Partial Composite Action Research Articles

FIELD EVALUATION OF UNINTENDED COMPOSITE ACTION BETWEEN STEEL PLATE GIRDERS AND CONCRETE SLAB IN HIGHWAY BRIDGES

AbstractUnintended composite action between steel plate girders and concrete slab is a well‐recognized, but challenging aspect of evaluating highway bridge behaviour because the degree of slip between the slab and girder is difficult to predict. In this study, a method to evaluate the effect of unintended composite action using field testing is presented. The method is illustrated using a four‐span five girder highway bridge instrumented with strain gages at maximum positive and negative moment locations and subjected to a vehicle with a calibrated load. Results indicate that all the girders exhibited partial composite action. Measurement of composite action was less reliable when the instrumented location was not close to the load.

Lumped GFRP star connector system for partial composite action in insulated precast concrete sandwich panels

This paper introduces a novel composite shear connectors system used to transfer interface shear forces in a precast concrete sandwich panel. The shear connectors consist of non-proprietary non-composite commercial glass fiber reinforced polymer (GFRP) pin connectors that are laid out in a star pattern and clustered at the top and bottom of the panels. The testing program consisted of thirty-four push-off, twenty-three pullout, and eight full-scale flexural specimens was conducted to evaluate the structural performance of the new shear connectors. The effect of concrete wythe thickness, insulation wythe thickness, and concrete compressive strength was investigated throughout these tests. Additionally, the effect of bond between insulation and concrete wythes was investigated using push-off tests. The flexural test results were compared with predicted fully composite, non-composite, and partially composite values to evaluate the overall panel performance. The comparison showed satisfactory performance with a lower bound of 90% composite action for specimens with 100 mm thick insulation wythe and full composite action for most panels with 50 mm thick insulation. Idealized shear load-slip curves were also developed that account for various parameters to assist design engineers in designing insulated sandwich wall panels with the proposed shear connectors system.

Stress mitigation for adhesively bonded photovoltaics with fibre reinforced polymer composites in load carrying applications

Structural loads, especially in-plane compression, may cause local buckling and debonding of the photovoltaic (PV) cells that are mechanically integrated with structural members and this may lead to degradation in their electrical performance. This paper proposes an approach to mitigate the strains transferred from structural members to PV cells through the partial composite action provided by low-modulus adhesives. Specimens were fabricated by bonding amorphous silicon (a-Si) PV cells to glass fibre reinforced polymer (GFRP) structural components by an adhesive layer of 0.5- or 2.0-mm thickness. Two types of adhesives were used including a two-part rigid epoxy adhesive and a low-modulus silicone adhesive. These integrations were then submitted to in-plane compressive loadings. PV cells bonded by the silicone adhesive showed no damages during loading. While for PV cells bonded by epoxy adhesives, obvious electrical performance degradations were observed, when the strain reached 0.62% or 0.23% for specimens bonded by epoxy with a layer thickness of 0.5 mm or 2.0 mm respectively. Debonding and local-buckling of the PV cells were also witnessed. Theoretical analysis was conducted to understand the strain mitigation of the adhesive as a result of the induced partial composite action. Results demonstrate that such strain differences between the GFRP and the bonded PV cell are dominated by the shear modulus and thickness of the adhesive layer as well as elastic modulus, thickness and length of the PV cell. The theoretical analysis was validated by finite element (FE) modelling and design suggestions are provided accordingly.

Experimental Investigation of the Natural Bonding Strength between Stay-In-Place Form and Concrete in FRP-Concrete Decks/Beams

The Fiber Reinforced Polymer (FRP)-concrete hybrid deck/beam is a structural system that combines the durable thin-walled FRP composite profiles and the cost-effective concrete by interfacial shear connections. The interfacial slip can reduce the composite action, thereby causing a degradation of flexural rigidity and capacity. Therefore, using stay-in-place (SIP) forms is a simple way to fully utilize the natural bonding between FRP and concrete, which plays a pivotal role in the structural design of FRP-concrete hybrid decks/beams. This paper presents an experimental study on the natural bonding provided by the SIP forms and the in situ cast concrete. First, four comparative push-out test specimens revealed that the use of SIP forms could improve the ultimate shear capacity of steel bolts by 11.1%. Moreover, it could provide an initial stage with nearly zero slip. The average natural bonding strength of FRP-concrete was evaluated as 0.27 MPa, which agreed well with previous tests in the literature. Second, the beam specimen also confirmed that there was a load response stage with nearly zero slip along the FRP-concrete interface when SIP forms were used as the permanent form. Third, the strain measurements on the steel bolts, FRP profile, and concrete revealed that the failure of the natural bonding was a brittle process. Finally, the flexural response of the FRP-concrete hybrid beam was analytically modeled as three distinct stages, namely the full composite action stage, the slipping stage caused by a natural bonding decrease, and the partial composite action stage.

