrete composite systems.

Effects of random material and geometrical properties on structural safety of steel-concrete composite systems

A stochastic finite element-based algorithm for probabilistic analysis of structural systems made of composite sections with random material and geometrical properties under earthquake forces is proposed in this paper. Uncertainties in the structural parameters can be taken into account in this algorithm. For the perturbation-based stochastic finite element method, only the first two moments of random variables need to be known, and is numerically much more efficient and feasible than simulation techniques. The efficiency and accuracy of the proposed algorithm are validated by comparison with results of Monte Carlo simulation method. A summary of stiffness matrix formulation and perturbation-based stochastic finite element dynamic analysis formulation of structural systems made of composite sections is given. These are followed by suitable numerical examples, which indicate that employment of such a dynamic stochastic finite element method leads to significant economical, efficient and accurate solutions for the dynamic analysis of composite structures with stochastic parameters under earthquake forces. Copyright © 2010 John Wiley & Sons, Ltd.