Steel Composite Beams Research Articles

Optimum Design of Fully Composite, Unstiffened, Built-Up, Hybrid Steel Girder Using GRG, NLR, and ANN Techniques

Composite steel beams are commonly used element in multistorey steel buildings to enhance floor economy and serviceability and provide more clear height. Due to the low level of stress in the webs of such beams, hybrid sections are used where the flanges have higher strength than the webs. A lot of earlier research was carried out to optimize the design of the hybrid and nonhybrid composite steel beams under both static loading and dynamic behavior. However, there is still a need to develop a more practical optimization method. The aim of this research is to develop simple and practical equations to determine the optimum cross section dimensions for both shored and unshored, simply supported, hybrid and nonhybrid, composite steel beam under static loads. To achieve that goal, a research program of two phases was carried out. The first phase was generating a database of 504 composite beams with different steel grades for flanges and webs, subjected to different values of bending moment. The cross section of each beam in the database was optimized using GRG technique to minimize the cost considering the unit price of each steel grade. In the second phase, the generated database was divided into training and validation subsets and used to develop two predictive models using Nonlinear Regression (NLR) technique and Artificial Neural Network (ANN) technique to predict the optimum cross section dimensions and hence the optimum weight and cost. The accuracies of the developed models were measured in terms of average error percent. NLR and ANN models showed average error percent of 16% and 11%, respectively.

CONNECTIONS BETWEEN STEEL-CONCRETE COMPOSITE COLUMN AND STEEL BEAM

Composite steel-concrete columns of circular cross-section have high strength and stiffness, which theoretically could help to reduce the cost of construction, but their advantages are still widely unexploited. In comparison with other constructions, composite columns account for a diminutive market share. One of the many reasons for this, is the complexity of connections that may require on-site welding, which not only slows down the construction, but also makes it more expensive. With the recent extensive development of blind bolts, new design options for the tube columns emerged. Such bolted joints would eliminate onsite welding and speed up installation. In this review a particular attention is paid to the circular columns, because these columns have the least studied connections. This article reviews the most recent stage in the development of the connections between steel-concrete composite columns and steel beams, as well as provides provisions for using such connections and outlines the directions for further research.

Experimental investigation of composite steel–concrete beams using symmetrical and asymmetrical castellated beams

Abstract This study aims to investigate the behavior of concrete slabs acting compositely with symmetrical and asymmetrical castellated beams. Stud connectors are used to connect the concrete slab and steel section. The use of castellated steel beams to build up composite steel-concrete beams is now common practice in building construction. Five simply supported composite beams were examined under two-point loading. Two specimens built up from standard steel beams were used as control specimens and three specimens were built up from castellated steel beams. One of these specimens was built up using a castellated steel beam with an asymmetrical cross-section fabricated from two different standard sections (IPE120/HEA120). The concrete slab of all composite specimens had the same dimensions and properties. The experimental results showed that strength and rigidity were considerably greater for composite castellated steel beams compared to composite beams built up from the parent sections. The ultimate load capacity of a composite castellated beam fabricated from an IPE120 section was 46% greater than that of a composite beam built up using the parent beam, and the ultimate load capacity of a composite castellated beam fabricated from a wide-flanged HEA120 section resulted in an increase of 21% over the parent beam control specimen. The ultimate load capacity of the composite specimen built up using the asymmetrical castellated beam (IPE120/HEA120) achieved increases of 69% and 12%, respectively, compared to the control specimens built up from standard sections.

Experimental study of composite concrete cellular steel beams

The main objective of this study is to compare the structural behavior of composite steel– concrete beams using cellular beams with and without steel ring stiffeners placed around the web openings. An IPE140 hot rolled I-section steel beam was used to create four specimens: one without openings (control beam); one without shear connectors (non-composite); a composite steel–concrete beam using a cellular beam without strengthening (CLB1); and a composite steel–concrete beam using a cellular beam (CLB4-R) with its openings strengthened by steel ring stiffeners with geometrical properties Br = 37mm and Tr = 5mm. CLB1 was fabricated with openings of 100mm diameter and a 1.23 expansion depth ratio, while CLB4-R was fabricated with openings of 130mm diameter, a 1.42 expansion depth ratio. Both beams were 1700mm in length with ten openings. The results of this experiment revealed that the loads applied to CLB1 and CLB4-R at deflection L/360 exceeded the load applied to the control specimen at the same deflection by 149.3% and 177.3%, respectively. The results revealed that the non-composite beam had an ultimate load 29% lower than that of the control beam. The ultimate load on CLB1 was 5.3% greater than that of the control beam, and failure occurred due to web-post buckling. While the ultimate load of the CLB4-R beam was 18.43% greater than that of the control beam, the Vierendeel mechanism was indicated as the failure mode.