Flexural Behavior of Hybrid Composite Beam (HCB) Bridges

A new hybrid composite beam (HCB) has recently been used in the construction of three bridges in Missouri, USA. HCB consists of self-consolidating concrete (SCC) that is poured into classical arch shape and tied at the ends by steel tendons. Both the concrete and the steel are tucked inside a durable fiberglass shell, and the voids are filled with polyiso foam. This paper aims to examine the flexural behavior of an in-service HCB, evaluate the current methodology and assumptions, and propose modifications to that methodology. To achieve these goals, the strains induced in HCB elements due to different loading stages were experimentally measured. Numerical predictions of the strains were performed via the existing methodology, the modified procedure, and a finite element model (FEM) that was constructed using ANSYS V14. The linear FEM predicted the strains with acceptable accuracy. The model clarified that the foam achieves partial composite action between the HCB elements, resulting in a strain incompatibility between them. The current methodology was found to be unable to predict the maximum compressive strain in the concrete arch. The modified procedure is based on the strain compatibility assumption. However, it models the HCBs as curved beam rather than a straight one, using a simplified spring model to represent the beam supports. These modifications achieved significant enhancements in estimating the strains under service loads.

Nonlinear finite element analysis of composite precast concrete sandwich panels made with diagonal FRP bar connectors

Composite precast concrete sandwich panels made with diagonal FRP bar connectors have increasingly been used in the last few decades mainly due to their excellent thermal insulating properties. However, there is a lack of standards, design guidelines and reliable models that can be used for their analysis and design. In this paper, a finite element model is developed for investigating their structural behaviour, which aims to clarify their response and to provide a basis for establishing design guidelines. The model accounts for cracking and tension stiffening, material nonlinearity of concrete in compression, and geometric nonlinearity. The modelling challenges and assumptions are investigated, and the model is validated by comparing with other models and test results from the literature. The results explain the structural behaviour of these panels, which exhibit a partial composite action. The results also show that the failure mode of typical panels is ductile and dominated by yielding of the flexural steel reinforcement. A preliminarily investigation of the thermal effects shows that temperature gradients can lead to significant arching action in the panel and can affect its stability. The influence of the diameter and shape of the shear connectors and the stiffness of the insulation are investigated.

Girder–Deck Interface: Partial Debonding, Deck Replacement, and Composite Action

Girder–Deck Interface: Partial Debonding, Deck Replacement, and Composite Action

Analytical and numerical study of the serviceability performance of partial composite steel-FRP beams

PurposeThe purpose of this paper is to introduce a closed-form analytical solution to evaluate the nominal moment capacity and associated deflections of steel-FRP beam systems. The proposed solution takes into consideration the partial composite behavior resulting from the interfacial contact and slip between the subcomponents of the system.Design/methodology/approachThe partial composite action theory was used to develop an elastic analytical solution for the deflection of simply supported composite steel-FRP beams subjected to a mid-span point load. The solution takes into consideration the partial composite behavior of the system that arises from the interlayer slip at the steel-FRP interface.FindingsThe developed analytical model is used to predict the nominal moment capacity of the composite beam and the load value at the onset of yielding in the steel subcomponent of the section. The distribution of shear forces induced in the steel fasteners due to the interfacial slip is also obtained analytically. A comparative study is conducted by comparing the analytical results to their counterparts resulting from finite element modeling of the composite steel-FRP system. The agreement between analytical results and finite element predictions validates the accuracy of the derived analytical solution for partial composite steel-FRP beams.Research limitations/implicationsThe proposed solution applies only to the FRP strips and 6 mm steel bolts used in the study.Originality/valueRecent studies revealed a promising efficiency of using mechanically fastened hybrid FRP sheets in strengthening steel beams. A major advantage of this technique is the ductile behavior of the steel-FRP system. The current paper introduces a closed-form analytical solution to evaluate the nominal moment capacity and associated deflections of steel-FRP beam systems. Forces developed at the steel-FRP interface due to the relative slip between both components are considered in the proposed analytical solution.

