Behavior Of Composite Beams Research Articles

Flexural behaviour of composite steel–concrete beams utilising blind bolt shear connectors

This paper investigates the feasibility of utilising blind bolts as shear connectors to develop demountable steel–concrete beams. The flexural behaviour of composite beams with two blind bolt types and welded stud connectors were experimentally investigated using full-scale beam specimens. A set of push-test specimens was tested based on the Eurocode 4 to compare the slip response of these connectors. The ultimate design loads of the test beams were calculated based on rigid plastic analysis (RPA) using the actual material properties. The beam experiments were simulated by using three-dimensional non-linear finite element models (FEMs). The material behaviour for concrete and steel in FEMs was described using concrete damage plasticity and steel plasticity models respectively. The FEMs were validated by comparing the load–midspan deflection curves of the beam specimens obtained from the experiments and modelling. The effects of the concrete compressive strength, steel yield strength and the shear connection ratio on the flexural behaviour of the composite beams were studied by utilising the validated FEMs. The experimental and numerical results suggest that the ability of the blind bolts to achieve and maintain composite action in steel–concrete beams under flexural loading is comparable to that of the welded stud connectors.

Flexural Capacity of Composite Beams Subjected to Fire: Fiber-Based Models and Benchmarking

This paper presents the development and verification of a fiber-based modeling technique to predict the fundamental moment–curvature–temperature (M–Φ–T) response of a composite steel beam cross-section in fire conditions. Experimental investigations and 3D finite element models can provide insight to the behavior of composite beams subjected to fire. However, these experimental and numerical approaches can be expensive and cumbersome for conducting extensive parametric studies. Therefore, a simpler 2D fiber-based modeling technique was developed for calculating the flexural behavior and moment capacity of composite steel beams at elevated temperatures. This simpler fiber-based approach can be implemented relatively easily and independently by designers. The 2D fiber-based approach is a simplified model that accounts for temperature dependent (steel and concrete) material properties and the level of slip at the concrete-to-steel interface at elevated temperature. The model does not account for membrane action or rupture of reinforcement, but it can be used to calculate the moment capacity of partially composite steel beams without an extensive finite element analysis. The fiber-based model was benchmarked using experimental results from composite steel beam tests subjected to fire, illustrating that it was capable of predicting moment capacity corresponding to the applicable limit state (i.e., full yield of the steel beam, concrete crushing or limiting stud slip) at elevated temperature. The fiber model predictions were typically conservative, and on average, the predicted moment capacity was 95% of the capacity determined from the experimental tests.

초고강도 콘크리트 바닥판과 역T형 강재 합성보의 휨 성능 평가

In this paper, when the composite beam is made with UHPC deck and steel girder, the steel girder takes the form of the inverted-T shape without top flange because of high strength and stiffness of UHPC deck. There is no evaluation by experiment and analysis about the shear connector behavior on the web of steel girder and flexural behavior of inverted-T shape composite beam. By this reason, this study compares between experiment and analysis by using tension softening model of UHPC on the basis of flexural test results of 16 members considering compressive strength of UHPC, spacing of stud and thickness of deck as variables. The results of tensile strength of UHPC by inverse analysis were 6.57 MPa(in case of 120 MPa) and 9.57 MPa(in case of 150 MPa). In case of the test members with small stud spacing, the results of analysis and test were close clearly, and the test members with thick deck and low UHPC compressive strength also similar, but effects were small. As it compared between analysis and experiment totally, the results of analysis and experiment agree well. So the tension softening model of UHPC is reasonably reflected on the real behavior of composite beam of UHPC.