Experimential Study on Failure Mode and Ultimate Shear Bonding Force of CFRP Plate-Steel Interface under Anchor Compression

In order to study the paste failure mode and ultimate shear bonding force of CFRP plate-steel interface anchor bonding, a single-sided shear test was carried out on a total of 15 carbon fiberboard (CFRP)-steel composite beam structure specimens in five groups. The test results show that for organic adhesives, the uniform anchoring method can improve the bearing capacity of the construction; for organic adhesives, the ultimate shearing when the specimen is peeled with inorganic glue is used. The bonding capacity is greater than that of specimens with organic adhesives.

Experimental investigation on fatigue behavior of composite beams with different studs arrangements

Connections between steel beams and concrete slabs that reduce the number of shear connectors by using studs with a larger size or partial shear connections could be advantageous by reducing installation time and provide additional working space for construction workers to move on the top steel flange. In this paper, steel and concrete composite beams with different headed stud shear connector arrangements were tested under fatigue loading to evaluate the crack patterns in concrete slabs, deformations, and strains in the composite sections and shear connectors. These arrangements included full shear connections achieved by 22.2 mm and 15.9 mm diameters headed stud connectors arranged in one and two rows, respectively, and a partial shear connection with two rows of 15.9 mm diameter shear connectors. Distributing the required resistance of shear to a larger population of smaller studs produced more beneficial behavior over that of a smaller population of larger diameter studs. The concrete slab fully shear connected by the one-row arrangement experienced longitudinal cracks during fatigue loading, which led to more stiffness degradation and strength deterioration, while such cracks were eliminated in the two-row arrangement. Therefore, 77.1%, 177.7%, and 152.5% increase in the incremental deflection, slippage, and studs’ strains, respectively, were obtained for this specimen. Moreover, reductions of 83.0% and 66.7% were obtained in the composite action in terms of the cyclic slippage for the specimens with the one- and two-row arrangements, respectively. Final residual static tests up to failure were conducted to explore the residual behavior of the fatigued specimens. Degradations in the residual stiffness and strength of the fatigued specimens occurred and more partially composite effects were obtained, which led to higher residual strains in the headed stud connectors and extreme fibers of the composite sections of 12.6% and 16.6%, respectively.

A new type of hollow-shallow steel and concrete composite floor beam

Recently in Vietnam, steel-concrete composite structures especially composite beams are widely constructed in high-rise buildings. To apply broader in construction field mainly in secondary beam systems, the new type of slim-floor composite beam is proposed to aim at reducing the cost, saving the raw material, and decreasing the overall floor depth for sustainable development orientation. This type of floor beam structure consists of built-up hollow-shallow steel beam mandatory connected with cast in situ concrete slab through the openings at both side of web along the beam. The shear connection level of composite beam is depended on not only the friction at the connected surface between hollow steel section and concrete but also the shear resistance of concrete dowels, which go through the openings. The paper deals with an innovative shape of cross-section and design philosophy of composite beam according to EN 1994-1-1.

An experimental study on structural performance of U-shaped shear connector in composite cold-formed steel floor joists

Since few studies have focused on the shear connectors in the composite cold-formed steel beams so far, this paper studies the behavior of the U-shaped shear connectors which can be used in the composite beams comprising cold-formed steel beam and concrete slab. Accordingly, ten full scale push-out tests were conducted to investigate the ultimate load, failure modes, ductility and stiffness of the U-shaped shear connectors. For this purpose, four types of shear connectors by different screw diameters and orientation of U-shaped shear connectors with respect to the direction of the load were considered; and utilized by two types of cold-formed steel beams with thickness of 1 and 2 mm. The results have shown that change of the screws’ diameter from 4.8 to 6.3 mm, leads to an increase of the ultimate load about 25% and 40% for 1 mm and 2 mm thick specimens, respectively. It is also concluded that transverse shear connectors have a better performance than longitudinal ones considering both ultimate load and ductility. The main observed failure mode of all specimens was tilting and bearing in shear connectors except for two specimens which was incorporated with pull-over mode. Moreover, ductility of the shear connectors was examined according to EC4 code. The results show that except for two specimens, the other U-shaped shear connectors used in this study can be accounted ductile.