Mechanical performance and numerical simulation of GFRP-concrete composite panel with circular hollow connectors and epoxy adhesion

Effective shear transfer at the interface of glass fibre reinforced polymer (GFRP) and concrete sections is crucial to achieve structural integrity of the composite panel. This study proposed a shear connector consisting of circular hollow sections (CHS) to enhance shear transfer between concrete and GFRP. Push-out and three-point bending tests were conducted to evaluate the static response of the proposed connectors compared to the adhesive bonding. The results showed that GFRP-concrete composite section using proposed shear connectors achieved partial composite action and non-linear behavior could be observed before the GFRP section failed in shear along the fibre direction at the contact zone. The mechanical properties of the connectors can affect the bearing capacity and stiffness of the composite structure. Numerical simulation using finite element (FE) method was able to capture the overall mechanical response with respect to loading force and deformation. Using a validated FE modelling technique, a comprehensive parametric study was carried out. Results showed that flange thickness, fibre orientation and shear connector arrangement can significantly affect the flexural capacity of GFRP-concrete composite.

Finite Element Modeling and Parametric Study on Floor Steel Beam Concrete Slab System in Non-Composite Action.

This study aims to show, the strength of steel beam-concrete slab system without using shear connectors (known as a non-composite action), where the effect of the friction force between the concrete slab and the steel beam has been investigated, by using finite element simulation.
 The proposed finite element model has been verified based on comparison with an experimental work. Then, the model was adopted to study the system strength with a different steel beam and concrete slab profile. ABAQUS has been adopted in the preparation of all numerical models for this study.
 After validation of the numerical models, a parametric study was conducted, with linear and non-linear Regression analysis. An equation regarding the concrete slab-steel beam system strength in non-composite action has been pointed out. Where the actual strength of the beam without using shear connectors has been located in between the full composite action and non-composite action. However, partial-composite action has been noted, due to the effectiveness of friction force which makes the beam behave as composite before the slip occurs.

A constitutive numerical modelling of hybrid-based timber beams with partial composite action

This work focuses on the development of a three dimensional constitutive model for timber to simulate the flexural behaviour of hybrid timber-steel and timber-concrete beams. This is motivated by the lack of dedicated non linear material behaviour laws for timber in the commercial finite element software by compared to the conventional materials such as concrete and steel.The flexural behaviour of hybrid timber beams is very complex because of the combination of the two different material behaviours and their nonlinar and partial compostion action. Numerical simulation of such behaviour requires an accurate description of the nonlinear material behaviour, in particular that of timber because of its anisotropic nature. A realistic description of the material nonlinearities and of the composite action between the different materials could aid considerably in achieving acceptable predictions. An incremental approach based on the strong coupling between orthotropic elasticity, anisotropic plasticity with mixed nonlinear isotropic hardening and an isotropic damage is used. The developed constitutive model for timber is implemented in Abaqus code using an external subroutine. The 3D FE model is calibrated and validated through comparison with experimental data reported in literature. The model is able to predict the nonlinear structural response of hybrid beams in terms of load-midspan deflection, and provides an acceptable accuracy.

Exact static analysis of eccentrically stiffened plates with partial composite action

Stiffened plates are common forms used in engineering structures. Extensive research efforts have been devoted to investigating the behavior of stiffened plates under static loading. In the existing models, two issues have not been always appropriately addressed. One is the eccentricity of the stiffeners and the other is the composite action between the plate and stiffeners. In the present paper, static deformation of an eccentrically stiffened plates with partial composite action was analyzed by using the variational approach. In order to investigate the eccentricity and composite action issues, the stiffened plates were idealized as assemblies of plate and beam elements, in such way the stiffeners are discretely connected to the plate elements. Based on the principle of the minimum potential energy, the governing differential equations were derived by using the variational approach with taking into consideration of strain energy of connectors between plate and stiffeners and associated boundary conditions as well. Five displacement functions were defined as double Fourier series to solve the static deflection of simply-supported eccentrically stiffened plates. A relative stiffness factor K with a range of zero to one was introduced to represent the composite action between the plate and stiffeners from no interaction (i.e., K=0) to rigidly connected (i.e., K=1). Finally, the proposed energy approach was compared with previously published methods through numerical examples of the plates reinforced by one to fourteen stiffeners in two orthogonal directions.