Time-dependent Composite Effect of the Curved Steel-concrete Composite Beams in Construction Stage

In order to accurately analyze the mechanical behavior of the steel-concrete composite beams in construction stage, firstly the change law of the shear strength of the stud connectors with the concrete age was studied using the push-out test, in which the time-dependent shear strength formula of the stud connectors was obtained. Secondly, model tests of two simply-supported curved composite beams were carried out during the casting process of concrete slab, the ANSYS finite element models were build with the time-dependent shear strength formula applied in it, and then the experimental and numerical results were verified for each other. On the above basis, a three-span curved continuous composite beam bridge was taken as the sample, by which the influence of the stud connector’s timedependent shear connector strength on the stress behaviors of composite beam in construction stage was studied. The analysis results indicate that the shear strength and stiffness of stud connectors cannot be ignored even when the concrete is in rather early stage, and the early shear strength increases more quickly, whereas the later shear strength slowly. During the segmental casting process of concrete slab, if the casting time interval is between 6 hours and 7 days, the time-dependent characteristics of the early composite action should be considered in the stress behaviors analysis of composite beam in construction stage. Meanwhile, for the hardened concrete segment, the relative slip between the steel girder and concrete slab should also be considered, or else unsafe calculation results will be induced.

Nonlinear Free and Forced Vibration Behavior of Shear-Deformable Composite Beams with Shape Memory Alloy Fibers

The nonlinear free and forced vibration of the composite beams embedded with shape memory alloy (SMA) fibers are investigated based on first-order shear deformation beam theory and the von Kármán type nonlinear strain-displacement equation. A thermomechanical constitutive equation of SMA proposed by Brinson is used to calculate the recovery stress of the constrained SMA fibers. The equations of motion are derived by using Hamilton’s principle. The approximate solution is obtained for vibration analysis of the composite beams based on the Galerkin approach. The parametric study is carried out to display the effect of the actuation temperature, the volume fraction, the initial strain of SMA fibers, and the length-to-thickness ratio. The shear deformation is shown to have a significant contribution to nonlinear vibration behavior of the composite beams with SMA fibers.

Headed steel stud connectors for composite steel beams with precast hollow-core slabs with structural topping

Composite beams of steel and concrete have been studied for a long time. The transfer of longitudinal shear stresses at the interface between the beam and the slab is a key point in obtaining the composite beam behaviour, which is usually achieved by means of shear connectors. In this case, the joint behaviour of the two materials depends on the strength and stiffness of the interface connector. Headed stud connectors for solid concrete slabs are the most common solution to achieve the composite behaviour. However, there is little information on shear connectors associated with precast concrete hollow-core slabs. This study aims to determine, through push-out tests, the shear strength of headed stud connectors associated with precast hollow-core slabs with a structural concrete topping. The analysed hollow-core slabs have two different heights and a minimum structural concrete topping of 40mm. The strength of the in situ concrete infill joints and the rate of transverse reinforcement were varied in the present study. The results were compared to code prescriptions, and a proposition to modify an existing design equation for the ultimate shear capacity of headed studs in composite precast hollow-core slab beams is presented, focusing on the influence of the structural concrete topping.

유리섬유강화폴리머 판을 영구거푸집 및 인장 보강재로 활용한 현장타설 고강도콘크리트 합성보의 휨 파괴거동에 관한 실험적 연구

본 연구에서는 유리섬유강화폴리머 판을 영구거푸집 및 인장 보강재로 활용한 현장타설 고강도콘크리트 합성보를 대상으로 판 하부의 잔골재 부착여부, 웨브의 천공유무 및 간격, 상부플랜지 폭을 변수로 하여 휨 파괴실험을 수행하였다. GFRP 판 웨브를 천공하지 않은 경우 잔골재 부착효과 여부를 위한 실험 결과, 잔골재를 부착한 경우 미부착의 경우 보다 약 43% 높은 극한하중 값을 보여주었으며, 웨브의 천공유무 및 간격효과는 잔골재를 부착하지 않은 경우 천공간격이 3배인 경우가 약 23% 정도 높은 극한하중 값을 보여주었으며, 잔골재를 부착한 경우 천공 간격이 5배인 경우가 약 11% 정도 높은 극한하중 값을 보여주었다. 상부플랜지 영향을 살펴보면, 폭 20mm 경우가 40mm에 비해 약 12% 정도 큰 극한하중 값을 보여주었다. An experiment of composite beam was performed which utilized glass fiber reinforced polymer (GFRP) plank as the permanent formwork with cast-in-place high strength concrete. This research analyzed the flexural failure behavior of composite beam by setting the sand coated at GFRP bottom surface, the perforation and interval of the GFRP plank web, and the width of the top flange as the experimental variables. As a result of the experiments for effectiveness of sand attachment in case of not perforated web, approximately 43% higher ultimate load value was obtained when the sand was coated than not coated case. For effectiveness of perforation and interval of gap, approximately 23% higher maximum load value was seen when interval of the perforation gap was 3 times and the fine aggregate was not coated, and approximately 11% higher value was observed when the perforation gap was 5 times on the coated specimen. For effectiveness of top flange breadth, the ultimate load value was approximately 12% higher in case of 20mm than 40mm width.