Flexural behaviours of Engineered Cementitious Composites – High strength steel composite beams

Since the compressive strain of normal strength concrete (NSC) (0.23 – 0.3%) is too low to work compatibly with high strength steel (HSS) with typical yield strain greater than 0.35%, Engineered Cementitious Composites (ECC) which generally has a minimum compressive strain of 0.5%, is an attractive alternative to replace NSC when constructing composite beams using HSS sections. This study investigated experimentally the flexural behaviours of composite beams comprising HSS I-section and hybrid Polyethylene-steel fibres (PE-ST) ECC slab. Shear interactions between the HSS beam and the PE-ST ECC slab was provided by normal profiled steel sheeting (PSS) and headed shear studs. Four composite beams including three ECC-HSS beams and one NSC-HSS beam were tested under four-point bending until failure. The test results indicated that while the flexural capacity of ECC-HSS beams only showed a slight improvement, its ductility was significantly enhanced when comparing with the NSC-HSS beam. All ECC-HSS beams failed in a ductile manner and gradual softening behaviours were observed after the peak load. In contrast, the NSC-HSS beam showed a less ductile failure mode with a sudden crushing of NSC and a sharp drop of bending resistance after the peak load. To complement the test results, a 3D nonlinear finite element (FE) model was also developed and validated against the experimental results. Well agreements between the FE and test results were observed. This confirmed that the FE model could be employed to evaluate the general behaviours of ECC-HSS composite beams.

Numerical study on fire resistance of rectangular section stainless steel-concrete composite beam

To investigate the fire resistance of stainless steel-concrete composite beams (referred to as stainless steel composite beam), numerical simulations of rectangular section stainless steel composite beams under fire were carried out. The influences of load ratio, thickness of concrete slab, width of concrete slab, reinforcement ratio of concrete slab, height of stainless steel beam, width of stainless steel beam and span of composite beam on the fire resistance of rectangular section stainless steel composite beams were analyzed. Due to the large coefficient of thermal expansion of stainless steel material, the expansion of stainless steel beam will produce an additional bending moment in the stainless steel composite beam under fire, which has a great influence on the fire resistance of stainless steel composite beams. Finally, a simplified calculation method of temperature field distribution of rectangular section stainless steel composite beam was proposed. To adjust and enlarge the maximum bending moment at the mid-span of stainless steel composite beam, the coefficient of temperature additional bending moment was introduced into the calculation formula of critical temperature of stainless steel composite beams, which effectively improves the accuracy of the fire-resistant design method for stainless steel composite beams.

Hysteretic Behaviour of Shear Stud Connectors in Composite Steel Moment‐Resisting Frames

AbstractIn steel moment resisting frames (MRFs) with composite floor slabs, seismic loads are transmitted from the slab into the beam through shear studs. Shear strength degradation of the studs due to cyclic loading results into the loss of the load transfer mechanism and composite action. To date, several low‐cyclic, high‐amplitude push‐out tests have been conducted to characterize the shear stud hysteretic behaviour. These isolated tests showed considerable degradation in the shear stud resistance; nevertheless, they do not simulate the actual hysteretic behaviour of shear studs within a composite steel beam. To elaborate, conventional cyclic push‐out tests do not replicate the actual stress state in the concrete slab, nor do they account for the force redistribution between the shear studs. This paper investigates the hysteretic behaviour of shear studs in steel MRFs with composite floor slabs. The load‐slip hysteretic behaviour of the shear studs is examined through continuum finite element (CFE) models of 2‐bay sub‐systems and their corresponding cruciform subassemblies. Moreover, shear force and interlayer slip envelopes are obtained along the composite steel beams. Results of the CFE models are used to propose new design recommendations for shear studs in composite‐steel MRFs.