Mechanical performance of two-way modular FRP sandwich slabs

This paper presents a modular GFRP sandwich assembly for two-way slab applications. The sandwich assemblies were built-up sections made from pultruded web-core box profiles incorporated between two flat panels, connected via adhesive bonding or novel blind bolts. Two different pultrusion orientations were examined: flat panels with pultrusion directions either parallel (unidirectional orientation) or perpendicular (bidirectional orientation) to the box profiles. The effects of pultrusion orientation, shear connection and the presence of foam core materials on strength and stiffness were investigated by testing two-way slab specimens until failure. Sandwich slabs with unidirectional orientation showed premature cracking of the upper panel between fibres, whereas those with bidirectional orientation showed local out-of-plane buckling of the upper flat panel. The unidirectional slab also showed greater bending stiffness than bidirectional slabs due to the weak in-plane shear stiffness provided by the web-core profiles, which introduced partial composite action between the upper and lower flat panels of the bidirectional slab. Finite element models and analytical techniques were developed to estimate deformation, failure loads and the degree of composite action, and these showed reasonable agreement with the experimental results.

Effect of Partial Shear Interaction in Steel Concrete Composite Girders

Steel concrete composite (SCC) structural system has been commonly used both in the buildings and in the bridges because of the advantages it associates when compared to its counterparts such as RC and steel structures. A typical SCC girder consists of a concrete element placed over a steel element. The effectiveness of this composite system is characterized by the type of connection that exists between the two connecting elements. More commonly shear stud connectors are used to connect the two elements. If the shear studs are infinitely rigid, then it brings about full composite action, on the contrary there is no composite action if the studs are not used, between the two connecting elements. It has been observed that generally the composite action exists somewhere between the full composite action and the no composite action, and is called the partial composite action or the partial interaction. More often the partial composite action is overlooked during the design of SCC girders, and the girder is designed assuming that there exists full composite action, because of the complexities in the analysis incorporating the partial composite action. This might lead to the serviceability issues in the SCC girders. Keeping this in mind the present work has been carried out to understand the significance of the partial interaction in SCC girders. In the present work, a comparative study has been made between the available analytical model and the numerical model. Numerical modeling is performed by using commercially available tool such as SAP2000. The main objective of this work is to bring out the relative significance of the partial interaction with respect to the full composite action, with the help of parametric study. Here, the parametric study has been carried by considering various design parameters, such as, span length, degree of shear connection, cross section geometry of steel girder and concrete slab. It is observed that there is significant increase in deformations of the SCC girder, on account of the partial interaction. The results of the numerical model and the analytical model are in good agreement.

Bending behaviour of novel Textile Reinforced Concrete-foamed concrete (TRC-FC) sandwich elements

A novel sandwich element design consisting of two facings made of carbon reinforced Textile Reinforced Concrete (TRC), a low density foamed concrete (FC) core and glass fibre reinforced polymer (GFRP) connecting devices was experimentally investigated according to quasi-static and cyclic quasi-static four-point bending. Optical measurements based on Digital Image Correlation (DIC) were taken during testing to enable a detailed analysis of the bending behaviour and level of composite action. A model, verified by the experiments, was developed based on non-linear finite element analysis (NLFEA) to gain further insight on the failure mechanisms. Under both loading conditions, the bending behaviour of the TRC-FC composite elements was characterized by favourable load bearing capacity, partial composite action, superior ductility and multiple fine cracking. The connecting devices were found to be the critical elements causing the initial failure mechanism in the form of localized pull-out within an element.

Practical nonlinear inelastic analysis method of composite steel-concrete beams with partial composite action

This paper presents an efficient computer method for nonlinear inelastic analysis of composite steel-concrete beams with partial composite action. The proposed formulation is intended to model the combined effects of partial composite action and distributed plasticity using only one 2-noded beam-column element per structural member. Based on elasto-plastic cross-sectional analyses the behaviour model is able to take into account the effects of partial composite action between the concrete slab and the steel beam. Gradual yielding throughout the cross-section is described through basic equilibrium, compatibility, material and shear connection nonlinear constitutive equations. Tangent flexural and axial rigidity of the cross-section are derived and then using the flexibility approach the elasto-plastic tangent stiffness matrix and equivalent nodal loads vector of the beam-column element including the shear deformability of the partially connected composite beam has been developed. The proposed nonlinear analysis formulation has been implemented in a general nonlinear static purpose computer program, NEFCAD. Advanced finite element simulations have been conducted by using the specialized software for nonlinear analysis of structures, ABAQUS. Several computational examples are given to validate the accuracy and efficiency of the proposed method by comparing the results predicted by NEFCAD with those given by the ABAQUS software and other results retrieved from the open literature.