Modeling composite beams with partial interaction

This paper presents a finite element model for the analysis of composite beams with partial interaction. In this model, the elements of the composite beams are modeled by six different types of frame elements. Compared with other methods presented in the literature, the main advantages of the proposed method are as follows: (1) intuitiveness, as the different elements of the model present a close and easy to understand relation with the structural behavior of the composite beam; (2) applicability as the method directly provides useful information for the design work; (3) versatility and generalization in dealing with any combination of loading and boundary conditions (Furthermore, the proposed model enables the analysis of statically indeterminate structures, tapered beams as well as structures with non-uniform shear connector distributions.); (4) easy elaboration of models; and (5) possible widespread use of the model, as the proposed method can be implemented in any structural software. To validate the accuracy and the efficiency of the proposed model, a set of FEMs are verified against those results obtained by analytical equations available in the literature for different boundary and loading conditions. Furthermore, a set of parametric studies are performed to investigate the effects of the size of the FEMs along with the influence of the connection stiffness on the behavior of composite beams with different I beams.

Experimental Investigation of Composite Beams with Shear Connections Subjected to Fire Loading

AbstractThis paper presents the results from experimental investigations focused on the thermal and structural behavior of composite beams with shear connections subjected to fire conditions. Five partial composite beams with flat, lightweight concrete slabs were designed according to current U.S. codes and standards. Vertical loading was applied to the composite beams, and the surfaces of the steel and concrete were heated using high-temperature ceramic radiant heaters. Variations in the loading and heating protocol provided insight into the mechanical response and failure modes of composite beams and connections. There was an overall reduction in the composite beam load-carrying capacity due to heating, both at elevated temperatures as well as postfire ambient conditions. Concrete compression failure occurred at moderate steel temperatures (350–500°C) combined with overloading. In cases where service level loading was applied, the composite beams and connections sustained the loading and heating up to s...

Composite beam generally connected: Analytical model

This research has dealt with composite beams, with continuous or discrete connection between the components (laminated, hybrid or sandwich beams), subjected to transverse loads. This paper is devoted to an analytical model for describing the mechanical behavior of composite beams, under no restrictive assumptions on the connection and interaction. The model, which did not exist in the literature, predicts stresses, strains, and displacements due to loads that induce elastic or inelastic behavior in the connection; it may also predict the load that causes the connection to fail.The governing differential equations are expressed in closed-form, and, as such, help comprehend and interpret the structural behavior. The solution of the equations is numerical, and, as such, allows the results to be obtained easily for all kinds of restraints and loads. The paper presents the mathematical formulation and a case study. The application proves that this model is a viable and easy-to-use tool. The model results are also compared to those of a previous analytical model based on assumptions that may seem somewhat restrictive.