Behaviour and design of stainless steel-concrete composite beams

Stainless steel-concrete composite beam has been regarded as a new application that is widely applied in offshore bridges and high-rise buildings and is attracting increasing interest from engineering community. The benefits brought by stainless steel, such as superior corrosion and fire resistance, high strength and ductility as well as improved durability, could offer optimal and sustainable solutions for infrastructures and highways. However, the current design provisions for composite beams are based on the assumption of an elastic-perfectly-plastic steel model which is different to stainless steel material with a rounded stress-strain curve and significant strain hardening. To develop rational design guidance, this paper carried out a comprehensive experimental, numerical and analytical study on the behaviour of stainless steel-concrete composite beams. A series of tests were conducted on eighteen full-scale stainless steel composite beams under bending, shear as well as combined bending and shear. Three dimensional finite element (FE) model was developed in ABAQUS and FE simulations were carried out to complement the experimental program. New analytical models were proposed for predicting the moment capacity of stainless steel-concrete composite beam. Additionally, a modified design approach for shear capacity was recommended based on the design guidance in AS/NZS 2327. The applicability of current moment-shear interaction defined in AS/NZS 2327 and EN 1994-1-1 was assessed by the obtained results.

Ultimate capacity and failure mechanism of SCS and S-UHPC composite deep beams: Test and modeling

In this study, a type of steel–concrete–steel (SCS) composite deep beam with ultra-high-performance concrete, named S-UHPC deep beam, was developed. Eight simply supported deep beams, including three SCS deep beams and five S-UHPC deep beams, were tested under static loads. The effects of different parameters (including the shear span ratio, concrete type, and shear stud spacing) on the ultimate capacity, ductility, and interfacial slip of the specimens were explored. Moreover, the observed failure modes were categorized into shear failure without slip, slip failure, and flexural failure with the snapping of steel fibers. To analyze the failure mechanism systematically, finite element (FE) models of the specimens were established and validated. By analyzing the FE simulation results on the compressive damage and stress distribution of the filled concrete, the von Mises stress distribution of shear studs, and the equivalent plastic strain distribution of the bottom steel faceplate, the failure mechanism of the specimens with the observed failure modes was simplified as a modified Strut-and-Tie model. Based on the force transfer analysis of the modified Strut-and-Tie model, a slip coefficient was deduced to quantify the composite action and provide theoretical supports for the reasonable design of shear connectors. Theoretical models of SCS deep beams and S-UHPC deep beams with different failure modes were presented to predict the ultimate capacity.

Performance of axially restrained carbon and stainless steel perforated beams at elevated temperatures

This article compares the fire performance of axially restrained perforated carbon and austenitic stainless steel composite beams with circular and rectangular web openings. Finite element models, validated against experimental tests from the literature, were used to perform parametric analysis. The beams were analysed under various levels of load ratio and axial restraint stiffness covering the ranges which may exist in practice. It is concluded that austenitic stainless steel perforated beams show a more ductile fire response compared to carbon steel beams of similar geometry. It is shown that despite stainless steel’s higher thermal expansion, the beams exhibit lower thermal-induced peak compressive forces than carbon steel beams giving rise to lower levels of thermal-induced compressive force on the adjacent cold structures. The load ratio was found to determine the relative survivability of stainless steel and carbon steel beams, where at load ratios lower than 0.6, stainless steel beams show superior fire resistance than their carbon steel counterparts. The article also assesses the applicability and accuracy of the Steel Construction Institute method for the design of carbon and stainless steel perforated beams, and recommendations for future improvements are made.

Presenting innovative ensemble model for prediction of the load carrying capacity of composite castellated steel beam under fire

The main aims of this study are related to present nonlinear analysis and prediction model for evaluating and predicting the performance of composite castellated steel beam (CCSB) under fire and static load. This study includes two parts, including parametric study and the prediction models. The beam size, concrete thickness, temperature, and beam length are considered as the independent variables in the parametric study. Among considered independent variables in this study, the increasing concrete thickness has a negligible positive effect on the load carrying capacity. In addition, gene expression programming (GEP), three regression models such as multiple linear regression (MLR), principal component regression (PCR), and multiple Ln equation regression (MLnER), the combination of GEP and MLR, and the combination of GEP, MLnER, and MLR are used to predict the load carrying capacity of the castellated beam. The maximum positive and negative errors, mean of absolute percentage error (MAPE), and statistical parameters such as the coefficient of determination, root mean square error (RMSE), normalized square error (NMSE), and fractional bias are utilized to evaluate and compare the performance of the models. According to the results of these parameters, the two best models specify. In addition, a distribution error table is used to specify the best model. Based on the results of this table and statistical parameters, the combination of GEP and MLR is considered as the best model for predicting the load carrying capacity of CCSBs.