Analysis and Parametric Study of Partially Composite Precast Concrete Sandwich Panels under Axial Loads

AbstractThis paper presents a numerical model developed to predict the response of partially composite load bearing concrete sandwich panels under axial loads applied to the structural wythe at any eccentricity. The model accounts for material nonlinearity, second-order effects, and cracking of concrete and plasticity of steel reinforcement, and can also model fiber-reinforced polymer (FRP) connectors. The analysis uses a bond-slip model to simulate partial composite action between the two wythes resulting from various configurations of insulation and shear connectors. A variety of failure modes can be detected, including concrete crushing, flexural yielding, connectors yielding, pullout or rupture, and stability failures. Progressive failure of connectors is also modeled. The degree of composite action (κu) can be calculated for a given design. The model was verified against experimental data and used to conduct a comprehensive parametric study. It was shown that κu increases with panel length. Connector...

Mechanical performance of modular FRP-steel composite beams for building construction

This paper presents an experimental and modelling investigation into modular web-flange fibre-reinforced polymer (FRP)-steel composite systems for use in building floor construction. The modular FRP slabs are formed from adhesively bonding pultruded box profiles sandwiched between two flat panels. They are then connected via adhesive or novel bolted connections to steel beams to form a composite system. Two different fibre (pultrusion) configurations are investigated in this paper: flat panel pultrusion with direction either parallel or perpendicular to the box profiles. Composite beams were tested under four-point bending and evaluated for bending stiffness, load-carrying capacity, and the degree of composite action within the FRP web-flange sandwich slab and that provided by the shear connections. All the composite beams showed ductile load–deflection responses, with yielding of the composite beam commencing prior to failure of the FRP slabs. Furthermore, adhesive bonding provided full composite action, but the novel bolted connections with a certain spacing provided either full or partial composite action, dependent on the pultrusion configuration of the FRP slab. Finally, an analytical procedure is presented to evaluate the bending stiffness and load-carrying capacity of the composite beams. Finite element analysis was also employed in this study, showing good comparisons to the experimental results.

Analytical Model for Deck-On-Girder Composite Beam System with Partial Composite Action

AbstractIn a deck-on-girder composite beam system, the deck and supporting girders work together to effectively provide loading capacity. This system has been widely used for bridges, buildings, and other structures. Effective flange width is typically used to reduce a three-dimensional behavior of the composite beam system to the analysis of a T-beam section with a reduced width of deck. Current studies, including AASHTO specifications, are mainly focused on concrete decks with full-composite action. This paper presents a closed-form solution to study the composite beam system, which considers different degrees of composite action (DCAs) between the deck and supporting girders and can be applied to decks with orthotropic materials. The analytical model is verified through close correlations among test, finite-element, and analytical results for two T-beams with concrete and fiber-reinforced polymer (FRP) decks, in terms of both deflections and stress distributions. A parametric study is then conducted by...

Bilinear load-deflection model of fiber-reinforced polymer–concrete composite beam with interface slip

The design of fiber-reinforced polymer–concrete hybrid beam is usually governed by deformation. Due to the rigidity degradation caused by fiber-reinforced polymer–concrete slip, the load–slip and load–deflection curves demonstrate a bilinear characteristic. The originality of this article is to propose a bilinear analytical model and to determine two dominant parameters in this model, namely, initial bond stress and slip modulus of the interconnection. This model consists of two distinct linear stages. In Stage I, full composite action between fiber-reinforced polymer and concrete is obtained, and no slip exists; Stage II commences once interfacial bond force diminishes, when slip increases linearly versus load, and the overall beam rigidity drops compared with that in Stage I, indicating only partial composite action is realized. Finally, three large-scale specimens were tested to validate the proposed bilinear model and to calculate the two parameters.