영구거푸집으로 사용한 유리섬유 FRP 판과 현장타설 고강도콘크리트로 이루어진 합성보의 휨/전단파괴거동에 관한 실험적 연구

유리섬유강화폴리머(GFRP) 판을 현장타설 고강도콘크리트 구조물의 영구거푸집으로 사용하기 위한 실험을 수행하였다. 현재 생산되는 GFRP 판의 경우 표면이 매끈하여 콘크리트와 일체 거동에 다소 문제점을 갖고 있다. 따라서 본 연구에서는 GFRP 판 하부의 잔골재 부착여부, GFRP판 웨브의 천공유무 및 간격, 상부 플랜지 폭을 실험 변수로 하여 현장타설 고강도콘크리트와 GFRP를 영구거푸집으로 활용한 전단경간비가 짧은 합성보의 휨/전단파괴거동을 분석하였다. GFRP 판 웨브를 천공하지 않은 경우 잔골재 부착효과 여부를 위한 실험 결과, 잔골재를 부착한 경우 미부착의 경우 보다 약 47% 정도의 높은 극한하중 값을 보여주며, 파괴형태도 휨/전단파괴모드를 보여 주었다. 웨브의 천공유무 및 간격효과는 잔골재를 부착하지 않은 경우 천공간격이 조밀한 경우가 약 24% 정도 높은 극한하중 값을 보여주었으며, 잔골재를 부착한 경우 천공 간격이 조밀하지 않은 경우가 약 25% 정도 낮은 극한하중 값을 보여주었다. 상부플랜지 영향을 살펴보면, 폭 40mm 경우가 20mm에 비해 약 17% 정도 큰 극한하중 값을 보여주었다. In this study, an experiment which utilized glass fiber reinforced polymer(GFRP) plank as the permanent formwork of cast-in-place high strength concrete structures was performed. The GFRP plank currently being produced has smooth surface so that it causes problems in behavior with concrete. Therefore, this research analyzed the flexure/shear failure behavior of composite beams, which used GFRP plank as its permanent formwork and has short shear span ratio, by setting the sand coated at GFRP bottom surface, the perforation and interval of the GFRP plank web, and the width of the top flange as the experimental variables. As a result of the experiments for effectiveness of sand attachment in case of not perforated web, approximately 47% higher ultimate load value was obtained when the sand was coated than not coated case and bending/shear failure mode was observed. For effectiveness of perforation and interval of gap, approximately 24% higher maximum load value was seen when interval of the perforation gap was short and the fine aggregate was not coated, and approximately 25% lower value was observed when the perforation gap was not dense on the coated specimen. For effectiveness of top flange breadth, the ultimate load value was approximately 17% higher in case of 40mm than 20mm width.

Behaviour and Design of Composite Beams with Stiffened and Unstiffened Web Openings

This paper presents an investigation on behaviour and design of composite beams with stiffened and unstiffened web openings. The composite beams were simply supported and had profiled steel sheeting oriented transversely to the steel beams. Nonlinear 3-D finite element models were developed to analyse the inelastic behaviour of composite beam components comprising the steel beam, concrete slab, profiled steel sheeting, headed stud shear connectors, reinforcement bars as well as interfaces among these components. In addition, the load-slip characteristic of the headed stud shear connectors in composite slabs with profiled steel sheeting were carefully incorporated into the finite element models. The finite element models of the composite beams have been validated against published experimental results. The composite beams had different moment-to-shear (M/V) ratios at the openings, stiffened and unstiffened web opening sizes, web opening locations, profiled steel sheeting, shear connections, beam lengths, concrete slab strengths and steel beam strengths. The ultimate loads of the composite beams, load-deflection relationships and modes of failure of the beams were predicted from the finite element analysis and compared well against the test results. Furthermore, the variables that influence the composite beam behaviour and ultimate load comprising different stiffened and unstiffened web opening sizes, M/V ratios at openings, web opening locations, beam lengths, concrete strengths and steel beam strengths, were also investigated in an extensive parametric study. It is shown that the ultimate loads of composite beams with stiffened web openings with horizontal stiffeners located above and below the openings, having an opening height equal to 0.6 the steel beam depth, can be considerably increased compared with that of unstiffened openings. It is also shown that the increase in structural steel strength has a remarkable effect on the composite beam ultimate loads. In addition, the ultimate loads of the composite beams with stiffened and unstiffened web openings predicted from the finite element analysis were compared with the design ultimate loads calculated using the Eurocode 4 and technical report SCI P355 published by the Steel Construction Institute for composite beams with profiled steel sheeting and rectangular stiffened and unstiffened web openings. Generally, it is shown that the design ultimate loads accurately predicted the ultimate loads of the composite beams within an average of 6% difference from the ultimate loads predicted using the finite element analysis.