Behaviour of interlocking concrete slab and steel composite beam incorporated bolt shear connector

ABSTRACT The complexity of concrete and steel in composite beam has been addressed in many studies previously. However, the use of precast concrete slab in steel–concrete composite construction is considered as new, hence many factors that affect its behaviour need to be investigated. It becomes interesting when the application of interlocking tongue and groove joints between precast concrete slabs is introduced. For this purpose, a performance comparison between normal precast slab and interlocking tongue and groove precast slab in composite construction is conducted using finite element analysis. Both are designed to have full composite action using bolted shear connector. In this research, a total of five models including a control model were developed to study the flexural behaviour of designated composite beam. The model has been verified against experimental results, which showed a good agreement . Parametric studies were performed to investigate the effects of bolt size and height on flexural behaviour of the beam. The present study demonstrated that the presence of interlocking joints between slabs with larger diameter bolt can efficiently improve the stiffness of the composite system.

Numerical studies on steel-concrete composite structures

The paper focuses on the seismic performances of steel-concrete composite structures made with fully encased steel-concrete composite columns and steel beams. An important objective is to study the influence of the structural steel ratio on the behaviour of composite columns. To meet the proposed objectives, a numerical study was developed on composite structures. Some comments, design recommendations and an economical study conclude the paper.

Push-out Test of Profiled Metal Decking Slabs with Cold-formed Steel Beams and Rebar Shear Connector

New methods to provide shear strength on the cold-formed steel (CFS) lipped c-channel section composite beam encased with concrete partially is proposed using rebars embedded in concrete. The development of research on the CFS composite beams technology with partial encasement shows that the section of the composite beam encased with concrete partially can provide ductile flexural action for the composite beam. The application of profiled metal decking slabs in the composite beam is becoming increasingly popular compared to solid slabs. However, it has a detrimental effect on the structural behavior of a composite beam. This research is aimed primarily at presenting the behavior of the rebar shear connector to evaluated ductility, shear capacity, and modes of failure. Two samples using a rebar 12 mm in diameter in the profiled metal decking slabs and solid slabs were tested using the standard push-out test till failure. For the composite beam design, the proposed shear connector embedded in the slab concrete and the CFS encased with concrete partially used the test results’ shear capacity, greater than the values as proposed by section 3.1, BS 5950. Due to rebars shear-off, the solid slab specimen failed with the highest load of 489.6 kN while the Profiled Metal Decking Slab specimen failed due to the formation of the cracks on the PMDS at 421.1 KN ultimate loading.
 HIGHLIGHTS
 
 A new system of the rebar shear connectors for the Cold-Formed Steel (CFS) composite beam partially encased in concrete have been developed
 The main purpose of push-out testing is to investigate the shear capacity and ductility of the proposed shear connector failure modes and load-slip connections
 The shear capacity of the test results is greater than the values as indicated by BS 5950 Part 3.1
 The proposed rebars as a shear connector for partly embedded CFS can be used in the construction
 
 GRAPHICAL ABSTRACT

Experimental and numerical investigations on slim floor beams exposed to fire

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

Fragility Assessment of Beam-Slab Connections for Informing Earthquake-Induced Repairs in Composite-Steel Moment Resisting Frames

Earthquake loss estimation in composite-steel moment resisting frames (MRFs) necessitates a proper estimation of the level of damage in steel beam-to-slab connections. These usually feature welded headed shear studs to ensure the composite action between the concrete slab and the steel beam. In partially composite steel beams, earthquake-induced damage in the shear studs and the surrounding concrete occurs due to shear stud slip demands. Within such a context, this paper proposes shear slip-based fragility functions to estimate the probability of being or exceeding four damage states in steel beam-slab connections. These damage states include cracking and crushing of the concrete slab in the vicinity of the shear studs, as well as damage in the shear studs themselves. The developed fragility functions are obtained from a gathered dataset of 42 cyclic push-out tests. They incorporate uncertainty associated with specimen-to-specimen variability, along with epistemic uncertainty arising from the finite number of available experimental results. An application of the proposed fragility functions is conducted on a six-story building with composite-steel MRFs. It is shown that steel beam-slab connections along the building height only exhibit light cracking (i.e., crack sizes of 0.3 mm or less) at design basis seismic events. At seismic intensities associated with a low probability of occurrence seismic event (i.e., return period of 2475 years) the nonlinear building simulations suggest that the 25% reduction of the shear stud resistance in steel beam-slab connections with beam depths of 500 mm or less is not imperative to maintain the integrity of the shear stud connectors.