Time-dependent behaviour of composite beams with blind bolts under sustained loads

The use of blind bolts in steel–concrete composite beams is beneficial for promoting sustainable design and for retrofitting existing steel structures. This paper presents an experimental study as well as finite element (FE) modelling analyses for the time-dependent behaviour of composite beams with blind bolts subjected to sustained loads. Four full-scale simply supported beams utilising different types of bolts and studs were tested under long-term static loads. The mid-span deflections were monitored for a period of over 260days. Short-term push-out tests were also carried out on the connectors used in the composite beams, and their slip deformation was recorded for determining the initial stiffness. The experimental results were modelled by using a three-dimensional FE model, in which the creep of the concrete was simulated through defining a viscoelastic response and the shrinkage of concrete was incorporated by means of notional thermal expansion. The FE model was validated against the experimental results reported herein and other independent results of composite beams using conventional welded studs reported elsewhere, and it was subsequently applied to carry out parametric studies. An extensive body of parameters was considered to clarify their effects on the time-dependent behaviour of composite beams with blind bolts, including the mechanical properties and configuration details of shear connectors, the concrete strength, the loading conditions, the span-to-depth ratio and the reinforcement ratio. It was demonstrated that the time-dependent behaviour was sensitive to the stiffness and the bolt-to-hole clearance of connectors, and some other parameters also possessed effects with different degrees. The research findings implied that using blind bolts in composite beams was beneficial to the time-dependent response due to their relatively lower deflections resulting from the creep and shrinkage of the concrete over time. The outcome may provide an important basis and guidance for designing such composite beams when considering their long-term response with time effects.

Fire behavior of composite beams with simple connections: Benchmarking of numerical models

This paper focuses on the development and benchmarking of 3D finite element models for predicting the behavior and failure of composite beams with simple (shear) connections subjected to gravity loads and fire conditions, which include both heating and cooling phases. The simple connections included are the shear-tab, single-angle, and double-angle connections commonly used in the U.S. engineering practice. All the structural components including the steel beam, concrete slab, shear connectors, and connection elements (bolts, plates, angles etc.) were modeled in detail using appropriate finite elements, contact interaction models, and material and component behavior at elevated temperature. The detailed finite element models were benchmarked using results from large-scale tests of composite beams and connections subjected to fire loading including heating and cooling phases. The numerical results including the midspan displacement histories and the connection rotation histories were compared with those measured experimentally by the authors. These comparisons indicate that the detailed models reasonably predict the experimental deformation histories and observed failure modes. The models were used to provide additional insight into the axial forces developed in the connections, particularly during the cooling phase, thus enhancing experimental findings. The benchmarked model is recommended for conducting analytical parametric studies to supplement experimental investigations of composite beams and simple connections under fire.

Hybridization effects on lateral buckling behavior of laminated composite beams

The aim of this study is to investigate the influence of hybridization on lateral buckling behavior of composite beams consists of symmetrical and unsymmetrical ply orientations, various cutout shapes, and length/thickness ratio. Carbon, S-glass, and Aramid fibers are used as reinforcement with epoxy resin. Experiments are performed to see the effects of various combinations of fibers on lateral bucking loads with [(0/90)3]s, [(30/-60)3]s, [(45/-45)3]s symmetrical, and [(0/90)6]us unsymmetrical ply orientations. Numerical studies are also performed to see the effects of length/thickness ratio, and various cutout shapes on the lateral buckling loads using finite element analysis software ANSYS. It is concluded that stiffness and shear properties are affecting the lateral buckling characteristics of the composite beams. Also, fibers having higher stiffness and higher shear properties in the upper layers increase the lateral buckling strength. POLYM. COMPOS., 37:2511–2521, 2016. © 2015 Society of Plastics Engineers

Analysis of Composite Steel-concrete Beams Exposed to Fire using OpenSees

OpenSees is an open-source object-oriented software framework developed at UC Berekeley. The OpenSees framework has been recently extended to deal with structural behaviour under fire conditions. This paper summaries the key work done for this extension and focuses on the validation and application of the developed OpenSees to study the behaviour of composite steel-concrete beams under fire conditions. The performance of the developed OpenSees are verified by four mechanical tests and two fire tests on simply supported composite beams. A parametric study is carried out using OpenSees to study the influence of boundary condition as well as composite effect of slab on the behavior of composite beams exposed to fire. The stress and strain along the beam section is output and compared with yield stress limit at elevated temperature to explain these influences in detail. The results show that the stress distribution in the web of the steel beam is more complex due to the support effects.

Experimental and Numerical Study of Fire Resistance of Composite Beams

In this paper, the standard fire resistance test under load and associated numerical study were carried out to evaluate the fire resistance of unprotected partially encased beams and slimfloor beams. The temperature evolution and the deflection increase of the composite beam specimens were investigated and the effects of the key behavioral parameters including the load ratio, the reinforcement, and the fire exposure were analyzed. The test results showed that the temperature rise of the partially encased beams and slimfloor beams is considerably slow compared to the conventional H-shape composite beams. Up to at least 90 minutes, the reinforcements in the partially encased composite beams maintained below the temperature at which the cold steel strength is sustained. Unprotected partially encased beams and slimfloor beams in the experimental program achieved the fire resistance more than 2 hours according to the limiting deflection criteria. This implies that unprotected partially encased beams and slimfloor beams can be very promising alternatives to enhancing the fire resistance of steel beams. This study also conducted the fully coupled thermal-stress analysis by using the commercial code ABAQUS to the thermal and structural behaviour of composite beams in fire. The numerical predictions provide acceptable correlations with the experimental results. Keywords - Partially encased beam, Slimfloor beam, Fire resistance test under load, Coupled thermal-stress analysis, Fire resistance

Elastoplastic Cross-Sectional Behavior of Composite Beams with High-Strength Steel: Analytical Modeling

AbstractComposite steel-concrete beams that use high-strength (HS) steel sections are more sustainable from an environmental low-carbon perspective than those that use mild steel because less steel is needed. Quantifying the elastoplastic cross-sectional behavior of composite beams using HS steel sections is important because HS steel has significant differences in its plastic properties when compared with conventional mild steel. It is also important to establish this behavior in order to apply the principles of rigid plastic design. This paper develops a new analytical model for the cross-sectional analysis of HS steel-concrete composite beams to elucidate this elastoplastic response, so as to ascertain the validity of applying rigid plastic design. Both material nonlinearity and partial shear connection are incorporated in the analysis. The constitutive model for the steel is specified by using a multilinear stress-strain relationship, and that of the concrete is based on a model in terms of its axial ...

A higher order steel–concrete composite beam model

This paper presents a model for the analysis of composite beams in which the constrained kinematics encompasses the overall shear deformability, warping of the slab cross section and of the steel beam and partial shear interaction between slab and girder. The warping functions are obtained by considering the problem of unrestrained thin-walled members subjected to self-equilibrated elementary load schemes. The governing equations are derived, according to the stiffness method, both in the weak and strong forms starting from the Virtual Work Theorem which makes it possible to consistently obtain the resultants of stresses, the applied forces and the inertia involved in the problem. The analytical solution is obtained from the governing differential equations and the relevant boundary conditions exploiting exponential matrices. Some simple applications show the capability of the model to accurately describe both the global behaviour of composite beams, in terms of displacements and stress resultants, and local effects, in terms of normal stresses. The comparisons with results obtained with a refined shell finite element model are very satisfactory.

Estimation of friction contribution in the behavior of steel-concrete composite beams with flexible shear connectors

A shear connector, developed to be applied to a composite beam whose steel profile is a thin-walled box profile, displayed much greater flexibility than the conventional welded shear connector, leading to particular issues in the composite beam behaviour. One of these issues is the role played by friction at the interface between the steel profile and the slab which, under particular circumstances, may be relevant for serviceability limit states and also for ultimate limit states. The Brazilian and American Standards do not yet recognize the friction contribution in the behaviour of composite beams, though they recognize this contribution in composite slabs. This paper presents the experimental tests carried out with and without friction contribution on simple supported composite beams with flexible connectors and the numerical models developed to simulate the behaviour of the tested beams. The experimental tests revealed significant increases in strength and stiffness of the composite beam due to friction contribution and the comparisons between numerical and experimental results displayed good correlations.